Sana Shahzad horticulture 2019 uaf prr.pdf

IN THE NAME OF ALLAH THE MOST BENEFICENT AND MERCIFUL

ii

Pre and postharvest management to improve yield and quality of

strawberry (Fragaria × ananassa) cv. ‘Chandler’

By

SANA SHAHZAD

M.Sc. (Hons.) Horticulture

2007-ag-2502

A thesis submitted in the fulfillment of the

requirements for the degree of

DOCTOR OF PHILOSOPHY

IN

HORTICULTURE

INSTITUTE OF HORTICULTURAL SCIENCES

FACULTY OF AGRICULTURE

UNIVESITY OF AGRICULTURE,

FAISALABAD-PAKISTAN

2019

iii

iv

v

vi

DEDICATION

This Humble Effort is Dedicated to

My Beloved Parents

And

My Respected Supervisor

vii

ACKNOWLEDGEMENT Allah never spoils any effort. Every piece of work is rewarded according to the

nature of devotion in it. I am, though, never be feeling myself able to offer my thanks

to Almighty ALLAH, the propitious, the sole creator of the universe, the source of all

knowledge and wisdom. Trembling lips and wet eyes praise for Holy Prophet

Muhammad (P.B.U.H), who is a torch of guidance and knowledge for humanity

forever, for his sacredness, due to whom I have been able to achieve this milestone of

my academic career. I wish to record my sincerest appreciations to my Supervisor

Prof. Dr. Saeed Ahmad, Institute of Horticultural Sciences, University of

Agriculture, Faisalabad, for her valuable comments and guidance.

I feel highly privileged to take this opportunity to express my heartiest

gratitude and deep sense of indebt to my worthy supervisory committee, Dr. Raheel

Anwar Assistant Professor and Prof. Dr. Rashid Ahmed, Dept. of Agronomy, for

their incentive teaching and valuable suggestions. I offer my gratitude especially to

my Grandfather Mian Abdul Khaliq, my Father Shahzad Khaliq, my Mother Azra

Begum, my Brother Zunair Shahzad and my Sister Sundas Shahzad, whose prayers

and inspirations are the torch to my destination and my honorable Uncle, Kashif

Hussain and my Aunties Shazia Kashif, Nazia Tariq who inspired me to higher

ideas of life and whose hands always rise in prayer of my success.

I would like to record my sincerest thanks to all my seniors, university friends

and colleagues Dr. Waqar Shafqat, Dr. Mehwish Liaquat, Dr. Kanval Shaukat,

Samra Asghar, Furkhanda Kalsoom, Aliya Hanif and special thanks to Mr. Shakeel

(Lab. Assistant) and Mr. Farhan (J.L.A) from pomology Lab. for their generous help,

cooperation and Memorial Company. Whatever I am today, could never have been

without the efforts, prayers, good wishes and sympathetic attitude of my very kind

and loving parents and family members.

Sana Shahzad

viii

ix

2.13 Pre harvest problems of strawberry 12

2.14 Pre harvest management practices to improve yield and quality 12

2.14.1 Effect of mulching material 12

2.14.2 Effect of plant spacing 12

2.14.3 Protected cultivation 12

2.14.4

Effectiveness of calcium chloride (CaCl2) for improving

growth, yield and qualitative characteristics of other

strawberry cultivars

13

2.14.5

Effectiveness of zinc sulfate (ZnSO4) for improving growth,

yield and qualitative characteristics of other strawberry

cultivars

14

2.14.6

Effectiveness of salicylic acid (SA) for improving growth,


cultivars

15

2.14.7

Effectiveness of gibberellic acid (GA3) for improving growth,


cultivars

16

2.15 Postharvest problems of strawberry 17

2.16 Effect of storage application of calcium chloride (CaCl2) on

quality and shelf life of fruits 17

2.17 Effect of storage application of salicylic acid (SA) on quality

and shelf life of fruits 18

Chapter 3 Materials and Methods 20

3.1 Experimental site detail 20

3.1.1 Site selection 20

3.1.2 Soil preparation 20

3.1.3 Preparation of beds 20

3.1.4 Selection of runner plants 20

3.1.5 Planting of runners 20

3.1.6 Foliar application 21

3.1.7 Plant protection with polythene tunnel 21

x

3.2 Study 1 (Salts) 21

3.2.1

Experiment No. 1: Foliar application of calcium chloride

(CaCl2) to improve the vegetative growth, yield and quality of

strawberry cv. „Chandler‟.

21

3.2.2

Experiment No. 2: Foliar application of zinc sulfate (ZnSO4)

to improve the vegetative growth, yield and quality of

strawberry cv. „Chandler‟.

22

3.3 Study 2 (Growth regulators) 22

3.3.1

Experiment No. 1: Foliar application of salicylic acid (SA) to

improve the vegetative growth, yield and quality of strawberry

cv. „Chandler‟.

22

3.3.2

Experiment No. 2: Foliar application of gibberellic acid (GA3)


Strawberry cv. „Chandler‟.

23

3.4 Study 3 (Confirmatory trial) 24

3.4.1

Comparison of calcium chloride (CaCl2), zinc sulfate (ZnSO4),

salicylic acid (SA) and gibberellic acid (GA3) to improve the

vegetative growth, yield and quality of strawberry cv.

„Chandler‟.

24

3.5 Parameters 24

3.5.1 Vegetative parameters 24

3.5.1.1 Number of leaves (plant-1

) 24

3.5.1.2 Leaf area (cm2) 25

3.5.1.3 Flower anthesis (days after foliar application) 25

3.5.1.4 Number of crowns (plant-1

) 25

3.5.1.5 Number of runners (plant-1

) 25

3.5.2 Yield parameters 25

3.5.2.1 Marketable (g plant

-1) 25

3.5.2.2 Unmarketable (g plant

-1) 25

3.5.2.3 Small size (g plant

-1) 26

xi

3.5.3 Fruit quality parameters 26

3.5.3.1 Firmness (kg. cm-2

) 26

3.5.3.2 TSS (ºBrix) 26

3.5.3.3 Titratable acidity (%) 26

3.5.3.4 TSS: TA ratio 26

3.5.3.5 Vitamin C (mg 100 g-1

) 26

3.5.3.6 Total phenolic contents (TPC) and total antioxidants (TA) 27

3.5.3.7 Total phenolic contents (mg GAE 100 g-1

) 27

3.5.3.8 Total antioxidants (% DPPH) 27

3.5.4 Activities of antioxidant enzymes (CAT, SOD and POD)

determination 27

3.5.4.1 Catalase (U mg−1

protein) 28

3.5.4.2 Peroxidase (U mg−1

protein) 28

3.5.4.3 Superoxide dismutase (U mg−1

protein) 28

3.5.5 Survival (%) 28

3.6 Study 4 (Postharvest) 29

3.6.1

Postharvest application of calcium chloride (CaCl2) and

salicylic acid (SA) maintain the quality and improve storage

life of strawberry cv. „Chandler‟.

29

3.6.1 Fruit weight loss (%) 30

3.6.2 Fungal decay (%) 30

3.7 Statistical analysis 30

3.8 Six months internship program at University of Florida, USA. 30

Chapter 4 Results and Discussion 32

4.1 Study- 1 (Salts) 32

4.1.1

Experiment No. 1: Foliar application of calcium chloride

(CaCl2) to improve the vegetative growth, yield and quality

of strawberry cv. ‘Chandler’.

32

4.1.1.1 Vegetative parameters 32

xii

4.1.1.1.1 Number of leaves (plant-1

) 32

4.1.1.1.2 Leaf area (cm2) 32

4.1.1.1.3 Flower anthesis (days after foliar application) 33

4.1.1.1.4 Number of crowns (plant-1

) 33

4.1.1.1.5 Number of runners (plant-1

) 33

4.1.1.2 Yield parameters 34

4.1.1.2.1 Marketable (g plant

-1) 34

4.1.1.2.2 Unmarketable (g plant

-1) 34

4.1.1.2.3 Small size (g plant

-1) 35

4.1.1.3 Fruit quality parameters 35

4.1.1.3.1 Firmness (kg. cm-2

) 35

4.1.1.3.2 TSS (ºBrix) 36

4.1.1.3.3 Titratable acidity (%) 36

4.1.1.3.4 TSS: TA ratio 36

4.1.1.3.5 Vitamin C (mg 100 g-1

) 36

4.1.1.3.6 Total phenolic contents (mg GAE 100 g-1

) 37

4.1.1.3.7 Total antioxidants (% DPPH) 37

4.1.1.4 Activities of anti-oxidative enzymes 41

4.1.1.4.1 Catalase (U mg−1

protein) 41

4.1.1.4.2 Superoxide dismutase (U mg−1

protein) 41

4.1.1.4.3 Peroxidase (U mg−1

protein) 42

4.1.1.5 Survival (%) 42

4.1.1 Discussion 44

4.1.1 Conclusion 47

4.1.2

Experiment No. 2: Foliar application of zinc sulfate

(ZnSO4) to improve the vegetative growth, yield and

quality of strawberry cv. ‘Chandler’.

48



) 48

4.1.2.1.2 Leaf area (cm2) 48

xiii



) 49


) 49



-1) 50


-1) 50


-1) 51

4.1.2.3 Fruit quality Parameters 52


) 52

4.1.2.3.2 TSS (ºBrix) 52


4.1.2.3.4 TSS: TA ratio 52

4.1.2.3.5 Vitamin C (mg 100 g-1

) 53

4.1.2.3.6 Total phenolic contents (GAE mg 100 g-1

) 53




protein) 57


protein) 57


protein) 58

4.1.2.5 Survival (%) 58

4.1.2 Discussion 60

4.1.2 Conclusion 63

4.2 Study-2 64

4.2.1

Experiment No. 1: Foliar application of salicylic acid (SA)


strawberry cv. ‘Chandler’.

64



) 64

4.2.1.1.2 Leaf area (cm2) 64


xiv


) 65


) 65



-1) 66


-1) 66


-1) 67

4.2.1.3 Fruit quality parameters 67


) 67

4.2.1.3.2 TSS (ºBrix) 68


4.2.1.3.4 TSS: TA ratio 68

4.2.1.3.5 Vitamin C (mg 100 g-1

) 68

4.2.1.3.6 Total phenolic contents (GAE mg 100 g-1

) 69




protein) 73


protein) 73


protein) 74

4.2.1.5 Survival (%) 74

4.2.1 Discussion 76

4.2.1 Conclusion 79

4.2.2

Experiment No. 2: Foliar application of gibberellic acid

(GA3) to improve the vegetative growth, yield and quality

of strawberry cv. ‘Chandler’

80



) 80

4.2.2.1.2 Leaf area (cm2) 80



) 81


) 81

xv



-1) 82


-1) 82


-1) 83

4.2.2.3 Fruit quality Parameters 83


) 83

4.2.2.3.2 TSS (ºBrix) 84


4.2.2.3.4 TSS: TA ratio 84

4.2.2.3.5 Vitamin C (mg 100 g-1

) 85


) 85




protein) 89


protein) 89


protein) 90

4.2.2.5 Survival (%) 90

4.2.2 Discussion 92

4.2.2 Conclusion 95

4.3 Study-3 (Confirmatory Trial) 96

4.3

Comparison of calcium chloride (CaCl2), zinc sulfate

(ZnSO4), salicylic acid (SA) and gibberellic acid (GA3) to

improve the vegetative growth, yield and quality of

strawberry cv. ‘Chandler’

96

4.3.1 Vegetative parameters 96


) 96

4.3.1.2 Leaf area (cm2) 96

4.3.1.3 Flower anthesis (days after foliar application) 97


) 97


) 97

xvi

4.3.2 Yield parameters 98


-1) 98


-1) 98


-1) 99



) 100

4.3.3.2 TSS (ºBrix) 100



4.3.3.5 Vitamin C (mg 100 g-1

) 101

4.3.3.6 Total phenolic contents (GAE mg 100 g-1

) 101


4.3.4 Activities of anti-oxidative enzymes 105


protein) 105


protein) 105


protein) 106

4.3.5 Survival (%) 106

4.3 Discussion 108

4.3 Conclusions 110

4.4 Study-4 (Postharvest study) 111

4.4

Postharvest application of calcium chloride (CaCl2) and

salicylic acid (SA) maintain the quality and improve

storage life of strawberry cv. ‘Chandler’

111

4.4.1 Physical Parameters 111

4.4.1.1 Fruit weight loss (%) 111

4.4.1.2 Fungal decay (%) 112


) 112


4.4.2.1 TSS (ºBrix) 116


xvii


4.4.2.4 Vitamin C (mg 100 g-1

) 119

4.4.2.5 Total phenolic contents (GAE mg 100 g-1

) 119


4.4.3 Activities of anti-oxidative enzymes 123


protein) 123


protein) 124


protein) 124

4.4 Discussion 128

4.4 Conclusion 132

Chapter-5 Summary 133

5.2 Future Recommendations 136

5.3 Recommendation for farmer 136

5.4 Study- 5 137

5.4.1 Six months internship (International Research Support

Initiative Program) at University of Florida, USA supported by

Higher Education Commission Islamabad Pakistan.

137

5.4.2 Introduction about GCREC 137

5.4.3 Strawberry production in Florida 137

5.4.4 FSHS Proceeding paper presented in (131st annual meeting of

Florida State Horticultural Society)

138

5.4.4 Optimization of Early-season Nitrogen Fertilization Program

for New Strawberry Cultivar „Florida Beauty‟

138

Literature Cited 146

xviii

LIST OF FIGURES

Figure

No. Description

Page

No.

2.1 Vegetative description of strawberry plant

6

2.2 World strawberry production in 2014 (FAO, 2014) 10

2.3 Increasing area of strawberry production from 2010-15 (GOP, 2015)

11

2.4 Increasing production of strawberry from 2010-15 (GOP, 2015)

11

4.1.1.1

Effect of foliar application of CaCl2 on firmness (kg. cm2) of strawberry

fruit. Vertical bars represent ± S.E of means.

38

4.1.1.2

Effect of foliar application of CaCl2 on TSS (ºBrix) of strawberry fruit.

Vertical bars represent ± S.E of means.

38

4.1.1.3

Effect of foliar application of CaCl2 on titratable acidity (%) of strawberry


39

4.1.1.4 Effect of foliar application of CaCl2 on TSS: TA ratio of strawberry fruit.

Vertical bars represent ± S.E of means. 39

4.1.1.5 Effect of foliar application of CaCl2 on vitamin C (mg 100 g

-1) contents of

strawberry fruit. Vertical bars represent ± S.E of means. 40

4.1.1.6 Effect of foliar application of CaCl2 on total phenolic contents (mg GAE 100

g-1

) of strawberry fruit. Vertical bars represent ± S.E of means. 40

4.1.1.7 Effect of foliar application of CaCl2 on total antioxidants (% DPPH) of

strawberry fruit. Vertical bars represent ± S.E of means. 41

4.1.1.8

Effect of foliar application of CaCl2 on survival (%) of strawberry plants.


43

4.1.2.1

Effect of foliar application of ZnSO4 on firmness (kg. cm2) of strawberry

fruit.

54

4.1.2.2

Effect of foliar application of ZnSO4 on TSS (ºBrix) of strawberry fruit.

54

xix

4.1.2.3 Effect of foliar application of ZnSO4 on titratable acidity (%) of strawberry

fruit. 55

4.1.2.4

Effect of foliar application of ZnSO4 on TSS: TA ratio of strawberry fruit.

55

4.1.2.5 Effect of foliar application of ZnSO4 on vitamin C (mg 100 g

-1) contents of

strawberry fruit. 56

4.1.2.6

Effect of foliar application of ZnSO4 on total phenolic contents (mg GAE

100 g-1

) of strawberry fruit.

56

4.1.2.7 Effect of foliar application of ZnSO4 on total antioxidants (% DPPH) of


4.1.2.8

Effect of foliar application of ZnSO4 on survival (%) of strawberry fruit.

59

4.2.1.1

Effect of foliar application of SA on firmness (kg. cm-2


70

4.2.1.2

Effect of foliar application of SA on TSS (ºBrix) of strawberry fruit.

70

4.2.1.3

Effect of foliar application of SA on titratable acidity (%) of strawberry fruit.

71

4.2.1.4

Effect of foliar application of SA on TSS: TA ratio of strawberry fruit.

71

4.2.1.5

Effect of foliar application of SA on vitamin C (mg 100 g-1

) contents of

strawberry fruit.

72

4.2.1.6 Effect of foliar application of SA on total phenolic contents (mg GAE 100

g-1

) of strawberry fruit. 72

4.2.1.7 Effect of foliar application of SA on total antioxidants (% DPPH) of


4.2.1.8 Effect of foliar application of SA on survival (%) of strawberry plants.

75

xx

4.2.2.1

Effect of foliar application of GA3 on firmness (kg. cm-2


86

4.2.2.2

Effect of foliar application of GA3 on TSS (ºBrix) contents of strawberry

fruit.

86

4.2.2.3

Effect of foliar application of GA3 on titratable acidity (%) of strawberry

fruit.

87

4.2.2.4 Effect of foliar application of GA3 on TSS: TA ratio of strawberry fruit.

87

4.2.2.5

Effect of foliar application of GA3 on vitamin C (mg 100 g-1

) contents of

strawberry fruit.

88

4.2.2.6 Effect of foliar application of GA3 on total phenolic contents (mg GAE 100

g-1


4.2.2.7 Effect of foliar application of GA3 on total antioxidants (% DPPH) of


4.2.2.8

Effect of foliar application of GA3 on survival (%) of strawberry plants.

91

4.3.1 Effect of foliar application of salts and growth regulators on on firmness (kg.

cm-2


4.3.2

Effect of foliar application of salts and growth regulators on TSS (ºBrix) of

strawberry fruit.

102

4.3.3 Effect of foliar application of salts and growth regulators on titratable acidity

(%) of strawberry fruit. 103

4.3.4

Effect of foliar application of salts and growth regulators on TSS: TA ratio of

strawberry fruit.

103

4.3.5 Effect of foliar application of salts and growth regulators on vitamin C (mg

100 g-1

) contents of strawberry fruit. 104

4.3.6 Effect of foliar application of salts and growth regulators on total phenolic

contents (GAE mg 100 g-1


xxi

4.3.7

Effect of foliar application of salts and growth regulators on total

antioxidants (% DPPH) of strawberry fruit.

105

4.3.8

Effect of foliar application of salts and growth regulators on survival (%) of

strawberry plants.

107

4.4.1 Effects of CaCl2 and SA different treatments on physical parameters of

strawberry during cold storage 113

4.4.2 Effects of CaCl2 and SA different treatments on TSS, Titratable acidity and

TSS: TA ratio of strawberry during cold storage 117

4.4.3 Effects of CaCl2 and SA different treatments on vitamin C, TPC and TA

activities of strawberry during cold storage 121

4.4.4 Effects of CaCl2 and SA different treatments on enzymatic activities of


xxii

LIST OF TABLES

Table

No. Description

Page

No.

2.1 Nutritional value of strawberry fruit (USDA, 2017) 8

4.1.1.1 Effect of foliar application of CaCl2 on vegetative growth of strawberry cv.

„Chandler‟ Mean ± S.E. 34

4.1.1.2 Effect of foliar application of CaCl2 on yield of strawberry cv. „Chandler‟ Mean ±

S.E. 35

4.1.1.3 Effect of foliar application of CaCl2 on enzymatic activities of strawberry cv.


4.1.2.1 Effect of foliar application of ZnSO4 on vegetative growth of strawberry cv.


4.1.2.2 Effect of foliar application of ZnSO4 on yield of strawberry cv. „Chandler‟ Mean ±

S.E. 51

4.1.2.3 Effect of foliar application of ZnSO4 on enzymatic activities of strawberry cv.


4.2.1.1 Effect of foliar application of SA on vegetative growth of strawberry cv.


4.2.1.2 Effect of foliar application of SA on yield of strawberry cv. „Chandler‟ Mean ±

S.E. 67

4.2.1.3 Effect of foliar application of SA on enzymatic activities of strawberry cv.


4.2.2.1 Effect of foliar application of GA3 on vegetative growth of strawberry cv.


4.2.2.2 Effect of foliar application of GA3 on yield of strawberry cv. „Chandler‟ Mean ±

S.E. 83

4.2.2.3 Effect of foliar application of GA3 on enzymatic activities of strawberry cv.


4.2.2.4 Effect of foliar application of salts and growth regulators on vegetative growth of

strawberry cv. „Chandler‟ Mean ± S.E. 98

xxiii

4.3.2 Effect of foliar application of salts and growth regulators on yield of strawberry cv.


4.3.3 Effect of foliar application of salts and growth regulators on enzymatic activities of

strawberry cv. „Chandler‟ Mean ± S.E. 106

4.4.1 Interaction effects of different treatments on fruit weight loss (%) of strawberry

during cold storage 114

4.4.2 Interaction effects of different treatments on fungal decay (%) of strawberry during

cold storage 114

4.4.3 Interaction effects of different treatments on firmness (kg. cm

-2) of strawberry


4.4.4 Interaction effects of different treatments on TSS (ºBrix) of strawberry during cold

storage 118

4.4.5 Interaction effects of different treatments on titratable acidity (%) of strawberry


4.4.6 Interaction effects of different treatments on TSS: TA ratio of strawberry during cold

storage 119

4.4.7 Interaction effects of different treatments on vitamin C (mg 100 g

-1) contents of


4.4.8 Interaction effects of different treatments on total phenolic contents (mg GAE 100

g-1

) of strawberry during cold storage 122

4.4.9 Interaction effects of different treatments on total antioxidants (% DPPH) activities

of strawberry during cold storage 123

4.4.10 Interaction effects of different treatments on catalase (U mg

−1 protein) activity of


4.4.11 Interaction effects of different treatments on superoxide dismutase (U mg

−1 protein)

activity of strawberry during cold storage 126

4.4.12 Interaction effects of different treatments on peroxidase (U mg

−1 protein) activity of


xxiv

ABSTRACT

Strawberry is highly nutritious and economically important small fruit crop. In Pakistan

strawberry yield and area is very less. Poor and irregular pre harvest practices cause decrease

in marketable yield and shelf life. This research was executed to observe the pre and

postharvest effects of salts and growth regulators on marketable yield and qualitative

characteristics of strawberry. Pre harvest foliar practices consisted of CaCl2 (0, 3, 5, 7 mM),

ZnSO4 (0, 50, 100, 150 mg L-1

), GA3 (0, 50, 100, 150 mg L-1

) and SA (0, 3, 6, 9 mM) those

were sprayed on strawberry plants at different growth stages (three to four leaves stage and

during fruit setting) to enhance the growth, marketable yield and quality attributes of

strawberry. Among the CaCl2 treatments 7 mM was found best for enhancing leaf growth

(15.25 plant-1

), leaf area (37.0 cm2), crown growth (6.50 plant

-1) and runners (7.0 plant

-1)

during growing season. Maximum marketable yield (348.50 g plant

-1), fruit firmness (0.96

kg. cm-2

), vitamin C contents (55.69 mg 100 g-1

) and TPC (186.50 GAE mg 100 g-1

) were

also observed with 7 mM CaCl2 treatment. Foliar spray of 100 mg L-1

ZnSO4 was found best

for enhancing leaf growth (18.25 plant-1

), leaf area (52.0 cm2), crowns (7.0 plant

-1) and

marketable yield (369.0 g plant

-1) with lower unmarketable fruit. Foliar application of 9 mM

SA was observed better for increasing the leaf production (19.25 plant-1

), leaf area (51.0

cm2), crowns (7.50 plant


-1). Minimum numbers of days (20.0) were

required for flower anthesis when plants were sprayed with 9 mM SA foliar spray. Maximum

marketable yield (414.25 g plant-1

), vitamin C contents (56.72 mg 100 g-1

), phenolic contents

(191.50 GAE mg 100 g-1

) and higher antioxidant activities (71.25% DPPH) were also noted

from strawberry fruits where plants were treated with 9 mM SA foliar spray. Gibberellic acid

(150 mg L-1

) showed the superiority for enhancing the vegetative growth while marketable

yield and fruit quality was not improved with same concentration of GA3. Maximum


), fruit TSS contents (7.85 ºBrix), vitamin C contents

(52.23 mg 100 g-1

) and higher antioxidant activities (64.75% DPPH) were observed from 100

mg L-1

GA3. Confirmatory trial was conducted for comparing the previous year best

treatments from each experiment. By comparing, it was concluded that 9 mM SA foliar spray

increased the marketable yield; improved quality attributes and extended the survival

mechanism of strawberry plants during growing season. In postharvest study, maximum

vitamin C contents (43.90 mg 100 g-1

), TPC (132.75 mg 100 g-1

), reduction in weight loss

(6.08%) of strawberries and maximum firmness (0.42 kg. cm-2

) was retained with higher

concentration of CaCl2 (6 mM). During storage minimum TSS (7.85 ºBrix), maximum acid

contents (0.62%) and total antioxidants (39.0% DPPH) were observed with SA (5 mM)

application. In postharvest study it was confirmed that dipping application of CaCl2 (6 mM)

and SA (5 mM) retained the quality attributes during 15 days of storage.

1

CHAPTER 1 INTRODUCTION

Strawberry (Fragaria × ananassa Duch.) is delicious, sweet flavored small fruit

belongs to family Rosaceae (Sharma, 2002). Amongst all small fruits strawberry is most

popular and highly nutritious fruit crop (Santos and Chandler, 2009). Strawberry species are

native to temperate regions and there are over 20 different cultivated species of strawberry

plant (Trinklein, 2012). It is hybrid of two species (F. virginiana and F. chiloensis) native to

America. The origin of F. virginiana is North America while F. chiloensis is wild specie

native to Chile (Sharma and Sharma, 2004). Among all the berry fruits strawberry has

important place due to its bright red color and high nutritive value (Sharma et al. 2013).

Strawberry species differ with each other on the basis of number of chromosomes. Most of

the species are diploid and tetraploid (Staudt, 2008).

Major planting regions for commercial strawberry production throughout the world

are North America, Europe, Russia, Chile, Southwest Asia and Australia (Wu et al., 2012).

The major production of strawberries comes from United States with 52673 hectares of land

and 1.4 million tonnes of strawberries (Brennan et al. 2014). In United States, California is

the top strawberry producing state and produce all year around followed by Florida and

Oregon. Florida is the major producer of winter strawberries (Boriss, 2006).

Nature has gifted Pakistan with different climatic conditions which are preferable for

production of strawberry. Strawberry plants require low chilling condition and can be planted

in various soil types except saline soil (Asad, 1997). Strawberry is newly emerging small

fruit crop in Pakistan; therefore yield is very less due to improper research techniques and

lack of knowledge regarding strawberry production among farmers (Mabood, 1994). In

Pakistan strawberry is cultivated on 179 hectares with 609 tons annual production (GOP,

2015).

Strawberries are cultivated in northern areas of Pakistan and major growing areas are

Swat, Abbottabad, Mansehra, Haripur, Mardan and Charsadda (Dad, 2011). Main varities of

strawberry are Missionery, Toro, Chandler, Howard, Honeyo, Tufts, Gorella and Corona

2

(Murtaza, 2014). In Pakistan, strawberry yield is limited and fruit is consumed as fresh and in

processed form (Mabood, 1994; Murtaza, 2014).

Strawberries are delicious, low calorie fruits having anthocyanins and phenolics

(Adda Bjarnadottir, 2012). Strawberries lower the level of cholesterol, blood pressure, reduce

inflammation and decrease oxidative stress. Important characteristic of strawberry fruit

include aroma, taste and flavor (Giampieri et al., 2012). Ripe strawberries contain 10% total

soluble solids contents and 90% water. Strawberry fruit is extremely abundant source of

ascorbic acid (59 mg/100g), dietary fiber and fructose that helps in controlling blood sugar

levels in the body by slowing down the process of digestion. These nutritive values have

great potential in controlling cardiovascular diseases and cancer related health problems

(Basu et al., 2010; Seeram, 2008). Strawberries are rich source of anthocyanin contents and

anti-carcinogenic materials such as ellagic acid (Da-Silva et al., 2007).

Strawberry plant has low chilling requirement and can be cultivated successfully in

tropical and sub-tropical areas. Maturity period of strawberry is very short and ranges

between 30-40 days (Amin, 1996). Rapid top-growth of strawberry (crowns, leaves, runners

and daughter plants) can occur within 2-3 months, which depends on nutrients, light,

temperature, salinity and water conditions (Li et al. 2010).

Strawberry has fast growth habit which demands macro and micro nutrients

synchronized with growth stages of the crop (Medeiros et al., 2015). Both, macro and micro

nutrients play major role in strawberry growth and development (Haifa, 2014).

Micronutrients increase the hormonal activity and uptake efficiency of macronutrients by

acting as catalyst (Phillips, 2004).

Foliar application enhances plant growth and nutrient concentration in certain above

ground plant organisms (Swietlik and Faust, 1984). Foliar application of micronutrients is a

supplemental application method to supply nutrients during critical growth stages when

plants cannot uptake adequate nutrients from soil due to complex soil chemistry, leaching of

nutrients, low soil temperature, immobile nutrients and low water availability which

solubilize the nutrients (Growing Produce, 2018). In general, through foliar spray essential

3

nutrients enter through the stomata of leaves more rapidly as compared to soil application

(Alshaal and Ramady, 2017).

