Manifestation of Heterosis for Grain Weight in Wheat (Triticum Aestivum L.)

Five lines having different grain weights were selected from populations of three crosses, viz., UP368 × WC457, UP368 × Shailza, and WH157 × Bulk 1858, which were passed through three cycles of mechanical mass selection. These lines along with variety Sonalika were crossed in all possible combinations excluding reciprocals. The boldest seeded (65 g) line had almost similar grain weight as the hybrid with highest grain weight. The hybrids involving parents with different degree of association were equal or inferior to midvalue depending on the degree of association and thus exhibited negative or no heterosis. The hybrids involving parents with dispersed allelic state had high grain weight as well as high positive heterosis. Thus, allelic dispersion was the major cause of heterosis. The combining ability effects were affected by the pattern of allelic distribution among parents. Parents with association state exhibited positive general combining ability (gca) effects, while those with dispersion state showed negative gca effects.