EFFECT OF PLANT GROWTH REGULATORS ON DE- GREENING & COLD … · Cold storage 6.6 10.1 6.2 7.8 6.3 De-greening 5.8 9.4 6.3 7.6 9.3 Results Increase in temperature, increased brix‐acid

EFFECT OF PLANT GROWTH REGULATORS ON DE-

GREENING & COLD STORAGE OF TANGO AND SUGAR BELLE

CITRUS VARIETIES

Daniel Adu Boakye [email protected]

1

Introduction Tango and sugar belle growers prefer uniform color break or maturation

to ensure harvesting of fruits within specific periods with good internal

qualities.

Gibberellic Acid (GA3)

Brassinosteroid (HBr)

Abscisic Acid (ABA)

Influence color break ormaturation in citrus.

These plant growth regulators influence color maturation but no report has beenmade on their effects on tango and sugar belle.

GA3 retards fruit senescence while brassinosteriods increase fruit peel coloration. ABA hastens ripening and chlorophyll breakdown, thus advancing peel coloration

or maturation.

2

Objective

To assess the effect of plant growth regulators on de-greening

and cold storage conditions of Tango and Sugar belle citrus

varieties

To evaluate the effect of plant growth regulators on internal

qualities after de-greening and cold storage

Daniel Adu Boakye [email protected]

3

Materials and Methods

Varieties: Sugar belle and Tango

Treatments Used

Abscisic acid (ABA), 1 mM

Gibberellic Acid (GA3), 20 ppm.

Brassinosteriods (HBr), 1 uM

Control (water)

Daniel Adu Boakye [email protected]

Samples for cold storage and de‐greening were collected from two groves. That is, sugar belle from UF - SWFREC Demonstration groves, Immokalee and tango from Martin’s grove, Labelle

4

Harvested fruits for Cold storage & De‐

greening

Treatments were applied after 

harvesting of fruits

Data Collected 

Cold storage at 45 F (7.2 C)

84 o F and 95 % RH with 5 ppm of ethylene (de‐greening)

84 o F and 95 % RH with no ethylene (de‐greening control)

Color advancement

Internal qualities • Brix• Titratable acidity

Data Collection Interval• Cold storage – 6 days interval• De‐greened fruits – 2 days (48

hours)

Materials and Methods

Data AnalysisTreatments Application

Chroma meter  was used to measure peel color at initial stage and periodically  for fruits that were de‐greened and cold room storage.Brix‐acid ratio was determined by dividing brix by titratable acidity. Where levels of brix or solid soluble content was determined using refractometer and % titratable acidity (% acid) was evaluated using garner et al., method and with the formula above

5

Results

‐0.7

‐0.6

‐0.5

‐0.4

‐0.3

‐0.2

‐0.1

0water HBr (1 µM) GA (20 ppm) ABA (1mM)

Chan

ge in

 color

a/b

PGRs

Figure 1: Sugar belle peel coloration after PGR treatments in cold storage room (45oF)

Day 0 Day 6 Day 12

Daniel Adu Boakye [email protected]

The plant growth regulators had slight effect (or no effect) on the peel coloration or maturation by Day 12 particularly as water (control) influenced the peel coloration more than all the PGR. But the mild peel color advancement from Day 0 to Day 6 can be link to loss of the sensible heat due to the cold storage

6

‐0.6

‐0.5

‐0.4

‐0.3

‐0.2

‐0.1

0

Water HBr GA3 ABA

Chan

ge of color

a/b

PGRs

Day 0 Day 6 Day 12

Figure 2: Effect of plant growth regulators (PGRs) on peel coloration of tango fruits in cold

Results

In cold storage, the plant growth regulators did not have significant effect on peel color advancement or coloration particularly when compared with water (control). Though there were slight changes in coloration on Brassinosteroid (HBr) and Abscisic acid (ABA) which may be as a results of shedding off the sensible heat.  Tango’s response to the PGRs is very low according to this study.

7

Some photos

Daniel Adu Boakye [email protected]

Control (water)

Abscisic acid

3a 3b

4c 4d

Figures 3-4: Effect of Plant growth regulators on sugar belle and tango fruits before (3a, 3c, 4a & 4c) cold storage and after 12 days (3b, 3d, 4b & 4d)

of cold storage

Control (water)

Abscisic acid

4a 4b

4c 4d

Sugar belle Tango

Comparatively, the control is not different from Abscisic acid (as well as the other growth regulators) especially on day 12. This confirms that these plant growth regulators were not able to advance peel color maturation of sugar belle and tango in  cold storage

8

Results

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0 water HBr (1 µM) GA (20 ppm) ABA (1mM)

a/b

PGRs

Figure 5a: Effect of plant growth regulators (PGRs) on peel coloration of Tango fruits stored at temperature (84 F) and Relative Humidity (95 %)