Foliar application of salts and growth regulators enhance the canopy growth (plant

spreading, crowns, runners and leaf area), also improve the nutritional value of fruit and yield

(Qureshi et al., 2013). Plants obtain calcium from soil solution through root system via

xylem. Deficiency of calcium in root system disturbs the normal life cycle of plants and

causes malformation (White, 2000). The cationic form of Ca improves the inflexibility of

plant cells and promote the cell expansion process (Bakshi et al., 2013). Zinc plays important

role in normal plant metabolism and increase the activity of enzyme called tryptophan which

improve the level of Indole acetic acid (IAA) hormone in plant which further enhance the

growth (Nasiri et al., 2010). In sweet cherry zinc (Zn) plays major role in pollination, fruit

setting and increases total yield (Motesharezade et al., 2001).

Foliar application of growth regulators promote the natural plant hormones which

regulate the process of plant growth. Gibberellic acid (GA3) promotes the canopy growth

including leaf growth, leaf area and also initiates flowering (Sharma and Singh, 2009). Fruit

set percentage increases with application of GA3 but sometimes higher concentration

decrease the total marketable yield of strawberry (Paroussi et al., 2002). In plant defense

mechanism salicylic acid induces the resistance against pathogens (Metwally et al., 2013).

When a pathogen attacks on plant surface, SA induces systemic acquired resistance (SAR) in

undamaged plant cells by activating natural defense mechanism of plant (Tsuda et al., 2008).

Foliar treatment of SA enhances the endogenous level of SA; due to that pathogenesis related

genes activated where pathogen attack and create resistance against pathogen (Van Loon et

al., 2006). As general, foliar applied SA significantly increases the overall vegetative growth

including shoot length, leaf area and canopy growth (Khodary, 2004).

4

The nature of strawberry fruit is non-climacteric due to that it has short shelf life and

major storage issues are rapid metabolic activity, sensitive to fungal decay and grey mold

disease (Hernandez-Munoz et al., 2006). Quality of strawberry fruit deteriorates rapidly due

to water loss, bruising, mechanical damage and soft texture (Khreba et al., 2014). Treatment

of calcium chloride (CaCl2) delays the senescence process and act as physical barrier for the

reduction of water from fruit (Pila et al., 2010). Calcium chloride slows down the metabolic

process of kiwi fruit and decreased the TSS contents by delaying ethylene cycle (Fisk et al.,

2008). During storage CaCl2 maintained firmness, TSS contents of peaches and decreased the

sugar accumulation (Prussia et al., 2005). Dipping treatment of SA reduced the fruit

softening, ripening process, senescence, inhibits the rapid ethylene activity and also reduced

fungal problem of fruit (Zhang et al., 2010). Treatment of SA reduced the fungal problem

and enhanced the antioxidant activity of peaches (Khademi and Ershadi, 2013).

In literature, very little information available but not complete answers regarding the

efficiency of salts and growth regulators for increasing the marketable yield, improving fruit

quality and especially relating to antioxidants and enzymatic activities of strawberry. Pre and

postharvest application of fungicides is largely used practice in Pakistan which causes the

health issues but not focus on non-chemical techniques which reduce the health issues in

humans. By keeping in view previous studies, the present study was executed to pursue the

following goals:

To evaluate the role of foliar applied salts and growth regulators on vegetative

growth, marketable yield and quality attributes of strawberry.

Optimization of best concentrations of salts and growth regulators which enhance the

marketable yield and also improve the quality of strawberry.

Enhancement in storage life of strawberries and to retain quality by using CaCl2 and

SA.

5

CHAPTER 2 REVIEW OF LITERATURE

2.1 Specie introduction

Strawberry Fragaria × ananassa is hybrid specie belongs to family Rosaceae and

genus Fragaria, cultivated worldwide (Manganaris et al., 2014). The symbol „×‟ showed that

it is hybrid of two species Fragaria virginiana and Fragaria chiloensis and these species are

native to America (Hummer and Hancock, 2009). Historical references showed that

strawberry was mentioned as old as 234 BCE when a roman senator became popular due to

medicinal importance of strawberries. Presently cultivated Fragaria × ananassa introduced

by Duchesne in 1766 and called as „pineapple strawberry‟. The reason was its aroma

resembles with pineapple. It is popular specie for commercial strawberry cultivation

(Hummer and Hancock, 2009).

2.2 Vegetative structure of strawberry plant

Strawberry plant comprises of five important parts including trifoliate leaves, crowns,

roots, runners and new plants which called as daughter plants (Plants, 2010). Crown is major

part of plant which is short and thick stem that gives rise to roots and flowering truss of plant.

Four crowns per plant potentially improved the growth and play important role in strawberry

yield (Handley, 2003). Strawberry leaves are trifoliate and contain three leaflets which

arranged as spiral fashion and capture light for the process of photosynthesis and play major

role for the development of plant canopy and yield (Poling, 2012). Strawberry has

adventitious root system and roots grow positively geotropic (Neri and Savini, 2004).

Flowering inflorescence occurs at growing tip of crown. Strawberry flower has five sepals

that cover the flower at bud stage. The receptacle is cone shaped and has large number of

pistils that develops into fruit during maturity. Stamens and pistils are respective male and

female parts of strawberry flower (Poling, 2012). For commercial strawberry production

runner plants are used for best production (Andriolo et al., 2014). During summer runner

growth is stimulated due to warm temperature and majority of runners develops from mother

plant (Handley, 2003). Runner plants grow during summer and stored at 0ºC until planting

and used as bare root transplants. Plug transplants are also used for strawberry propagation

(Hochmuth et al., 2006).

https://en.wikipedia.org/wiki/Fragaria

6

Fig. 2.1 Vegetative description of strawberry plant

2.3 Fruit type

Strawberry is classified as an aggregate accessory fruit botanically it is not a berry.

Receptacle is covered with five petals, thirty stamens and also covered with 500 pistils each

an individual carpel. After pollination receptacle become enlarged, turn red and develop into

berry (Martin and Tepe, 2014). Fleshy part of strawberry is derived from the receptacle

which holds the ovaries. Achenes develop from carpel which further converted into fruit

(Himelrick et al., 2002).

2.4 Strawberry cultivars

Cultivars can be distinguished into three important types based on their growth habit

and photoperiod. Which are June-bearers, ever-bearers and day neutrals.

2.4.1 June bearer

These are short day plants and produce largest crop. In June bearer plants apices

differentiate into flowers during short days (< 12 hours of photoperiod). This type is used for

commercial production. These types of cultivars are planted in late summer or autumn and

https://en.wikipedia.org/wiki/Receptacle_(botany)

https://en.wikipedia.org/wiki/Ovary_(botany)

7

harvested from spring to autumn. Examples are cavendish, chandler, darselect, earliglow

elsanta and jewel (Hancock 1999; Haifa, 2014).

2.4.2 Ever bearer

These types of cultivars produce all year around, first harvest in spring and another in

the late summer or fall. In ever bearer plants apices differentiate into flowers during long

days (12 hours of photoperiod). Most common examples are Ogallala and Ozark Beauty

(Haifa, 2014).

2.4.3 Day neutral

Flowering occurs in day neutral strawberry plants regardless of photoperiod, three

months after planting. Flower buds initiate during the entire growth season. Maximum

production achieve from day neutral plants during the first year of plantation. Flowering

occurs in these plants whenever the temperature is 2°C to 29°C. Examples are

seascape, tribute, and tristar. Both produce good quality fruits (Sharma and Sharma, 2004;

Haifa, 2014).

2.5 Chandler strawberry

Chandler (Fragaria × ananassa) was released in 1983 from California (Sharma and

Sharma, 2004). The fruit is of good quality with bright colour, flavor, texture and quite

resistant to physical damage from rain. Chandler is June bearer short day variety. Full sun is

beneficial for Chandler strawberry just like all other strawberries. However, Chandler

strawberry is susceptible to root rot. In well-drained soil it can be planted properly. The

preferred soil pH for chandler is 6-7 and sufficient amount of water is needed in the absence

of rainfall (Strawberry, 2018).

2.5.1 Important aspects of chandler strawberry

Good for commercial purpose

Good for growing in subtropical

Good for larger production

Higher yield of strawberries

Excellent Flavor and color

8

2.6 Nutritional value of strawberry fruit

One serving (100 g) of strawberries contains 41 calories and rich source of vitamin C,

manganese, vitamins and dietary minerals (USDA, 2017).

Table 2.1 Nutritional value of strawberry fruit (USDA, 2017)

2.7 Fruit color

Red color of strawberry fruit is due to major anthocyanin content (Pelargonidin-3-

monoglucoside) and also due to (Cyanidin-3-glucoside) which is found in smaller amounts.

In green strawberries chlorophyll synthesis stopped and anthocyanin production begins at

white stage of growth. Anthocyanin‟s stored in vacuoles of epidermal and cortical cells

(Giampieri et al., 2012).

2.8 Strawberry fruit ripening enzymes

Pectinmethylesterase and polygalacturonase enzymatic activities increase during

strawberry fruit ripening and cause fruit softening. Cellulose activity also increases between

green and dark red stages of strawberry fruit (Nogota et al., 1993).

Composition of strawberry fruit

Total energy 130 k

Carbs 8.68 g

Sugars 5.89 g

Fat 0.3 g

water 91%

Protein 0.7 g

Ca 16 mg

Fe 0.41 mg

Mg 13 mg

Vit. A 1 μg

Vit. C 59 mg

Vit. D 0 μg

Vit. K 2.2 μg

Vit. E 0.29 mg

P 24 mg

K 153 mg

Mn 0.39 mg

Folate 24 μg

https://en.wikipedia.org/wiki/Vitamin_C

https://en.wikipedia.org/wiki/Manganese

https://en.wikipedia.org/wiki/Pelargonidin-3-glucoside

https://en.wikipedia.org/wiki/Pelargonidin-3-glucoside

https://en.wikipedia.org/wiki/Cyanidin-3-glucoside

9

2.9 Changes in activities of antioxidant enzymes during strawberry fruit ripening

Reactive oxygen species (ROS) produce during biochemical changes in strawberry

fruit such as O2-, H2O2, and OH

- which cause oxidative stress (Jimenez et al. 2003). These

(ROS) species cause early fruit ripening and leading towards senescence process. The

response of various activities of antioxidant enzymes (POD, CAT and SOD) appear during

different growth stages. Reactive oxygen species produce due to decline in these activities

(Anand et al., 2009). Maximum catalase activity found during strawberry fruit ripening. It

increases in white and red color fruit. Superoxide dismutase activity increase during

maturation stages up to highest level in white fruits. Peroxidase activity increase in white

color fruits and rapidly decrease in red color strawberry fruits (Lopez et al., 2010).

2.10 Phenolic contents of strawberry fruit

Strawberry fruit contain important polyphenols including chlorogenic acid and D-

catechin also called as tannins. Total soluble phenols decrease during ripening up to 0.5-0.6%

in green strawberries and 0.2-0.3% in red berries. Peroxidase and polyphenol oxidase

activities also decrease about 80% during fruit ripening stage (Spayd and Morris, 1981).

2.11 World strawberry production

For strawberry production United States accounted as major producer all over the

world. Major strawberry producing state in United States is California with 90% production,

followed by Florida with 10% of strawberry production (Brennan et al., 2014; Boriss, 2006).

US produce 1.4 billion kg of strawberries in which 1.2 billion kg comes from California (Wu

et al. 2012). Major importer of US strawberries is Canada which received 118 million kg of

strawberries (ERS, 2013). Mexico, Spain, Egypt, Poland and Turkey are other world leading

strawberry producers (Wu et al. 2012).

10

Fig. 2.2 World strawberry production in 2014 (FAO, 2014)

In 2014 United States was largest producer of strawberries in comparison with other

strawberry producing countries. US recorded as export of fresh strawberries 274 million

pounds in 2014, while Canada showed 83 percent of the total strawberry exports (FAO,

2014). China ranked 1st for strawberry production in 2016 with production of 3,801,865

(tonns) and United States ranked 2nd

with 1,420,570 (tonns) strawberry production. So, the

production trend changed in 2016.

Source: (FAO, 2016-17; Fact fish Statistics, 2018)

2.12 Strawberry production in Pakistan

In Pakistan, the production of strawberry is very less due to poor pre and postharvest

management practices. It is used as in fresh form or processed forms to make james, jellies

and squashes. Main varieties which grown in Pakistan are Chandler, Black more, Cruz,

Missionary and Tufts. Major producing areas are Swat, Charsadda, Peshawar, Abbotabad,

Sialkot, Karachi, Chakwal and Multan. Retail price of strawberry in the range of 120-140

PKR/kg during peak season. Harvesting started in the month of January and continued till

end of May (Murtaza, 2014).

11

Fig. 2.3 Increasing area of strawberry production from 2010-15 (GOP, 2015)

Fig. 2.4 Increasing production of strawberry from 2010-15 (GOP, 2015)

In Pakistan strawberry area and production is very less due to improper research

techniques and lack of knowledge regarding strawberry production among growers (Murtaza,

2014). From 2010-15 some increasing trend regarding production was observed but still need

to use such technologies which increase the yield of strawberry.

12

2.13 Pre harvest problems of strawberry

Major pre-harvest problems are poor flowering, poor fruit setting, inadequate nutrient

application, lower yield per plant, maturity factors, poor quality, insect pests, diseases, weeds

and climatic changes (Di-Vittori et al., 2018).

2.14 Pre harvest management practices to improve yield and quality

2.14.1 Effect of mulching material

Mulching material has strong impact on early harvesting, quality and yield of

strawberry because it provides better soil environment, moisture conservation, changed soil

temperature, increased nutrient availability, suppressed weed growth, protection from frost

injury and reduce berry diseases (Sharma, 2002). Black polyethylene mulch reduced the

weed growth, improved plant canopy, number of fruits per plant and also improved vitamin

C contents of strawberry fruit (Bakshi et al., 2014).

2.14.2 Effect of plant spacing

Plant spacing played important role to attain higher yield per unit area (Petersen,

1998). In strawberry marketable yield showed higher response with narrow spacing as

compared with wider spacing showed less response (Legard et al., 2000). Early season and

total marketable yields of strawberry increased with 35 cm within-row plant spacing as

compared with 17.5 cm row spacing (Paranjpe et al., 2008).

2.14.3 Protected cultivation

Plastic greenhouses used for forcing and for increasing fruit retention by protecting

against adverse climatic conditions (Gast et al., 1991). Microclimate of protected strawberry

resulted in better plant growth, dark green foliage, earlier flowering and reduce frost damage

of crop. Different row covers including polypropylene, polyster and polyamide showed better

responses, induced early flowering and fruit was ready to harvest 10 days earlier than control

(Pollard et al., 1988).

13

2.14.4 Effectiveness of calcium chloride (CaCl2) for improving growth, yield and

qualitative characteristics of other strawberry cultivars

Calcium is important plant nutrient related to fruit quality and firmness. It involved in

improving firmness because it is major component of pectin which improved the inflexibility

of plant cells (Sams, 1999; Maas, 1998). Foliar nutrition of calcium considered as cultural

practice for improving fruit calcium contents and it also reduced grey mould disease

(Bramlage et al., 1985; Elad and Volpin, 1993). Foliar applied CaCl2 at rate of 20 kg per ha

before harvest delayed tissue softening, fruit ripening process and reduced grey mould (B.

cinerea) disease in strawberries (Cheour et al., 1990).

Kazemi (2013a) evaluated the effectiveness of foliar spray of calcium chloride (2.5

and 5 mM) and salicylic acid (0.25, 0.5 and 0.75 mM) on strawberry yield and quality.

Results revealed that SA and CaCl2 either combined or separate foliar spray enhanced the

runner growth (6.12), leaf area (31.12 cm2), rooting density and flower production. Fruit

quality and yield was also improved by combine application of CaCl2 and SA.

Bakshi et al. (2013) examined the effects of foliar applied CaCl2 (0.2, 0.4 and 0.6 %)

and ZnSO4 (0.2, 0.4 and 0.6 %) on strawberry cultivar chandler. Leaf growth (19.6), leaf area

(64.7 cm2), flowering density (27.6) and marketable fruits per plant (21.0) increased with

CaCl2 and micronutrients foliar application. Fruit (size, length and diameter), TSS (8.34 ºB)

and ascorbic acid (62.88 mg/100g) contents of strawberry increased with increasing

concentration of calcium and other micro nutrients.

Kazemi (2014a) evaluated the effects of foliar applied CaCl2 on strawberry cultivar

„Pajaro‟. Calcium enhanced the weight of primary fruit but reduced the length of flowering

period. Calcium spray increased the TSS contents (9.8 ºB), ascorbic acid contents (65.7

mg/100g) and lower acidity than control. For the betterment of fruit quality Ca acted as

secondary messenger and played significant role in inflexibility of cell wall functions by

delaying the process of fruit softening and senescence activity (Sams, 1999). Foliar

application of calcium containing products improved the firmness of kiwifruit cultivar

„Tsechelidis‟ as compared with control treatment. Higher ascorbic acid contents and total

14

antioxidant activities were recorded and leaves Ca concentration was also increased with

foliar application (Koutinas et al., 2010).

2.14.5 Effectiveness of zinc sulfate (ZnSO4) for improving growth, yield and qualitative

characteristics of other strawberry cultivars

Zinc is major component of several enzymes, proteins and important metal element

for normal metabolic process of plants. It increased the activity of enzyme called tryptophan

which, further enhanced the production of growth hormone (IAA) and acted as growth

promoter (Nasiri et al., 2010). Zinc is major trace element for plant growth which is involved

in enzymatic reactions and regulate protein and carbohydrate metabolism (Lolaei et al.,

2012). Through foliar application nutrients absorbes very quickly and transported to different

plant parts to perform different functions and helpful for the correction of nutrient

deficiencies. Zinc played significant role for enhancing the quality attributes of fruits and

reduced the different physiological disorders in fruit trees (Meena et al., 2014).

Abdollahi et al. (2010) conducted experiment on „Selva‟ strawberry by using PBZ

and H3BO3 different concentrations along with ZnSO4 (0, 100, 200 mg L-1

) to maximize the

canopy growth, yield and quality attributes. Hydroponic system was used for the growth of

runners in green house. Results revealed that reduction in vegetative growth was observed

with PP333 while zinc application showed positive effects regarding fruit quality. Yield was

also increased with foliar spray of ZnSO4. Number of leaves (16.2) increased with zinc

application but fresh shoot/root ratio decreased.

Kazemi (2015) studied the effects of foliar applied CaCl2 with two levels (5 and 10

mM) and ZnSO4 also with three levels (50, 100, 150 mg L-1

) on canopy growth, yield and

qualitative properties of strawberry cultivar „Pajaro‟. Zinc sulfate @ 150 mg L-1

and CaCl2 @

10 mM increased the runner growth (5.1), leaf area (46.3 cm2), size of fruits, total soluble

solids (9.95 °B), acid contents and vitamin C contents (67.41 mg/100 g) of strawberry. High

dose of zinc and calcium maximize the yield and nutritional value.

Lolaei et al. (2012) observed the effects of ZnSO4 (0, 50, 100, 150 mg L-1

) on

vegetative parameters, yield and some quality attributes of strawberry cultivar „Camarosa‟. It

was reported that ZnSO4 @ 150 mg L-1

increased the TSS contents (8.31 ºB) but leaf area

15

(42.20 cm2) maximized with 100 mg L

-1 of ZnSO4. High dose of ZnSO4 @ 150 mg L

-1

showed the positive effects regarding fruit set (%), yield and flowering density. Strawberry

yield and quality increased with higher application of ZnSO4.

2.14.6 Effectiveness of salicylic acid (SA) for improving growth, yield and qualitative

characteristics of other strawberry cultivars

Salicylic acid found in plants as important phenolic compound which acted as

signaling molecule against oxidative stresses and provide tolerance. It performed various

functions including plant growth, ion uptake and transport, reduce transpiration rate and leaf

abscission (Ashraf et al., 2010). Foliar applied SA increased the endogenous level of SA and

also activated the pathogenesis related genes at the site of pathogen attack by creating

pathogenic resistance in plants (Van Loon et al., 2006).

Kazemi (2013a) noticed the effects of foliar spray of SA with three doses (0.25, 0.5

and 0.75 mM) and calcium chloride (CaCl2) with two doses (2.5 and 5 mM) on canopy

growth and yield components of strawberry plants. Foliar applied SA (0.25 mM) and CaCl2

(2.5 mM) alone or combined application improved the vegetative and reproductive growth.

Maximum no. of runners (5.98), leaf area (28 cm2), flower production and fruit weight

enhanced with combine spray of SA and CaCl2.

Combined (salt and growth regulator) foliar spray improved the yield and qualitative

characteristics of strawberry. It is because of SA induced the resistance in plants against

abiotic stresses and CaCl2 acted as a messenger for these environmental stimuli that activated

defense mechanism (Qureshi et al., 2013).

Lolaei et al. (2012) examined pre and postharvest effects of SA on strawberry cultivar

„Camarosa‟ by using 4 different levels of SA (0, 3, 5 and 7 mM) on 60 plants. Results

revealed that SA @ 7 mM delayed the ripening of strawberry fruit and showed higher

titratable acidity TA (0.95%) and vitamin C contents (75 mg/100 g) as compared with

control. Fruit ripening decreased due to slow down of metabolic activities and carbohydrate

depletion rate by increasing SA concentration.

16

It is also reported that 5-sulfosalicylic acid at (2.5 mM) increased the quality

attributes including TPC, flavonoids, TSS, TA and vitamin C contents of strawberry due to

delay in senescence activity (Kazemi, 2013b).

2.14.7 Effectiveness of gibberellic acid (GA3) for improving growth, yield and

qualitative characteristics of other strawberry cultivars

External application of PGR on plants acted as growth promoter and played important

role in development and regulation of different processes. Gibberellins are known to promote

stem growth by increasing the cell division and enlargement (Canli and Orhan, 2009).

Gibberellic acid (GA3) is natural plant hormone which promoted the growth and encouraged

the desirable effects including plant height and flower production (Srivastava and Srivastava,

2007). Fruit production and growth increased in clementine oranges by application of GA3

(Van Rensburg et al., 1996). Gibberellic acid showed the significant responses in many

horticultural crops to improve the flowering and fruit setting (Taylor and Knight, 1986).

Jamal Uddin et al. (2012) stated that foliar treatment of 75 ppm of GA3 enhanced the

canopy growth and marketable yield of strawberry because it increased the hormonal activity

due to that rapid cell division and elongation process in different parts of plants. It also

enhanced the sweetness of strawberries.

In literature it is reported that foliar treatment of 100 mg L-1

of GA3 maximize the

runners (6.8) and leaf area (33.5 cm2) of strawberry cultivar „Camarosa‟ because it acted as

bio regulator and greatly influenced on growth and development. Strawberry TSS contents

not affected by GA3 concentration and titratable acidity decreased (Kazemi, 2014b).

Asadi et al. (2013) examined the effects of GA3 doses (0, 25 and 50 mg L-1

) on

strawberry cultivar „Gaviota‟. Runner growth (4.5) increased with GA3 (50 mg L-1

)

application although no. of leaves and crown growth was not affected by same GA3

concentration.

Growth regulators enhanced the flowering, fruit production, while they have no

significant impact on other biochemical attributes including fruit pH, TA and TSS contents.

17

They enhanced the total anthocyanin concentration and total phenolic contents of

strawberries (Roussos et al., 2009).

2.15 Postharvest problems of strawberry

Strawberries are extremely perishable crop and require careful handling and

appropriate management practices for increasing the shelf life. These required rapid removal

of field heat to retained fruit quality (Picha, 2006). Low temperature during storage (0 to 4ºC)

play important role for retaining its quality. Improper harvesting stage, high temperature,

short shelf life, fungal decay, weight loss, loss of brightness and color darkening are major

postharvest problems of strawberry (Khreba et al., 2014).

2.16 Effect of storage application of calcium chloride (CaCl2) on quality and shelf life of

fruits

Postharvest application of calcium means applying calcium directly on fruit surface,

which is best method for increasing internal calcium content of fruit. Different methods used

including dipping, vacuum infiltration or pressure infiltration which increased the fruit

calcium content and firmness in storage (Conway et al., 1994). Calcium played significant

role for retaining fruit quality and firmness. It involved in maintaining fruit firmness because

major component of pectin which improved the inflexibility of cells, membrane rigidity and

maintained cell structure (Sams, 1999; Maas, 1998). During storage Ca reduced the growth

of pathogens, conidia germination by disturbing the process of germ tube elongation and also

acted as barrier for nutrients availability to pathogens on the fruit surface (Moline, 1994).

Lysiak et al. (2008) evaluated shelf life of peaches by dipping in 2% CaCl2 solution

for 30 minutes and then kept at 4°C for next 2 weeks in boxes, in which some boxes were

uncovered or covered with polyethylene. Calcium chloride application proved better for

maintaining firmness, soluble solids contents and reduced the weight loss of peaches as

compared with untreated fruits.

Pre storage application of CaCl2 (1, 1.5, and 2.0%) showed positive responses against

anthracnose disease of papaya. Six pre harvest sprays were applied on papaya to observe the

effects of CaCl2 on internal calcium content of fruit, spore germination, mycelial growth,

disease incidence and shelf life. Internal Ca content of papaya fruit improved with 2.0%

18

spray of calcium, anthracnose disease was reduced and shelf life was extended up to 5 weeks

(Madani et al., 2014).

Dipping treatment of CaCl2 3% delay the softening of kiwi fruit and slow down the

process of degradation of ascorbic acid contents by retarding disintegration of cell walls and

reduced the enzymatic activity of L ascorbic acid (Franco et al., 2008).

Bagheri et al. (2015) evaluated storage life and quality of persimmon fruit kept at 0°C

for next 4 months dipped in solutions containing (0.5, 1, and 2%) CaCl2. Fruit weight loss

and chilling injury was decreased with CaCl2 treatments compared with control. Total

phenolic contents were increased with 2% CaCl2 treatment. Lower antioxidant activity was

recorded in untreated fruits as compared with CaCl2 treated fruits. Maximum catalase activity

was noted in 2% CaCl2 treated fruits. Tissue browning occurred in control treatment due to

increased CAT activity.

2.17 Effect of storage application of salicylic acid (SA) on quality and shelf life of fruits

Storage applied SA provides resistance against oxidative stresses (Asghari and

Aghdam, 2010). Salicylic acid has capability for delaying ripening process, maintaining

nutritional value and reducing storage diseases of fruits (Zhang et al., 2010). Fruit softening

occurred due to rapid metabolic activity of polygalactosidases and pectin methylesterases

which are cell wall degrading enzymes. Salicylic acid delayed the cell wall enzymatic

activity by decreasing metabolic process (Srivastava and Dwivedi, 2000).

Salari et al. (2013) studied postharvest effects of SA (1, 2, 3 and 4 mM) on 3

strawberry cultivars (Paros, Camarosa and Selva) kept at 3°C for 12 days. Results showed

that the response of 4 mM SA was highest for retaining vitamin C contents (86.48 mg/100 g).

Highest rotten fruit (%) was noted in untreated fruits as compared with SA treated.

Strawberry cultivar „Paros‟ showed highest contents of vitamin C and TSS: TA ratio with 2

mM SA. Interaction between cultivar and SA treatments was not significant.

19

Salicylic acid is important phenylpropanoid compound which enhanced the fruit

resistance against pathogens and other stress causing factors. It activated ascorbate

peroxidase activity due to that activity total antioxidants increased which prevent destruction

of ascorbic acid contents during storage (Stolfa et al., 2014).

Postharvest treatment of SA is beneficial to inhibit tissue softening by delaying

hydrolases activities which retained cell membrane consistency. Dipping of tomatoes in SA

before storage at low temperature induced heat shock proteins (HSPs) biosynthesis which

create resistance against low temperature (Baninaiem et al., 2016).

Khademi and Ershadi (2013) studied the effects of SA on peach shelf life. According

to their results 2 mM SA was more effective for maintaining firmness, TPC and TA activity

of fruits as compared with 4 mM SA because higher concentration damaged the fruits and

not found best for retaining fruit quality.

20

CHAPTER 3 MATERIALS AND METHODS

3.1 Experimental site detail

3.1.1 Site Selection

Field experiments were conducted at Ayub Agricultural Research Institute (AARI),

Jhang Road Faisalabad Pakistan in the Fruit Research area during November, 2015 to April,

2016 and confirmatory trial was conducted from November, 2016 to April, 2017. This site

was selected because it was fully equipped with good characteristics of soil, water and

drainage system and availability of labors.

3.1.2 Soil preparation

Two plots with same size for field experiments were selected for runner

transplantation. Soil was prepared in the month of September by adding FYM 120-150 kg

and DAP 2.5-3 kg for each plot which length was 66 feet and width was 20 feet. Silt was

mixed in soil for soil fertility, better root penetration and crown development. Soil was

prepared one month before runner transplantation.

3.1.3 Preparation of beds

Raised beds were prepared after one month of soil preparation and their width was

1.5 feet. Black polyethylene sheet as mulching material was used to cover the beds and for

controlling weeds. Holes were made in sheet for runner transplantation and plant to plant

distance was 9-10 inches. Runners were transplanted in double rows with 20 plants on each

bed.

