Abstract

The magnitude and nature of heterosis and combining ability in a set of diallel crosses of wheat (Triticum aestivum L. om Theil.). involving five genotypes, were studied for grain yield, 100-kernel weight, spike number and plant height. Positive overall heterosis was observed for all the characters except for 100-kernel weight. Over dominance was evident only for grain yield. Heterosis and over dominance effects for grain yield were positive in all the crosses except Sharbati Sonora x IR Amber, where partial-dominance for yield was observed. For kernel weight except the cross WG 423 x Sharbati Sonora. negative heterosis was observed. Heterosis ranged from 20.54 to 64.95 per cent and over- dominance effects from 26.16 to 38.85 per cent for spike number. For plant height heterosis was positive in eight crosses and over-dominance in one cross only. Both GCA and SCA variances were significant for all the characters except in the case of number of spikes where the GCA variance alone was found to be significant. For grain yield the magnitude of GCA and SCA variances were of the same order. For other characters the GCA variances were of relatively higher order than the corresponding SCA values. The additive effects were predominant in general. For grain yield, however, dominance/ over-dominance effects were equally important.

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