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Correlations among characters
In order to identify the suitable plant traits for selection under
irrigated and rainfed conditions, the correlation coefficients among
various characters were worked out in F2 generation
(Table 4). Grain yield/plant was positively
associated with tillers/ plant, harvest index and biological yield
under both environments. In addition, plants with higher number of
grains/spike were also higher yielders (r=0.17*) under E1
whereas the plants with high 100-grain weight and early heading type
had high yields under E2. Although direct selection for
grain yield could be practised on the basis of correlations
especially under rainfed conditions, yet its low heritability,
involvement of high magnitude of non-additive variations within and
between environments could limit the progress through selection (Blum
1988, Acevedo et al. 1991). Therefore, the selection for the
characters having high heritability and relatively simply inherited
could be more fruitful than the grain yield alone.
Among yield components, plants having high tillers/plant under
E1 also had high grain yield (r=0.24*), 100- grain weight
(r=0.27*), grains/spike (r=0.16*) and harvest index (r=0.22*).
Similarly, the plants having high 100-grain weight under
E2 were also high in yield (r=0.19*), harvest index
(r=0.18*) and biological yield (r=0.34**). The positive association
of lOO-grain weight with biological yield under rainfed conditions
may be due to the better ability of biological yield to support the
kernel growth by stem reserve mobilization under moisture stress
conditions (Aggarwal and Sinha 1987, Blum 1989, Bansal and Sinha
1991). However, this trait has considerable heritability, but the
limited variation in the progenies may restrict its exploitation
through selection in this material. Grains/spike was relatively
unimportant character because of its negative correlation with
100-grain weight (-0.23*) under E1 and, with tillers/plant
(-0.17*) under E2.
Days to heading and days to maturity had, in general, poor
correlations under both the environments which may be attributed
either to high sampling errors or limited variations in the progenies
(Table 3). Biological yield and harvest
index appeared to be more important traits under E2 than
under E1 because of their associations with each other as
well as with other variables in terms of magnitude and number. Tanner
and Sinclair (1983), Blum et al. (1983) and Turner and Nicholas
(1988) have also suggested that the grain yield was strongly
dependent on biological yield under water-limited environments.
Thus, the correlation studies indicated that tillers/plant under
E1 and biological yield under E2 were the
important traits for improving the grain yield. Harvest index was
appeared to be an important character under both the environments.
Gene action studies indicated that these characters were
predominantly governed by additive genetic variance with the
involvement of dominance and epistatic effects. Therefore, selection
would be effective if dominance and epistatic effects are reduced
after a few generations of selfing and/or intermating in early
segregating generations (Singh et al., 1986). This would not only
reassemble the adaptive genes in the population but also increase the
population mean and retain greater variability for selection over a
longer span of time.
Acknowledgemens
The financial assistance given to the first author in the form of
Senior Research Fellowship by the Council of Scientific and
Industrial Research, New Delhi, towards his Ph.D. thesis is duly
acknowledged.
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