الفهرس 
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Abstract
SUMMARY
The main objectives of this study were to (1) evaluate performance
and degree of drought stress tolerance of six barley genotypes and their
F1’s for some agronomic and physiological traits under well watered and
rainfed conditions, (2) identify the traits which can be used as selection
criteria for drought stress tolerance, (3) estimate of some genetic
parameters specially heterosis, combining ability and heritability as bases
of improving barley under rainfed conditions at Maryout region and (4)
study the interrelationships among traits under the two irrigation regimes.
Six parents of barley (Hordeum vulgare L.) namely: the cv. G126
(P1), L Su12303 (P2) (are local genotypes), L 105/20 (P3), L105/27 (P4),
L105/32 (P5) and L 105/36 (P6) (are introduced from ICARDA) were
chosen to achieve the present study. The experiments of the present study
were carried out at the Maryout Agriculture Experiment Station of Desert
Research Center (North Western Coast of Egypt). In 2008/09 season, the
six parents were handy crossed in all possible combinations, excluding
reciprocals and seeds of the 15 F1’s were obtained. In 2009/10 season,
two adjacent field trials each included the 15 F1 crosses and their
respective parents (21 genotypes) were conducted in a randomized
complete block design with three replications. Each experiment was
devoted to one of the following two irrigation treatments; a) rainfall
treatment (drought stress treatment) and b) rainfall + 2 supplemental
irrigations given at sowing date and flowering stage (well watered
treatment). Experimental unit consisted of one row for each genotype.
Row was 3.5 m in length and rows spacing and distance between plants
within row were 30cm and 10cm, respectively. Sowing date was on 20th
November. Plants were thinned at one plant per hill after about three
weeks from sowing date.
Days to heading and maturity were recorded. Also, flag leaf area,
flag leaf angle, as well as relative water content (RWC), proline content,
chlorophyll a (chl.a and b) content and carotenoids content as
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
physiological traits were recorded at anthesis stage. At harvest, ten
guarded plants randomly taken from each plot were used for recording
data of the following traits; plant height, no. of spikes/plant, spike length,
number of spikelets/spike, number of grains/spike, 100-kernel weight,
grain yield/plant, straw yield/plant and harvest index.
Data of all traits recorded from each experiment were subjected to
the ordinary analysis of variance and combined analysis over the two
irrigation regimes was done when the homogeneity test was insignificant.
Significant differences between means were tested by using the least
significant differences (L.S.D) test at 5% level of probability. Heterosis,
combining ability and heritability were estimated for the studied traits.
Estimates of combining ability effects were made by applying Griffing’s
(1956) method 2 and model 1. Different groups of phenotypic correlation
were estimated between the studied traits under both irrigation treatments.
The obtained results can be summarized as follows:
A. Analysis of variance
The results revealed that irrigation regimes mean squares were
highly significant for all studied traits, indicating that the genotypes
performance differed under the two irrigation treatments. Also, mean
squares due to genotypes were highly significant under the two irrigation
treatments and their combined data, indicating the existence of sufficient
genetic variability among the genotypes for the studied traits. Highly
significant mean squares due to interactions of genotypes with irrigation
treatments were observed for all studied traits, reflecting the fact that
these genotypes were inconsistent in their responses to irrigation
treatments.
B. Mean performance of barley genotypes under normal irrigation
and drought stress conditions
1. Results revealed that drought stress caused significant reduction in all
traits with different degrees of reduction, except proline content
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SUMMARY
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which was increased under drought stress condition. Overall
genotypes, harvest index recorded the lowest reduction (6.06%)
followed by 100-kernel weight (7.74%) and spike length (8.41%),
while carotenoids content recorded the highest reduction (43.32%)
followed by chl. ”b” content (30.74%) and RWC (30.67%). On the
other hand proline content recorded an increase percentage amounted
73.39% under drought stress conditions.
2. The cross P4xP6 for heading date, P1xP4 for maturity date, the cv. G126
for plant height, the parental line 105/32 for flag leaf area and RWC,
the cross P2xP5 for flag leaf angle and spike length, P2xP6 for no. of
spikes/plant and grain yield/plant, P1xP2 for no. of spikelets/spike,
straw yield/plant and harvest index, P2xP4 for chl. ”a” content and
carotenodis content and the parental line 105/20 for chl. ”b” content
registered lowest means reduction, while the parental line 105/32
registered the highest reduction percentage under drought stress
treatment.
3. Rainfed conditions significantly decreased (earliered) time to heading
and maturity of various barley genotypes. The average reduction in
heading date was relatively higher (17.27%) than that of maturity
date (14.97%). The cross P1xP6 and the cv. G126 were the earliest
genotypes in heading date under the two irrigation regimes,
respectively, while the cross P1xP4 under both irrigation regimes as
well as the parental line 105/20 and the crosses; P2xP3, P3xP4 and
P3xP5 under rainfed treatment were the earliest in maturity date.
