MORPHOLOGICAL CHARACTERISTICS AND YIELD OF GRAIN SORGHUM (Sorghum bicolor L. Moench) by JOHN C. BICKEL, B.S. A THESIS IN CROP SCIENCE Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the degree of MASTER OF SCIENCE Approved Accepted August, 1983
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MORPHOLOGICAL CHARACTERISTICS AND YIELD OF
GRAIN SORGHUM (Sorghum bicolor L. Moench)
by
JOHN C. BICKEL, B.S.
A THESIS
IN
CROP SCIENCE
Submitted to the Graduate Faculty of Texas Tech University in
Partial Fulfillment of the Requirements for
the degree of
MASTER OF SCIENCE
Approved
Accepted
August, 1983
/ -I
r;i',h , " ACKNOWLEDGMENTS
The author wishes to thank the chairman of the committee. Dr. Kent
R. Keim, for his many helpful suggestions and patience during the
preparation of this manuscript. The aid of the members of the
committee. Dr. R. C. Jackson and Dr. D. R. Krieg, is appreciated as
well. For their help during the collection of the data, thanks go to
Pam Nafzger and Michelle Fritz. The patience and understanding of my
wife, Connie, is deeply appreciated. Many thanks are given to my
father and mother. Bill and Priscilla Bickel, who have supported me at
all times in many ways. Thanks are extended to the typist, Jan Readio.
Acknowledgement is also given to the Dryland Crop Improvement Grant,
without which this work and thesis would not have been possible.
11
TABLE OF CONTENTS
ACKNOWLEDGMENTS ii
LIST OF TABLES v
I. INTRODUCTION 1
II. REVIEW OF LITERATURE 3
Physiological Features 3
Leaf Area and Yield 4
Panicle and Yield 6
Stalk and Yield 7
Number of Leaves 8
Height of Plant 8
Morphological Trait Correlations with Grain Yield 9
III. MATERIALS AND METHODS 12
Germplasm 12
Field Layout 12
Characters Investigated 13
Statistical Analysis 14
IV. RESULTS AND DISCUSSION 16
Morphological Characteristics 16
Dry Weights 19
Grain Yield and Related Traits 23
Morphological Trait Means 25
Dry Weight Means 33
Mean of Grain Yield and Related Traits 34
111
Correlations Between Morphological Traits, Dry
Weights, and Grain Yield 35
V. SUMMARY AND CONCLUSIONS 48
APPENDIX 51
REFERENCES CITED 53
IV
LIST OF TABLES
1. Analysis of variance (mean squares) of data on morphological traits of inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels (1980) 17
2. Analysis of variance (mean squares) of data on morphological traits of inbred lines over water levels (1980). . . . 18
3. Analysis of variance (mean squares) of data on plant dry weights for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels (1980) 20
4. Analysis of variance (mean squares) on data for plant dry weights over water levels (1980) 21
5. Analysis of variance (mean squares) of data on plot grain yield and related traits for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels (1980) 22
6. Analysis of variance (mean squares) on data for field plots over water levels (1980) 24
7. Means of morphological traits for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels and over water levels (1980) 26
8. Means of plant dry weights and plot grain yield for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP +3) irrigation levels and over water levels (1980) 31
9- Correlations of morphological traits and dry weights on morphological traits and dry weights for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels (1980) 36
10. Correlations of morphological traits and dry weights on morphological traits and dry weights for inbred lines over water levels (1980) 37
11. Correlations of grain yield and related traits on morphological traits and dry weights of inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels (1980) 39
V
12. Correlations of grain yield and related traits on morphological traits and dry weights of inbred lines over water levels (1980) ^0
13. Correlations between grain yield and related traits for inbred lines grown under preplant plus one (PP + l)i preplant plus three (PP +3) irrigation levels and over water levels (1980) 47
VI
CHAPTER I
INTRODUCTION
Grain sorghum (Sorghum bicolor L. Moench) is an important crop in
the United States, particularly in the semiarid region of the
Southwest. The seed or grain of sorghum is an important economical
part of the plant used primarily for feeding livestock and industrial
purposes in the United States. Grain sorghum is important for human
consumption in parts of China, India and Africa.
