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To get an idea of relative
contribution of the yield components on grain yield under normal and
stress conditions, path coefficient analysis was conducted.
Table
4 gives the
direct and indirect effects on grain yield per plant under normal and
stress conditions. A high direct effect was observed for 1000 grain
weight under saline and sodic conditions, while that had a high
indirect effect via number of grains per ear, under normal
conditions. Number of grains per ear had a high direct effect under
normal conditions but it was counter balanced by high negative,
indirect effects via number of ear-bearing tillers per plant, as a
result there was no significant genotypic correlation with grain
yield. The situation was nearly the same under saline conditions.
However, under sodic conditions there were high direct effects as
well as indirect effects through plant height and number of spikelets
per ear. Number of effective tillers per plant had high direct
effects under normal conditions, with some negative indirect effects
via grain number per ear and plant height, resulting in a high
genotypic correlation with grain yield. Under salinity, tiller number
had high direct effects, while under sodic conditions it had
comparatively low direct effects and more indirect effects via plant
height and 1000 grain weight. Plant height had high direct effects
under normal conditions, though its effect was canceled by high
negative indirect effects via number of ear-bearing tillers per
plant. Under sodic conditions, there were equal contributions of
direct effect of plant height and indirect effects via number of
grains per ear. Ear length had a positive direct effect and indirect
effect via number of ear-bearing tillers per plant under salinity,
while number of spikelets per ear had high indirect effects via
number of grains per ear and plant height under sodic stress. To
conclude, under normal conditions number of ear-bearing tillers per
plant contributed to grain yield per plant, while under salinity
conditions, that and ear length contributed directly, and indirectly
through number of ear-bearing tillers per plant. Under sodicity, 1000
grain weight contributed directly to grain yield per plant; grain
number per ear directly and indirectly via plant height; number of
ear-bearing tillers per plant directly and indirectly via plant
height and grain weight; plant height directly and indirectly via
number of grains per ear; and number of spikelets per ear directly
and indirectly via plant height. However, grain weight, number of
grains per ear, plant height and number of spikelets per ear were the
most important characters under sodic stress. Thus, number of
ear-bearing tillers per plant under salinity stress and grain weight,
number of grains per ear, tiller number, plant height and number of
spikelets per ear under sodic stress were the important characters
which require breeders' attention for achieving increases in grain
yield under such edaphic conditions.
Bread wheat lines produced through tissue culture techniques thus
showed considerable variability in grain yield and its component
characters under normal as well as stress conditions, indicating that
they can be a good source of variability under salt stress. The
information on genotypic correlations and path coefficients does
provide criteria to help plant breeders in deciding the appropriate
selection strategy under saline and sodic stress conditions for such
materials.
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