3.1.4 Selection of runner plants

Healthy and disease free bare root transplants of strawberry cv. „Chandler‟ were

collected from Agricultural Research Institute North Mingora, Swat, Khyber Pakhtoonkhwa.

3.1.5 Planting of runners

Initially treat the runner roots with Topsin-M @ 2g/L fungicide to reduce the problem

of anthracnose and other soil-borne diseases before planting. Strawberry has shallow root

21

system so; runners were planted 2-3 inches deep to avoid crown damage. At the start, surface

irrigation was done weekly and then according to crop requirement.

3.1.6 Foliar application

Foliar application of salts and growth regulators were applied after 2 weeks of runner

transplantation when old leaves were dried and new sprouting was occur. When plants were

at 3-4 leaves stage 1st foliar application was applied and 2

nd application was done at fruit

setting stage.

3.1.7 Plant protection with polythene tunnel

From mid-December till end of January polythene tunnel was used for protecting

against frost damage, for better plant growth and fresh green foliage.

3.2 Study 1 (Salts)

3.2.1 Experiment No. 1:

Foliar application of calcium chloride (CaCl2) to improve the vegetative growth, yield

and quality of Strawberry cv. ‘Chandler’

Different doses of calcium chloride were applied on plants to optimize the best dose

which improve the vegetative growth, yield and quality of fruit. Following concentrations

were applied.

Treatments:

T1 = Control

T2 = 3 mM CaCl2

T3 = 5 mM CaCl2

T4 = 7 mM CaCl2

This experiment was consisted of 4 treatments with 4 replications. There were 40

plants in each treatment and each replication was consisted of 10 plants. Total 160 plants

used for this experiment. Calcium chloride easily dissolved in water and recommended

concentration was mixed separately in one liter of water for 10 plants. For foliar spray 100

22

ml water was used for single strawberry plant for better absorption and penetration. For foliar

application Tween-20 (0.01%) was added as wetting agent. Foliar application was applied

during morning time (6-7 am) with handheld sprinkler in a very gentle way. Vegetative, yield

and quality parameters were measured during whole growing season. At the end of

strawberry season plants survival (%) was also recorded.


Foliar application of zinc sulfate (ZnSO4) to improve the vegetative growth, yield and

quality of Strawberry cv. ‘Chandler’

Treatments:

T1 = Control

T2 = 50 mg L-1

ZnSO4

T3 = 100 mg L-1

ZnSO4

T4= 150 mg L-1

ZnSO4

Same materials and methods were followed as previous described. Vegetative, yield

and fruit quality parameters were also recorded in this experiment.

3.3 Study 2 (Growth regulators)


Foliar application of salicylic acid (SA) to improve the vegetative growth, yield and


Treatments:

T1 = Control

T2 = 3 mM SA

T3 = 6 mM SA

T4 = 9 mM SA

23

This experiment was performed to check the effects of different concentrations of SA

on vegetative, yield and fruit quality parameters of strawberry. Each treatment was consisted

of 4 replications and in each replication there were 10 plants. Total 160 plants used for this

experiment. Salicylic acid not easily dissolved in water so firstly recommended concentration

was dissolved in 10 ml ethanol and then further dissolved in one liter of water for 10 plants.

For foliar spray 100 ml water was used for single strawberry plant for better absorption and

penetration. For foliar application Tween-20 (0.01%) was also added as wetting agent. Foliar

application was applied during morning time (6-7 am) with handheld sprinkler in a very

gentle way. Vegetative, yield, fruit quality parameters and survival (%) was recorded.


Foliar application of gibberellic acid (GA3) to improve the vegetative growth, yield and


Treatments:

T1 = Control

T2 = 50 mg L-1

GA3

T3 = 100 mg L-1

GA3

T4 = 150 mg L-1

GA3

Gibberellic acid also not dissolved easily in water so, recommended concentration

was mixed in 10 ml ethanol and then further added in the water to make 1 liter solution for 1

experimental unit (10 plants). All vegetative, yield and quality relating parameters were also

measured.

24

3.4 Study 3 (Confirmatory trial)

3.4.1 Comparison of calcium chloride (CaCl2), zinc sulfate (ZnSO4), salicylic acid (SA)

and gibberellic acid (GA3) to improve the vegetative growth, yield and quality of

strawberry cv. ‘Chandler’

Treatments:

T1 = Control

T2 = 7 mM CaCl2

T3 = 100 mg L-1

ZnSO4

T4 = 9 mM SA

T5 = 100 mg L-1

GA3

In this trial previous year best treatments from each experiment were compared with

each other to find out the best treatment which increased the vegetative growth, marketable

yield and also improve the quality of strawberries. Same method of foliar spray was followed

as in previous experiments. Each treatment was consisted of 4 replications and in each

replication there were 10 plants. Total 200 plants used for this experiment. All vegetative,

yield and quality relating parameters were measured as described in previous experiments.

3.5 Parameters

3.5.1 Vegetative parameters


)

Leaf growth was observed during and after end of strawberry season. Three healthy

plants from each replication were pull out from beds and then each plant was cut into two

halves in such way that trifoliate leaves with petioles separated and below portion (crown)

separated. After cutting of each plant numbers of leaves were counted.

25

3.5.1.2 Leaf area (cm2)

Healthy, disease free and large size leaves were collected from each replication. It

was calculated with leaf area meter (LI-COR, 3100C).

3.5.1.3 Flower anthesis (days after foliar application)

Runners were transplanted during 2, November 2015 and after 2 weeks when new

sprouting was occurred then foliar application was applied. Numbers of days required for 1st

flower anthesis (opening) were counted after foliar application.


)

Same plants which were used for numbers of leaves their below portion (crown)

separated and then numbers of crowns per plant were counted.


)

Total numbers of runners per plant were estimated during whole strawberry season.

Runner growth was discouraged during whole season for better plant growth.

3.5.2 Yield parameters

Strawberry harvesting was started during end of January and continued till mid-April.

Yield was accounted as marketable, unmarketable and small size.


-1)

Strawberries which were 75-80% fully mature, bright red color, larger size and

disease free counted as marketable yield during whole season.


-1)

Strawberries which were affected due to Grey mould disease (Botrytis cinerea),

Anthracnose fungal disease (Colletotrichum), Powdery mildew (Podosphaera aphanis),

Thrips attack, Phyllody (abnormal development of floral parts into leafy structures caused by

phytoplasma or virus infections) and due to environmental factors (chilling injury and frost

injury) counted as unmarketable yield during season.

26


-1)

Strawberries which were (< 10 g) and bullet shaped counted as small size yield during

whole season.

3.5.3 Fruit quality Parameters


)

Fruit firmness was observed with digital penetrometer (Humboldt H-1240D) by using

3mm diameter probe which measure the penetration force.

3.5.3.2 TSS (ºBrix)

Total soluble solids measured with digital TSS/Acid meter (Atago, Japan). TSS was

measured by adding one drop of fruit extract on scanner of the meter and it showed values.

3.5.3.3 Titratable acidity (%)

Acidity was measured with digital TSS/Acid meter (Atago, Japan) by diluting 1 ml

fruit extract in 50 ml distilled water after dilution put one drop on the scanner which shows

the acidity values.

3.5.3.4 TSS: TA ratio

When both TSS and acidity values were expressed on the meter then it shows TSS:

TA ratio by dividing the value of TSS with the value of the TA.

3.5.3.5 Vitamin C (mg 100 g-1

)

For the measurement of vitamin C contents in strawberry extract, first of all

strawberry extract was filtered then (10 ml) aliquot was taken in 100 ml flask by making

volume up to mark with the addition of (0.4%) oxalic acid. For titration purpose 5 ml aliquot

was titrated with (2, 6-dichlorophenol indophenol) when pink color appeared it was

indication of end point. Calculations were done with the procedure mentioned by Ruck

(1969).

27

3.5.3.6 Total phenolic contents (TPC) and Total antioxidants (TA)

For the estimation of TPC and TA in strawberry extract supernatant was prepared.

Enzymatic activities rapidly changed due to fluctuation in temperature, so for estimation

purpose liquid nitrogen was used immediately and samples stored at (-80°C). For

homogenization purpose mortar and pestle was used. Strawberry extract (1 ml), methanol,

acetone and HCl were taken in ratio of (10: 8: 2) then homogenization was done by adding

(200 mg) sand. After it prepared sample was taken in 2 eppendorf tubes and vortexed for

only 2 minutes. The process of centrifugation was done and supernatant was added in new

eppendorf tubes for TPC and TA analysis.


)

For the determination of TPC of strawberry extract FC method was used. It is called

as Folin–Ciocalteu method. Extracted sample (100 μL) and FC reagent (200 μL) was taken in

centrifuge tube and vortexed only for one minute. After it sodium carbonate (800 μL) was

added in it and it was vortexed again only for one minute. Incubation was done for 2 hours at

ambient temperature and then read the absorbance at 765 nm against the Gallic acid (R2 =

0.7884) standard curve. Calculations were performed according to procedure detailed by

Ainsworth and Gillespie (2007).

3.5.3.8 Total antioxidants (% DPPH)

For TA determinations take supernatant (50 μL) and methanolic solution 0.004 % (5

ml) in test tube. Samples were tested with the interval of 30 minutes. Changes in absorbance

were measured at 517 nm. Calculations were done by using method detailed by Brand-

William et al., 1995.

3.5.4 Antioxidant enzymatic activities (CAT, SOD and POD) determination

For antioxidant enzymatic activities potassium phosphate buffer (2 ml) and

strawberry extract (1 ml) were homogenized. After it centrifugation was done and

supernatant collected for further estimation of enzymatic activities.

28


protein)

For this activity hydrogen peroxide was used to initiate the reaction mixture.

Enzymatic extract (100 μL) was mixed in H2O2 (100 μL) and then activity was observed 240

nm. Calculations were performed by adopting procedure described by (Liu et al., 2009;

Jimenez et al., 2003).


protein)

For POD activity reaction mixture was prepared by using potassium phosphate buffer

(0.1 M), hydrogen peroxide (20 mM) and guaiacol (20 mM) with different ratios (8: 1: 1).

Enzymatic extract (100 μL) was also added in reaction mixture (100 μL) and then absorbance

was noted at 470 nm. Calculations were performed by using procedure detailed by Liu et al.,

2009.


protein)

For estimation of this activity nitro blue tetrazolium was used for 50% inhibition of

photochemical reduction. Reaction was initiated by adding phosphate buffer (600 μL),

methionine (300 μL), riboflavin (150 μL), distilled water (1000 μL) and enzyme extract (100

μL). Illumination of this mixture was done with fluorescent lamp. The range of absorbance

was 560 nm. Calculations were performed by using protocol detailed by (Stanger and

Popovic, 2009; Jimenez et al., 2003).

3.5.5 Survival (%)

Number of diseased, damaged and dead plants was removed from field during entire

season. At the end of season remaining plants were counted for plants survival percentage.

Survival % = Number of disease, damage and dead plants x 100

Total number of plants

29

3.6 Study 4 (Postharvest)

3.6.1 Postharvest application of calcium chloride (CaCl2) and salicylic acid (SA)

maintain the quality and improve storage life of Strawberry cv. ‘Chandler’.

Treatments:

T1 = Control

T2 = 2 mM CaCl2

T3 = 4 mM CaCl2

T4 = 6 mM CaCl2

T5 = 3 mM SA

T6 = 5 mM SA

T7 = 7 mM SA

For postharvest experiment best quality strawberries were collected from strawberry

farm (Sharaqpur Sharif Lahore, Pakistan). Same size and same stage of mature fruits were

harvested. After harvesting strawberries were pre cooled at 0°C to remove field heat. Each

treatment (240 strawberries) was consisted of 4 replications and in each replication there

were 60 strawberries. For this experiment 1680 marketable strawberries were used. Calcium

chloride easily dissolved in water while salicylic acid firstly dissolves in 10 ml ethanol and

then added in water to make 2 L solution for each replication. Strawberries were in dipped in

different concentration of solutions for 10 minutes. After dipping strawberries were dried at

room condition and then packed in plastic punnets and stored at 4°C, 80-85% RH. Quality

analysis was performed during 0, 3, 6, 9, 12 and 15 days of interval. Fruit physical

parameters including fruit weight loss (%) and fungal decay (%) were also recorded only for

postharvest experiment.

30

3.6.1 Fruit weight loss (%)

For weight loss estimation from each replication separate strawberries were packed in

plastic punnets and weighed. Weight was balanced in each packing for the observation of

weight loss in different intervals.

Weight loss (%) = Fresh weight of strawberries - Final weight of strawberries × 100

Fresh weight of strawberries

3.6.2 Fungal decay (%)

Decay (%) was recorded during 3, 6, 9, 12 and 15 days of storage interval by using

following formula.

Fungal decay (%) = Number of diseased and decayed strawberries in each treatment × 100

Total number of strawberries per treatment

3.7 Statistical Analysis

The data regarding field experiments and postharvest study was statistically analyzed

by using MINITAB®18.0 and SPSS 21 Software (Steel et al., 1997).

3.8 Study 5

Six months internship program at University of Florida, GCREC, USA.

FSHS proceeding paper presented in (131st annual meeting of Florida State Horticultural

Society).

31

Optimization of Early-season Nitrogen Fertilization Program for New

Strawberry Cultivar ‘Florida Beauty’

32

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Study- 1 (Salts)


Foliar application of calcium chloride (CaCl2) to improve the vegetative

growth, yield and quality of strawberry cv. ‘Chandler’

In this experiment foliar spray of CaCl2 was applied after 2nd

week of runner

transplantation when old leaves were dried and new sprouting occurred. When strawberry

plants were at 3-4 leaves stage 1st foliar application was applied and 2

nd was applied after

fruit setting. Treated strawberry plants were compared with control plants. Plants canopy

growth; yield and quality were observed during growing season. Complete methods are

mentioned in previous chapter.

4.1.1 Results

4.1.1.1 Vegetative parameters (Table 4.1.1.1)


)

Statistical results regarding strawberry leaves treated with foliar spray of CaCl2

showed significant (p < 0.05) increased results. Maximum leaves (15.25 plant-1

) were

observed in strawberry plants those were sprayed with 7 mM CaCl2 followed by the plants

sprayed with 5 mM and 3 mM where numbers of leaves were 13.50 and 12.0 plant-1

,

respectively. While less leaves (8.0 plant-1

) were in control plants. Calcium chloride

treatments were highly responsive for increasing the number of leaves during season as

compared with control plants.

4.1.1.1.2 Leaf area (cm2)

Statistical analysis regarding strawberry leaf area showed significant increased

results. Leaf area was increased with foliar application of CaCl2. Increasing trend in leaf area

(37.0 cm2) was found in plants sprayed with higher concentration of CaCl2 (7 mM) followed

by the plants sprayed with 5 mM and 3 mM which showed leaf area values 31.50 and 28.0

cm2, respectively. Strawberry plants which were sprayed with lower concentration of CaCl2

33

(3 mM) and control plants these treatments were statistically similar. Leaf area (27.50 cm2)

was minimum in control plants. It was observed that the treatment of CaCl2 is effective to

increase the leaf area when sprayed during growth stages.

4.1.1.1.3 Flower anthesis (days after foliar application)

Statistical analysis regarding flower anthesis showed non-significant results. First

foliar application was applied when strawberry plants were at 3-4 leaves stage. Numbers of

days required for flower anthesis for each treatment were recorded after 1st foliar application.

Statistically there was no difference among different CaCl2 treatment means and control

treatment. Numbers of days required for flower anthesis were almost similar in all

treatments.


)

Statistical results regarding crown growth of strawberry plants affected by foliar

application of CaCl2 showed significant increased results. Crown growth was noted at the

end of strawberry season and maximum number of crowns (6.50 plant-1

) was noted in 7 mM

CaCl2 treatment followed by plants sprayed with 5 mM which showed number of crowns

(4.50 plant-1

). Strawberry plants sprayed with 3 mM CaCl2 and control plants where numbers

of crowns were 3.25 and 2.50 plant-1

, respectively. Numbers of crowns were increased in the

strawberry plants due to foliar application of CaCl2 which was observed at the end of

strawberry season.


)

Increasing trend was noted in runner production during season. Maximum runners

(7.0 plant-1

) were found in strawberry plants those were sprayed with 7 mM CaCl2 followed

by the plants sprayed with 5 mM and 3 mM where numbers of runners were 4.75 and 3.75

plant-1

, respectively. At the end of strawberry season minimum runners (2.50 plant-1

) were

found with control plants. It was noted from results that CaCl2 spray was more responsive for

increasing runner growth.

34

Table 4.1.1.1 Effect of foliar application of CaCl2 on vegetative growth of strawberry cv.

‘Chandler’ Mean ± S.E.

Treatments No. of leaves Leaf area Flower anthesis No. of crowns No. of runners

(plant-1

) (cm2) (days) (plant

-1) (plant

-1)

Control 8.00±1.08 c 27.50±1.04 c 40.25±0.48 a 2.50±0.29 c 2.50±0.29 d

3 mM CaCl2 12.00±0.41 b 28.00±0.41 c 41.50±0.65 a 3.25±0.25 c 3.75±0.25 c

5 mM CaCl2 13.50±0.29 b 31.50±1.71 b 41.25±0.63 a 4.50±0.29 b 4.75±0.25 b

7 mM CaCl2 15.25±0.25 a 37.00±1.08 a 41.00±0.71 a 6.50±0.29 a 7.00±0.41 a

LSD (p=0.05) 2.2 3.86 1.84 0.93 0.75

C.V. % 10.44 7.37 2.82 13.93 10.48

4.1.1.2 Yield parameters

Strawberry harvesting was started at the end of January and continued till mid-April.

Harvested strawberries were separated into three important categories such as marketable,

unmarketable and small size (Table 4.1.1.2).


-1)

Statistical analysis regarding strawberry marketable yield (75-80% mature, disease

free, large size and bright red) demonstrated significant differences among treatments. As it

was exhibited that marketable yield was increased throughout strawberry season. Calcium

chloride treated plants showed more marketable fruit. Maximum marketable yield (348.50 g

plant-1

) was noted with 7 mM CaCl2 followed by the plants sprayed with 5 mM and 3 mM

which showed marketable yield 218.25 and 177.25 g plant

-1, respectively. Lower marketable

yield (126.75 g plant

-1) was obtained with control treatment.


-1)

Minimum unmarketable yield (43.50 g plant

-1) was recorded with 7 mM CaCl2 spray

followed by plants sprayed with 5 mM and 3 mM which showed unmarketable yield 72.25

and 92.25 g plant

-1, respectively. Maximum unmarketable yield (107.0 g

plant

-1) was resulted

from control plants. Higher dose of CaCl2 was more effective to increase marketable yield

and to reduce unmarketable yield.

35


-1)

Statistical results regarding small size yield of strawberry affected by CaCl2 foliar

spray showed significant decreased results. Yield of small sized strawberries (84.0 g plant

-1)

was maximum in control plants. Lower yield (38.0 g plant

-1) was noted with 7 mM CaCl2 and

plants treated with 5 mM and 3 mM those showed small size yield 4.25 and 65.0 g plant

-1,

respectively. Calcium chloride foliar spray was highly effective in reducing the production of

small sized strawberries when compared with control.

Table 4.1.1.2 Effect of foliar application of CaCl2 on yield of strawberry cv. ‘Chandler’

Mean ± S.E.

Treatments Marketable Unmarketable Small size

(g plant

-1) (g

plant

-1) (g

plant

-1)

Control 126.75±1.31 d 107.00±3.49 a 84.00±2.27 a

3 mM CaCl2 177.25±8.33 c 92.25±1.11 b 65.00±1.47 b

5 mM CaCl2 218.25±4.23 b 72.25±1.11 c 54.25±1.11 c

7 mM CaCl2 348.50±7.08 a 43.50±1.55 d 38.00±1.29 d

LSD (p=0.05) 17.28 7.06 5.6

C.V. % 4.59 5.61 5.81

4.1.1.3 Fruit quality Parameters


)

Calcium chloride as firming agent improved strawberry firmness during ripening.

More strawberry firmness (0.96 kg. cm-2

) was noted with 7 mM CaCl2 followed by 5 mM

and 3 mM treatments which showed firmness values 0.75 and 0.58 kg. cm-2

, respectively.

Strawberry plants treated with different concentrations of CaCl2 produce fruits more firm

while less firmness (0.33 kg. cm-2

) was noted in control fruits (Figure 4.1.1.1).

36

4.1.1.3.2 TSS (ºBrix)

The statistically analyzed data exhibited significant differences among different

calcium chloride treatments regarding strawberry TSS values. Total soluble solids increased

with different concentrations of CaCl2. Maximum amount of TSS (8.03 ºBrix) were noted in

strawberries sprayed with 5 mM CaCl2 followed by 7 mM (6.90 ºBrix) and 3 mM (6.28

ºBrix), respectively while minimum TSS values (5.70 ºBrix) were observed in control

treatment. Our results suggested that medium dose of CaCl2 showed its superiority for

increasing strawberry TSS contents (Figure 4.1.1.2).

4.1.1.3.3 Titratable acidity (%)

Recorded results were non-significant regarding foliar spray of CaCl2 on acid

contents of strawberry fruit. Numerically acid contents were more in control treatment as

compared to CaCl2 treatments. Over all, no difference was noted between different means of

treatments (Figure 4.1.1.3).

4.1.1.3.4 TSS: TA ratio

Statistical data regarding strawberry fruit TSS: TA ratio affected by foliar application

of CaCl2 showed increasing trend. Maximum TSS: TA ratio (7.63) was noted with 5 mM

CaCl2 followed by the plants treated with 7 mM (5.55) and 3 mM (5.14), respectively. TSS:

TA ratio is an important fruit quality parameter which expresses fruit ripening stage.

Minimum ratio was exhibited in control (4.48) treatment. Foliar spray of CaCl2 was more

responsive for increasing TSS: TA ratio in strawberry fruits (Figure 4.1.1.4).

4.1.1.3.5 Vitamin C (mg 100 g-1

)

Maximum vitamin C contents (55.69 mg 100 g-1

) were noted in strawberry fruits

sprayed with 7 mM CaCl2 followed by the plants treated with 5 mM (46.85 mg 100 g-1

) and 3

mM (41.17 mg 100 g-1

), respectively while lower vitamin C contents (35.55 mg 100 g-1

) were

found in control fruits. Calcium chloride as foliar spray played significant role for increasing

the vitamin C contents of strawberry fruits during season (Figure 4.1.1.5).

37


)

Strawberry plants treated with CaCl2 7 mM, 5 mM and 3 mM produced the

strawberries with total phenolic contents of 186.50, 160.50 and 151.50 mg GAE 100 g-1

,

respectively and significant differences were exhibited. Lower phenolic contents were

observed in control (132.75 mg GAE 100 g-1

) fruits as compared to other treatments. It can

be concluded that CaCl2 spray was effective to produce strawberries with maximum total

phenolic contents (Figure 4.1.1.6).

4.1.1.3.7 Total antioxidants (% DPPH)

Higher antioxidant activities (65.50% DPPH) were noted in strawberry fruits where

plants were treated with 5 mM CaCl2 followed by 7 mM (55.50 % DPPH) and 3 mM (49.25

% DPPH), respectively. The response of medium concentration of CaCl2 (5 mM) was highly

effective for increasing antioxidant activities in strawberry fruits while minimum activities

were observed in control (41.50% DPPH) treatment (Figure 4.1.1.7).

38

Figure 4.1.1.1 Effect of foliar application of CaCl2 on firmness (kg. cm2) of strawberry


Figure 4.1.1.2 Effect of foliar application of CaCl2 on TSS (ºBrix) of strawberry fruit.


0

0.2

0.4

0.6

0.8

1

1.2

Control 3 mM 5 mM 7 mM

Fir

mn

ess

(kg

. cm

-2)

Treatments (CaCl2)

0

1.5

3

4.5

6

7.5

9


TS

S (

°Bri

x)

Treatments CaCl2

39

Figure 4.1.1.3 Effect of foliar application of CaCl2 on titratable acidity (%) of

strawberry fruit. Vertical bars represent ± S.E of means.

Figure 4.1.1.4 Effect of foliar application of CaCl2 on TSS: TA ratio of strawberry


0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5


TA

(%

)

Treatments (CaCl2)

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8


TS

S:

TA

rati

o

Treatments (CaCl2)

40

Figure 4.1.1.5 Effect of foliar application of CaCl2 on vitamin C (mg 100 g-1

) contents

of strawberry fruit. Vertical bars represent ± S.E of means.

Figure 4.1.1.6 Effect of foliar application of CaCl2 on total phenolic contents (mg GAE 100

g-1

) of strawberry fruit. Vertical bars represent ± S.E of means.

25

30

35

40

45

50

55

60


Vit

am

in C

(m

g 1

00

g-1

)

Treatments (CaCl2)

110

120

130

140

150

160

170

180

190


TP

C (

mg G

AE

100 g

-1)

Treatments (CaCl2)

41

Figure 4.1.1.7 Effect of foliar application of CaCl2 on total antioxidants (% DPPH) of

strawberry fruit. Vertical bars represent ± S.E of means.

4.1.1.4 Activities of anti-oxidative enzymes (Table 4.1.1.3)


protein)

Quantitatively higher catalase activity (8.88 U mg−1

protein) was estimated in control

fruits while lower (8.81 U mg−1

protein) was noted in those fruits treated with 7 mM CaCl2

but results were non-significant. Over all, calcium chloride spray was effective for reducing

catalase activity.


protein)

Calcium chloride treatments were highly responsive to maximize superoxide

dismutase activity in strawberry fruit and significant increased results were noted. Maximum

SOD activity (22.4 U mg−1

protein) was exhibited with 7 mM CaCl2 spray followed by 5 mM

(20.3 U mg−1

protein) and 3 mM (19.2 U mg−1

protein), respectively while lower activity

(18.0 U mg−1

protein) was noted in control treatment.

30

35

40

45

50

55

60

65

70


TA

(%

DP

PH

)

Treatments (CaCl2)

42


protein)

Lower peroxidase activity (0.35 U mg−1

protein) was noted in fruits sprayed with 7

mM CaCl2 and 5 mM (0.46 U mg−1

protein) and these treatments were statistically similar.

Maximum peroxidase activity was noted in control (2.89 U mg−1

protein) treatment. The

response of foliar spray of CaCl2 on reducing peroxidase activity of strawberry fruit was

highly effective during growing season.

Table 4.1.1.3 Effect of foliar application of CaCl2 on enzymatic activities of strawberry

cv. ‘Chandler’ Mean ± S.E.

Treatments CAT (U mg-1

protein) SOD (U mg-1

protein) POD (U mg-1

protein)

Control 8.88±0.01 a 18.0±0.11 d 2.89±0.26 a

3 mM CaCl2 8.87±0.01 a 19.2±0.12 c 1.34±0.03 b

5 mM CaCl2 8.85±0.01 a 20.3±0.22 b 0.46±0.01 c

7 mM CaCl2 8.81±0.01 a 22.4±0.23 a 0.35±0.02 c

LSD (p=0.05) 0.02 0.71 0.41

C.V. % 1.67 3.4 20.54

4.1.1.5 Survival (%)

Maximum survival (%) was observed in the strawberry plants those were sprayed

with 7 mM CaCl2 (94.75%) followed by the plants sprayed with 5 mM (80.5%) and 3 mM

(72.25%), respectively as compared with control (64.25%) treatment. Strawberry plants

survival increased with CaCl2 applications as compared with control plants during whole

growing season (Figure 4.1.1.8).

43

Figure 4.1.1.8 Effect of foliar application of CaCl2 on survival (%) of strawberry

plants. Vertical bars represent ± S.E of means.

50

55

60

65

70

75

80

85

90

95

100


Su

rviv

al

(%)

Treatments (CaCl2)

44

4.1.1 Discussion

Strawberry has fast growing habit which needs sufficient amount of nutrients

throughout growing season (Medeiros et al., 2015). For successful strawberry production

micronutrients play major role especially calcium which is classified as secondary nutrient

for strawberry plant requirement and structural part of cell walls and promote rapid plant

growth (Haifa, 2014). Micronutrients increased the hormonal activity and nutrient uptake

efficiency by acting as catalyst (Phillips, 2004). Foliar application of Ca promoted plant

growth and nutrient levels in certain above ground plant organism (Swietlik and Faust,

1984). Foliar application of micronutrients is a supplemental application method to supply

nutrients during critical growth stages when plants cannot uptake adequate nutrients from soil

due to complex soil chemistry, leaching of nutrients, low soil temperature, immobile

nutrients and low water availability which solubilize nutrients and reduce their efficiency

(Growing Produce, 2018). In general, through foliar application plants uptake essential

nutrients by penetrate in the cuticle or enter through the stomata of leaves more rapidly as

compared to soil application (Alshaal and Ramady, 2017).

In current study, different concentrations of calcium chloride were applied through

foliar application. Vegetative growth of strawberry plants was significantly increased with

calcium chloride applications as compared with control plants. Maximum leaves growth

(15.25 plant-1

), leaf area (37.0 cm2), crowns (6.50 plant


-1) were

increased with highest concentration of CaCl2 (7 mM) as compared with other treatments.