Texas grain sorghum acreage has decreased yearly from a high of 3
million hectares harvested in 1975 to a present estimated level of 1.5
million hectares. During the same period, on the semiarid Rolling
Plains region, the sorghum area decreased 66%. Average yield in the
period 1975 to 1980 ranged from 995 kg/ha to 2386 kg/ha (Clark and
Pietsch, 1980).
Grain yield of sorghum is related to previous environmental in
fluences during the growing season and effect of such influences on
various physiologic systems during development. Water and temperature
are the major factors influencing yield in the Rolling Plains region
and are largely responsible for the wide variations in grain yield.
Effects such as those caused by water stress are manifest through
influences on various morphologic characteristics of the developing
sorghum plant. An understanding of these effects could provide
information useful in developing desirable types in a sorghum genetics
and breeding program.
Previous studies with wheat indicate a potential for use of
various morphological traits at various growth stages (especially
anthesis) and their association with grain yield as a selection tool
in a breeding program. However, little information exists for sorghum
concerning the relationship of grain yield with morphologic traits
during development.
The main objective of this study was to determine if biologically
important relationships exist between grain yield and various
morphologic characters for eight sorghum genotypes grown under two
water levels. If genotype by water level interactions occur, then
hybridization and extraction of segregates suited to environmental
conditions will be possible.
CHAPTER II
REVIEW OF LITERATURE
Physiological Features
Blum (1974) evaluated sorghum cultivars and found low initial
water use prior to anthesis relative to the total used at maturity to
be a positive drought response. Of two sorghum genotypes grown under
water stress in the field, Stout, Kannangara and Simpson (1978)
observed one genotype to be capable of responding by shortening
developmental sequences, thus taking advantage of early season
moisture. When compared to the irrigated treatment, this genotype was
found to be in a later stage of inflorescence development.
According to Acevedo, Hsiao and Henderson (1971), water uptake
provides impetus for cell enlargement. Water use efficiency is the
ratio of dry matter produced to water used. Under conditions of
limited moisture, there is an optimal level of vegetative growth,
depending on the available water supply, for maximum grain yield
(Fisher and Kohn, 1966b).
Fisher and Kohn (1966b), working with wheat, found large
differences in vegetative growth caused relatively small differences
in evapotranspiration rates when soil moisture was adequate. An
increase in total dry matter of lOOg/m^ was associated with an
increase in cumulative evapotranspiration of 1.27 cm.
Sorghum has been shown to use water more efficiently for grain
production than some other grain crops (Major and Haman, 1981;
Sanchez-Diaz and Kramer, 1971; El-Sharkaway and Hesketh, 1964). Major
3
and Haman (1981) found that sorghum used water more efficiently than
barley (Hordeum vulgare L. 'Gait') or wheat (Triticum aestivum L.
'Neepawa'). Kernel growth ceased after whole-plant growth ceased for
barley and wheat, but for sorghum there was continued kernel growth.
Sanchez-Diaz and Kramer (1971) compared corn (Zea mays L.) and sorghum
water deficits on leaf segment samples. The greatest deficit of
sorghum was only 29% at a leaf potential of -15.7 bars while corn was
56.6% at -12.8 bars. This indicated that sorghum retained a larger
fraction of its water at given water potentials. El-Sharkaway and
Hesketh (1964) used temperature and water stress as treatments to
compare young fully expanded leaves of sorghum (Sorghum vulgare L.
PP + 1, and plant weight was not significant in PP + 3 when correlated
with plant height. Over water levels, peduncle length resulted in the
highest positive significant correlation (0.577) (Table 10) with plant
height as would be expected since internode length is directly related
to plant height, being measurements of the same overall genetic
expression.
An observation of the means (Tables 7 and 8) indicates wide
variation of all inbred lines for plant height and head dry weight
except R 9188 and TX 2737 which remained essentially constant over
water levels (LSD not significant). All morphological traits gave
significant negative correlations with grain yield in PP + 1 and PP +
3 except head dry weight which gave highly significant positive
correlations for both plot head weight and adjusted yield (Table 9).
