Abstract

The present studies reveal that general combining ability was more important as compared to spacific combining ability in American cotton although latter was also operative. It would thus, be more appropriate first to concentrate additive genetic variance in the parents by selection procedures. This may be followed by a recurrent selection programme to utilize both additive and non-additive genetic variances in the segregating population. The g.c.a. component of variance was quite stable while s.c.a. was inconsistent from location to location except for halo length and ginning percentage for which both types of variances were stable. RS 455, H 297, RS 277 and PS 10 were overall the best parents for yield characters. TH 46. PS 10, CP 1998F, and Nectoriless were the best combining parents for ginning percentage, while RS 9, CPI 998F, RS 76, and SH 369 were superior parents for halo length. All crosses exhibiting the highest speci- fic combining ability and mean, possess at least one parent which is a good or average combiner. Except for instance, in no case a low x low combiner exhibited high specific effects. General combining ability is thus, a good guide for initial selection of parents for improvement of various traits in cotton.

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