Calcium as important secondary nutrient for strawberry plant growth enhanced the vegetative

growth because it improve the inflexibility of plasma membrane of plant cells, most

prominent in the apoplast, the cell wall space where it plays major role for cross-link within

pectin polysaccharide matrix and contribute their stability (Haifa, 2014). The quantity of

calcium which plants uptake through soil solution, most of it translocated to the leaves but

very little amount goes to the fruit (Kadir, 2004). Therefore, for better plant growth plants

need regular supply of calcium for vigorous canopy development (Del-Amor and Marcelis,

2003). Our findings regarding foliar spray of calcium chloride enhanced vegetative growth of

strawberry similar with previous findings in which they observed that foliar spray of calcium

chloride (0.6%) enhanced the leaf growth, leaf area and improved canopy of strawberry plant

45

(Bakshi et al., 2013). Our results exhibited that strawberry flowering was not affected by

CaCl2 application and these results were similar with previous findings where foliar applied

0.3% CaCl2 not increased the cluster of flowers in tomato crop (Rab and Haq., 2012).

During whole growing season marketable yield (348.50 g plant-1

) showed increasing

trend and fruit setting was increased with 7 mM CaCl2 as compared with other treatments.

Maximum unmarketable strawberries (107.0 g plant-1

) were resulted from control plants. Our

results proved that CaCl2 treatments reduced unmarketable strawberries and increased the

marketable yield. Maximum small sized strawberries (84 g plant-1

) were noticed in control

treatment while 7 mM CaCl2 treatment was highly effective for reducing small sized

strawberries during season. The mechanism through which external application of CaCl2

improved growth and marketable yield of strawberries, it is because of calcium on plant

surface create electrochemical potential gradient which favors inward movement of calcium.

Calcium sequestered into vacuole through transport across the tonoplast, binds to calcium

binding proteins (calmodulin) and also with intracellular organelles such as mitochondria,

nucleus, endoplasmic reticulum and chloroplast. After binding, it is transmitted to receptor

proteins that elicit proper responses to the stimulus (Taiz and Zeiger, 2006). Our results

showed that marketable yield increased with foliar spray of CaCl2 similar with some previous

findings where foliar application of 10 mM CaCl2 improved the yield and qualitative

characteristics of strawberry cultivar „Pajaro‟ (Kazemi, 2015). The beneficial aspect of CaCl2

for increasing fruit setting and yield was due to maximum capability of photosynthesis and

CaCl2 increased the process of hormone metabolism due to that process auxin synthesis

increase in strawberry plants which is essential for yield and growth.

Maximum strawberry firmness (0.96 kg. cm-2

) was achieved with 7 mM CaCl2 foliar

spray as compared with control (0.33 kg. cm-2

) treatment. Firmness quality increased with

foliar spray of CaCl2 because calcium spray increased the level of pectin in fruit cells due to

that cell wall rigidity increased and fruits nature was more firm (Sams, 1999; Maas, 1998).

Maximum total soluble solids were found in those strawberries which were treated with

CaCl2 (5 mM) as compared with other treatments. It is because of carbohydrates and starch

converted into sugars during ripening stages of strawberry. Statistically acid contents were

found non-significant during season but maximum were noted with control treatment it is

46

because of less production of TSS contents. Maximum TSS: Acid ratio (7.63) was noted with

5 mM CaCl2 treatment. TSS: Acid was major indication of strawberry ripening and maturity.

Vitamin C known as ascorbic acid acted as an antioxidant which increased the

nutritional value of fruit (Rapisarda et al., 2008). Higher amount of vitamin C (55.69 mg 100

g-1

) was observed with 7 mM CaCl2 as compared with other treatments. Vitamin C increased

with CaCl2 application because calcium spray enhanced the activity of several catalytic

enzymes which played major role in biosynthesis of vitamin C contents (Kadir, 2014). Over

all, fruit quality was increased because calcium spray played major role in plant cell wall

integrity and improved the nutritional status of fruits. Calcium deficiency in fruits showed

less resistance against pathogens and increased the chances of disease occurrence in plants,

so calcium spray suggested as for disease management (Naradisorn, 2013). Kazemi (2014)

also observed similar findings regarding foliar application of CaCl2 10 mM enhanced the

quality of strawberry. In literature it was proved that foliar spray of calcium chloride 0.6%

increased the TSS contents (8.31 ºBrix), ascorbic acid contents (60.88 mg/100g) of

strawberry and lower acidity than control (Bakshi et al., 2013). In previous findings it was

confirmed that foliar application of calcium containing products improved firmness of

kiwifruit cultivar „Tsechelidis‟ compared with control (Koutinas et al., 2010).

In current study, it was evaluated that application of CaCl2 significantly increased

phenolic compounds and antioxidants in strawberry. Maximum phenolic contents

(186.50 mg GAE 100 g-1

) were found with 7 mM CaCl2 as compared with other treatments.

Higher antioxidants (65.50 % DPPH) increased with 5 mM CaCl2 because sometimes higher

doses were less effective to increase all quality attributes due to climatic, soil and varietal

response. External application of calcium activated environmental and developmental

responses against severe conditions (high light intensity, long day length, high temperature,

extreme drought, osmotic stress and attack of pathogens) in plant cell membranes and

enhanced calcium concentration which increased the level of antioxidants and phenolic

compounds in plants (Taiz and Zeiger, 2006).

Our results showed that enzymatic activities were also influenced with CaCl2

treatments. Catalase activity was found maximum in all the treatments and no difference was

observed. Superoxide dismutase activity was noted maximum with CaCl2 treatments.

Peroxidase activity was maximum in control plants and significantly lowered with CaCl2

47

spray because at very higher rate it cause off flavor. In literature it was observed that reactive

oxygen species (ROS) produced during biochemical changes in strawberry such as the

superoxide radical and it cause oxidative damage (Jimenez et al. 2003). These (ROS) species

caused early fruit ripening and leading towards senescence. Enzymatic activities including

POD and SOD produce during different growth stages and increased the defense responses.

Reactive oxygen species produce due to decline in these enzymatic activities (Anand et al.,

2009). According to our results it was clear that maximum survival (94.75%) achieved with 7

mM CaCl2 treated strawberry plants as compared to control (64.25%) plants. Previous studies

showed that calcium signaling played critical role in plant resistance to diseases; create

defense mechanism against insects and acclimatization against non-biological stresses (Sun

et al., 2009). As second messenger calcium played important role in signal transduction

pathways particularly ABA signal transduction process. When calcium encountered with

abiotic stresses (cold and drought) it rapidly accumulated ABA and increased calcium ions

concentration in plant cell. So, in that way enzymatic activities increased which enhanced the

survival mechanism (Sun et al., 2009). During whole season CaCl2 treated strawberry plants

showed better response as compared with untreated plants.

4.1.1 Conclusion

Calcium as secondary messenger play important role for strawberry plant growth and

development. In current study 7 mM CaCl2 treatment was proved best for improving the

vegetative growth, marketable yield and survival mechanism of strawberry plants during

growing season. Fruit quality was also improved with 7 mM CaCl2 foliar spray while TSS

contents, TSS: Acid ratio and total antioxidants were observed maximum with medium dose

of CaCl2 (5 mM) as compared with higher and lower doses because sometime higher doses

not increase the all quality attributes.

48


Foliar application of zinc sulfate (ZnSO4) to improve the vegetative growth,

yield and quality of strawberry cv. ‘Chandler’

In this experiment ZnSO4 was applied as foliar spray during growth stages. Treated

plants were compared with control plants. Canopy growth, yield and quality were observed

during growing season. Complete methods are mentioned in previous chapter.

4.1.2 Results



)

Statistical analysis regarding strawberry leaves affected by foliar spray of ZnSO4

showed significant (p < 0.05) differences among different treatments means. Maximum

leaves (18.25 plant-1

) were observed with 100 mg L-1

ZnSO4 followed by other treatments

including 150 and 50 mg L-1

ZnSO4 which showed numbers of leaves (13.50 and 10.75

plant-1

), respectively. Minimum (8.25 plant-1

) leaves were observed in control plants.

Numbers of leaves increased with ZnSO4 foliar spray when compared with control plants.


Leaf area was increased with foliar spray of ZnSO4. Maximum leaf area (52.0 cm2)

was noted with 100 mg L-1

ZnSO4 spray followed by other treatment 150 mg L-1

ZnSO4

which showed leaf area (42.75 cm2). Plants those were sprayed with ZnSO4 (50 mg L

-1) and

control plants these treatments were statistically same. Leaf area did not increase in control

plants. It was exhibited from results that foliar application of 100 mg L-1

ZnSO4 was more

efficient for maximizing the leaf area as compared to other treatments.

49


Minimum numbers of days (27.50) were required to open 1st flower when sprayed

with 150 mg L-1

ZnSO4 followed by other treatments 100 mg L-1

(33.75) and 50 mg L-1

(39.75), respectively. Maximum numbers of days (43.75) to open 1st flower were observed in

control treatment. It was noted that higher concentration of ZnSO4 initiate early flowering.


)

Maximum crowns (7.0 plant-1

) were observed in those strawberry plants sprayed with

100 mg L-1

ZnSO4 followed by 150 and 50 mg L-1

ZnSO4 where numbers of crowns were

4.50 and 3.50 plant-1

, respectively. Higher dose of ZnSO4 was not effective for increasing the

number of crowns when compared with 100 mg L-1

ZnSO4. Minimum numbers of crowns

(2.50 plant-1

) were noted in control treatment. It was noted that treatment of ZnSO4 (100 mg

L-1

) was more responsive to increase the crown growth.


)

Statistical analysis regarding runner growth of strawberry plants affected by foliar

spray of ZnSO4 showed non-significant (p > 0.05) results. Runner growth was not increased

with foliar spray of ZnSO4 and no significant difference was noted among treatments.

Statistically all treatment means were same and similar numbers of runners per plant were

observed.

50

Table 4.1.2.1 Effect of foliar application of ZnSO4 on vegetative growth of strawberry cv.



(plant-1


-1) (plant

-1)

Control 8.25±0.48 d 37.75±0.85 c 43.75±0.75 a 2.50±0.29 d 2.50±0.29 a

50 mg L-1

ZnSO4 10.75±0.48 c 39.50±0.65 c 39.75±0.25 b 3.50±0.29 c 2.71±0.25 a

100 mg L-1

ZnSO4 18.25±0.48 a 52.00±0.91 a 33.75±0.75 c 7.00±0.00 a 2.75±0.25 a

150 mg L-1

ZnSO4 13.50±0.29 b 42.75±1.38 b 27.50±0.29 d 4.50±0.29 b 2.78±0.29 a

LSD (p=0.05) 1.25 2.32 1.69 0.79 0.79

C.V. % 6.2 4.4 2.92 11.43 19.05






-1)

Statistical analysis regarding strawberry marketable yield demonstrated significant

(p < 0.05) increased results. Marketable yield (disease free, large size and bright red color)

was increased with foliar spray of ZnSO4 during whole season. Maximum marketable yield

(369.0 g plant

-1) was found with 100 mg L

-1 ZnSO4 spray followed by the plants sprayed with

150 mg L-1

(285.0 g plant

-1), respectively. It was noted that marketable yield was found

higher with foliar treatment of ZnSO4 while decreasing trend was observed when dose was

increased from 100 mg L-1

. Minimum marketable yield (159.75 g plant

-1) was observed with

50 mg L-1

ZnSO4 and control (126.75 g plant

-1) plants and these treatments were statistically

same.


-1)

Strawberry fruits affected by grey mould disease, anthracnose, powdery mildew,

thrips attack and due to any environmental factor were considered as unmarketable yield

during whole season. Minimum unmarketable yield (54.75 g plant

-1) was noted with 100 mg

51

L-1

ZnSO4 followed by other treatments including 150 mg L-1

(65.50 g plant

-1) and 50 mg L

-1

(90.0 g plant

-1), respectively. Maximum unmarketable yield (107.0 g

plant

-1) was found with

control treatment. It was suggested that foliar spray of ZnSO4 was more efficient for

maximizing the marketable yield and to reduced unmarketable yield during season.


-1)

Strawberry fruits which were less than (10 g) in weight were considered as small size

yield. Maximum (84.0 g plant

-1) yield of small sized strawberries were observed in control

plants as compared to ZnSO4 treatments. Less (41.75 g plant

-1) yield was found with 100 mg

L-1


(53.0 g plant

-1) and 50 mg L

-1

(63.75 g plant

-1), respectively. Zinc sulfate as foliar spray was found highly effective to

reduce the production of small sized strawberries but the optimum dose 100 mg L-1

ZnSO4

was found more responsive as compared to lower and higher doses.

Table 4.1.2.2 Effect of foliar application of ZnSO4 on yield of strawberry cv. ‘Chandler’

Mean ± S.E.


(g plant

-1) (g

plant

-1) (g

plant

-1)

Control 126.75±11.31 c 107.00±3.49 a 84.00±2.27 a

50 mg L-1

ZnSO4 159.75±12.97 c 90.00±0.41 b 63.75±0.85 b

100 mg L-1

ZnSO4 369.00±15.03 a 54.75±1.60 d 41.75±0.48 d

150 mg L-1

ZnSO4 285.00±14.30 b 65.50±1.94 c 53.00±0.91 c

LSD (p=0.05) 36.28 6.59 4.42

C.V. % 9.65 5.2 4.56

52



)

Statistical analysis of strawberry relating to firmness demonstrated significant (p <

0.05) differences among treatments. Higher firmness value (0.75 kg. cm-2

) was found in

those fruits where plants were sprayed with 100 mg L-1

ZnSO4 followed by other treatments

including 150 and 50 mg L-1

which showed firmness values (0.63 and 0.43 kg. cm-2

),

respectively while control treatment showed value (0.32 kg. cm-2

) which was less than others.

Strawberry plants sprayed with different concentrations of ZnSO4 produced fruits more firm

but trend regarding medium concentration of ZnSO4 (100 mg L-1

) improve the firmness was

similar as found in previous parameters (Figure 4.1.2.1).

4.1.2.3.2 TSS (ºBrix)

Total soluble solids increased with different concentrations of ZnSO4. Maximum

amount of TSS (8.1 ºBrix) were observed with 100 mg L-1

ZnSO4 followed by other

treatments 150 mg L-1

(6.22 ºBrix) and 50 mg L-1

(5.97 ºBrix), respectively while minimum

TSS values (5.70 ºBrix) were observed in control treatment (Figure 4.1.2.2).


Non-significant trend (p > 0.05) was recorded regarding foliar spray of ZnSO4 on acid

contents of strawberry fruit. Quantitatively acid contents were maximum in control treatment

as compared to ZnSO4 treated plants but statistically there was no difference between

different treatments means (Figure 4.1.2.3).


TSS: TA ratio is major indicator of quality which directly affects the shelf life of

fruit. Maximum ratio (7.05) was observed with 100 mg L-1

ZnSO4 followed by other


(5.06) and 50 mg L-1

(4.61), respectively. Minimum ratio (4.48) was

observed in control treatment. Medium concentration of ZnSO4 was more responsive for

increasing TSS: TA ratio in strawberry fruits (Figure 4.1.2.4).

53

4.1.2.3.5 Vitamin C (mg 100 g-1

)

Significant increased trend was noted regarding vitamin C contents of strawberry

fruit. Maximum (53.30 mg 100 g-1

) values were noted in strawberries sprayed with 100 mg

L-1


(43.29 mg 100 g-1

) and 50 mg

L-1

(40.77 mg 100 g-1

), respectively. While lower vitamin C values (32.80 mg 100 g-1

) were

observed in control treatment. Similar to other parameters medium dose of ZnSO4 was found

most effective as compared to higher and lower doses (Figure 4.1.2.5).


)

Strawberry plants treated with ZnSO4 100, 150 and 50 mg L-1

produced the

strawberries with total phenolic contents of 177.5, 158.5 and 146.5 mg GAE 100 g-1

,

respectively. Lower phenolic contents (134.5 mg GAE 100 g-1

) were found in control

treatment as compared to treated fruits. Again medium dose of ZnSO4 (100 mg L-1

) showed

its superiority over lower and higher doses and showed significant increased trend (Figure

4.1.2.6).


Statistical data regarding total antioxidant activities in strawberry affected by foliar

spray of ZnSO4 showed significant increased trend. Higher antioxidant activities (74.3%

DPPH) were noted in strawberry fruits where plants were sprayed with 100 mg L-1

ZnSO4

followed by treatments including 150 and 50 mg L-1

where TA values were 54.5 and 46.7%

DPPH, respectively. Zinc sulfate treatments were highly responsive for increasing the

antioxidant activities in strawberry fruits while minimum (41.0% DPPH) activities were

observed in control treatment (Figure 4.1.2.7).

54

Figure 4.1.2.1 Effect of foliar application of ZnSO4 on firmness (kg. cm-2

) of

strawberry fruit.

Figure 4.1.2.2 Effect of foliar application of ZnSO4 on TSS (ºBrix) of strawberry fruit.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Control 50 100 150

Fir

mn

ess

(kg

. cm

-2)

Treatments (ZnSO4 mg L-1)

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

Control 50 100 150

TS

S (

°Bri

x)


55

Figure 4.1.2.3 Effect of foliar application of ZnSO4 on titratable acidity (%) of

strawberry fruit.

Figure 4.1.2.4 Effect of foliar application of ZnSO4 on TSS: TA ratio of strawberry

fruit.

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

Control 50 100 150

TA

(%

)


3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

Control 50 100 150

TS

S:

TA

rati

o


56

Figure 4.1.2.5 Effect of foliar application of ZnSO4 on vitamin C (mg 100 g-1

) contents

of strawberry fruit.

Figure 4.1.2.6 Effect of foliar application of ZnSO4 on total phenolic contents (mg

GAE 100 g-1


25

30

35

40

45

50

55

Control 50 100 150

Vit

am

in C

(m

g 1

00

g-1

)


110

120

130

140

150

160

170

180

Control 50 100 150

TP

C (

mg G

AE

100 g

-1)


57

Figure 4.1.2.7 Effect of foliar application of ZnSO4 on total antioxidants (% DPPH) of

strawberry fruit.



protein)

Significant increased trend was obtained from catalase activity in strawberry fruit but

all ZnSO4 treatments were non-significant and statistically at par with each other.

Quantitatively higher catalase activity (14.3 U mg−1

protein) was estimated in control fruits.


protein)

Zinc sulfate treatments were highly responsive to maximize superoxide dismutase

activity in strawberry fruit and showed significant increased trend. Maximum (26.4 U mg−1

protein) activity was estimated in strawberries sprayed with 150 mg L-1

ZnSO4 followed by


(24.2 U mg−1

protein) and 50 mg L-1

(22.1 U mg−1

protein),

respectively while lower (20.0 U mg−1

protein) activity was exhibited in control treatment.

0

10

20

30

40

50

60

70

80

Control 50 100 150

TA

(%

DP

PH

)


58


protein)


protein) was found in strawberry fruit

sprayed with 150 mg L-1


(1.65 U

mg−1


(1.75 U mg−1

protein), respectively while maximum (2.39 U

mg−1

protein) peroxidase activity was noted in control treatment. It was noted that foliar

treatment of ZnSO4 on reducing peroxidase activity of strawberry fruit was highly effective

and showed significant variation among treatments.

Table 4.1.2.3 Effect of foliar application of ZnSO4 on enzymatic activities of

strawberry cv. ‘Chandler’ Mean ± S.E.




protein)

Control 14.3±0.26 a 20.0±0.35 d 2.39±0.11 a

50 mg L-1

ZnSO4 13.8±0.25 b 22.1±0.36 c 1.75±0.02 b

100 mg L-1

ZnSO4 13.7±0.24 b 24.2±0.37 b 1.65±0.02 c

150 mg L-1

ZnSO4 13.6±0.21 b 26.4±0.38 a 1.57±0.02 d

LSD (p=0.05) 0.4 1.61 1.19

C.V. % 21.72 3.57 11


Statistical analysis regarding strawberry plants survival during whole season showed

significant variations among treatments. Maximum (90.75%) survival was exhibited in those

plants sprayed with 100 mg L-1

ZnSO4 followed by treatments including 150 mg L-1

(83.5%)

and 50 mg L-1

(71.5%), respectively as compared to control (61.75%) treatment. Survival (%)

of plants also showed the superiority of medium dose over higher and lower doses (Figure

4.1.2.8).

59

Figure 4.1.2.8 Effect of foliar application of ZnSO4 on survival (%) of strawberry

plants.

0

15

30

45

60

75

90

Control 50 100 150

Su

rviv

al

(%)


60

4.1.2 Discussion

Foliar application of micro nutrients at proper and regular intervals plays major role

in increasing fruit set and productivity of strawberry plants (Abdollahi et al., 2010b). Zinc is

metal compound associated with many enzymes and proteins which played functional role

for improving normal plant growth and developmental processes (Nasiri et al., 2010).

Through foliar spray nutrients absorbed very quickly and perform different functions and

also helpful for correction of nutrient deficiencies to restore disrupted supply of

micronutrients (Alshaal and Ramady, 2017). Zinc played important role for reducing

different physiological disorders in fruit trees (Meena et al., 2014).

In current study, vegetative growth was enhanced with foliar spray of zinc sulfate.

Maximum leaves (18.25 plant-1

) and leaf area (52.0 cm2) were noted with 100 mg L

-1 ZnSO4.

Flower anthesis was also affected with higher concentration of ZnSO4. Maximum number of

crowns (7.0 plant-1

) was also noticed with 100 mg L-1

ZnSO4. In current study vegetative

parameters were found improving and flowering initiation was earlier in ZnSO4 sprayed

plants compared to control plants. This trend showed the superiority over control plants. It is

because of when ZnSO4 applied as foliar spray, it quickly penetrates into plant through

cuticle and epidermal walls (Meena et al., 2014). It is also reported that adsorption occurs on

the surface of plasmalemma, which is layer of protection. Nutrients enter through

plasmalemma into the cytoplasm and acted as growth promoter (Swietlik and Faust., 1984).

Zinc is necessary for increasing the level of tryptophan enzyme which further increased the

level of indole acetic acid hormone in plants and acted as growth promoter (Nasiri et al.,

2010). Therefore, maximum leaf growth, leaf area and flower initiation was earlier in treated

plants. It is proved that ZnSO4 improved the vegetative parameters but for this purpose the

optimum dose of ZnSO4 (100 mg L-1

) is important. Lower doses did not show maximum

influence but when these increased above optimum level again started to lose its influence

and parameters showed declining trend. In some previous studies it was estimated that foliar

spray of ZnSO4 maximized the growth of strawberry cultivar „Camarosa‟. Leaf area and

number of flowers increased with 100 mg L-1

ZnSO4 (Lolaei et al., 2012). In literature it was

recorded that foliar application of ZnSO4 showed positive effects regarding vegetative growth

of strawberry cultivar „Selva‟. Number of leaves and runner growth increased with zinc

61

application but fresh shoot/root ratio decreased (Abdollahi et al., 2010a). These results

confirm our findings that ZnSO4 improved the vegetative growth of strawberry during

season.

During season maximum marketable yield (369 g plant-1

) increased with foliar spray

of 100 mg L-1

ZnSO4. Minimum marketable yield was found in control plants. The response

of ZnSO4 for increasing marketable yield was highly effective throughout season but at very

higher and lower concentrations response was less effective than 100 mg L-1

ZnSO4.

Unmarketable yield was maximum in control plants as compared to treated plants. Minimum

small size strawberries (41.75 g plant-1


ZnSO4 as compared

to other treatments while maximum small sized strawberries (84 g plant-1

) were noted in

control plants. Marketable yield maximized due to foliar spray of ZnSO4, it is because of zinc

activated plant enzymes which played functional role in carbohydrate metabolism, synthesis

of protein structures and regulation process of auxin hormone (Abdollahi et al., 2010b). Zinc

is essential for rigidity of plant cellular membranes which protect the internal orientation of

macromolecules and increased the process of ion transport system in plant. Through foliar

spray zinc interacted with plant cell membrane phospholipids and sulphydryl groups which

played important role in maintenance of cellular structure (Hafeez et al., 2013). Kazemi

(2015) also indicated that ZnSO4 increased the yield of strawberry and also improved the

physical appearance of fruits. In Previous studies best results were obtained with higher dose

of ZnSO4. According to our findings the best results were obtained with medium dose of

ZnSO4 it could be due to climatic, soil and varietal response but the mechanism to improve

the yield and quality was confirmed.

Maximum amount of TSS (8.1 ºBrix) was found with 100 mg L-1

ZnSO4.

Quantitatively acidity was found maximum in control treatment as compared with ZnSO4

treatments but statistically no difference between different treatments means. But increasing

trend regarding TSS in treated plants confirmed the findings of Abedy (2001) who reported

that zinc has functional role in increasing photosynthetic activity and related enzymes,

convert starch into sugar which resulted in increasing sugar and decreasing acidity.

Maximum TSS: Acid ratio was also observed with 100 mg L-1

ZnSO4 as compared with other

treatments. Various researches have examined changes in enzymes during fruit development

62

under field conditions. Sucrose a major carbohydrate in many plants played important role in

metabolic process. During ripening enzymes including sucrose synthase and sucrose

invertase catalyze the conversion of sucrose to fructose and glucose in different fruits

(Archbold and Nosarszewski, 2004; Koch, 2004). As general foliar application of zinc

increased the reducing sugar concentration; it could be due to increasing sorbitol

dehydrogenase activity, sucrose synthase and acid invertase activity at the early fruit stage

(Zhang et al., 2014). So, foliar applied Zn increased the activity of carbohydrate metabolism

due to that TSS and sugar contents increased. In present study, maximum vitamin C contents

(53.30 mg 100 g-1


ZnSO4 as compared with other treatments,

it is because of foliar spray of zinc reduced the degradation process of vitamin C contents.

Abdollahi et al. (2010a) also noted strong relation between vitamin C and ZnSO4 foliar

application. Previous findings confirm our results that ZnSO4 enhanced the vitamin C

contents.

Our results showed that maximum TPC (177.5 mg GAE 100 g-1

) and TA activities

(74.3 % DPPH) were observed in those strawberry fruits where plants sprayed with 100 mg

L-1

ZnSO4. Foliar applied zinc increase the phenylalanine ammonia lyase activity, due to that

enzymatic activity TPC and TA activities become increase in fruits (Roussos and Tassis,

2011). Our results suggested that higher catalase and peroxidase activities were noted in

control treatment as compared with ZnSO4 treatments. Higher catalase activity leading

towards senescence activity and higher peroxidase activity caused off flavor. High value of

SOD activity was noted in strawberry fruits where plants were sprayed with 150 mg L-1

ZnSO4 while less activity was observed in control treatment. In some previous studies it was

exhibited that reactive oxygen species (ROS) produced during biochemical changes in

strawberry such as hydrogen peroxide and hydroxyl radical which cause oxidative damage

(Jimenez et al. 2003). These (ROS) species caused early fruit ripening and led to senescence.

Activities of various antioxidant enzymes produced during different growth stages of

strawberry fruit and increase the defense response against these ROS species (Anand et al.,

2009). Zinc played major role in defense mechanism of plant by increasing the regulation

process of those genes which required for creating resistance against environmental stresses

in plants (Marschner, 1995; Cakmak, 2000). During whole strawberry season maximum

survival (%) was found with 100 mg L-1

ZnSO4. In control treatment some deficiency

63

symptoms were observed during growth stages including chlorotic leaves and stunted

growth. In literature, it was noted that due to zinc deficiency stunted growth, smaller and

thinner internodes were observed in field grown tomatoes (Passam et al., 2007). Low level of

zinc in soil due to complex soil structure and competition with other micronutrients

(Srivastava and Singh, 2003). Soil applied Zn showed less efficiency for increasing plant

growth due to roots cannot uptake maximum nutrients and other major reasons including low

Zn mobility in soil and immobile in the phloem (Swietlik, 2002). From results, it was

observed that foliar application showed better and rapid response thus, foliar spray of Zn is

needed to overcome the Zn deficiency, to improve plant growth, yield and qualitative

characteristics of strawberry fruit.

4.1.2 Conclusion

Zinc is a component of many enzymes improves vegetative growth of strawberry

plants during season. Medium dose of ZnSO4 (100 mg L-1

) was found best for enhancing the

vegetative growth during whole growing season but flower initiation was earlier with higher

dose of ZnSO4 (150 mg L-1

). Maximum marketable yield (369 g plant-1

) and fruit quality was

improved with 100 mg L-1

ZnSO4. However, higher dose of ZnSO4 (150 mg L-1

) was found

better for increasing the activities of antioxidant enzymes in strawberry fruit during growth

stages. Sometimes, higher concentration of ZnSO4 did not show better response due to metal

toxicity.

64

4.2 Study-2


Foliar application of salicylic acid (SA) to improve the vegetative growth,

yield and quality of strawberry cv. ‘Chandler’.

In this experiment salicylic acid (SA) as foliar spray was applied after 2nd

week of

runner transplantation when old leaves were dried and new sprouting occurred. When

strawberry plants were at 3-4 leaves stage 1st foliar application was applied and 2

nd was

applied at fruit setting stage. Treated strawberry plants were compared with control plants.

Canopy growth, yield and fruit quality was observed during growing season.