However, large variations in grain yield (1000 kg/ha) between
environments for R 9188 and TX 2737 may 'be evidence these are early
lines able to use available water for grain yield (Table 11).
Correlation of peduncle length with morphological traits in PP +
1 and PP + 3 were negative when significant, except number of leaves
in PP + 3 (Table 9), as were r-values for grain yield traits (Table
11). Over water levels, a positive highly significant (P = .01)
correlation was observed between head dry weight and peduncle length.
This relationship would be expected since peduncle length is related
to plant height, and plant height and head dry weight were positively
correlated (Table 10).
No significant positive correlation of peduncle length with grain
yield was observed (Tables 11 & 12), unlike results reported for wheat
w 39
Table 11. Correlations of grain yield and related traits on morphological traits and dry weights of inbred lines grown under preplant plus one (PP + 1) and preplant plus three (PP + 3 ) irrigation levels (1980).
PLOT
Head Weight
Adjusted Yield
Moisture Percentage
Plant Dry Weight
-0.044 -0.082
-0.152* -0.195*
0.330** 0.053
Threshing Percentage
Plant Height
Peduncle Length
Peduncle Area
Number of Leaves
Total Leaf Area
Total Photosynthetic Area
Head Dry Weight
Stalk Dry Weight
Leaf Dry Weight
0.002 t 0.218**tt
-0.055 -0.372**
-0.036 -0.209*
-0.060 -0.243**
0.041 -0.232**
0.040 -0.238**
0.324** 0.291**
-0.151* -0.214**
-0.048 -0.075
-0.079 -0.339**
-0.049 -0.444**
-0.038 -0.369**
-0.168* -0.270**
-0.062 -0.389**
-0.064 -0.400**
0.277** 0.210**
-0.258** -0.315**
-0.140 -0.192*
0.324** 0.423**
0.167* 0.515**
0.155* 0.622**
0.486** 0.497**
0.291** 0.203**
0.296** 0.221**
-0.232** ^0.320**
0.420** 0.186*
0.330** 0.051
-0.278** -0.023
-0.023 0.197*
-0.043 -0.326**
-0.310** -0.084
-0.278** -0.356**
-0.280** -0.366**
0.100 -0.106
-0.385** -0.234**
-0.267** -0.234**
-0.311** -0.231**
*, ** - significant at 0.05 and 0.01 probability level, respectively. t, ft - denotes value for PP + 1 and PP + 3, respectively.
40
Table 12. Correlations of grain yield and related traits on morphological traits and dry weights for inbred lines over water levels (1980).
PLOT PLANT
Head Weight
Adjusted Yield
Moisture Percentage
Threshing Percentage
Plant Height
Peduncle Length
Peduncle Area
Number of Leaves
Total Leaf Area
Total Photosynthetic Area
Head Dry Weight
Stalk Dry Weight
Leaf Dry Weight
Plant Dry Weight
0.521**
0.095
0.171**
-0.083
0.200**
0.204**
0.492**
0.060
0.181**
0.200**
0.296**
-0.029
0.010
-0.167
0.009
0.010
0.401**
-0.104
0.024
0.036
-0.310**
0.028
0.056
0.365**
-0.068
-0.067
-0.447**
0.075
-0.033
-0.065
-0.617**
-0.301**
-0.365**
-0.183**
-0.464**
-0.473**
-0.269**
-0.387**
-0.377**
-0.406**
** - significant at 0.01 probability level
41
by Briggs and Aytenfisu (1980). Correlations between peduncle area
and morphological traits and dry weights followed the same patterns as
peduncle length except for a significant negative correlation with
head dry weight of -0.194 in PP + 1 (Table 10). No positive
correlation between peduncle area and leaf area or photosynthetic area
indicates that size of peduncle area in relation to photosynthetic
area was either too small to have an effect or leaf area and peduncle
area develop independently.
Peduncle length and plant height are the result of internode
expansion. The positive significant association (Tables 9 & 10) of
peduncle length with plant height indicates taller inbreds had longer
peduncles. However, an observation of the means (Table 7) reveals
that even though SC 170-6-17 had large variations for height from PP +
1 and PP + 3 of about 20 cm, peduncle length remained essentially
constant as did peduncle length of TX 7078 and NSA 440. Selection of
types not varying for peduncle length in various environments would
result in a genotype with a good combine harvest characteristic.
