HETEROSIS AND COMBINING ABILITY FOR YIELD AND FIBRE QUALITY IN GMS-BASED BT HYBRIDS OF UPLAND COTTON ACROSS THREE ENVIRONMENTS

Abstract

Cotton hybrid breeding requires simultaneous exploitation of heterosis and informed parent choice. This study quantified heterosis, general combining ability (GCA), specific combining ability (SCA), and the associated gene-action pattern for yield, yield components, and fibre quality in a GMS-based Bt upland-cotton population. Forty F1 hybrids generated by crossing four GMS lines with ten Bt testers were evaluated with 14 parents and four standard checks in a randomized block design with two replications across three environments during Kharif 2025–26. Genotypic differences were significant for every studied trait in the pooled analysis. The cross mean for seed-cotton yield was 118.97 g plant−1, compared with 98.71 g for lines, 98.29 g for testers, and 125.86 g for checks. The leading hybrid, GNH-105A × NH22065Bt, yielded 169.57 g plant−1 and expressed 53.59% heterobeltiosis, 34.92% heterosis over NHH 44 BG II, and an SCA effect of 39.52. Other high-value combinations were GNH-101A × NH22160Bt and GNH-111A × NH22037Bt. Non-additive gene action predominated for seed-cotton yield, bolls plant−1, sympodia plant−1, boll weight, seed index, lint index, and uniformity ratio, whereas additive action predominated for flowering time, plant height, ginning outturn, UHML, fibre fineness, and fibre strength. GNH-105A was the strongest female general combiner for yield architecture; NH22037Bt was the strongest tester for yield and boll number; and GNH-101A, GNH-111A, and NH22158Bt contributed complementary fibre-quality effects. The results support a two-stage breeding strategy in which high-GCA parents are used to enrich breeding populations and high-SCA combinations are advanced for hybrid evaluation.