Initial color 96 hrs after Temp (84 F) & RH (95%)

Peel coloration of tango fruits were not significantly influenced by temperature at 84 F and relative humidity at 95 %. Higher temperature and relative humidity are known to advance maturation in climacteric fruits but they have slight effect on non‐climacteric fruits or products since ethylene production is minimal

9

Results

‐0.45

‐0.4

‐0.35

‐0.3

‐0.25

‐0.2

‐0.15

‐0.1

‐0.05

0

water HBr (1 µM) GA (20 ppm) ABA (1mM)

Ch

ang

e in

co

lor

a/b

PGRs

Figure 5b: Effect of Plant growth regulators (PGRs) on de‐greening on tango 

Before Degreening

End of 48 hrs of Degreening

After Degreening (48 hrs)

Brassinosteroid (HBr)  and GA3  did not make any significant contribution in the peel color advancement when compared with control but comparatively abscisic acid was significant than all the other treatments after 48 hours of de‐greening.But when this figure 5a is compared with figure 5b, it can be revealed that addition of ethylene had significant influence in peel coloration or advancement of the fruits, thus when the initial or before de‐greening is compared with 48 hours after de‐greening

10

Results

‐0.45

‐0.4

‐0.35

‐0.3

‐0.25

‐0.2

‐0.15

‐0.1

‐0.05

0 water HBr (1 µM) GA (20 ppm) ABA (1mM)

Ch

ang

e in

co

lor

a/b

PGRs

Figure 6a: Effect of plant growth regulators (PGRs) on color maturation of sugar belle fruits at temperature (84 F) and relative humidity (95 %)

Initial color

96 hrs after Temp (84 F) & RH(95%)

The temperature and relative humidity advanced peel coloration but it cannot be fully associated to the plant growth regulators since the control (water) changed or advanced in color more than all the PGRs. Also abscisic acid (ABA) and Brassinosteroid were expected to advance in color more than GA (20 ppm) since ABA is known to advance peel color development and GA (20 ppm) delay senescence or peel coloration.

11

Results

‐0.5

‐0.4

‐0.3

‐0.2

‐0.1

0

0.1

0.2water HBr (1 µM) GA (20 ppm) ABA (1mM)

Ch

ang

e in

co

lor

(a/b

)

PGRs

Figure 6b: Effect of Plant growth regulators on De-greening of Sugar belle

 Before Degreening

 End of 48 hrs of Degreening

48 hrs After   Degreening

Comparatively, the effect of Plant growth regulators on color break or maturation of sugar belle is mild. The color maturation of the control (water) is similar to all the plant growth regulators especially after 48 hours of de‐greening. Effect of de‐greening is significant in advancing peel coloration when figure 6a and 6b are compared. Thus, sugar belle advanced in coloration with de‐greening than tango which means that sugar response to 5 ppm ethylene, 84 F and 95 % RH treatment more than tango

12

Some Photos onSugar belle & Tango Before and after De-greening

Daniel Adu Boakye [email protected]

Figures 7 & 8: Sugar belle fruits before (1A) de‐greening and after (1B) de‐greening; 2A‐before de‐greening of tango and after de‐greening 

7a 7b 8a 8b

The figure 7 (a & b) is the control for sugar belle while figure 8 (a & b) is the Brassinosteroid (HBr) for tango 

13

Brix-acid ratio of Tango and Sugar belle

Figure 9b: Tango

Initial water HBr (1 µM) GA (20 ppm) ABA (1mM)

Cold storage 12.8 10.1 9.8 10 8.7

84 F & 95 % (no ethylene) 11.4 14.5 12 18.3 14.2

Figure 9a: Sugar belleInitial water HBr (1 µM) GA (20 ppm) ABA (1mM)

Cold storage 6.6 10.1 6.2 7.8 6.3

De-greening 5.8 9.4 6.3 7.6 9.3

Results

Increase in temperature, increased brix‐acid ratio either with ethylene or without ethylene when compared with cold storage of all the two varieties irrespective of the plant growth regulator except sugar belle’s control and GA (20 ppm).

Brix‐acid ratio is very essential since it constitutes a measure of the balance between sugars and acids. It serves as indicator of the palatability of the juice where larger values indicate sweeter taste. (Note: Brix‐acid ratio= Brix/Titratable acidity). At an increased temperature irrespective of relative humidity result to increase in brix‐acid ratio in the fruits as a result of decrease in titratable acidity or citric acid (Burdon et al., 2006). 

14

Conclusion

t

De-greening enhanced coloration in sugar bellethan in tango.

The mild effects of ABA and HBr suggest thatplant growth regulators interaction with de-greening might have been impaired

There was increase brix‐acid ratio either withethylene (de‐greened) or without ethylene whencompared with cold storage of all the two varietiesexcept sugar belle’s control and GA (20 ppm)

15