Correlation coefficients for number of leaves were positive and
highly significant (P = .01) with all dry weights in PP + 1 and PP + 3
(Table 9) and over water levels (Table 10) except head dry weight
being negative when significant. Data indicates as leaf number
increased dry weight increases as expected since number of leaves is
directly related to leaf weight and so to plant weight. Negative
correlation between head dry weight and number of leaves could be due
to inbreds SC 56-14, SC 35-14 and R 9188 having small head dry weights
and large leaf numbers in PP + 1 and PP + 3. Correlations between
42
number of leaves and grain yield were negative when significant for PP
+ 1, PP + 3, and over water levels (Tables 11 & 12). This type of
association with head dry weight and grain yield could relate to
optimal vegetative production for maximum grain yield under water
stress referred to by Fisher and Kohn (1966b). SC 56-14, SC 35-14,
and R 9188 may have put on excess leaf area using water needed later
t-
for grain filling. The excess leaf area could be due to June 30
irrigation near the time of panicle initiation resulting in more
leaves being initiated or allowing leaves already initiated, but not
mature, to increase in size.
Correlations between leaf area and total photosynthetic area with
dry weights in PP + 1 and PP + 3 (Table 9) and over water levels (Table
10) were all positive and highly significant (P = -01). Leaf number,
leaf area, and total photosynthetic area are directly related being
similar measurements of the same genetic expression. Correlations of
these three traits with dry weights followed the same pattern, except
for a significant negative correlation in PP + 1 between leaf number
and head dry weight.
Leaf area and photosynthetic area correlations between grain
yield and associated traits were negative when significant in PP + 1
and PP + 3 (Table 11) and were not significant over water levels
(Table 12). This contradicts results reported by Voldeng and Simpson
(1967) and Simpson (1968) of positive correlations between grain yield
of wheat and photosynthetic area. Stickler and Pauli (1961) reported
increased relative yield per unit leaf area when leaves were removed,
implying that less leaf area may give a compensation effect allowing
43
assimilates that may otherwise be diverted to leaf area production to
be used for grain yield.
From the photosynthetic area data, conclusions can be made that R
9188 and TX 2737 were the most consistent (LSD not significant), each
varying only slightly between water levels. No significant positive
correlation between photosynthetic area and grain yield was observed
(Tables 11 & 12), contrary to results obtained by Leeton (1978). An
observation of the means (Table 7) indicates TX 2737 and R 9188 had
consistent photosynthetic areas, but wide variation (LSD significant)
in grain yield between water levels. In contrast, TX 7000 and SC 170-
6-17 had wide variation (LSD significant) in photosynthetic area, but
grain yields between treatments (LSD for TX 7000 not significant, but
SC 170-6-17 significant) were not as variable as other inbred lines.
Inbreds TX 7000 and SC 170-6-17, added extra leaf area with additional
water. However, these two lines not having a corresponding increase
in grain yield, may be an indication of inefficient partitioning.
This relates to the optimal amount of vegetative growth produced in
relation to grain yield referred to by Fisher and Kohn (1966b).
Over water levels correlations were positive and highly
significant (P = -01) between plant height and photosynthetic area
(Table 10), evidence that the taller lines produced more leaves and
stalk, and larger peduncles at maturity. This indicates that
selection for any one of these traits would have an effect on other
traits for these inbred lines.
Correlations between plant dry weights were all highly signifi
cant and positive for PP + 1, PP + 3, and over water levels as expected
44
since these similar measurements of the same genetic system. Over
water levels correlations of head dry weight, leaf dry weight and
plant dry weight with plot head weight were positive and highly
significant (P = .01) (Table 12). Correlations between dry weights
and plot head weight and adjusted yield were negative when significant
in PP + 1 and PP + 3 (Table 11). Over water levels head dry weight,
leaf dry weight and plant dry weight gave positive, highly significant
(P = .01) correlations with plot head weight (Table 12). Only head
dry weight gave positive significant correlations with adjusted yield
(Tables 11 & 12). The highly significant positive correlation between
head dry weight at bloom and plot head weight can be explained as
being due to florets produced in the panicle leading to final grain
yield.
