Division of Botany, Indian Agricultural Research Institute, New Delhi-12
In an intervarietal cross in cotton, H. 14 X S.A. 594, the mode of inheritance of two yield components, namely, boll number per plant and boll weight, was studied by a biometrical analysis of overall generation means and variances. In the case of boll number, the F1 mean indicated a significant amount of heterosis, which was shown to be mainly due to dominance as well as complementary type of epistasis. Thus, there seems to exist a great possibility of improving the boiling capacity of the variety H. 14 through selection among the segregates of successive selfed or backcrossed generations, since such a form of heterotic vigour might be fixable. In the case of boll weight, on the other hand, the gene action seemed to fit better to an additive model with only partial dominance and no significant epistatic terms. The nonsignificant phenotypic and genotypic correlations between boll number and boll weight further suggest that it may be possible to combine them in the same strain. The validity of various assumptions underlying the simple models for the sort of analysis presented above have also been discussed briefly.