4. Reduction percentages in vegetative growth traits revealed that flag leaf
area was more sensitive to drought stress compared with flag leaf
angle and plant height. The cross P3xP6 under the two irrigation
regimes as well as the cv. G126 and the two crosses; P4xP6 and P5xP6
under rainfed treatment were the tallest among all genotypes.
Meantime, the cross P5xP6 under the two irrigation treatments had the
highest flag leaf area. For flag leaf angle, the parental line 105\20 and
the crosses P1xP4 and P3xP6 under the two irrigation regimes as wel
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
as the cross P2xP4 under normal irrigation and the crosses; P1xP5,
P3xP4, P4xP6 and P5xP6 under drought stress gave the highest values
for this trait.
5. Results revealed that reduction was relatively high in no. of
grains/spike, which averaged 19.24% relative to the control treatment
followed by grain yield/plant (15.68%), no. of spikes/plant (15.68%),
no. of spikelets/spike (10.92%), spike length (8.41%) and100-kernel
weight (7.74%), demonstrating that no. of grains/spike caused the
greatest reduction in grain yield/plant under water stress treatment
and was more sensitive to water deficit than other yield components.
The cross P5xP6 had high grain yield/plant under well watered and
stressed treatments, therefore this cross can be used in barley
breeding programs for improving tolerance to drought stress. For no.
of spikes\plant the crosses; P2xP5, P3xP5 and P3xP6 under normal
irrigation and P5xP6 under the two irrigation treatments had the
highest means for this trait, while the parental line 105/32 and the
crosses; P5xP6 and P2xP3 under the two irrigation treatments gave the
highest values for spike length. The cross P5xP6 under normal
irrigation and P3xP5 under drought stress recorded the highest means
for no. of spikelets/spike, while the cross P3xP6 followed by P5xP6
under the two irrigation treatments recorded the highest means for no.
of grains/spike. For 100-kernel weight, the two crosses; P3xP6 and
P5xP6 under normal irrigation as well as the parental line 105/27 and
the two crosses; P1xP5 and P2xP5 under rainfed conditions had the
highest mean values for this trait.
6. The results indicated that low soil moisture stress significantly
decreased straw yield by 10.53% compared to well watered
treatment. The cross P1xP2 recorded the lowest reduction (1.98%).
The cross P1xP6 under both irrigation treatments as well as the cross
P3xP5 and P5xP6 under rainfed treatment gave the highest mean
values for this trait.
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7. Results showed that harvest index significantly affected by drought
stress which reduced by 6.06% than under well watered treatment.
The parental line L105/36 under normal irrigation treatment as well
as the cross P4xP6 under drought stress treatment had the highest
mean values of 0.40 and 0.37, respectively.
8. Results revealed that the physiological traits are greatly affected by
drought stress, where the relative water content, chlorophyll ”a” and
”b” content and carotenoids content were significantly reduced by
drought stress, while proline content was significantly increased
(73.39%) when plants subjected to drought stress. Meantime,
carotenoids content was adversely affected (43.32% reduction)
followed by chlorophyll ”b” content (30.74%), relative water content
(30.67%) and chlorophyll ”a” content (26.90%) by drought stress.
The cross P5xP6 had the highest values for RWC under the two
irrigation regimes. For chl. ”a” content and carotenoids content, the
cv. G126 under normal irrigation and the cross P5xP6 under rainfed
treatment recorded the highest means for the two traits, while the
same cross under normal irrigation and the cross P2xP3 under rainfed
treatment gave the highest means for chl. ”b” content. For proline
content, the parental line 105\32 under normal irrigation and the cross
P1xP4 under rainfed treatment gave the highest values for this trait.
9. As general conclusion from the above results of reduction percentages,
the traits studied can be classified into three categories as follows:
1- Drought tolerant traits included 100-kernel weight, spike length,
harvest index, straw yield/plant, no. of spikelets/spike, plant height and
maturity date which recorded reduction percentages less than 15%,
suggesting that these traits could be used as selection criteria for
screening drought resistant genotypes in barley breeding programs, 2-
Moderately tolerant traits included no. of spikes/plant, grain
yield/plant, heading date, no. of grains/spike, flag leaf angle,
chlorophyll ”a” content, and flag leaf area which recorded reduction
percentages more than 15% up to 30% and 3- Drought susceptible
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
traits included relative water content, chlorophyll ”b” content and
carotenoids content, which recorded reduction percentages more than
30%. It is worthy to note that the breeder should be taken into
consideration increase positive percentages in proline content occurred
under drought stress, which related to tolerance grain yield under such
conditions.
C- Drought susceptibility index (S)
Results indicated that S mean values ranged from 0.50 for the
cross P2xP6 to 1.73 for the parental line 105/36 with an average of 1.00.