4.2.1 Results



)


) were observed in strawberry plants those sprayed

with 9 mM SA followed by treatments including 6 mM and 3 mM where numbers of leaves

were 12.75 and 9.75 plant-1

, respectively. While less leaves (6.25 plant-1

) were observed in

control plants. Salicylic acid treatments were highly responsive for increasing the number of

leaves during whole growing season as compared with control plants.


Statistical analysis regarding strawberry leaf area affected by foliar spray of SA

showed significant increased results. Higher value of leaf area (51.0 cm2) was observed in

plants sprayed with higher dose of SA (9 mM) followed by the plants sprayed with 6 mM

and 3 mM which showed leaf area values 43.75 and 30.75 cm2, respectively and these two

treatments were statistically same. Minimum value regarding leaf area (27.0 cm2) was

exhibited from control treatment. It was suggested that SA treatments showed their

superiority for enhancing leaf area of strawberry plants when sprayed during growth stages.

65


Minimum numbers of days (20.0) were required for flower initiation when strawberry

plants were sprayed with 9 mM SA followed by the plants sprayed with 6 mM (25.50) and 3

mM (24.0), respectively and these two treatments were statistically same. Maximum numbers

of days (41.75) for flower anthesis were required in control plants. It was exhibited that

effect of foliar application of SA to produce early flowering was more significant.


)

Statistical results regarding crown growth of strawberry plants affected by foliar

application of SA showed significant increased trend. Crown growth was noted at the end of

strawberry season and maximum numbers of crowns (7.50 plant-1

) were noted in strawberry

plants those were sprayed with 9 mM SA followed by treatments including 6 mM and 3 mM

which showed numbers of crowns 5.50 and 4.25 plant-1

, respectively while less number of

crowns (2.75 plant-1

) was observed in the control plants. It was concluded that numbers of

crowns increased in the strawberry plants due to foliar spray of SA as compared to control

treatment.


)

Maximum runners (6.75 plant-1

) were found in strawberry plants those were sprayed

with 9 mM SA followed by plants sprayed with 6 mM and 3 mM where numbers of runners

were 4.50 and 3.25 plant-1

, respectively. During strawberry season minimum numbers of

runners (2.0 plant-1

) were estimated in control plants. It was exhibited that spray of SA for

increasing the runner growth was highly significant during growing season.

66

Table 4.2.1.1 Effect of foliar application of SA on vegetative growth of strawberry cv.



(plant-1


-1) (plant

-1)

Control 6.25±0.48 d 27.00±0.71 c 41.75±1.25 a 2.75±0.25 d 2.00±0.00 d

3 mM SA 9.75±0.48 c 30.75±0.48 b 25.50±0.29 b 4.25±0.25 c 3.25±0.25 c

6 mM SA 12.75±0.63 b 43.75±0.85 b 24.00±0.41 b 5.50±0.29 b 4.50±0.29 b

9 mM SA 19.25±0.48 a 51.00±2.27 a 20.00±0.41 c 7.50±0.29 a 6.75±0.25 a

LSD (p=0.05) 1.25 3.7 2.16 0.75 0.79

C.V. % 6.51 8.23 4.97 9.43 12.12






-1)

As it was exhibited that marketable yield (75-80% mature, disease free, large size and

bright red) was increased throughout strawberry season and showed significant increased

trend. Salicylic acid treated plants showed more marketable fruit. Maximum marketable yield

(414.25 g plant

-1) was achieved from strawberry plants those were sprayed with 9 mM SA

followed by the plants sprayed with 6 mM and 3 mM which showed marketable yield 318.50

and 128.25 g plant

-1, respectively. Lower marketable yield (101.75 g

plant

-1) was found from

control plants.


-1)

Strawberry fruits those were affected due to biotic and abiotic factors were considered

as unmarketable yield. Minimum unmarketable yield (34.75 g plant

-1) was noticed from 9

mM SA followed by treatments including 6 mM and 3 mM which showed unmarketable

yield 41.0 and 59.75 g plant


plant

-1)

67

was resulted from control plants. Higher dose of SA was more effective to increase

marketable yield and to reduce unmarketable yield.


-1)

Statistical results regarding small size (< 10 g) yield of strawberries affected by SA

showed significant (p < 0.05) decreased trend. Yield of small sized strawberries

(85.0 g plant

-1) were maximum in control treatment compared to treated plants. Lower yield

(27.75 g plant

-1) was noted with 9 mM SA treatment followed by treatments 6 mM and 3 mM

those showed small size yield of 41.25 and 63.25 g plant

-1, respectively. Salicylic acid as

foliar spray was highly effective to reduce the production of small sized strawberries.

Table 4.2.1.2 Effect of foliar application of SA on yield of strawberry cv. ‘Chandler’

Mean ± S.E.


(g plant

-1) (g

plant

-1) (g

plant

-1)

Control 101.00±1.47 d 94.25±1.89 a 85.00±1.78 a

3 mM SA 128.25±1.38 c 59.75±2.06 b 63.25±0.85 b

6 mM SA 318.50±6.18 b 41.00±1.29 c 41.25±0.48 c

9 mM SA 414.25±7.60 a 34.75±0.48 d 27.75±1.03 d

LSD (p=0.05) 13.08 5.54 3.51

C.V. % 3.4 6.03 4.05



)

Salicylic acid improved strawberry firmness as compared with control treatment.

Firmness value (0.94 kg. cm-2

) was increased in those fruits sprayed with 9 mM SA followed

by the plants sprayed with 6 mM and 3 mM which showed firmness values 0.67 and 0.54 kg.

cm-2

, respectively while less value (0.32 kg. cm-2

) was found in control fruits. Strawberry

plants sprayed with different concentrations of SA produce fruits more firm (Figure 4.2.1.1).

68

4.2.1.3.2 TSS (ºBrix)

Total soluble solids increased in strawberries (8.47 ºBrix) sprayed with 6 mM SA

followed by 9 mM (7.77 ºBrix) and 3 mM (7.0 ºBrix), respectively while minimum TSS

values (6.3 ºBrix) were observed in control treatment. It was concluded that medium

concentration of SA 6 mM was found best for increasing the TSS in strawberry fruits (Figure

4.2.1.2).


Statistical results were non-significant. Quantitatively acid contents were more in

control treatment as compared to SA treatments but statistically no difference was noted

between treatments means (Figure 4.2.1.3).


Statistical data regarding strawberry fruit TSS: TA ratio affected by foliar spray of

SA showed significant increased results. Maximum TSS: TA ratio (11.76) was noted in

strawberries where plants sprayed with 6 mM SA followed by the treatments 9 mM (10.87)

and 3 mM (9.84), respectively. TSS: TA ratio is an important fruit quality parameter which

indicates fruit ripening stage. Minimum ratio was found in control (8.9) treatment. Medium

concentration of SA was found better for increasing TSS: TA ratio in strawberry fruits

(Figure 4.2.1.4).

4.2.1.3.5 Vitamin C (mg 100 g-1

)

Maximum value (56.72 mg 100 g-1

) was found in strawberry fruits sprayed with 9

mM SA followed by treatments 6 mM (48.76 mg 100 g-1

) and 3 mM (41.20 mg 100 g-1

),

respectively while lower vitamin C contents (36.86 mg 100 g-1

) were observed in control

treatment. Our results suggested that foliar spray of SA on strawberry plants was highly

significant for increasing the vitamin C contents of strawberry fruits during growing season

(Figure 4.2.1.5).

69


)

Plants treated with SA 9 mM, 6 mM and 3 mM produced the strawberries with

total phenolic contents of 191.50, 169.50 and 152.50 mg GAE 100 g-1

, respectively while

lower phenolic contents were observed in control (148.5 mg GAE 100 g-1

) fruits. Higher dose

of SA was best for increasing the total phenolic contents of strawberry. It can be concluded

that SA 9 mM foliar spray was found best to increase the total phenolic contents in

strawberry fruit as compared with other treatments (Figure 4.2.1.6).


Higher antioxidant activities (71.25% DPPH) were noted in strawberry fruits where

plants were sprayed with 9 mM SA followed by treatments 6 mM (55.75% DPPH) and 3 mM

(47.5% DPPH), respectively and also showed significant increased trend. Salicylic acid

treatments were highly responsive for increasing the antioxidant activities in strawberry fruits

during growing season while minimum activities were observed in control (40.75% DPPH)

treatment (Figure 4.2.1.7).

70

Figure 4.2.1.1 Effect of foliar application of SA on firmness (kg. cm-2

) of strawberry

fruit.

Figure 4.2.1.2 Effect of foliar application of SA on TSS (ºBrix) of strawberry fruit ±

S.E.

0

0.2

0.4

0.6

0.8

1

1.2


Fir

mn

ess

(kg

. cm

-2)

Treatments (SA)

5

5.5

6

6.5

7

7.5

8

8.5

9


TS

S (

°Bri

x)

Treatments (SA)

71

Figure 4.2.1.3 Effect of foliar application of SA on titratable acidity (%) of strawberry

fruit.

Figure 4.2.1.4 Effect of foliar application of SA on TSS: TA ratio of strawberry fruit.

0.68

0.7

0.72

0.74

0.76


TA

(%

)

Treatments (SA)

6

7

8

9

10

11

12


TS

S:

TA

ra

tio

Treatments (SA)

72

Figure 4.2.1.5 Effect of foliar application of SA on vitamin C (mg 100 g-1

) contents of

strawberry fruit.

Figure 4.2.1.6 Effect of foliar application of SA on total phenolic contents (mg GAE 100

g-1


25

30

35

40

45

50

55

60


Vit

am

in C

(m

g 1

00

g-1

)

Treatments (SA)

120

130

140

150

160

170

180

190

200


TP

C (

GA

E m

g 1

00 g

-1)

Treatments (SA)

73

Figure 4.2.1.7 Effect of foliar application of SA on total antioxidants (% DPPH) of

strawberry fruit.



protein)

Maximum activity (17.3 U mg−1

protein) was recorded in control treatment.

Minimum activity (15.6 U mg−1

protein) was found in strawberries sprayed with 9 mM SA

and 6 mM SA (15.8 U mg−1

protein) and these treatments were statistically same. Effect of

foliar treatment of SA for reducing catalase activity was highly responsive.


protein)

Salicylic acid treatments were highly effective to maximize the superoxide dismutase

activity in strawberry fruit. Maximum SOD activity (28.4 U mg−1

protein) was noted in

strawberries where plants were sprayed with 9 mM SA followed by 6 mM (26.3 U mg−1


protein), respectively while lower activity (20.0 U mg−1

protein) was estimated in control treatment.

0

10

20

30

40

50

60

70

80


TA

(%

DP

PH

)

Treatments (SA)

74


protein)

Less activity (2.35 U mg−1

protein) was noted in strawberry fruits where plants were

sprayed with 9 mM SA followed by 6 mM (2.46 U mg−1


protein), respectively while maximum peroxidase activity was noted in control (3.95 U mg−1

protein) treatment. Statistically significant decreased trend was noted regarding foliar spray

of SA on peroxidase activity of strawberry fruit.

Table 4.2.1.3 Effect of foliar application of SA on enzymatic activities of strawberry cv.





protein)

Control 17.3±0.28 a 20.0±0.28 d 3.95±0.05 a

3 mM SA 16.8±0.02 b 22.2±0.30 c 2.54±0.01 b

6 mM SA 15.8±0.01 c 26.3±0.31 b 2.46±0.02 c

9 mM SA 15.6±0.02 c 28.4±0.34 a 2.35±0.02 d

LSD (p=0.05) 0.45 0.63 0.09

C.V. % 16.89 6.3 7.03


Maximum survival (97.25%) was observed in the strawberry plants those were

sprayed with SA (9 mM) followed by the plants sprayed with 6 mM (90.75%) and 3 mM

(81.25%), respectively as compared with control (62.0%) plants. Our results suggested that

foliar application of SA was found better for increasing the maximum survival of strawberry

plants during season.

75

Figure 4.2.1.8 Effect of foliar application of SA on survival (%) of strawberry plants.

40

50

60

70

80

90

100


Su

rviv

al

(%)

Treatments (SA)

76

4.2.1 Discussion

Salicylic acid naturally occurs in plant body during developmental stages and acted as

signaling molecule and provides the resistance against oxidative damage. It performs various

functions including plant growth, ion uptake and transport, reduced transpiration rate and leaf

abscission (Ashraf et al., 2010). Foliar applied SA increased the endogenous level of SA

which activated pathogenesis related genes at the site of pathogen attack by creating

pathogenic resistance in different plants (Van Loon et al., 2006).

In current study plant growth was increased with SA spray. Salicylic acid spray of 9

mM was highly effective for increasing the vegetative growth. Maximum leaves growth

(19.25 plant-1

) and leaf area (51 cm2) was noted with higher dose of SA 9 mM. In some

previous studies it was proved that foliar spray of SA improved the growth and productivity

of strawberry plants. In this regard, Metwally et al. (2013) found that foliar treatment of SA

(1.0 and 2.0 mM) with different number of applications (once, twice and thrice) enhanced the

vegetative growth of strawberry cv. Sweet Charlie. Positive effect of SA for improving the

vegetative growth could be due to it increased the endogenous level of phytohormones

specially the growth promoters including auxins, gibberellins and cytokinins which played

important role for the enhancement of vegetative growth (Mady, 2014). Our findings

regarding flower anthesis showed that minimum number of days (20) were required for

flower anthesis when strawberry plants were sprayed with 9 mM SA as compared with

others. Our results regarding flower anthesis affected by foliar application of SA similar with

previous findings, who stated that SA acted as chelating agent and initiate the early flowering

(Oata, 1975; Pieterse and Muller, 1977). Our results suggest that crown and runner growth of

strawberry plants was also increased with SA. Higher amount of crowns (7.50 plant-1

) and

runners (6.75 plant-1

) increased with 9 mM SA foliar application. Overall, higher

concentration of SA 9 mM was found better for increasing the vegetative growth during

growing season. Our results regarding foliar application of SA enhanced vegetative growth

are in aid with previous studies where foliar applied SA 5.0 mM had positive and significant

effects on the vegetative parameters of strawberry cv. „Festival‟ (Youssef et al., 2017). It is

because of SA regulates the internal mechanism of plant such as plant growth, nutrient

uptake and transport system, plant water relations, membrane permeability, stomatal

77

conductance, photosynthesis and specially enhanced hormonal metabolism which promoted

cell division and enlargement (Hayat et al., 2010). So, due to increasing internal metabolic

process of plant canopy growth was increased.

Maximum marketable yield (414.25 g plant-1

) was exhibited from strawberry plants

which were sprayed with 9 mM SA. These results similar with previous study where foliar

spray of 5 mM SA improved the marketable yield of strawberry cv. „Festival‟ as compared to

water sprayed plants (Youssef et al., 2017). In some other studies it was also noted that foliar

treatment of SA at highest concentration resulted in higher early and total marketable yield of

strawberry. Maximum yield could be due to increase in vegetative growth which induced

more flowers and hence more fruits (Metwally et al., 2013; Kalaki et al., 2014). Our results

suggest that unmarketable yield (34.75 g plant-1

) was reduced with higher application of SA

as compared with other treatments. It might be due to SA activated defense mechanism of

plants against pathogen attack by creating systemic acquired resistance in whole plant body

for further spreading of disease (Tsuda et al., 2008). Small size yield was maximum (85.0 g

plant-1

) in control plants as compared to SA treated plants which effectively reduced the

small size yield during season.

Fruit firmness was improved in those strawberry fruits where plants were treated with

9 mM SA. Foliar application of SA produced more firm fruits as compared to control plants

which produced less firm fruits. It is because of during ripening, fruit softening occurs which

increased the cell wall degradation process by increasing enzymatic activity of

polygalactosidases and pectin methylesterases which leading towards senescence process

(Srivastava and Dwivedi, 2000). In current study, foliar applied 9 mM SA was found better

for improving the strawberry firmness. Our findings are in accordance with previous results

where SA decreased the metabolic activity of cell degrading enzymes and retained the

firmness of banana fruit (Srivastava and Dwivedi, 2000). In present study maximum total

soluble solids (8.47 °Brix) were increased with 6 mM SA as compared with higher or lower

concentrations of SA; it is because of higher concentration may have increased enzymatic

activity due to which some quality attributes showed declining trend. Increment in TSS

contents could be due to addition of sucrose in fruit during ripening process which increased

the activity of sucrose phosphate synthase and due to that enzymatic activity TSS contents

78

increased during ripening (Asghari and Aghdam, 2010). Salicylic acid acted as ethylene

inhibitor and reduces the maximum increment in activity of sucrose phosphate synthase

during ripening of banana and delayed the senescence process (Srivastava and Dwivedi,

2000; Hubbard et al., 1991; Asghari and Aghdam, 2010). Higher TSS: TA ratio (11.76) was

estimated with 6 mM SA while less ratio was found in control. TSS: TA ratio was maximum

in SA treated strawberries could be due to maximum TSS contents and lower acid contents

while in control fruits the ratio was minimum because of more acid and less TSS contents.

Maximum vitamin C contents were observed with higher application of SA 9 mM as

compared with other treatments. Salicylic acid application reduced the degradation of

vitamin C contents of strawberry fruit during ripening by delaying the senescence process

and improved fruit quality (Lolaei et al., 2012).

According to our results maximum TPC (191.50 mg GAE 100 g-1

) and TA activities

(71.25% DPPH) were noted in those strawberry fruits where plants sprayed with 9 mM SA.

Phenolic contents have capability for scavenging reactive oxygen species. It is because of

their contribution to qualitative characteristics of fruits, such as improving fruit color, texture

and reduction in bitterness (Hassanpour et al., 2011). Previous literature showed that SA

acted as potential molecule for activating the organic componds (phenylpropanoid-flavonoid)

synthesis in cherry fruit and enhanced the total phenolic contents (Dokhanieh et al., 2013).

Previous studies exhibited that when cherry fruit was treated with 1 mM SA total antioxidant

activities were found maximum (Hassanpour et al., 2011; Dokhanieh et al., 2013). Our

results demonstrated that enzymatic activities were highly influenced with foliar spray of SA.

Maximum catalase activity was estimated in control while minimum activity was found with

SA (9 mM). Superoxide dismutase activity was found higher with SA 9 mM as compared

with others. Maximum peroxidase activity was estimated in control fruits while SA

treatments were highly effective for reducing peroxidase activity in strawberry fruits during

growing season. In some previous findings it was proved that ROS produce during ripening

stages in the strawberry fruit such as superoxide radical which cause oxidative stress

(Jimenez et al. 2003). Enzymatic activities (CAT, POD and SOD) produce during different

growth stages and increase the defense responses (Anand et al., 2009). Due to decline in

enzymatic activities ROS produce during ripening. Numerous researchers have exhibited that

SA have inhibitory effects for reducing ROS species by enhancing the antioxidant power in

79

plants (Knorzer et al., 1999; Imran et al., 2007). Foliar treatment of SA at non-toxic level

increased the activities of those genes which have capability for producing proteins such as

chitinase which enhanced the defense mechanism of plants (Meena et al., 2001; Hussain et

al., 2015). Our results concluded that foliar treatment of 9 mM SA was highly effective for

increasing the maximum survival (97.25%) of strawberry plants during whole growing

season as compared to control plants.

4.2.1 Conclusion

Salicylic acid as signaling molecule enhanced the vegetative growth of strawberry

plants during whole growing season. Overall, it was suggested that foliar spray of 9 mM SA

was effective strategy for increasing the canopy growth, marketable yield, quality and

survival mechanism of strawberry plants during season.

80


Foliar application of gibberellic acid (GA3) to improve the vegetative

growth, yield and quality of strawberry cv. ‘Chandler’.

In this experiment foliar spray of GA3 with different concentrations was applied after

2nd

week of runner transplantation when old leaves were dried and new sprouting was

occurred. First foliar spray was applied at 3-4 leaves stage and 2nd

was applied at fruit setting

stage. Following parameters were measured:

4.2.2 Results



)


) were noted in strawberry plants which were sprayed

with 150 mg L-1

GA3 followed by other treatments including 100 and 50 mg L-1

GA3 which

showed numbers of leaves 20.50 and 11.50 plant-1

, respectively. Less leaves (7.0 plant-1

)

were noted in control plants. According to results 150 mg L-1

GA3 showed the superiority for

increasing the number of leaves during season.


Increasing trend in leaf area was observed with foliar spray of GA3. Higher value of

leaf area (65.75 cm2) was observed in plants those were treated with 150 mg L

-1 GA3

followed by treatments including 100 and 50 mg L

-1 GA3 which showed leaf area values 58.0

and 21.75 cm2, respectively. Leaf area was less in control treatment. It was exhibited from

results that foliar spray of 150 mg L-1

GA3 was highly significant for maximizing the leaf

area.

81


Minimum numbers of days (20.50) were required to open 1st flower when strawberry

plants were sprayed with 150 mg L-1

GA3 followed by the plants sprayed with 100 mg L-1

(23.25) and 50 mg L-1

(27.0), respectively. Maximum numbers of days (41.75) to open

flowers were observed in control plants. It was concluded that GA3 reduced the number of

days to initiate the flowers but 150 mg L-1

GA3 was highly responsive to initiate the flowers

earlier.


)


) were noted in strawberry plants those were sprayed

with 150 mg L-1

GA3 followed by treatments including 100 and 50 mg L-1

GA3 where the

numbers of crowns were 6.75 and 4.0 plant-1

, respectively. Higher dose of GA3 was found

more effective for increasing the number of crowns as compared with other treatments.

Minimum crowns (2.75 plant-1

) were noted in control plants. It was clear from results that

foliar spray of GA3 increased the crown growth during season.


)


) were found in plants those were treated with 150 mg

L-1

GA3 followed by treatments including 100 and 50 mg L-1

GA3 where the numbers of

runners were 8.50 and 3.75 plant-1

, respectively. During strawberry season minimum

numbers of runners (2.25 plant-1

) were noted in control plants. It was clear that higher dose of

GA3 played significant role for increasing the number of runners per plant.

82

Table 4.2.2.1 Effect of foliar application of GA3 on vegetative growth of strawberry cv.



(plant-1


-1) (plant

-1)

Control 7.00±0.41 d 17.50±1.04 d 41.75±1.25 a 2.75±0.25 d 2.25±0.25 d

50 mg L-1

GA3 11.50±0.65 c 21.75±0.48 c 27.00±1.08 b 4.00±0.00 c 3.75±0.48 c

100 mg L-1

GA3 20.50±0.29 b 58.00±1.22 b 23.25±0.85 c 6.75±0.00 b 8.50±0.58 b

150 mg L-1

GA3 23.50±0.29 a 65.75±1.11 a 20.50±0.29 d 8.00±0.25 a 11.00±0.29 a

LSD (p=0.05) 1.16 2.99 3.38 0.46 1.48

C.V. % 5.24 5.76 7.87 5.37 14.56






-1)

Statistical analysis regarding strawberry marketable yield (75-80% mature, disease

free, large size and bright red) affected by foliar spray of GA3 demonstrated significant

(p < 0.05) results. Marketable yield was increased with foliar spray of GA3 during whole

growing season. Maximum marketable yield (381.50 g

plant-1

) was found from the

strawberry plants those were treated with 100 mg L-1

GA3 followed by treatments 150 mg L-1

and 50 mg L-1

which showed marketable yield 288.75 and 124.0 g plant

-1, respectively. It was

noted that marketable yield was found maximum with foliar application of GA3 while higher

concentration was not much effective as compared with optimal concentration. Minimum

marketable yield (101.0 g plant

-1) was found with control treatment.


-1)

Significant differences were noted regarding unmarketable yield (affected by biotic

and abiotic factors) of strawberry. Minimum unmarketable yield (36.0 g plant

-1) was noted

with 100 mg L-1


(47.0 g plant

-1) and 50 mg L

-1 GA3

83

(51.0 g plant

-1), respectively. Maximum unmarketable yield (94.25 g

plant

-1) was found with

control treatment. It was noted that foliar application of GA3 was highly effective for

increasing the marketable yield and to reduce the unmarketable yield during season.


-1)

Maximum yield of small sized strawberries (85.0 g plant

-1) was estimated in control

treatment as well as 150 mg L-1

GA3 (82 g

plant

-1) and these treatments were statistically

same. Minimum small size yield (33.50 g plant

-1) was exhibited with 100 mg L

-1 GA3.

Gibbrellic acid as foliar spray was found highly effective to reduce the production of small

sized strawberries as compared to control plants. Optimum dose of 100 mg L-1

GA3 was

found more responsive when compared with lower and higher doses.

Table 4.2.2.2 Effect of foliar application of GA3 on yield of strawberry cv. ‘Chandler’

Mean ± S.E.


(g plant

-1) (g

plant

-1) (g

plant

-1)

Control 101.00±1.47 d 94.25±1.89 a 85.00±1.78 a

50 mg L-1

GA3 124.00±1.29 c 51.00±0.41 b 52.75±0.85 b

100 mg L-1

GA3 381.50±3.10 a 36.00±0.71 d 33.50±0.87 c

150 mg L-1

GA3 288.75±3.73 b 47.00±0.71 c 82.00±0.82 a

LSD (p=0.05) 7.94 3.04 3.95

C.V. % 2.22 3.33 3.91



)

Higher firmness value (0.77 kg. cm-2

) was observed in those fruits where the plants

were treated with 100 mg L-1

GA3 followed by treatments 150 and 50 mg L-1

GA3 where fruit

firmness values were 0.57 and 0.49 kg. cm-2

, respectively. During strawberry ripening foliar

spray of GA3 produce firm fruits as compared to control treatment which showed firmness

(0.32 kg. cm-2

) which was less than others. Trend regarding best dose of GA3 for improving

the firmness was similar as found in previous parameters (Figure 4.2.2.1).

84

4.2.2.3.2 TSS (ºBrix)

Total soluble solids increased in those strawberry fruits where plants were sprayed

with different doses of GA3. Maximum amount of TSS (7.85 ºBrix) were observed in

strawberries where plants sprayed with 100 mg L-1


(6.65 ºBrix) and 50 mg L-1

(6.63 ºBrix), respectively and these were statistically same.

Minimum TSS values (6.30 ºBrix) were noted in control treatment (Figure 4.2.2.2).


Non-significant trend was recorded regarding acid contents of strawberry fruit.

Quantitatively acid contents were maximum in control as compared to GA3 treatments. All

treatments were statistically same (Figure 4.2.2.3).


Higher ratio (10.73) was noted with 100 mg L-1

GA3 followed by treatments 150 and

50 mg L-1

where TSS: TA ratios were 9.30 and 9.15, respectively. Minimum ratio (8.90) was

observed in control treatment. Foliar spray of GA3 was more effective for maximizing the

TSS: TA ratio in strawberry fruits (Figure 4.2.2.4).

85

4.2.2.3.5 Vitamin C (mg 100 g-1

)

Maximum (52.23 mg 100 g-1

) contents were observed in strawberry fruits sprayed

with 100 mg L-1


(46.44 mg 100 g-1

) and 50 mg L-1

(39.80 mg 100 g-1

), respectively. While minimum (36.86 mg 100 g-1

) contents were observed

in control treatment. Results showed that medium dose of GA3 showed its superiority over

lower and higher doses for increasing the vitamin C contents of strawberry (Figure 4.2.2.5).


)

Strawberry plants treated with GA3 100, 150 and 50 mg L-1

produced the strawberries

with total phenolic contents of 181.50, 164.50 and 141.50 mg GAE 100 g-1

, respectively.

Lower contents (138.50 mg GAE 100 g-1

) were observed in control treatment as compared to

other treated fruits. Again medium dose of GA3 (100 mg L-1

) showed its superiority over

lower and higher doses (Figure 4.2.2.6).


Higher antioxidant activities (64.75% DPPH) were found in strawberry fruits where

plants were sprayed with 100 mg L-1

GA3 followed by other treatments 150 mg L-1

(47.50%

DPPH) and 50 mg L-1

(44.75% DPPH), respectively. Gibberellic acid treatments were highly

effective for increasing the antioxidant activities in strawberry fruits while minimum

activities were observed in control (35.75% DPPH) treatment (Figure 4.2.2.7).

86

Figure 4.2.2.1 Effect of foliar application of GA3 on firmness (kg. cm-2

) of strawberry

fruit.

Figure 4.2.2.2 Effect of foliar application of GA3 on TSS (ºBrix) contents of strawberry

fruit.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Control 50 100 150

Fir

mn

ess

(kg

. cm

-2)

Treatments (GA3 mg L-1)

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

Control 50 100 150

TS

S (

°Bri

x)


87

Figure 4.2.2.3 Effect of foliar application of GA3 on titratable acidity (%) of

strawberry fruit.

Figure 4.2.2.4 Effect of foliar application of GA3 on TSS: TA ratio of strawberry fruit.

0.65

0.66

0.67

0.68

0.69

0.7

0.71

0.72

0.73

0.74

0.75

Control 50 100 150

TA

(%

)


6

7

8

9

10

11

12

Control 50 100 150

TS

S:

TA

rati

o


88

Figure 4.2.2.5 Effect of foliar application of GA3 on vitamin C (mg 100 g-1

) contents of

strawberry fruit.

