| There were 10, 6 and 11 crosses under E1, E2 and
E3, respectively which had shown high positive and significant
sca effects. The top four crosses under each of the three environments are
presented in Table 3. The cross Kalyansona x Safed
Lerma was the unique combination which had manifested high sca effects under
all the three conditions. Both the parents involved in this cross are good
general combiners and thus is expected to release desirable segregants in
subsequent generations since it involved additive and additive x additive
interactions. The two other promising crosses, NP 884 x E 4845, E 5477 x
Kalyansona which had also shown high sca effects under two of the three
conditions, involved at least one parent having good general combining ability.
Therefore, such combinations are likely to throw transgressive segregates
if the additive genetic system present in the good combiner and complementary
epistatic effects act in the same direction to maximize the desirable effect.
The estimates of components of genetic variation are presented in Table 4. The component D and H1 were found to be highly significant under all the three situations. This further supports the role of both additive and non-additive effects in the inheritance of grain number. The estimated degree of dominance which was less than one under two of the three environments (E2 and E3), denoting partial dominance and thereby, preponderance of additive gene effects. Further, significant and negative value of the component F under an the three environments reaffirms the results obtained through combining ability analysis. The ratio H2/4H1 indicated deviation from symmetrical distribution of genes with positive and negative effects. The ratio h2/H2 showed that at least two to three dominant genes or gene groups were responsible for the control of grain number/ear under all three environments. 250-Grain weight As expected, the grain weight was higher under timely sown experiments E1 and E2, whereas it was badly reduced under late sowing (E3). The parental range was 10.87 to 6.87 gms/250 grains under E1, 10.63 to 6.49 gms under E2 and 8.27 to 4.0 gms under E3. Sonalika had the highest and E 4845 the lowest grain weight under all the three conditions. The corresponding range for F1 hybrids was 11.67 to 7.83, 11.73 to 7.10 and 8.57 to 4.97 gms/250 grains under E1, E2 and E3 conditions, respectively. In general, the F1 fell in between the parental limits and none except one, NP 884 x Sonalika under E2 could transgress the parental limit significantly. Mean squares for general combining ability were highly significant under all the three environments. While the specific combining ability mean squares were also of statistical significance, the magnitude of the effect was considerably less than that of general combining ability effect for this trait. This suggests that the major portion of the total genetic variability is the result of additive gene action. These results are in conformity with those of Singh et al. (1969), Paroda and Joshi (1970), Knott & Talukdar (1971), Sharma et al. (1978), Schmidt et al. (1978) and Singh et al. (1985). The gca effects showed that Sonalika, NP 884 and NP 852 were the good general combiners and all the remaining parants were poor in their combining ability. A number of crosses exhibited significant sca effects. Most prodigious cross combinations under each of the environment are presented in Table 3. It would be seen that the three crosses, namely NP 884 x Kalyansona, NP 852 x E 4845 and NP 4 x E 4845 had shown high sca effects under all the three conditions. Two of these crosses involved at least one parent having good general combining ability whereas the 3rd cross was between Average x Poor combiners. In general, the crosses between two good combiners did not exhibit sca effects in the desired direction. This suggests epistatic interactions resulting in internal cancellation of components of heterosis. (Murty 1965). |
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