The crosses; P1xP3, P1xP4, P2xP6, P3xP4, P3xP5, P4xP5, P4xP6 and P5xP6
showed stress susceptibility index (S) values less than unity ranging from
0.5 to 0.79, indicating that these genotypes are the most drought tolerant
for grain yield/plant.
D. Estimates of genetic parameters
D.1. Heterosis
Results revealed that values of heterosis greatly varied under the
two irrigation regimes and heterotic effects were more pronounced under
soil moisture stress than under well watered conditions for most studied
traits. The crosses showing the best heterobeltiosis under well watered
and/or rainfed conditions could be recommended to improve the
respective traits. Overall crosses, values of heterosis over mid-parents
ranged from -19.43% for carotenoids content to 23.04% for relative water
content under well watered treatment, whereas values ranged from -
27.12% for chlorophyll ”a” content to 25.46% for carotenoids content
under rainfed conditions. For better-parent heterosis, values ranged from -
27.10% for carotenoids content to 8.44% for RWC under well watered
treatment, whereas values ranged from -31.59% for chlorophyll ”a”
content to 14.33% for days to maturity and grain yield/plant under rainfed
conditions. The cross P5xP6 gave the maximum mid-parents heterosis
value of 317.28% for chlorophyll ”b” content under well watered
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
conditions, whereas the cross P3xP5 gave the maximum value of 98.36%
for carotenoids content under rainfed conditions. For better-parent
heterosis, the cross P5xP6 recorded the highest value of 284.09% under
well watered conditions, whereas the cross P2xP4 recorded the highest
value of 94.52% for carotenoids content under rainfed conditions. The
obtained results also indicated that the five F1 hybrids; P2xP4, P3xP4,
P3xP5, P3xP6 and P5xP6, expressed higher mid and better parent heterosis
under rainfed condition than under well watered condition for grain
yield/plant, therefore if the hybrids development is feasible in barley these
hybrids are considered more desirable to be grown under water shortage
conditions for increasing grain yield per unit area and selection could be
exercised in segregating generations for developing drought tolerant
genotypes.
D.2. Combining ability
D.2.1. Combining ability analysis
The results revealed that mean squares associated with
general(GCA) and specific (SCA) were found to be highly significant for
all the studied traits under both irrigation regimes and combined analysis,
indicating that both additive and non-additive genetic effects were
involved in the inheritance of these traits. The ratios of k2GCA/k2SCA
were less than unity under the two irrigation treatments and combined
data, suggesting that the studied traits were mainly controlled by the nonadditive
gene effects. The interactions of GCA and SCA with irrigation
treatments were also highly significant for all the studied traits, revealing
that variance magnitudes of different types of gene action were fluctuated
from one environment to another. Such results indicate that the irrigation
treatments are considered as an effective factor for declaring GCA and
SCA variances. Thus, the breeder should utilize the appropriate breeding
method under each environment for developing desired barley genotypes.
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
D.2.2. Evaluation of the six parents for desired GCA effects were as
followes:
- The cv. G126: for earliness in heading and straw yield\plant under the
two irrigation treatments, earliness in maturity, flag leaf area, chl. ”a”
and ”b” contents and carotenoids content under normal irrigation and for
proline content under drought stress.
- LSu12303: for carotenoids content under the two irrigation regimes,
hrvest index under well watered treatment, earliness in heading, RWC
and chl. ”a” and ”b” contents under drought stress
- L150/20: for improving earliness in maturity and RWC under the two
irrigation regimes, plant height under normal irrigation and chl. ”a” and
”b” contents under drought stress.
- L150/27: for improving 100-kernel weight under the two irrigation
treatments, flag leaf area under well watered treatment, earliness in
heading, harvest index, proline content and chl. ”a” content under
drought stress treatment.
- L150/32: for flag leaf area, no. of spikes/plant, spike length, no. of
spikelets/spike, grain yield/plant, straw yield/plant, RWC and
carotenoids content under the two irrigation levels, no. of grains/spike,
proline content and chl. ”a” content under normal irrigation and 100-
kernel weight under drought stress.
- L150/36: for improving the traits of plant height, flag leaf area, no. of
spikes/plant, spike length, no. of grains/spike, 100-kernel weight, grain
yield/plant, harvest index and RWC under the two irrigation levels,
earliness in heading, chl. b content and carotenoids content under
normal irrigation and no. of spikelets/spike under drought stress.
D.2.3. Some crosses exhibited desirable SCA effects and included at
least one parent as good general combiner as follows
- P1xP2: for maturity date, flag leaf area and spike length under the two
irrigation treatments, proline content under normal irrigation, no. of
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
spikelets/spike, straw yield\plant, chl ”a” content and carotenoids
content under drought stress.