Data for means of dry weights and adjusted yield (Table 8)
indicate that genotype by water level interactions resulted in wide
variation between treatments. TX 7000 had a decrease in head weight
of about 6 grams from PP + 3 to PP + 1, but only a 500 kg/ha decrease
in grain yield (Table 8). This contrasts with R 9188 and TX 2737
which had essentially the same head dry weight with either water
level, but grain yield decreases of over 1000 kg/ha.
Stalk dry weight was reduced for TX 7000 and SC 170-6-17 while
other genotypes did not decrease as greatly from PP + 3 to PP + 1. The
observation of Wardlaw (1967) and Boyer (1976) that assimilates are
translocated from the stalk to fill the grain could explain part of
the grain yield results obtained for TX 7000 and SC 170-6-17.
45
NSA 440 also had a large decrease in head dry weight from PP + 3
to PP + 1, and although grain yield was only decreased 300 kg/ha, rank
in relation to other lines for grain yield was low (Table 8).
Head dry weight at bloom was positively correlated with grain
yield (Tables 11 & 12). An observation of the data indicates that
although TX 7000 and SC 170-6-17 had large decreases in head dry
weight, the reductions in grain yield were not as substantial as the
reduction for R 9188 and TX 2737. NSA 440 ranked second in PP + 1 for
head dry weight, but sixth for adjusted yield, indicating an inability
to fill the grain.
Head dry weight over water levels (Table 8) for SC 170-6-17 was
lower than TX 2737, TX 7078, and TX 7000, but adjusted yields of these
lines were not significantly different. In the PP + 1, head dry
weights for TX 2737 and TX 7078 were significantly different from SC
170-6-17 and TX 7000, but adjusted yield was not significant. In PP +
3, head dry weight and adjusted yield for the four lines were not
significantly different.
The means for adjusted yield of TX 7000 and SC 170-6-17 were more
consistent over both water levels (Table 8). If stability of yield
over a range of environments was desired, these would be the types of
lines selected for use in a breeding program due to their ability to
produce grain yield when water is limiting.
Data for plant dry weight (Table 8) indicates TX 7000 and SC 170-
6-17 had large variation in dry matter production between water levels
at bloom while R 9188 and TX 2737 remained essentially the same in
both treatments. Adjusted yield of TX 7000 and SC 170-6-17, though
46
not significantly different, exceeded TX 7078 by 400 kg/ha and 240
kg/ha, respectively. Evidence is provided that TX 7000 and SC 170-6-
17 were able to use the available moisture in PP + 1 for grain fill
rather than vegetative growth.
Plant dry weight of inbred lines R 9188 and TX 2737 remained
essentially the same in either environment (Table 8). However, wide
variations in grain yield indicate an interaction of water level with
genotype for grain yield, but not vegetative growth. This could be
due to early maturity or extensive growth of the root system.
Correlations between plot head weight, grain weight, and adjusted
yield were highly significant and positive in PP + 1, PP + 3, and over
water levels (Table 13) as would be expected since these are directly
related. However, correlations between these grain yield traits and
moisture percentage were significant and negative in PP + 1 and PP +
3, and over water levels. Threshing percentage had a highly
significant (P = .01) negative correlation with plot head weight over
water levels (Table 13). This indicates excess nonseed portions were
produced in relation to grain.
An observation of the means indicates that inbreds with the
largest grain yield had the lowest moisture percentage and highest
had low grain yields, high moisture percentage, and low threshing
percentage, evidence that late maturity could account for some of the
low yielding potential for these inbred lines.
47
Table 13. Correlations between grain yield and related traits for inbred lines grown under preplant plus one (PP +1) and preplant plus three (PP + 3) irrigation levels and over water levels (1980).
