Combining-ability analysis in cotton for agronomic characters, fruiting efficiency, photosynthesis and bollworm resistance

Abstract

SummaryHeterosis and combining abilities for yield, bollworm resistance, fruiting efficiency and photosynthesis were studied in a five-parent diallel involving cotton (Gossypium hirsutum) strains differing in their resistance to the bollworm complex (Heliothis zea and H. virescens).Substantial magnitudes of useful heterosis (over the commercial cultivar ‘Coker 304’) were observed for yield and other agronomic characters. Useful heterosis for yield ranged from 1 to 32·7%. The highest yielding hybrid was Coker 304 × PD 695. The strain PD 695 is moderately resistant to bollworms.All the hybrids having at least one resistant strain as their parent suffered less damage from bollworms than Coker 304. The resistant strains (BW 76–31, PD 695 andred leaf cotton) had desirable general combining ability (GCA) effects for bollworm damage. Relative yield (yield without protection expressed as percentage of yield with protection) was used as a measure of bollworm resistance. The high gossypol strain BW 76–31 had desirable GCA effects for relative yield, bollworm damage to buds, number of live worms and for bolls per plant. The fruiting efficiencies and photosynthetic rates of some bollworm-resistant strains were similar to those of a high-yielding, moderately susceptible cultivar.Combining-ability analysis indicated BW 76–31 to be a desirable parent for use in hybridization programmes for improving agronomic performance, fruiting efficiency, photosynthetic rate and bollworm resistance. It was also observed that bollworm-resistant cottons do not always have lower fruiting efficiencies and photosynthetic rates and it might be possible to combine this resistance with high yields.