- P1xP3: for flag leaf area and spike length under the two irrigation
treatments, straw yield\plant and RWC under normal irrigation, 100-
kernel weight and proline content under drought stress.
- P1xP3: for maturity date and flag leaf area under normal irrigation,
RWC, proline content and carotenoids content under drought stress
treatment.
- P1xP5: for 100-kernel weight and carotenoids content under the two
irrigation regimes, harvest index and RWC under normal irrigation and
chl. ”b’ content under drought stress.
- P1xP6: for heading date, spike length and straw yield\plant under the
two irrigation treatments, heading date and plant height under normal
irrigation, 100-kernel weight and RWC under drought stress.
- P2xP3: for flag leaf area, spike length, chl. ”b” content and carotenoids
content under the two irrigation treatments, heading date under normal
irrigation, RWC, proline and chl. ”a” contents.
- P2xP4: for no. of spikes/plant, no. of spikelets/spike, no. of grains/spike,
grain yield\plant, straw yield/plant, RWC, chl. ”a” content and
carotenoids content under the two irrigation treatment, maturity date
and flag leaf angle under normal irrigation and proline content under
drought stress.
- P2xP5: for maturity date, no. of spikelets/spike and straw yield\plant
under the two irrigation regimes, no. of spikes/plant, no. of
grains\spike, grain yield/plant and RWC under normal irrigation and
100-kernel weight under drought stress treatment.
- P2xP6: for spike length under the two irrigation regimes, heading and
maturity dates and chl. ”a” and crotenoids contents under normal
irrigation treatment, no. of spikes\plant, no. of spikelets/spike and 100-
kernel weight under drought stress.
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- P3xP4: for no. of spikes\plant under the two irrigation treatments, 100-
kernel weight under normal irrigation and grain yield/plant under
drought stress.
- P3xP5: for no. of spikes/plant, spike length, no. of spikelets/spike, no. of
grains/spike, grain yield/plant, straw yield\plant and chl.”a” and
carotenoids contents under the two irrigation treatments, plant height,
flag leaf area and RWC under normal irrigation and heading date under
drought stress.
- P3xP6: for plant height, no. of spikes\plant, no. of spikelets/spike, no. of
grains/spike, 100-kernel weight, grain yield\plant, RWC and proline
content under the two irrigation treatments, maturity date and harvest
index under normal irrigation, flag leaf area, straw yield/plant and chl.
”a” and ”b” contents under drought stress.
- P4xP5: for heading date under the two irrigation regimes, spike length
under normal irrigation treatment, flag leaf area, RWC and proline
content under drought stress treatment.
- P4xP6: for RWC under the two irrigation treatments, heading and
maturity date, proline and carotenoids contents under normal irrigation,
plant height, no. of spikes\plant, no. of spikelets/spike and no. of
grains\spike under drought stress conditions.
- P5xP6: for plant height, flag leaf area, no. of spikes/plant, spike length,
no. of spikelets/spike, no. of grains/spike, grain yield/plant, straw
yield\plant, RWC, prolin content, chl. ”a” and ”b” contents and
carotenoids content under the two irrigation treatments as well as 100-
kernel weight under well watered treatment.
D.3. Hertability
Results showed that high to moderate or low broad sense
heritability estimates were obtained which ranged from 62.85% for flag
leaf angle to 99.83% for chlorophyll ”b” content under well watered
conditions and from 38.68% for flag leaf angle to 99.86% for spike length
under rainfed conditions. However, the wide range between heritability
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SUMMARY
Soad S. Abou El-Fotoh, M.Sc. Thesis, 2015
values attributable to irrigation treatments, reveal that heritability
percentages are altered ’in some extent’ from normal irrigation to drought
stress conditions Moreover, heritability estimates under drought stress
were higher than those under normal irrigation conditions for heading and
maturity dates, plant height, flag leaf angle, 100-kernel weight, straw
yield, harvest index, chl. ”b” content and carotenoids content , while the
opposite was true for the other traits, indicating that selection for
improving these traits would be effective under rainfed than under well
watered conditions.
E- Correlation studies
Significant and positive phenotypic correlation coefficients were
found between grain yield/plant and each of no. of spikes/plant, no. of
spikelets/spike, no. of grains/spike and RWC under the two irrigation
treatments, indicating that selection for one or more of these traits may be
amenable for grain yield/plant improvement under any of the two
irrigation treatments. Also, results of correlation between every trait under
normal irrigation treatment and drought stress treatment revealed the
presence of positive and significant correlation for all the studied traits
except, proline and chl. ”b” contents which correlation was not
significant. Meantime the correlation between mean performance of
genotypes for different studied traits under normal irrigation treatment
and reduction percentages under drought stress treatment was positive and
significant for the traits of maturity date, flag leaf angle, 100-kernel
weight, straw yield/plant, harvest index and proline and chl. ”b” contents.