Figure 4.2.2.6 Effect of foliar application of GA3 on total phenolic contents (mg GAE

100 g-1


25

30

35

40

45

50

55

Control 50 100 150

Vit

am

in C

(m

g 1

00

g-1

)


100

110

120

130

140

150

160

170

180

190

Control 50 100 150

TP

C (

mg G

AE

100 g

-1)


89

Figure 4.2.2.7 Effect of foliar application of GA3 on total antioxidants (% DPPH) of

strawberry fruit.



protein)

Statistically non-significant trend was achieved from catalase activity in strawberry

fruit sprayed with foliar application of GA3. Statistically there was no variation among

different GA3 treatments means and control treatment but quantitatively maximum activity

was found in control.


protein)

Gibberellic acid treatments were highly effective to maximize superoxide dismutase

activity in the strawberry fruit. Maximum SOD activity (34.2 U mg−1

protein) was found in

strawberry fruits where plants were treated with 100 mg L-1

GA3 followed by 150 mg L-1

(32.0 U mg−1


(31.1 U mg−1

protein), respectively while lower activity

(30.0 U mg−1

protein) was noted in control treatment.

0

10

20

30

40

50

60

70

Control 50 100 150

TA

(%

DP

PH

)


90


protein)


protein) was noted in strawberries sprayed

with 100 mg L-1

and 150 mg L-1

GA3 (0.54 U mg−1

protein) and these treatments were

statistically same. While maximum peroxidase activity (2.72 U mg−1

protein) was estimated

from control fruits and those fruits which were sprayed with 50 mg L-1

GA3 showed

peroxidase activity (1.75 U mg−1

protein). It was noted that spray treatment of GA3 on

decreasing peroxidase activity of strawberry fruit was highly effective.

Table 4.2.2.3 Effect of foliar application of GA3 on enzymatic activities of strawberry

cv. ‘Chandler’ Mean ± S.E.




protein)

Control 17.8±0.21 a 30.0±0.21 d 2.72±0.10 a

50 mg L-1

GA3 16.8±0.20 a 31.1±0.25 c 1.75±0.02 b

100 mg L-1

GA3 16.8±0.20 a 34.2±0.28 a 0.45±0.01 c

150 mg L-1

GA3 16.3±0.18 a 32.0±0.26 b 0.54±0.02 c

LSD (p=0.05) 0.23 0.45 0.15

C.V. % 2.47 7.28 8.85


Maximum survival (95.0%) was obtained in strawberry plants sprayed with 100 mg

L-1


(80.75%) and 50 mg L-1

(71.5%), respectively

while minimum survival (%) was observed with control (62.0%) treatment. Strawberry plants

survival increased with GA3 applications as compared with control plants. Strawberry plants

survival also showed the superiority of medium dose of GA3 over higher and lower doses

(Figure 4.2.2.8).

91

Figure 4.2.2.8 Effect of foliar application of GA3 on survival (%) of strawberry plants.

50

55

60

65

70

75

80

85

90

95

100

Control 50 100 150

Su

rviv

al

(%)


92

4.2.2 Discussion

Foliar spray of growth regulators enhance the fruit production and improve the

qualitative characteristics of fruits. They have potential for increasing the flowering density

and fruit setting percentage (Dutta and Banik, 2007). Gibberellic acid a type of

phytohormone belongs to family tetracyclic diterpenoids acids it plays prominent role in

biological functions of plant growth including leaf expansion, flower development, runner

production, cell division and elongation in different plants (Saddon and Al-Zubaidy, 2017).

In strawberry, gibberellic acid induced early flowering, early fruit development, increased

number of flowering truss per crown. It also increased the number of runners in all

strawberry varieties during long days (Sharma and Sing, 2009).

In current study different concentrations of GA3 were foliar applied on strawberry

plants. Vegetative growth significantly increased in all GA3 treatments but maximum leaves

(23.50 plant-1

) and leaf area (65.75 cm2) was noted with 150 mg L

-1 GA3. It could be due to

GA3 which promotes rapid cell division process in strawberry plants (Turner, 1963). The

response of GA3 for initiation of early flowering was highly significant. Minimum numbers

of days (20.25) were required for flower anthesis when plants sprayed with 150 mg L-1

GA3.

Our results regarding GA3 effects on flower anthesis were similar with previous findings who

reported that GA3 reduced the days of flower emergence, accelerated the level of internal

growth hormones due to that it enhanced the flower buds in strawberry cultivar „Seascape‟ in

all growing conditions (Paroussi et al., 2002). In current results increasing trend was

estimated regarding vegetative growth and maximum crowns (8.0 plant-1

) and runners (11.0

plant-1


GA3. Our findings are in accordance with previous

results where foliar applied GA3 increased the number of runners and crown growth in

strawberry cultivar „Gaviota‟ (Asadi et al., 2013). The mechanism through which GA3

increased the vegetative growth it involved rapid increase in mitosis in the region of

meristem after foliar spray of GA3 which increased the cell division activity and also

stimulated the cell elongation in plant (Taiz and Zeiger, 2002b). Gibberellic acid stimulated

growth due to increased activity of enzyme (xyloglucan endotransglycosylase) which

involved in cell wall extension. When GA3 is applied on plant surface it regulates the activity

93

of XET during growth and development (Taiz and Zeiger, 2002b). Overall, the vegetative

growth increased with higher dose of GA3 (150 mg L-1

) as compared with other treatments.

According to present findings it was shown that marketable yield significantly

increased in all GA3 treatments throughout strawberry season. Maximum marketable yield

(381.50 g plant-1

) was obtained with 100 mg L-1

GA3 as compared to other treatments.

Unmarketable yield was lowered in all GA3 treatments. These findings are supported by the

results of Jamal Uddin et al. (2012) who stated that 75 ppm of GA3 enhanced the fruit

production but also improved the weight of strawberries. Our results suggested that

maximum yield of small sized strawberries (85.0 g plant-1

) was estimated in control as well

as 150 mg L-1

GA3 (82 g plant-1

) while minimum small size yield (33.50 g plant-1

) was noted

with 100 mg L-1

GA3. It was observed from results that the response of higher and lower

concentrations of GA3 was less effective to reduce small size yield during season. Our

findings are in agreement with previous results where higher dose of 200 mg L-1

GA3 reduced

the marketable yield of strawberry and increased the production of maximum aborted

flowers, small size and malformed fruits (Paroussi et al., 2002). It is also stated that optimum

concentration of GA3 produced the normal fruit of tomato but as its concentration increased,

it resulted in production of smaller fruits per plant (Gelmesa et al., 2013).

Gibberellic acid treatments were highly effective for improving the quality of

strawberry. Higher firmness values were achieved in those strawberry fruits treated with 100

mg L-1

GA3. Firmness is important quality parameter because firmer fruits are considered

less sensitive to mechanical injury so its shelf life will be more as compared to softer fruits

(Taylor and Knight, 1986). Gibberellic acid application regulates the activities of cell wall

hydraulic enzymes so due to that fruit firmness increased. In literature similar findings were

observed when foliar application of 100 ppm GA3 was applied on two plum cultivars

„Obilnaja‟ and „Black Star‟ which showed higher flesh firmness as compared to control fruits

(Harman and Sen, 2016). According to our results maximum TSS values were observed in

fruits which were sprayed with 100 mg L-1

GA3. Total soluble solids increased in all GA3

treatments; it could be due to rapidly change of organic acid contents into sugars during fruit

ripening. Our results regarding increasing trend in TSS contents were similar with the

previous results of Rajput and Singh (1977) who reported that the increment in TSS could be

94

due to production of maximum auxin hormone in plants during development process which

further increased the level of secondary metabolites in plants and their rapid translocation

from different parts of plants to the fruits. Thus, those plants which treated with growth

regulators have potential for producing secondary metabolites which further increased the

TSS contents in fruits. In present study non-significant trend was recorded regarding acid

contents of strawberry fruit. In previous study similar results were found when foliar spray of

GA3 (25-75 ppm) was applied on guava fruit which showed decrease in acid contents, it was

because of GA3 foliar treatment caused the early fruit ripening due to that fruit respiration

process increased and acid contents rapidly converted into sugars (Singh et al., 2017). TSS:

Acid ratio is an important quality parameter of strawberry fruit which determined the

ripening stage and shelf life. This parameter is also beneficial for the growers that they can

get good quality fruit. Maximum ratio was noted with 100 mg L-1

GA3 as compared with

other treatments.

Higher vitamin C contents shows higher nutritive value of strawberry fruits.


) were noted with 100 mg L-1

of GA3. Higher

and lower application of GA3 was less effective for increasing the vitamin C contents during

season. Our results confirmed the previous findings where foliar treatment of GA3 (10, 20

and 30 ppm) improved the vitamin C contents of mandarin. It could be due to GA3 increased

the activity of L-ascorbic acid while in control fruits decrease in vitamin C could be due to

loss of this activity where it converted into 2-3-dioxy-L-gluconic acid (Rokaya et al., 2016).

From results it was clear that TPC and TA were increased with foliar treatment of GA3

during season. Maximum TPC (181.50 mg GAE 100 g-1

) and TA (64.75% DPPH) were

estimated with 100 mg L-1

GA3 treatment. It was noted that higher and lower doses were less

effective for increasing the TPC and TA during season. Similar results were also observed

from previous studies where foliar application of 100 ppm of GA3 on two plum cultivars

„Obilnaja‟ and „Black Star‟ increased TPC contents and TA activities. It is because of GA3

promoted biosynthesis of secondary metabolites in the fruit with higher antioxidant activity

(Harman and Sen, 2016). According to our results higher catalase and peroxidase enzymatic

activities were observed in control fruits while GA3 treatments were highly effective in

reducing these activities during season. Minimum superoxide dismutase activity was noted

with control while those fruits sprayed with 100 mg L-1

GA3 showed increment in superoxide

95

dismutase activity. In literature it was exhibited that maximum catalase activity found during

strawberry fruit ripening. It increased in white and red color fruit but higher activity of

catalase led to senescence (Jimenez et al. 2003). Superoxide dismutase activity increased

during maturation stages up to highest levels in white fruits. Decreased during turning stage

and increased during ripening stage of strawberry. Peroxidase activity increased in white

color fruits and decreased in red color strawberry fruits but during ripening higher peroxidase

activity caused off flavor of strawberry (Lopez et al., 2010). Not enough evidences are

available in the literature regarding the effects of GA3 on enzymatic activities of fruits but

GA3 has important role in biosynthesis of secondary metabolites which regulate the

enzymatic activities in the fruit. In present study maximum survival (95%) was observed

with medium dose of GA3 100 mg L-1

it might be due to climatic, soil and varietal response.

4.2.2 Conclusion

Gibberellic acid as growth promoter played important role in increasing the

vegetative growth throughout strawberry season. Higher dose of GA3 (150 mg L-1

) expressed

the superiority for enhancing the vegetative growth while marketable yield and fruit quality

was not improved with this concentration. Higher dose of GA3 caused maximum increase in

cell division activity due to that vegetative growth increased and most of the plant

photosynthetic products used for increasing leaves, crowns and runner growth and less

available for producing good quality fruit. So, present study proved that medium dose of GA3

(100 mg L-1

) increased the marketable yield and also improved the quality of strawberry.

96

4.3 Study-3

(Confirmatory Trial)

4.3 Comparison of calcium chloride (CaCl2), zinc sulfate (ZnSO4), salicylic

acid (SA) and gibberellic acid (GA3) to improve the vegetative growth,

yield and quality of strawberry cv. ‘Chandler’

In this study previous year optimized treatments from each experiment were compared

with each other to find out the best treatment which increase the canopy growth, marketable

yield and also improve the quality of strawberries. Same method of foliar spray was followed

as in previous experiments. Following parameters were measured:

4.3.1 Vegetative parameters (Table 4.3.1)


)

Number of leaves (21.25 plant-1

) increased with 100 mg L-1

GA3 followed by

treatments including 9 mM SA, 7 mM CaCl2 and 100 mg L-1

ZnSO4 which showed numbers

of leaves 18.25, 16.50 and 15.50 plant-1

, respectively. Strawberry plants those were sprayed

with salts CaCl2 and ZnSO4; their results were statistically same. Minimum leaves (10.50

plant-1

) were observed in control plants. It was concluded that numbers of leaves increased

with foliar spray of GA3 as compared to other treatments.

4.3.1.2 Leaf area (cm2)

Leaf area was increased with foliar application of salts and growth regulators.

Maximum leaf area (61.75 cm2) was increased with 100 mg L

-1 GA3 followed by treatments

including 9 mM SA, 7 mM CaCl2 and 100 mg L-1

ZnSO4 which showed leaf area values

49.25, 46.25 and 42.50 cm2, respectively. According to results SA and CaCl2 treatments were

statistically same. Leaf area was not increased in control plants. It was noted from results that

foliar spray of GA3 was more effective for increasing the leaf area as compared to other foliar

treatments.

97

4.3.1.3 Flower anthesis (days after foliar application)

Minimum number of days (15.50) was required for flower anthesis when strawberry

plants were treated with 100 mg L-1

GA3 followed by 9 mM SA (17.75) and these treatments

were statistically same. Strawberry plants sprayed with salts including 100 mg L-1

ZnSO4 and

7 mM CaCl2 also showed minimum numbers of days 30.50 and 35.0, respectively. Maximum

days (47.50) for flower anthesis were observed with control plants. It was concluded from

results that foliar spray of salts and growth regulators is highly effective strategy to initiate

early flowering and reduced the maximum number of days to open flowers.


)



GA3 followed by

treatments including 9 mM SA, 7 mM CaCl2 and 100 mg L-1

ZnSO4 where numbers of

crowns were 6.50, 6.25 and 6.0 plant-1

, respectively. The response of different foliar sprays

of salts and growth regulators was highly effective for increasing the crown growth while

minimum crowns (3.0 plant-1

) were observed in control plants.


)



GA3 followed by

treatments including 9 mM SA (5.50 plant-1

), 7 mM CaCl2 (5.0 plant-1

) and 100 mg L-1

ZnSO4 (4.50 plant-1

), respectively. During whole strawberry season minimum runners (2.75

plant-1

) were observed in control plants. It was noted that numbers of runners were

significantly increased with different foliar applications as compared with control plants.

98

Table 4.3.1 Effect of foliar application of salts and growth regulators on vegetative growth of


Treatments

No. of leaves Leaf area Flower anthesis No. of crowns No. of runners

(plant-1


-1) (plant

-1)

Control 10.50±0.29 d 25.50±0.65 d 47.50±1.04 a 3.00±0.00 d 2.75±0.25 d

7 mM CaCl2 16.50±0.29 c 46.25±1.75 b 35.00±1.78 b 6.25±0.25 bc 5.00±0.00 bc

100 mg L-1

ZnSO4 15.50±0.29 c 42.50±1.04 c 30.50±0.65 c 6.00±0.00 c 4.50±0.29 c

9 mM SA 18.25±0.48 b 49.25±1.55 b 17.75±0.48 d 6.50±0.29 b 5.50±0.29 b

100 mg L-1

GA3 21.25±0.48 a 61.75±0.85 a 15.50±0.29 d 8.00±0.00 a 11.00±0.41 a

LSD (p=0.05) 1.06 3.28 3.36 0.48 0.86

C.V. % 4.48 4.49 7.46 5.31 9.79

4.3.2 Yield parameters

Strawberry harvesting was started during end week of January and continued till

April. Harvested strawberries were separated into three important categories such as

marketable, unmarketable and small size (Table 4.3.2).


-1)

Statistical analysis regarding strawberry marketable yield affected by foliar sprays of

salts and growth regulators demonstrated significant increased results. Maximum (494.0 g

plant-1

) marketable yield was noted from those strawberry plants which were sprayed with 9

mM SA followed by the plants sprayed with 7 mM CaCl2, 100 mg L-1

GA3 and 100 mg L-1

ZnSO4 which showed marketable yield 408.75, 396.0 and 378.75 g plant

-1, respectively. It

was concluded that maximum increment in marketable yield was observed with 9 mM SA

while minimum (115.25 g plant

-1) marketable yield was noted from control plants during

season.


-1)

Minimum (31.75 g plant

-1) unmarketable yield was observed from those strawberry

plants which were sprayed with 9 mM SA followed by the plants sprayed with 7 mM CaCl2,

99

100 mg L-1

GA3 and 100 mg L-1

ZnSO4 which showed unmarketable yield 37.75, 42.25 and

52.25 g plant


plant

-1) was noted from

control plants. It was proved that previous year best treatments of salts and growth regulators

have capability for increasing the marketable yield and reduced the unmarketable yield.


-1)

Statistical results regarding small size yield of strawberry affected by different

concentrations of salts and growth regulators showed significant differences among

treatments. Maximum yield of small sized (80.0 g plant

-1) strawberries were observed in

control plants. Minimum small size yield (23.25 g plant

-1) was noted in those strawberry

plants which were sprayed with 9 mM SA followed by the plants sprayed with 7 mM CaCl2

(27.50 g plant

-1), 100 mg L

-1 GA3 (32.25 g

plant

-1) and 100 mg L

-1 ZnSO4 (32.75 g

plant

-1),

respectively. Small size yield was similar in GA3 and ZnSO4 treatments and these were

statistically at par with each other. The response of best doses of salts and growth regulators

for reducing small size yield of strawberry was highly effective during season.

Table 4.3.2 Effect of foliar application of salts and growth regulators on yield of



(g plant

-1) (g

plant

-1) (g

plant

-1)

Control 115.25±3.64 d 96.25±1.38 a 80.00±1.78 a

7 mM CaCl2 408.75±1.49 b 37.75±1.70 d 27.50±0.29 c

100 mg L-1

ZnSO4 378.75±4.13 c 52.25±1.31 b 32.75±1.80 b

9 mM SA 494.00±8.93 a 31.75±0.48 e 23.25±0.85 d

100 mg L-1

GA3 396.00±2.35 bc 42.25±1.11 c 32.25±0.85 b

LSD (p=0.05) 15.19 3.95 3.96

C.V. % 2.75 4.94 6.57

100

4.3.3 Fruit quality Parameters


)

Statistical analysis of strawberry fruit relating to firmness affected by different foliar

applications demonstrated significant (p < 0.05) increased results. Higher firmness value

(0.97 kg. cm-2

) was noted in those fruits where plants were sprayed with 7 mM CaCl2

followed by the plants sprayed with 9 mM SA, 100 mg L-1

ZnSO4 and 100 mg L-1

GA3

where firmness values were 0.83, 0.73 and 0.54 kg. cm-2

, respectively. Different

concentrations of salts and growth proved best for improving firmness as compared to

control plants which showed fruit firmness 0.35 kg. cm-2

which was less than others (Figure

4.3.1).


Statistically analyzed data demonstrated significant (p < 0.05) increased results. Total

soluble solids increased in those strawberry fruits where plants were sprayed with different

concentrations of salts and growth regulators. Maximum amount of total soluble solids (8.48

ºBrix) were noted in fruits where plants were sprayed with 9 mM SA followed by the plants

sprayed with 7 mM CaCl2 (7.98 ºBrix), 100 mg L-1

GA3 (7.85 ºBrix) and 100 mg L-1

ZnSO4

(6.85 ºBrix), respectively. Minimum TSS values (5.95 ºBrix) were observed in control

treatment (Figure 4.3.2).


Non-significant trend was recorded regarding the effect of different foliar sprays on

acid contents of strawberry fruit. Quantitatively acid contents were found higher in control

treatment but statistically there was no difference between different treatments means. All

treatments were statistically same (Figure 4.3.3).


Statistical data regarding strawberry fruit TSS: TA ratio showed significant (p < 0.05)

increased results. Maximum TSS: TA ratio (11.76) was noted in those strawberry fruits

where plants were sprayed with 9 mM SA followed by the plants sprayed with 7 mM CaCl2

(10.73), 100 mg L-1

GA3 (10.57) and 100 mg L-1

ZnSO4 (9.68), respectively. TSS: TA ratio

101

indicates the fruit ripening stage and directly effects on shelf life of fruit. Minimum ratio

(8.4) was observed in control treatment. It was proved that TSS: Acid ratio was found

maximum with best doses of salts and growth regulators as compared with control (Figure

4.3.4).

4.3.3.5 Vitamin C (mg 100 g-1

)


) were observed in the strawberry

fruits where plants were sprayed with 9 mM SA followed by the plants sprayed with 7 mM

CaCl2 (53.69 mg 100 g-1

), 100 mg L-1

GA3 (51.23 mg 100 g-1

) and 100 mg L-1

ZnSO4 (48.80

mg 100 g-1

), respectively. While less vitamin C contents (41.86 mg 100 g-1

) were observed in

control treatment. Results showed that increasing trend was observed regarding vitamin C

contents of strawberry fruit when sprayed with best doses of salts and growth regulators

(Figure 4.3.5).


)

Strawberry plants treated with 9 mM SA, 7 mM CaCl2, 100 mg L-1

GA3 and 100 mg

L-1

ZnSO4 showed total phenolic contents 191.50, 181.25, 176.0 and 164.50 mg GAE 100

g-1

, respectively. Lower (150.50 mg GAE 100 g-1

) phenolic contents were noted in control

treatment as compared to other treatments. Again best doses of salts and growth regulators

proved better for increasing the total phenolic contents of strawberry fruit while 9 mM SA

showed the superiority for increasing TPC as compared to control (Figure 4.3.6).


Statistical data regarding total antioxidant activities in strawberry fruit affected by

foliar spray of salts and growth regulators showed significant (p < 0.05) increased results.

Higher antioxidant activities (76.50% DPPH) were noted in the strawberry fruits where

plants were sprayed with 9 mM SA followed by the plants sprayed with 7 mM CaCl2

(63.50% DPPH), 100 mg L-1

GA3 (58.75% DPPH) and 100 mg L-1

ZnSO4 (51.75% DPPH),

respectively. Lower (40.75% DPPH) activities were observed in control fruits. It is proved

that foliar spray of salts and growth regulators on strawberry plants enhanced the antioxidant

activities in strawberry fruit (Figure 4.3.7).

102

Figure 4.3.1 Effect of foliar application of salts and growth regulators on firmness (kg.

cm-2


Figure 4.3.2 Effect of foliar application of salts and growth regulators on TSS (ºBrix)

of strawberry fruit.

T1 = Control, T2 = 7 mM CaCl2, T3 = 100 mg L-1

ZnSO4, T4 = 9 mM SA, T5 = 100 mg

L-1

GA3

0

0.2

0.4

0.6

0.8

1

1.2

T1 T2 T3 T4 T5

Fir

mn

ess

(kg

. cm

-2)

Treatments

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

T1 T2 T3 T4 T5

TS

S (

°Bri

x)

Treatments

103

Figure 4.3.3 Effect of foliar application of salts and growth regulators on titratable

acidity (%) of strawberry fruit.

Figure 4.3.4 Effect of foliar application of salts and growth regulators on TSS: TA

ratio of strawberry fruit.


ZnSO4, T4 = 9 mM SA, T5 = 100 mg

L-1

GA3

0.64

0.66

0.68

0.7

0.72

0.74

0.76

0.78

0.8

0.82

T1 T2 T3 T4 T5

TA

(%

)

Treatments

0

2

4

6

8

10

12

14

T1 T2 T3 T4 T5

TS

S:

TA

rati

o

Treatments

104

Figure 4.3.5 Effect of foliar application of salts and growth regulators on vitamin C

(mg 100 g-1

) contents of strawberry fruit.

Figure 4.3.6 Effect of foliar application of salts and growth regulators on total phenolic

contents (mg GAE 100 g-1



ZnSO4, T4 = 9 mM SA, T5 = 100 mg

L-1

GA3

0

10

20

30

40

50

60

70

T1 T2 T3 T4 T5

Vit

am

in C

(m

g 1

00 g

-1)

Treatments

100

110

120

130

140

150

160

170

180

190

200

T1 T2 T3 T4 T5

TP

C (

mg

GA

E 1

00 g

-1)

Treatments

105

Figure 4.3.7 Effect of foliar application of salts and growth regulators on total

antioxidants (% DPPH) of strawberry fruit.


ZnSO4, T4 = 9 mM SA, T5 = 100 mg

L-1

GA3

4.5.4 Activities of anti-oxidative enzymes (Table 4.3.3)


protein)

The effect of different foliar sprays on catalase activity of strawberry fruit was

found non-significant. Quantitatively maximum catalase activity (18.7 U mg−1

protein) was

noted in control fruits. There was no difference among different salts and growth regulators

treatments.


protein)

Statistical results regarding SOD activity in strawberry fruit affected by different

treatments showed significant increased results. Maximum (38.3 U mg−1

protein) SOD

activity was exhibited in strawberry fruits where plants were sprayed with 9 mM SA

followed by the plants sprayed with 7 mM CaCl2 (36.8 U mg−1

protein), 100 mg L-1

GA3

(36.2 U mg−1


ZnSO4 (35.2 U mg−1

protein), respectively while

0

10

20

30

40

50

60

70

80

90

T1 T2 T3 T4 T5

TA

(%

DP

PH

)

Treatments

106

minimum (30.0 U mg−1

protein) SOD activity was noted in control fruits. The response of

CaCl2 and GA3 treatments was similar and these treatments were statistically same.


protein)

Statistical analysis was non-significant regarding peroxidase activity in strawberry

fruit sprayed with different foliar applications. There was no difference between different

treatments but quantitatively higher POD activity was found in control fruits.

Table 4.3.3 Effect of foliar application of salts and growth regulators on enzymatic

activities of strawberry cv. ‘Chandler’ Mean ± S.E.




protein)

Control 18.7±0.22 a 30.0±0.31 d 2.17±0.03 a

7 mM CaCl2 17.6±0.21 a 36.8±0.36 b 2.05±0.02 a

100 mg L-1

ZnSO4 17.7±0.21 a 35.2±0.33 c 2.10±0.02 a

9 mM SA 17.5±0.20 a 38.3±0.37 a 2.02±0.03 a

100 mg L-1

GA3 17.8±0.20 a 36.2±0.36 b 2.08±0.05 a

LSD (p=0.05) 0.38 0.02 0.09

C.V. % 22.45 6.1 3.12

4.5.5 Survival (%)

Statistical analysis regarding strawberry plants survival during whole season showed

significant variations among different treatments. Maximum survival (97.25%) was noted

with 9 mM SA followed by treatments including 7 mM CaCl2 (92.0%), 100 mg L-1

GA3

(94.25%) and 100 mg L-1

ZnSO4 (87.50%), respectively as compared to control (62.0%)

treatment. The response of best doses of salts and growth regulators for increasing the

survival (%) was highly effective but maximum survival (%) was observed with 9 mM SA

treatment during season (Figure 4.3.8).

107

Figure 4.3.8 Effect of foliar application of salts and growth regulators on survival (%)

of strawberry plants. Vertical bars represent ± S.E of means.


ZnSO4, T4 = 9 mM SA, T5 = 100 mg

L-1

GA3

40

50

60

70

80

90

100

110

T1 T2 T3 T4 T5

Su

rviv

al

(%)

Treatments

108

4.3 Discussion

Foliar application of salts and growth regulators play important role for increasing the

vegetative growth (canopy spreading, crowns, runner growth and leaf area), maximize the

nutritional value and yield of strawberry (Qureshi et al., 2013).

In current study previous year best treatments including 7 mM CaCl2, 100 mg L-1

ZnSO4, 9 mM SA and 100 mg L-1

GA3 from each experiment along with control were

compared each other to check their effects on vegetative, yield and quality parameters of

strawberry. Increasing trend was observed regarding vegetative growth affected by different

salts and growth regulators. Maximum leaves (21.25 plant-1

) and leaf area (61.75 cm2) was

exhibited with 100 mg L-1

GA3 as compared to other treatments. Leaf growth was increased

because GA3 promoted rapid cell division process and also increased cell elongation activity

in strawberry plants (Turner, 1963). Flower initiation was earlier in all treatments except

control plants and minimum numbers of days (15.50) were required when plants were

sprayed with 100 mg L-1

GA3. Maximum number of crowns (8.0 plant-1

) and runners (11.0

plant-1

) were observed in those strawberry plants sprayed with 100 mg L-1

GA3. Overall

vegetative growth was significantly increased with all foliar sprays but GA3 (100 mg L-1

)

showed the superiority for increasing the vegetative growth as compared to other treatments.

Our results proved that previous year best treatments of salts and growth regulators

significantly increased the marketable yield when again compared during next year.

Maximum (494.0 g plant-1

) marketable yield was noted with 9 mM SA foliar spray as

compared to other treatments. Unmarketable yield was minimum in all foliar applied

treatments as compared to control. Maximum (80.0 g plant-1

) small size yield was noted with

control plants as compared to treated plants during growing season. Salicylic acid improved

yield, it is because of SA acted as potential molecule for activating the defense mechanism of

plant against any pathogen attack by creating systemic acquired resistance in whole plant

body for further spreading of disease (Tsuda et al., 2008). Our results concluded that

strawberry fruits were more firm where plants were sprayed with different concentrations of

salts and growth regulators. Maximum firmness value (0.97 kg. cm-2

) was observed in those

strawberry fruits where plants were sprayed with 7 mM CaCl2 as compared to other

treatments. Calcium chloride improved firmness it could be due to calcium is major

109

component of pectin which improved the inflexibility of fruit cell wall and membrane

rigidity (Sams, 1999; Maas, 1998).