Plot Head Weight
Adjusted Yield
0.958**t 0.844**tt 0.900**^
Moisture Percentage
-0.419** -0.195* -0.618**
Threshing Percentage
0.387** -0.024 -0.375**
Plot Adjusted Yield -0.546** -0.323** -0.627**
0.614** -0.268** 0.035
Moisture Percentage -0.634** 0.504** 0.098
* * _
t, tt. significant at 0.05 and 0.01 probability level, respectively. ^ - denotes value for PP + 1, PP + 3, and over water levels,
respectively.
CHAPTER V
SUMMARY AND CONCLUSIONS
The major objectives of this study were to (1) determine what
genotypic variation existed among eight sorghum inbred lines, (2)
determine genotype by environment interaction, (3) determine if a
relationship existed between leaf area and related morphological
traits and grain yield, and (4) identify inbred lines suitable for
further genetic study.
Significant genotypic differences were consistently detected at
the 0.01 level of probability for all morphological traits and grain
yield, leading to the conclusion that variation exists among the eight
genotypes for traits tested. Water level by genotype interaction
resulted in significant differences for all morphological traits
excluding number of leaves. This observation is contradictory to
results obtained by others of decreased leaf numbers with water
stress. The lack of variation in number of leaves observed in this
study could be explained in part as resulting from the inbred lines
growing in comparable macroenvironments during the leaf initiation
period. More data should be obtained to determine if this lack of
variation is due to genetic effects or if the environmental effects of
this study were not effective in attaining a response.
Water level had a modifying effect on photosynthetic area,
causing significant increases from PP + 1 to PP + 3. TX 7000 and SC
170-6-17 added additional leaf area with additional water, but there
48
49
was little increase In grain yield observed indicating inefficient
partitioning of assimilates for grain production.
Evidence of differential water use was obtained from the
significant genotype by water level interactions of morphological
traits measured as dry weights. These results suggest certain inbreds
perform better under higher water levels and others under lower water
levels. Inbred lines should be evaluated to determine such responses
to water levels since, depending upon correlations with grain yield,
particular lines may be better suited to a specific water level, and
provide superior segregates for such traits in a breeding program.
Significant reductions in the stalk dry weights of TX 7000 and SC
170-6-17 and a small decrease in grain yield relative to other inbred
lines were observed. These results may imply utilization of stalk
stored assimilates in these two lines. However, no positive
significant correlation of stalk dry weight at bloom with grain yield
was observed. If stalk stored assimilates are important for grain
filling in sorghum, evaluations of this trait are needed. The ability
of an inbred to use stalk stored assimilates for grain yield during
periods of water stress would be an important factor from a breeding
standpoint.
Genetic differences were detected among inbred lines for grain
yield. Genotype by water level interaction was not significant for
grain yield. However, the interaction gave significant differences
for unthreshed head weight. These results indicate the relative
position of an inbred line did not change over water levels, and
additional water was used for vegetative, not reproductive growth.
50
This could be an indication of inefficient partitioning. Some of the
variation in performance among inbreds for grain yield could be
explained by early maturity and leaf senescence. While these
characteristics are desirable in some environments, they are not
always advantageous in all environments. The use of these character
istics by the breeder is dependent on the type of environment he is
concerned with in his breeding program.
Most positive significant correlations obtained were attributable
to measurement of the same overall genetic system. Significant
negative correlations between photosynthetic area or leaf area and
grain yield suggest less relative leaf area may be beneficial when
water is limiting. Head dry weight at bloom was the only
morphological characteristic exhibiting a positive significant rela
tionship with grain yield which could merit further evaluation to
determine usefulness in screening of inbred lines.
APPENDIX
1. Precipitation after June 4 for 1980 growing season and 1980 totals to date recorded at Texas Tech University Farm.
51
52
Appendix Table 1. Precipitation after June 4 for 1980 growing season and 1980 totals to date recorded at Texas Tech University Farm.
Precipitation Total to Date Total for Year
Date (mm) (mm) (mm)
June 8 5.1 5.1 90.6
June 11 23.3 28.4 113.9
July 27 14.4 42.8 128.3
August 4 26.9 69.7 155.2
August 14 16.2 85.9 171.4
August 15 7.6 93.5 179.0
September 1 2.0 95.5 181.0
September 9 7.1 102.6 188.1
September 10 15.2 107.8 203.3
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