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Results and
discussion
There were significant differences among tissue culture lines as
well as the edaphic environments for all the seven traits studied
under normal, saline and sodic soil conditions. The ANOVA results of
grain yield per plant and its component traits are shown in
Table
1. There were
significant lines x edaphic environment interactions for all the
characters. The means of all the characters declined when the lines
were grown in saline and sodic soil conditions, the depreciation
being maximum under sodic conditions (Table
2). The mean
grain yield was 6.63 g/plant under normal soil, decreased to 4.36
g/plant under saline soil, and further to 2.02 g/plant under sodic
conditions. The reduction in the means of various characters studied
was more under sodic conditions than Wine conditions. Similarly, the
range of all the characters narrowed down as the stress was
imposed.
The genotypic and phenotypic variances decreased under the stress
conditions for grain yield per plant, effective tiller number per
plant and number of spikelets per ear, while it was reverse for the
others (Table
2). The genotypic
and phenotypic coefficients of variation, which are more appropriate
parameters for the comparison, decreased under saline conditions for
grain yield per plant, effective tiller numbers per plant and number
of spikelets per ear, while the coefficients were nearly the same
under sodic soil conditions as compared to normal conditions.
Reduction in genetic variability under stress has also been reported
by Johnson and Frey (1967) in oats and by Mederski and Jeffers (1973)
in soybean. For characters like 1000 grain weight, number of grains
per ear, plant height and ear length, the coefficients of variation
increased under stress conditions. The reason for such an increase in
variability under stress conditions may be attributed to an enhanced
primary effect of the stress as has been discussed by Rosielle and
Hamblin (1981) under disease stress. Similar trends were also
observed for genetic advance. Heritability of grain yield and number
of spikelets per ear decreased under both types of stress, while that
for number of ear-bearing tillers per plant decreased only under
salinity and remained the same under sodic conditions. Most of the
characters exhibited high heritabilities owing to the high genotypic
variances among the tissue culture lines.
The association among the characters of bread wheat grown on normal
soils was modified under salinity and sodicity stresses. It was
evident from Table
3 that grain
yield per plant was significantly correlated with 1000 grain weight,
number of grains per ear, number of ear-bearing tillers per plant,
plant height and number of spikelets per ear only under sodic
conditions, while it had significant, positive correlation with
tiller number under normal as well as stress conditions. Grain yield
was only significantly correlated with number of ear-bearing tillers
per plant and ear length under salinity conditions. It appeared quite
apparent that number of ear-bearing tillers per plant was one of the
most significant component characters under normal and stress
conditions. Under sodic conditions most of the characters were
correlated with grain yield, except for ear length. A significant
correlation was observed between 1000 grain weight and number of
grains per ear only under normal soil conditions, and number of
grains per ear was highly correlated with plant height and car length
under sodic conditions. Number of tillers per plant was negatively
correlated with plant height under normal conditions, as tillering
ability was higher for semi-dwarf types than for tall types, while
under sodic condition it was positively correlated to plant height,
because both tiller number and plant height decreased under sodic
stress. Ear length was positively correlated to number of spikelets
per ear under normal and saline conditions while uncorrelated under
sodic conditions.
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