In current study strawberry quality attributes were improved with 9 mM SA as

compared to other treatments. Maximum TSS (8.48 ºBrix) contents were observed with 9

mM SA. Increasing trend relating to TSS contents was observed in all fruits where

strawberry plants were sprayed with different concentrations of salts and growth regulators.

Acid contents were found non-significant while TSS: Acid ratio was maximum with 9 mM

SA as compared to other treatments. Increment in TSS contents could be due to accumulation

of sucrose in fruit during development process which increased the activity of sucrose

phosphate synthase due to that activity acid contents decreased and TSS increased

(Srivastava and Dwivedi, 2000; Hubbard et al., 1991).

Higher vitamin C contents increased the fruit nutritional value and maximum (57.72

mg 100 g-1

) vitamin C contents were observed with 9 mM SA as compared to other

treatments. It could be due to salicylic acid application reduced degradation of vitamin C

contents of strawberry fruit during ripening by delaying the senescence process and improved

fruit quality (Lolaei et al., 2012). Maximum TPC (191.50 mg GAE 100 g-1

) and TA (76.50%

DPPH) activities were observed from those fruits where strawberry plants were sprayed with

9 mM SA. Other treatments including 7 mM CaCl2, 100 mg L-1

ZnSO4 and 100 mg L-1

GA3

also showed increasing trend regarding TPC and TA activities. Our results regarding TPC

and TA activities increased due to foliar spray of salts and growth regulators similar with

previous findings who reported that SA increased the organic compounds (phenylpropanoid–

flavonoid) synthesis in cornelian cherry fruit and stimulate the accumulation of phenolic

contents and maximum antioxidant activities (Dokhanieh et al., 2013). Enzymatic activities

were also influenced with different foliar applications. Maximum catalase activity was

exhibited in control fruits while minimum activities were observed in those fruits where

strawberry plants were sprayed with different foliar applications. Superoxide dismutase

activity was lowered in control fruits while foliar treatments increased the SOD activity in

strawberry fruit. Peroxidase activity was found lower in those fruits treated with different

foliar sprays while maximum was noticed in control plants. Overall, the effect of different

foliar sprays was highly effective for maintaining the balance between enzymatic activities

110

during growth stages. Activities of different antioxidant enzymes (CAT, POD and SOD)

produced during different growth stages and increased the defense response against ROS

species (Anand et al., 2009). Maximum survival (97.25%) was observed with 9 mM SA as

compared to control (62.0%) plants. In current study the response of previous year best doses

of salts and growth regulators for increasing the survival (%) was highly significant.

4.3 Conclusions

Vegetative growth was increased with different foliar sprays as compared to control

plants. Our results confirmed that maximum leaves, leaf area, crowns and runner

growth was observed with 100 mg L-1

GA3. It was proved that gibberellic acid

response was highly significant for increasing the vegetative growth as compared to

other treatments during whole growing season.

Marketable yield was significantly increased with 9 mM SA foliar spray as compared

to other treatments.

Maximum strawberry firmness was improved with 7 mM CaCl2 foliar spray as

compared to other treatments. Fruit quality was improved with different foliar sprays

but maximum response was observed with 9 mM SA foliar spray.

Overall, it was proved that from all foliar applied treatments 9 mM SA was found

best for increasing the marketable yield, for improving the maximum quality

attributes and extending the survival mechanism of strawberry plants during growing

season.

111

4.4 Study-4

(Postharvest study)

Postharvest application of calcium chloride (CaCl2) and salicylic acid (SA)

maintain the quality and improve storage life of strawberry cv. ‘Chandler’

This experiment was executed to check the effectiveness of CaCl2 and SA for

increasing the shelf life of strawberries. Marketable strawberries were dipped in different

concentrations of CaCl2 and SA solutions for 10 minutes to observe their effects on shelf life

and quality. After dipping strawberries were dried at room temperature then packed in plastic

punnets and stored at 4°C with 80-85% RH. All fruit quality parameters were analyzed

during 0, 3, 6, 9, 12 and 15 days of interval.

4.4.1 Physical Parameters

4.4.1.1 Fruit weight loss (%)

Weight loss (15.08%) was found maximum in control treatment after 15 days while

minimum weight loss (6.08%) was noticed in strawberries treated with 6 mM CaCl2 followed

by other treatments 5 mM SA (6.13%), 4 mM CaCl2 (6.89%), 7 mM SA (7.44%), 2 mM

CaCl2 (7.92%) and 3 mM SA (7.95%), respectively (Table 4.4.1). The response of lower and

medium concentrations of CaCl2 and SA was observed similar after 15 days and these were

statistically same. Results clearly indicated that control treatment showed rapid decline in

weight loss while minor changes were noted in treated fruits. According to results rapid

increment in weight loss was noticed in control treatment but CaCl2 and SA different

concentrations acted as barrier for reducing weight loss. Quantitatively 6 mM CaCl2 showed

the superiority over other treatments for reducing weight loss of strawberries (Figure 4.4.1).

112

4.4.1.2 Fungal decay (%)

Strawberries which were affected due to grey mold or anthracnose fungal disease

were recorded on daily basis (Table 4.4.2). In control treatment decay problem was started

after 6 days while in treated fruits decay problem was minimum during entire storage. Fungal

decay (56.80%) was found maximum in control treatment after 15 days while those fruits

treated with 5 mM SA showed minimum decay (3.50%) followed by other treatments 4 mM

CaCl2 (5.50%), 7 mM SA (6.50%), 6 mM CaCl2 (7.50%), 3 mM SA (8.50%) and 2 mM

CaCl2 (10.50%), respectively. Different concentrations of CaCl2 and SA were performed

effectively to reduce the decay incidence. The response of medium dose of SA (5 mM) for

reducing decay incidence was maximum as compared with other treatments (Figure 4.4.1).


)

Strawberry firmness was decreased during storage but fruits treated with different

doses of CaCl2 and SA maintained fruit firmness during entire storage. After 15 days of

storage maximum strawberry firmness (0.42 kg. cm-2

) was achieved with 6 mM CaCl2

followed by treatments 5 mM SA (0.39 kg. cm-2

), 4 mM CaCl2 (0.37 kg. cm-2

), 7 mM SA

(0.36 kg. cm-2

), 2 mM CaCl2 (0.34 kg. cm-2

) and 3 mM SA (0.32 kg. cm-2

), respectively

(Table 4.4.3). The response of control treatment and lower doses of CaCl2 and SA was non-

significant after 15 days. Interaction effects revealed that maximum decreasing trend in

firmness was observed in all treated fruits after 12 days while in control treatment it was

noted after 6 days. Overall results regarding strawberry firmness suggested that higher dose

of CaCl2 (6 mM) was more effective for maintaining strawberry firmness during storage

(Figure 4.4.1).

113

Figure 4.4.1 Effects of CaCl2 and SA different treatments on physical parameters of

strawberry during cold storage

T1 = Control, T2 = 2 mM CaCl2, T3 = 4 mM CaCl2, T4 = 6 mM CaCl2, T5 = 3 mM SA, T6

= 5 mM SA, T7 = 7 mM SA

0

4

8

12

16

20 T1 T2 T3 T4 T5 T6 T7

0

10

20

30

40

50

60

0

0.2

0.4

0.6

0.8

1

0 3 6 9 12 15

Days

Fru

it w

eigh

t lo

ss (

%)

F

un

gal

dec

ay (

%)

F

irm

nes

s (k

g. cm

-2)

114

Table 4.4.1 Interaction effects of different treatments on fruit weight loss (%) of strawberry

during cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 0.00 x 8.05 e 9.05 d 11.08 c 13.08 b 15.08 a 9.39 A

2 mM CaCl2 0.00 x 3.80 pq 4.23 no 5.64 k 6.63 h 7.92 f 4.70 B

4 mM CaCl2 0.00 x 3.53 qrs 3.34 st 4.50 mn 5.74 jk 6.89 h 4.00 D

6 mM CaCl2 0.00 x 2.04 w 3.01 uv 4.02 op 5.08 l 6.08 i 3.37 E

3 mM SA 0.00 x 3.64 qr 4.29 no 5.14 l 6.76 h 7.95 f 4.63 B

5 mM SA 0.00 x 2.75 v 3.12 tu 4.13 o 5.15 l 6.13 hi 3.55 D

7 mM SA 0.00 x 3.46 rs 3.45 rs 4.77 m 5.93 ij 7.44 g 4.17 C

Mean 0.00 F 3.89 E 4.35 D 5.61 C 6.91 B 8.21 A

Table 4.4.2 Interaction effects of different treatments on fungal decay (%) of strawberry

during cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 0.00 r 21.00 d 47.83 c 53.50 b 53.33 b 56.80 a 38.74 A

2 mM CaCl2 0.00 r 1.50 pq 3.50 m 7.50 g 8.50 f 10.50 e 5.25 B

4 mM CaCl2 0.00 r 1.13 q 1.50 pq 2.50 no 3.50 lm 5.50 i 2.35 E

6 mM CaCl2 0.00 r 1.23 pq 2.00 op 5.00 ij 5.50 i 7.50 g 3.54 C

3 mM SA 0.00 r 1.35 pq 2.50 no 4.00 kl 6.50 h 8.50 f 3.81 C

5 mM SA 0.00 r 1.00 q 1.00 q 1.50 pq 2.50 no 3.50 lm 1.58 F

7 mM SA 0.00 r 1.10 q 1.50 pq 3.00 mn 4.50 jk 6.50 h 2.77 D

Mean 0.00 F 4.04 E 8.55 D 11.00 C 12.05 B 14.11 A

115

Table 4.4.3 Interaction effects of different treatments on firmness (kg. cm-2

) of strawberry

during cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 0.91 a 0.58 m 0.32 z 0.29 z 0.27 z 0.23 z 0.43 G

2 mM CaCl2 0.91 a 0.72 f 0.67 i 0.55 o 0.43 u 0.34 z 0.60 E

4 mM CaCl2 0.91 a 0.74 de 0.68 h 0.56 n 0.48 s 0.37 x 0.62 C

6 mM CaCl2 0.91 a 0.81 b 0.74 e 0.62 l 0.52 q 0.42 v 0.67 A

3 mM SA 0.91 a 0.64 k 0.61 k 0.53 p 0.44 u 0.32 z 0.58 F

5 mM SA 0.91 a 0.78 c 0.70 g 0.58 m 0.49 r 0.39 w 0.64 B

7 mM SA 0.91 a 0.75 d 0.65 j 0.55 o 0.45 u 0.36 y 0.61 D

Mean 0.91 A 0.72 B 0.63 C 0.53 D 0.44 E 0.34 F

116

4.4.2 Fruit quality parameters


After 15 days maximum TSS contents (9.30 ºBrix) were noted in control treatment

while fruits which were treated with different concentrations of CaCl2 and SA retained TSS

contents of strawberry during storage. Minimum TSS contents (7.85 ºBrix) were noted with 5

mM SA followed by other treatments 4 mM CaCl2 (8.10 ºBrix), 7 mM SA (8.35 ºBrix), 6

mM CaCl2 (8.45 ºBrix), 3 mM SA (8.65 ºBrix) and 2 mM CaCl2 (8.85 ºBrix), respectively

(Table 4.4.4). Interaction effects indicated that treated fruits retained TSS contents of

strawberry while gradual increase in TSS contents were noticed in control treatment during

storage. Overall increasing trend was observed regarding TSS contents of strawberry during

storage but medium concentration of SA (5 mM) showed its superiority for retaining TSS

contents of strawberry (Figure 4.4.2).


After 15 days maximum TA (0.62%) was exhibited with 5 mM SA followed by other

treatments 4 mM CaCl2 (0.59%), 7 mM SA (0.57%), 6 mM CaCl2 (0.55%), 3 mM SA

(0.52%) and 2 mM CaCl2 (0.50%), respectively. During storage acid contents were rapidly

decreased in control fruits and showed values (0.35%) while in treated fruits minimum loss

was observed. Acid contents declined during storage but the response of SA (5 mM) was

highly effective for retaining acid contents (Figure 4.4.2).


TSS: Acid ratio is an important index of strawberry quality. Increasing trend in ratio

(26.96) was noticed in control treatment followed by 2 mM CaCl2 (17.62), 3 mM SA (16.64),

6 mM CaCl2 (15.51), 7 mM SA (14.72), 4 mM CaCl2 (13.79) and 5 mM SA (12.77),

respectively. Irrespective to treatments, increasing trend was noticed regarding TSS: TA ratio

during storage days (Figure 4.4.2).

117

Figure 4.4.2 Effects of CaCl2 and SA different treatments on TSS, Titratable acidity

and TSS: TA ratio of strawberry during cold storage

T1 = Control, T2 = CaCl2 2 mM, T3 = CaCl2 4 mM, T4 = CaCl2 6 mM, T5 = SA 3 mM, T6

= SA 5 mM, T7 = SA 7 mM

4

6

8

10

12T1 T2 T3 T4 T5 T6 T7

0

0.2

0.4

0.6

0.8

1

1.2

0

5

10

15

20

25

30

0 3 6 9 12 15

Days

TS

S (

ºBri

x)

T

A (

%)

TS

S:

TA

rati

o

118

Table 4.4.4 Interaction effects of different treatments on TSS (ºBrix) of strawberry during

cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 5.80 x 7.88 i 8.20 g 8.73 d 8.95 b 9.30 a 8.14 A

2 mM CaCl2 5.80 x 6.65 p 7.15 m 7.65 j 7.85 i 8.85 c 7.33 B

4 mM CaCl2 5.80 x 5.83 x 6.10 v 6.43 rs 7.10 m 8.10 h 6.56 E

6 mM CaCl2 5.80 x 6.33 t 6.50 qr 6.75 o 7.43 l 8.45 e 6.88 D

3 mM SA 5.80 x 6.45 r 6.90 n 7.13 m 7.58 jk 8.65 d 7.08 C

5 mM SA 5.80 x 6.00 w 6.28 tu 6.35 st 6.83 no 7.85 i 6.52 F

7 mM SA 5.80 x 6.23 u 6.55 q 6.88 n 7.55 k 8.35 f 6.89 D

Mean 5.80 F 6.48 E 6.81 D 7.13 C 7.61 B 8.51 A

Table 4.4.5 Interaction effects of different treatments on Titratable acidity (%) of


Treatments

Days

Mean 0 3 6 9 12 15

Control 1.01 a 0.55 u 0.42 x 0.39 y 0.38 z 0.35 a 0.51 G

2 mM CaCl2 1.01 a 0.81 g 0.75 j 0.63 p 0.58 s 0.50 w 0.71 F

4 mM CaCl2 1.01 a 1.00 b 0.84 e 0.79 h 0.68 n 0.59 rs 0.82 B

6 mM CaCl2 1.01 a 0.88 d 0.79 h 0.68 n 0.62 q 0.55 u 0.75 D

3 mM SA 1.01 a 0.83 f 0.73 k 0.64 o 0.60 r 0.52 v 0.72 E

5 mM SA 1.01 a 1.01 ab 0.91 c 0.82 f 0.71 l 0.62 q 0.85 A

7 mM SA 1.01 a 0.88 d 0.77 i 0.69 m 0.63 op 0.57 t 0.76 C

Mean 1.01 A 0.85 B 0.74 C 0.66 D 0.60 E 0.53 F

119

Table 4.4.6 Interaction effects of different treatments on TSS: TA ratio of strawberry during

cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 5.74 v 14.45 h 19.76 d 22.23 c 23.87 b 26.96 a 18.84 A

2 mM CaCl2 5.74 v 8.26 qr 9.54 p 12.14 l 13.48 j 17.62 e 11.13 B

4 mM CaCl2 5.74 v 5.84 v 7.31 t 8.19 r 10.52 n 13.79 i 8.56 F

6 mM CaCl2 5.74 v 7.23 t 8.28 qr 10.00 o 11.98 l 15.51 g 9.79 D

3 mM SA 5.74 v 7.82 s 9.52 p 11.13 m 12.73 k 16.64 f 10.60 C

5 mM SA 5.74 v 5.97 v 6.88 u 7.75 s 9.58 p 12.77 k 8.11 G

7 mM SA 5.74 v 7.08 tu 8.51 q 10.04 o 11.94 l 14.72 h 9.67 E

Mean 5.74 F 8.09 E 9.97 D 11.64 C 13.44 B 16.86 A

4.4.2.4 Vitamin C (mg 100 g-1

)

Significant differences were noted regarding vitamin C contents of strawberry fruit

during storage days. Interaction effects revealed that treated fruits showed increasing trend

during 3-9 days and then gradually decreased while in control fruits vitamin C contents

increased during 3-6 of storage then decreased (Table 4.4.4). Maximum vitamin C contents

(43.90 mg 100 g-1

) were noted in strawberries treated with 6 mM CaCl2 followed by other

treatments 5 mM SA (39.95 mg 100 g-1

), 4 mM CaCl2 (36.45 mg 100 g-1

), 7 mM SA (34.98

mg 100 g-1

), 2 mM CaCl2 (33.13 mg 100 g-1

) and 3 mM SA (31.03 mg 100 g-1

), respectively.

During entire storage the response of CaCl2 (6 mM) was highly effective for reducing

degradation of vitamin C contents of strawberry (Figure 4.4.3).


)

Maximum values for TPC (132.75 mg GAE 100 g-1

) were noted in strawberries

treated with 6 mM CaCl2 followed by other treatments 5 mM SA (126.50 mg GAE 100 g-1

),

4 mM CaCl2 (123.75 mg GAE 100 g-1

), 7 mM SA (120.25 mg GAE 100 g-1

) and 2 mM

CaCl2 (109.75 mg GAE 100 g-1

), respectively after 15 days. Treatments including CaCl2 (4

mM) and SA (7 mM) these were statistically similar. Minimum TPC (59.0 mg GAE 100 g-1

)

were found in control treatment after 15 days. Interaction effects revealed that increasing

120

trend was observed in treated fruits regarding TPC during 3-9 days while in control fruits it

was noticed during 3-6 days then gradually decreased (Table 4.4.8). From results it was

observed that CaCl2 (6 mM) was highly effective for retaining maximum TPC during storage

(Figure 4.4.3).


After 15 days maximum antioxidant activities (39.0% DPPH) were noted in

strawberries treated with 5 mM SA followed by other treatments 7 mM SA (36.50% DPPH),

4 mM CaCl2 (35.50% DPPH), 6 mM CaCl2 (33.25% DPPH), 3 mM SA (32.50% DPPH) and

2 mM CaCl2 (31.25% DPPH), respectively. The response of control treatment and lower

doses of SA and CaCl2 was similar after 15 days and these treatments were statistically same.

Interaction effects revealed that antioxidant activity of all treated strawberry fruits increased

during 3-9 days and then gradually decreased while in control fruits increasing trend was

observed during 3-6 days then decreased (Table 4.4.9). Minimum antioxidant activities

(28.75% DPPH) were noticed in control treatment during entire storage and after 15 days.

Medium dose of SA (5 mM) retained more antioxidant activities as compared with other

treatments (Figure 4.4.3).

121

Figure 4.4.3 Effects of CaCl2 and SA different treatments on vitamin C, TPC and TA

activities of strawberry during cold storage


= 5 mM SA, T7 = 7 mM SA

20

40

60

80

100T1 T2 T3 T4 T5 T6 T7

0

50

100

150

200

250

20

30

40

50

60

70

80

90

0 3 6 9 12 15

Days

Vit

am

in C

(m

g 1

00 g

-1)

T

PC

(G

AE

mg 1

00 g

-1)

T

A (

% D

PP

H)

122

Table 4.4.7 Interaction effects of different treatments on vitamin C (mg 100 g-1

) contents of


Treatments Days

Mean 0 3 6 9 12 15

Control 43.50 rs 45.85 v 49.15 z 33.65 z 28.08 z 24.90 z 32.52 G

2 mM CaCl2 43.50 rs 49.00 p 50.68 ln 55.25 g 42.98 s 33.13 y 45.75 E

4 mM CaCl2 43.50 rs 51.50 lm 53.03 ij 60.98 e 46.05 q 36.45 w 48.58 C

6 mM CaCl2 43.50 rs 53.50 hi 69.03 c 74.28 a 52.73 jk 43.90 r 56.20 A

3 mM SA 43.50 rs 49.58 op 50.58 n 53.78 h 41.90 t 31.03 z 45.06 F

5 mM SA 43.50 rs 53.28 hij 63.28 d 70.00 b 50.18 no 39.95 u 53.36 B

7 mM SA 43.50 rs 50.80 mn 52.08 kl 58.85 f 43.95 r 34.98 x 47.36 D

Mean 43.50 D 49.39 C 52.83 B 57.54 A 43.69 D 34.90 E

Table 4.4.8 Interaction effects of different treatments on total phenolic contents

(GAE mg 100 g-1

) of strawberry during cold storage

Treatments

Days

Mean 0 3 6 9 12 15

Control 155.00 p 160.75 r 162.50 y 101.00 z 69.75 z 59.00 z 101.33 E

2 mM CaCl2 155.00 p 165.50 l 177.50 hi 184.50 f 157.50 o 109.75 w 158.29 D

4 mM CaCl2 155.00 p 172.50 j 180.50 g 195.50 cd 160.50 n 123.75 u 164.63 C

6 mM CaCl2 155.00 p 184.75 f 207.50 b 218.50 a 177.00 hi 132.75 s 179.25 A

3 mM SA 155.00 p 163.50 m 178.75 gh 192.00 e 151.00 q 107.50 x 157.96 D

5 mM SA 155.00 p 176.50 i 195.00 d 207.50 b 167.00 l 126.50 t 171.25 B

7 mM SA 155.00 p 170.50 k 183.25 f 197.00 c 162.75 m 120.25 u 164.79 C

Mean 155.00 D 168.14 C 173.86 B 183.00 A 149.36 E 111.36 F

123

Table 4.4.9 Interaction effects of different treatments on total antioxidants (% DPPH)

activities of strawberry during cold storage

Treatments

Days

Mean 0 3 6 9 12 15

Control 43.00 r 44.50 t 48.25 w 34.50 z 31.25 z 28.75 z 35.88 F

2 mM CaCl2 43.00 r 45.25 o 51.50 k 58.75 f 38.75 v 31.25 z 44.75 E

4 mM CaCl2 43.00 r 51.75 k 57.50 g 71.50 b 44.50 p 35.50 y 50.63 B

6 mM CaCl2 43.00 r 48.50 m 53.25 j 60.75 e 41.50 s 33.25 yz 46.71 D

3 mM SA 43.00 r 45.50 o 52.00 k 57.25 g 39.50 u 32.50 z 44.96 E

5 mM SA 43.00 r 55.50 h 63.50 d 76.50 a 47.00 n 39.00 uv 54.08 A

7 mM SA 43.00 r 50.25 l 54.50 i 64.50 c 43.75 q 36.50 x 48.75 C

Mean 43.00 D 48.18 C 52.79 B 60.54 A 40.89 E 33.82 F

4.4.3 Activities of anti-oxidative enzymes


protein)

Catalase activity increased with different concentrations of CaCl2 and SA then

decreased with the advancement of storage days (Table 4.4.10). Maximum CAT activity

(12.8 U mg−1

protein) was noted with SA 5 mM followed by other treatments SA 7 mM

(11.6 U mg−1

protein), SA 3 mM (11.3 U mg−1

protein), CaCl2 4 mM (10.6 U mg−1

protein),

CaCl2 6 mM (10.5 U mg−1

protein) and CaCl2 2 mM (10.4 U mg−1

protein), respectively.

While minimum activity (10.2 U mg−1

protein) was noticed in control fruits after 15 days.

The response of different doses of SA was highly effective for retaining maximum CAT

activity during storage. Catalase activity was increased from 3-6 days then decreased in all

treatments (Figure 4.4.4).

124


protein)

Strawberry fruits treated with 5 mM SA exhibited maximum SOD activity (24.3 U

mg−1

protein) followed by treatments 7 mM SA (23.2 U mg−1

protein), 4 mM CaCl2 (21.3 U

mg−1

protein), 6 mM CaCl2 (19.2 U mg−1

protein), 3 mM SA (18.2 U mg−1

protein) and 2

mM CaCl2 (17.2 U mg−1

protein), respectively after 15 days (Table 4.4.11). Maximum

decline in SOD activity was noted in control treatment during entire storage. Increasing trend

regarding SOD activity was observed from 3-6 days of storage then decreased. From results

it was concluded that SA (5 mM) dipping application showed the superiority over all

treatments for retaining maximum SOD activity (Figure 4.4.4).


protein)

Maximum POD activity (0.39 U mg−1

protein) was exhibited with 5 mM SA after 15

days followed by other treatments 4 mM CaCl2 (0.35 U mg−1

protein), 7 mM SA (0.29 U

mg−1

protein), 6 mM CaCl2 (0.28 U mg−1

protein), 3 mM SA (0.26 U mg−1

protein) and 2

mM CaCl2 (0.26 U mg−1

protein), respectively (Table 4.4.12). Fruits treated with lower doses

of SA (3 mM) and CaCl2 (2 mM) were statistically same. Peroxidase activity was increased

in treated fruits during 3-6 days while in control fruits increasing trend was observed from 0-

3 days. Different doses of CaCl2 and SA retained POD activity during storage while in

control fruits minimum activity (0.15 U mg−1

protein) was observed after 15 days. From

results it was observed that medium concentration of SA (5 mM) retained maximum POD

activity in strawberry fruits during 15 days of storage (Figure 4.4.4).

125

Figure 4.4.4 Effects of CaCl2 and SA different treatments on enzymatic activities of



= 5 mM SA, T7 = 7 mM SA

8

9

10

11

12

13

14

15T1 T2 T3 T4 T5 T6 T7

5

10

15

20

25

30

35

40

0

0.2

0.4

0.6

0.8

1

1.2

0 3 6 9 12 15

C

AT

(U

mg

−1 p

rote

in)

S

OD

(U

mg

−1 p

rote

in)

P

OD

(U

mg

−1 p

rote

in)

Days

126

Table 4.4.10 Interaction effects of different treatments on catalase (U mg−1

protein)

activity of strawberry during cold storage

Treatments

Days

Mean 0 3 6 9 12 15

Control 10.8 o 11.7 l 11.8 k 10.4 r 10.2 s 10.2 s 10.8 G

2 mM CaCl2 10.8 o 11.8 k 12.9 h 11.7 l 10.5 q 10.4 r 11.3 F

4 mM CaCl2 10.8 o 12.9 h 13.7 e 12.9 h 11.7 l 10.6 p 12.1 C

6 mM CaCl2 10.8 o 12.8 i 13.5 f 12.8 hi 11.6 m 10.5 q 12.0 D

3 mM SA 10.8 o 11.8 k 12.9 h 11.7 l 11.3 n 11.3 n 11.6 E

5 mM SA 10.8 o 13.0 g 14.2 a 14.0 b 13.8 d 12.8 i 13.1 A

7 mM SA 10.8 o 12.9 h 13.9 c 13.9 c 12.7 j 11.6 m 12.6 B

Mean 10.8 E 12.4 B 13.2 A 12.5 B 11.6 C 11.1 D

Table 4.4.11 interaction effects of different treatments on superoxide dismutase

(U mg−1

protein) activity of strawberry during cold storage

Treatments

Days

Mean 0 3 6 9 12 15

Control 16.3 s 18.4 pq 20.2 o 18.2 q 17.1 r 16.1 t 17.7 G

2 mM CaCl2 16.3 s 19.3 op 23.4 l 19.3 op 18.2 q 17.2 r 19.0 F

4 mM CaCl2 16.3 s 23.5 l 32.5 c 30.5 e 26.4 i 21.3 n 25.0 C

6 mM CaCl2 16.3 s 22.4 m 29.5 f 28.3 g 24.3 k 19.2 p 23.3 D

3 mM SA 16.3 s 19.3 op 25.5 j 24.4 k 22.2 lm 18.2 q 21.0 E

5 mM SA 16.3 s 25.5 j 34.7 a 31.5 cd 28.4 fg 24.3 k 27.0 A

7 mM SA 16.3 s 24.4 k 33.5 b 31.4 d 27.3 h 23.2 l 26.0 B

Mean 16.3 F 21.8 D 28.5 A 26.2 B 23.4 C 20.0 E

127

Table 4.4.12 Interaction effects of different treatments on peroxidase (U mg−1

protein)

activity of strawberry during cold storage

Treatments Days

Mean 0 3 6 9 12 15

Control 0.45 q 0.46 p 0.35 u 0.24 x 0.21 y 0.15 z 0.31 G

2 mM CaCl2 0.45 q 0.48 o 0.58 h 0.41 r 0.31 uv 0.26 wx 0.41 F

4 mM CaCl2 0.45 q 0.57 i 0.70 c 0.59 g 0.49 n 0.35 u 0.53 B

6 mM CaCl2 0.45 q 0.51 m 0.62 e 0.52 l 0.41 r 0.28 w 0.46 D

3 mM SA 0.45 q 0.49 n 0.59 g 0.48 o 0.38 t 0.26 wx 0.44 E

5 mM SA 0.45 q 0.60 f 1.06 a 0.82 b 0.56 j 0.39 s 0.64 A

7 mM SA 0.45 q 0.53 k 0.63 d 0.53 k 0.45 q 0.29 v 0.48 C

Mean 0.45 C 0.52 B 0.65 A 0.51 B 0.40 D 0.28 E

128

4.4 Discussion

Strawberry is very sensitive fruit crop which requires careful handling and

appropriate management practices to retain fruit quality after harvest. Strawberry fruits

require rapid removal of field heat to extend its shelf life. Low storage temperature (0 to 4ºC)

plays important role for retaining its quality. Short shelf life, fungal decay, weight loss, loss

of brightness and color darkening are major postharvest problems of strawberries (Picha,

2006). Postharvest application of calcium means applying calcium directly on the fruit

surface, which is best method for retaining fruit quality. Calcium applied directly on fruit

surface by dipping method which improves the calcium content in fruit cell wall and due to

which firmness was maintained during storage (Conway et al., 1994). Storage application of

SA also delayed fruit softening, fruit ripening and senescence process due to inhibition of

ethylene process and also beneficial for reduction of fungal decay of strawberries (Zhang et

al., 2010).

In Present study increasing trend in fruit weight loss was noted during storage.

Increment in weight loss (15.08%) was found in control treatment after 15 days while

minimum (6.08%) was noticed with CaCl2 (6 mM) followed by other treated fruits. It could

be due to higher metabolic activity of fruit which occurred due to depletion of moisture from

surface of fruit because of higher transpiration process which still continued during whole

storage (Boynton et al., 2005). According to our results control treatment exhibited rapid

increment in weight loss during entire storage while minor changes in weight loss were noted

from all treated fruits. Our results regarding weight loss (%) of strawberry are also in aid

with Pila et al. (2010) who stated that CaCl2 on fruit surface acted as physical barrier reduced

the rapid metabolic activity due to its anti-senescent properties, so water loss from fruit

surface reduced and shelf life of tomato increased during storage. Bagheri et al. (2014) also

evaluated shelf life and quality of persimmon fruit dipped in different concentrations of

CaCl2 and stored at 0°C for 4 months. Fruit weight loss decreased with CaCl2 treatments

(0.5, 1, and 2%) as compared with control.

Although, strawberry decay is still serious problem which is caused by fungal

pathogens. During last storage interval, control fruits showed maximum decay (56.80%)

problem while minimum decay (3.50%) was estimated with 5 mM SA. Therefore, it was

129

noted from results that different concentrations of CaCl2 and SA effectively minimized the

decay incidence during entire storage. Salicylic acid reduced decay incidence during storage

because it increased the activity of proteins (chitinase and β-1, 3-glucanase) which played

significant role in enhancing defense mechanism in fruits against oxidative damage caused

by ROS species (Meena et al., 2001; Hussain et al., 2015). Our findings regarding SA

minimized decay during storage similar with Baninaiem et al. (2016) who exhibited that

different concentrations of SA (1, 2 and 4 mM) reduced the decay incidence of tomato fruit

when stored at 10°C for 40 days.

Strawberry firmness is a major fruit quality index during storage which was positively

affected by different concentrations of CaCl2 and SA as compared to control treatment.

Strawberry firmness was decreased during storage but treated fruits maintained fruit firmness

during entire storage. After 15 days of storage maximum strawberry firmness (0.67 kg. cm-2

)

was achieved with CaCl2 (6 mM) as compared to other treatments. Firmness decreased

during storage due to higher metabolic activity of strawberries after harvest which caused

more water loss from fruit surface and cells lose their rigidity (Maas, 1998). Our results

regarding firmness suggested that higher dose of CaCl2 (6 mM) was more effective for

maintaining strawberry firmness during storage. It is because of dipping application of

calcium improves the fruit cell wall pectin due to that membrane rigidity and cell structure

maintained during storage (Sams, 1999; Maas, 1998). In some previous studies it was shown

that dipping treatment of CaCl2 2% solution maintained firmness of peaches when stored at

4°C for 2 weeks (Lysiak et al., 2008). In some other studies it was also observed that salt

solution of CaCl2 3% maintained the firmness of nectarines during storage (Manganaris et

al., 2005).

Different doses of CaCl2 and SA effectively maintained the TSS contents of

strawberry during storage. Increment in TSS contents during storage due to higher respiration

process of fruit which converted starch contents into sugars (Avina et al., 2014). During last

storage interval maximum TSS contents were recorded in control fruits while minimum were

observed with SA (5 mM). Our results match with previous findings who stated that SA

application leads to reduction in invertase enzymatic activity and reduced maximum

increment in TSS contents of banana fruit during storage (Srivastava and Dwivedi, 2000).

130

Reduction in acid contents was observed during storage because of acids rapidly converted

into sugars but the response of SA (5 mM) was highly effective for retaining strawberry acid

contents as compared to other treatments. Our findings regarding acid contents of strawberry

similar with previous findings who reported that titratable acidity was more in SA treated

tomatoes as compared to control (Baninaiem et al., 2016). The level of TSS: TA ratio was

found higher among all treatments during storage period however; this increment was more

in control treatment because of maximum reduction in acidity and rapidly increasing TSS

and sugar contents.

According to our findings vitamin C contents reduced during storage. Degradation

process of vitamin C contents during storage due to fluctuation in temperature and higher

metabolic activity of fruit (Silva et al., 2013). Low temperature during storage cause

oxidation of vitamin C contents of fruit (Rapisarda et al., 2008). Maximum vitamin C (43.90

mg 100 g-1

) contents were noted in fruits treated with CaCl2 (6 mM) as compared to other

treatments after 15 days of storage. The reason of decreasing vitamin C during storage due to

reduction in ascorbate peroxidase enzymatic activity but CaCl2 application enhanced the

activity of several catalytic enzymes which played major role in biosynthesis of vitamin C

contents (Kadir, 2014). Our results are also in accordance with Akhtar et al. (2010) who

observed the effects of CaCl2 on storage behavior of loquat cultivar „Surkh‟ which were

dipped in calcium solutions for 2 minutes and then stored at 4°C for 10 weeks. Minimum loss

was observed regarding vitamin C contents when treated with CaCl2 (1% and 2%).

Our results investigated that maximum TPC (132.75 mg GAE 100 g-1

) were noted in

strawberry fruits treated with CaCl2 (6 mM) after 15 days of storage. Phenolic contents

maximize during storage due to low temperature while decrease in TPC due to higher

metabolic activity of fruit (Silva et al., 2013). Our results similar with previous findings

where shelf life and quality of persimmon fruit increased with different concentrations of

CaCl2 (0.5, 1 and 2%) at 0°C for 4 months. Total phenolic contents increased with 2% CaCl2

treatment. Phenolic contents have maximum antioxidant activity against oxidative stress

caused by scavenging free radicals. Phenolic contents reduced with increment in storage days

due to higher enzymatic activity and oxidation process (Bagheri et al., 2014).

131

Antioxidants (enzymatic and non-enzymatic) plays major role in decreasing oxidative

stress in fruits caused by ROS species and also helpful for reducing chronic diseases in

humans (Yamaguchi et al., 1998). Oxidative damage in fruits recovered with antioxidants

like total phenolic contents, flavonoids, anthocyanin‟s and ascorbic acid contents (Kinsella et

al., 1993). Maximum antioxidant activity (39.0% DPPH) was noted with SA (5 mM)

followed by other treated fruits while minimum antioxidant activities (28.75% DPPH) were

noticed in control treatment after 15 days. These results match with previous studies where

SA (1 mM) enhanced the antioxidant capacity of cornelian cherry fruit during storage

(Dokhanieh et al., 2013). Increasing concentration of SA enhanced antioxidant activity in

peach fruit (Tareen et al., 2012).

Antioxidant enzymatic activities (CAT, SOD and POD) play important role in

scavenging ROS species in different parts of cell in response to different stress conditions.

Due to ROS species homeostasis of the cell is disrupted. During stress condition enzymatic

activities which protect the cell structure by scavenging ROS species (Racchi, 2013). In

present study antioxidant enzymatic activities were noticed higher with SA (5 mM) while,

lower trend was noticed in control fruits after 15 days. Enzymatic activities activated the

defense mechanism of plant against biotic and abiotic stresses. Superoxide dismutase is

ubiquitous defensive enzyme which has ability to protect the plant cell from damage during

stress conditions. Catalase and peroxidase enzymatic activities are also responsible for

scavenging ROS species which damage the cells under stress conditions (Racchi, 2013;

Hertwig et al., 1992). However, decreasing trend regarding enzymatic activities due to

interaction with low temperature and higher metabolic activities of strawberries.

132

4.4 Conclusion

Maximum vitamin C contents, TPC, reduction in weight loss and strawberry firmness

was retained with higher concentration of CaCl2 (6 mM). Maximum retention of TSS, acid

contents, total antioxidants and enzymatic activities (CAT, SOD and POD) were found

maximum with SA (5 mM). Overall results showed that CaCl2 (6 mM) and SA (5 mM)

showed the superiority for retaining maximum quality attributes during 15 days of storage as

compared with other treatments.

133

Chapter-5

5.1 SUMMARY

Strawberry (Fragaria × ananassa Duch.) is delicious and sweet flavored small fruit

crop. Strawberry is newly introduced small fruit crop in Pakistan; therefore yield is very less

compared to major producers. Major pre-harvest problems are poor flowering, poor fruit

setting, inadequate nutrient application, lower yield per plant, maturity factors, poor quality,

insect pests, diseases, weeds and climatic changes. Strawberry is very sensitive fruit crop and

storage losses may reach up to 25-40%. Improper harvesting stage, high temperature, short

shelf life, fungal decay, weight loss, loss of brightness and color darkening are major

postharvest problems of strawberry. By knowing pre and postharvest problems and current

situation of strawberry production in Pakistan, present study was planned to explore such pre

and postharvest management practices which increase the marketable yield and improve

quality of strawberries.

Foliar application of CaCl2 in different concentrations was applied at 3-4 leaves stage

and then after fruit setting. In this study 7 mM CaCl2 was found best for increasing the

vegetative growth and survival mechanism during entire strawberry season. Marketable yield

(418.50 g plant

-1) increased with foliar application of 7 mM CaCl2. Unmarketable and small

sized yield was found maximum in control treatment. Fruit quality parameters including

vitamin C (55.69 mg 100 g-1

) and TPC (186.50 mg GAE 100 g-1

) also improved with 7 mM

CaCl2 except TSS contents (8.03 ºBrix) and TSS: Acid ratio (7.63) were found maximum

with 5 mM CaCl2 as compared to higher and lower doses because sometimes higher doses

increased the maximum activity of fruit ripening enzymes due to that some quality attributes

showed declining trend.

In second experiment 100 mg L-1

ZnSO4 was found best for enhancing the vegetative

growth during whole growing season but flower initiation was earlier with higher

concentration of ZnSO4 (150 mg L-1

). Maximum marketable yield (369.0 g plant

-1) and fruit

quality attributes including firmness (0.75 kg. cm-2

), TSS (8.1 ºBrix), vitamin C (53.30 mg

100 g-1

) and TPC (177.5 mg GAE 100 g-1

) were observed maximum with medium dose of

ZnSO4 100 mg L-1

as compared with higher and lower concentrations. However, antioxidant

134

enzymes (CAT, SOD and POD) were observed maximum with 150 mg L-1

ZnSO4. Higher

and lower doses of ZnSO4 were less effective for improving the quality attributes of

strawberry.

In third experiment SA was applied as foliar spray. Maximum marketable yield

(414.25 g plant-1

) was observed from strawberry plants treated with 9 mM SA as compared to

other treatments. Higher application of 9 mM SA was found better for reducing unmarketable

and small size yield. Strawberry quality attributes including firmness (0.94 kg. cm-2

), vitamin

C contents (56.72 mg 100 g-1

) and TPC (191.50 mg GAE 100 g-1

) were also improved with

higher concentration of 9 mM SA but TSS (8.47 ºBrix) and TSS: Acid ratio (11.76) was

increased with medium concentration of 6 mM SA. Overall, it was found that foliar spray of

9 mM SA was highly effective to increase the vegetative growth, marketable yield, quality

attributes and survival mechanism of strawberry plants during season.

In fourth experiment different concentrations of GA3 were applied on growth stages.

Higher dose of 150 mg L-1

GA3 showed the superiority over other doses to enhance the

vegetative growth. While maximum marketable yield and fruit quality was not improved

with higher concentration of 150 mg L-1

GA3. It is because of higher concentration of GA3

caused the maximum increase in cell division activity due to that more utilization of

photosynthetic products in vegetative growth. It might be possible that due to fewer products

fruit quality could not improve. So, this study proved that 100 mg L-1

GA3 increased the


), improved the TSS (7.85 ºBrix), vitamin C (52.23 mg 100

g-1

) and TPC (181.50 mg 100 g-1

) of strawberry.

Confirmatory trial was performed during next year to compare previous year best

treatments from each experiment and to find out the best treatment. In this experiment 100

mg L-1

GA3 was confirmed for increasing the vegetative growth as compared to other

treatments during whole growing season. Increasing trend was observed regarding


) with 9 mM SA foliar spray as compared to other

treatments. Unmarketable yield and small size yield was also minimum in treated plants.

Maximum strawberry firmness (0.97 kg. cm-2

) was improved with 7 mM CaCl2 foliar spray

while other quality attributes including TSS (8.48 ºBrix), TSS: TA ratio (11.76), vitamin C

(57.72 mg 100 g-1

), TPC (191.50 mg GAE 100 g-1

) and TA (76.50% DPPH) were improved

135

with 9 mM SA foliar spray. In this study, it can be concluded that 9 mM SA was best for

increasing the marketable yield, for improving the quality attributes and for extending the

survival mechanism of strawberry plants during whole growing season.

Postharvest study was executed to check the effectiveness of CaCl2 and SA different

doses on shelf life and quality attributes of strawberry during 15 days of storage. Maximum

vitamin C contents (43.90 mg 100 g-1

), TPC (132.75 mg GAE 100 g-1

), reduction in weight

loss (6.08%) of strawberries and firmness (0.42 kg. cm-2

) was retained with higher

concentration of CaCl2 (6 mM) dipping application. Higher concentration sometimes less

effective because during storage thick coating on fruit surface reduced gaseous exchange

between external and internal environment of fruit. Minimum TSS (7.85 ºBrix), maximum

retaining of acid contents (0.62%), total antioxidants (39.0% DPPH) and enzymatic activities

were observed with SA (5 mM) as compared with other treatments. In postharvest study it

was confirmed that dipping application of CaCl2 (6 mM) and SA (5 mM) showed the

superiority for retaining maximum quality attributes during 15 days of storage.

136

5.2 Future Recommendations

More work is needed on other strawberry cultivars such as Douglas, Toro,

Pocahontas, Honeyo and Tufts by using salts and growth regulators to increase the

marketable yield and to improve quality attributes.

Strawberry is extremely sensitive crop. So, more work on pre harvest practices such

as time of planting runners, planting density, proper mulching to reduce weeds,

protection from frost through tunnel and proper and timely nutrient application is

needed.

Drip irrigation system with fertilizer application (fertigation) is necessary to improve

the better plant growth and yield because strawberry has small root system. Due to

complex soil chemistry and leaching of nutrients strawberry plants cannot receive

proper nutrients.

Molecular level work is needed to identify those genes which develop resistance in

plants against frost damage and adverse climatic conditions.

From postharvest perspective proper packing material, temperature management and

use of other newly emerging salts and growth regulators need to be explored to

reduce decay incidence and to increase the shelf life of strawberries.

5.3 Recommendation for farmer

Strawberry is highly economic short duration (6 months) crop. By applying proper pre

harvest practices farmer can earn more.

Optimized concentrations of salts (7 mM CaCl2 and 100 mg L-1

ZnSO4) and growth

regulators (9 mM SA and 100 mg L-1

GA3) increase the vegetative growth,

marketable yield and improve the qualitative characteristics of strawberry fruit.

Postharvest dipping application of CaCl2 (6 mM) and SA (5 mM) increase the shelf

life and retain maximum quality attributes of strawberries during 15 days of cold

storage at 4°C.

137

5.4 Study- 5

5.4.1 Six months internship (International Research Support Initiative

Program) at University of Florida, USA supported by Higher

Education commission Islamabad Pakistan.

5.4.2 Introduction about GCREC

Gulf Coast Research and Education Center established in 1925 located in Balm/Wimauma

Florida, United States. In past it was only research laboratory where main focus on to

identify the cause and to develop protection measures for the control of fungi that was

causing major losses in tomato crop. Now days the center is known worldwide for the high

quality research and also for facilitating growers and the industry. Major areas of research are

vegetable, floral, strawberry production and breeding. For high quality strawberry production

different management practices are used which including planting density, different N rates,

mulch color, planting date and plant growth regulators.

5.4.3 Strawberry production in Florida

Major production of strawberries comes from United States with 24,000 hectares of land and

1.4 billion kilograms of strawberries (Brennan et al. 2014). In United States, California and

Florida are two major states for largest strawberry production. California produces all year

around but has major strawberry production during summer season and decreases in winter.

Florida is largest producer of winter strawberries and produce fresh strawberries from

November until late March but from the last few years there is competition between Florida

and Mexico for early production of winter strawberries. Mexico has same production pattern

as Florida and produce all year around but in small volumes. Florida growers want to

produce at the end of November and early December to get higher prices because early

season fruit receives maximum prices (Boriss, 2006).

138

5.4.4 FSHS Proceeding paper presented in (131st annual meeting of Florida

State Horticultural Society)

Optimization of Early-season Nitrogen Fertilization Program for New

Strawberry Cultivar ‘Florida Beauty’

Sana Shahzad1, Tia Silvasy

2 and Shinsuke Agehara

2

1

University of Agriculture, Faisalabad, Pakistan

2Gulf Coast Research and Education Center, University of Florida IFAS, Wimauma, FL 33598

Corresponding author: [email protected]

Additional index words. Fragaria × ananassa Duch., fruit earliness

Abstract

Strawberry (Fragaria × ananassa Duch.) growers in Florida generally apply 168–224 kg of

nitrogen (N) per hectare during the growing season, starting with 1.96–2.24 kg/ha/d during

establishment (e.g. 3 weeks) followed by lower rates at 0.56–1.12 kg/ha/d. The initial high-

dose fertilization is beneficial for improving the establishment of strawberry transplants, but

this practice must be tailored for each cultivar based on its growth characteristics and nutrient

requirements. Major aim of this study was to observe the optimal early-season fertilization

program for „Florida Beauty‟ which is a newly developed early-yielding cultivar. Treatments

were different durations of the high N fertilization at 2.24 kg/ha/d during establishment: 0, 3,

6, and 9 weeks. After these treatment durations, all treatments were subjected to the lower

rate at 1.12 kg/ha/d, providing 149 to 243 kg of N in the entire growing season. Transplants

were planted in the field on Sep. 28, 2017 and harvests were performed 30 times between

Nov. 2, 2017 and Feb. 26, 2018. Extending the high N fertilization duration from 0 to 9

weeks accelerated initial canopy development and increased leaf area by 30% during season.

It also increased the early yield (Nov.–Jan.) by 33% and the total season yield by 28%, while

reducing thrip damage fruit by up to 53% in the entire season. These results suggest that

initial high N fertilization (2.24 kg/ha/d) can be extended slightly longer for „Florida Beauty‟

than for other major cultivars in Florida. Delayed establishment of an ideal canopy size can

result in yield reductions and increased insect damage.

mailto:[email protected]

139

Introduction

„Florida Beauty‟ is a newly developed strawberry cultivar which released from University of

Florida in 2017 and originated from a cross between Queensland Australia selection and

„Florida Radiance‟. This cultivar has compact plant growth habit, bright color, low chilling

requirement and excellent fruit quality. The combination of these characteristics makes this

cultivar adaptable to early planting in Florida from 20 Sept. to 1st Oct. (Whitaker et al.,

2017).

Nitrogen is essential component of chlorophyll and plays major role for enhancing vegetative

growth of strawberry plants because chlorophylls allow plants to capture light energy from

the sun and produce carbohydrate molecules in the photosynthesis process. Nitrogen is major

part of plant proteins and also play important role for synthesis of genetic material (DNA and

RNA) (El-Sawy et al., 2012). In strawberry, N is one of the most abundant mineral nutrients,

with the optimal leaf N concentration ranging from 3% to 4% (Hochmuth et al., 1996).

Optimum N fertilization in strawberry produces maximum yield and improves quality. It has

been observed that maximum strawberry yields can be achieved by regular supply of N

irrespective of the N source (Hochmuth and Hanlon, 1999; Simmone et al., 2001). Nitrogen

deficiency caused reductions in total dry biomass and relative growth rate of plant mainly

through decreases in leaf area ratio and plant N contents (Deng and Woodward, 1998).

Increasing N fertilization increases the leaf N contents and promotes the development of

healthy and greener leaves (Albregts and Howard, 1982). Excessive N fertilization can

promote canopy growth (plant spread, leaf number and leaf area) and early marketable yield

but decrease flower production and total marketable yield during season (El-Sawy et al.,

2012).

Current N fertilization practices for increasing strawberry production in Florida are based on

previous studies which included different N sources, fertilizer placement methods, pre-plant

fertilization, and different N fertilization rates (Hochmuth and Hanlon, 1999; Albregts and

Howard, 1982; Agehara et al., 2017). In general, Florida strawberry growers apply 168–224

kg of nitrogen per hectare during the growing season, which starting from 1.96–2.24 kg/ha/d

during establishment (e.g. 3 weeks) followed by lower rates at 0.56–1.12 kg/ha/d (Sangha

and Agehara, 2016). The initial high-dose fertilization is beneficial for improving the

140

establishment of strawberry transplants, but this practice must be tailored for each cultivar

based on its growth characteristics and nutrient requirements.

Therefore, the aim of this study was to investigate the optimal early-season N fertilization

program for „Florida Beauty‟.

Materials and Methods

A field experiment was conducted at the Gulf Coast Research and Education Center in Balm,

FL, during the 2017-18 season. Raised beds were 122 cm apart at the center, 68 cm wide on

the top, 81 cm wide at the base, and 25 cm high. In each bed, one drip tape with emitters

spaced 30 cm apart and a flow rate per emitter of 0.91 L/h (Netafim USA, Fresco, CA) was

installed at 2-cm depth. Beds were fumigated with Pic-Clor 60 at 336 kg/ha and covered with

black polyethylene mulch. Bare root strawberry transplants of „Florida Beauty‟ were planted

on 28 Sept., 2017 with 38 cm plant spacing in double rows with 16 plants per plot. Sprinkler

irrigation was used for 2 weeks following planting for 8-10 hours per day to ensure sufficient

plant stand establishment. Thereafter, drip irrigation was used for irrigation and fertilization.

Table 1. Nitrogen (N) fertilization treatments in this study.

Treatments were different durations of the high N fertilization at 2.24 kg/ha/d during the

early season: 0, 3, 6, and 9 weeks, which are denoted thereafter as 0, 3, 6, and 9 weeks

treatments, respectively. After these treatment durations, all treatments were subjected to the

lower rate at 1.12 kg/ha/d, providing 149 to 243 kg of N in the growing season. Urea

ammonium nitrate (UAN) was used as an N source while phosphorous (P) and potassium (K)

were applied using a 0-2-8 (N-P2O5-K2O) liquid fertilizer. Harvests were performed 30 times

Duration Total N

of high Week 1-2 Week 3-5 Week 6-8 Week 9-11 Thereafter rate

N rate (kg/ha)

0 week 0 1.12 1.12 1.12 1.12 149

3 weeks 0 2.24 1.12 1.12 1.12 196

6 weeks 0 2.24 2.24 1.12 1.12 219

9 weeks 0 2.24 2.24 2.24 1.12 243

Nitrogen fertilization rate (kg/ha/d)

141

between 2 Nov. 2017 and 26 Feb. 2018. Fruits were graded according to the USDA grading

standards. Leaf area was noted using a leaf area meter (LI-3100C). Treatments were designed

according to randomized complete block design with four replicated plots per treatment. Data

was analyzed using SAS (version 9.2, USA). Tukey–Kramer test was used for multiple

comparisons of means.

Results and Discussion

Figure 1 shows the positive treatment effects of initial high N fertilization on canopy growth

54 days after transplanting. Increasing the duration of initial high N fertilization accelerated

the development of canopy.

Fig. 1. Canopy growth of ‘Florida Beauty’ strawberry 54 days after transplanting (21 Nov,

2017).

142

Leaf area measured at the end of season increased by 30.1% with extending the duration of

initial high N fertilization from 0 to 9 weeks (1576 vs 2051 cm2) (Fig. 2). This observation

suggests that initial high N fertilization has long-term effects on leaf area development of

„Florida Beauty‟ because N is major component of chlorophyll, essential for metabolic

processes especially, synthesis of proteins, nucleic acids, enzyme activation, energy transfer,

osmotic regulation, respiration and photosynthesis (Taiz and Zeiger, 2002). So, these

processes play major role in the establishment of productive canopy.

Sangha and Agehara (2017) examined root morphological responses of bare-root strawberry

„Florida Radiance‟ transplants to different N rates, 0.56, 1.12, 1.68, 2.24, 2.80 and 3.36

(kg/ha/d) by using a scanner-based rhizotron system. Higher N rates resulted in enhanced

canopy and root growth. Shoot growth recorded a more rapid response to N relative to root

growth. Both canopy area and crown diameter increased linearly with N rates. The increased

canopy area improved root elongation whereas primary root formation was enhanced as a

result of increased crown diameter. Their study suggests that shoot and root growth are

closely linked with each other, and this relationship likely explains the responsiveness of

canopy growth to initial N fertilization observed in this study.

Fig. 2. Leaf area of ‘Florida Beauty’ strawberry at the end of the growing season as

affected by the duration of high N fertilization (2.24 kg/ha/d and thereafter 1.12

kg/ha/d).

143

Early-season (Nov.-Jan.) yields were more responsive to initial high N fertilization than late-

season (Feb.) yields (Fig. 3). When initial high N fertilization was used for 0, 3, 6, and 9

weeks, early-season yields were 10.20, 11.44, 12.19 and 13.39 t/ha, respectively. Only the 9

week treatment was significantly different from the 0 week treatment, with the maximum

yield increase by 31.3%. By contrast, duration of initial high N fertilization had no

significant effect on late season yields. Total season yields increased by 22.7% with

increasing the duration of initial high N fertilization from 0 to 9 weeks. When the duration of

initial high N fertilization was 3 to 6 weeks, yield increases were not statistically significant.

Fig. 3. Marketable yield of ‘Florida Beauty’ strawberry during growing season as

affected by the duration of high N fertilization (2.24 kg/ha/d and thereafter 1.12

kg/ha/d).

144

Sangha and Agehara (2016) evaluated different N fertilization rates during the early season

using two strawberry cultivars, „Florida Radiance‟ and „Florida127‟. Their treatments were

five N rates during the early season (22 Oct.-14 Dec.), 0.22, 0.67, 1.12, 1.56 and 2.0 N

kg/ha/d, all of which were followed by 1.12 kg/ha/d during the rest of the season. „Florida

Radiance‟ showed continuous increases in total marketable yields by up to 57% (13.6 vs 21.3

t/ha) with increasing the early season N rate from 0.22 to 2.0 kg/ha/d. By contrast,

„Florida127‟ increased total marketable yields by up to 53% (12.1 vs 18.5 t/ha) with

increasing N rate from 0.22 to 1.12 kg/ha/d but no yield differences with further increases in

N rate. Therefore, their results suggest that „Florida Radiance‟ is more responsive to higher N

rates than „Florida127‟ during early season, similar to our findings initial high N fertilization

increased total marketable yield of „Florida Beauty‟. Similarity between „Florida Radiance‟

and „Florida Beauty‟ was the high yield response to N fertilization during establishment.

Major Florida strawberry cultivars, such as „Florida Radiance‟ and „FL 05-107‟, require a

medium level of fertilization to produce excellent fruit yields, which is generally up to 3

weeks of initial high N fertilization with the total N of 168 to 196 kg/ha (Whitaker et al.,

2008; Whitaker et al., 2012). By contrast, „Florida127‟ responds more strongly to N

application in terms of vegetative growth and requires lower N fertilization rates for fruit

production (Whitaker et al., 2014). Our study demonstrated that fruits yields of „Florida

Beauty‟ can be maximized using 9 weeks of initial high N fertilization with the total season

rate of 243 kg/ha, suggesting that this cultivar is highly responsive of N fertilization. This

cultivar generally has greater fruit loads than other cultivars in early- to mid-season

especially when planted early (e.g. 20 Sep. to 10 Oct.), possibly requiring higher N rates to

maintain plant health and productivity.

Our results suggest that high N fertilization is beneficial for more efficient N uptake during

establishment which results in improved fruit earliness and yields. Initial high N fertilization

for „Florida Beauty‟ can be extended up to 9 weeks to maximize fruit yields, thereby

requiring relatively large amounts of N for establishment compared to other major Florida

cultivars.

145

Conclusions

„Florida Beauty‟ is characterized by its compact plant habit, which is highly responsive to N

fertilization during establishment. We recommend using high N fertilization at 2.24 kg/ha/d

for 9 weeks during establishment, which is slightly longer compared to the recommendation

for other cultivars (Whitaker et al., 2008; Whitaker et al., 2012). Negative impact of

excessive N fertilization appears to be minimal for this cultivar. Delayed establishment of an

ideal canopy size can result in yield reductions especially during the early season.

146

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