Genetic variability predicting breeding potential of upland cotton (Gossypium hirsutum L.) for high temperature tolerance

Abstract Background High temperature stress at peak flowering stage of cotton is a major hindrance for crop productivity. This study aimed to increase genetic divergence regarding heat tolerance in newly developed cultivars and hybrids. The fifty cotton genotypes and 40F1 were tested under field conditions following the treatments viz., high temperature stress and control at peak flowering stage during August and October under April and June sowing, respectively. Results The means squares revealed significant differences among genotypes, treatments, genotype×treatment for relative cell injury, chlorophyll contents, canopy temperature, boll retention and seed cotton yield. The genetic diversity among 50 genotypes was analyzed through cluster analysis and heat susceptibility index (HSI). Based on HSI and cluster analysis eight tolerant genotypes (FH-Noor, NIAB-545, FH-466, FH-Lalazar, FH-458, NIAB-878, IR-NIBGE-8 and Weal-AG-Shahkar) and five sensitive (CIM-602, Silky-3, FH-326, SLH-12 and FH-442) were selected for hybridization. The breeding material, 40F1 and 13 parents evaluated following line×tester design. Higher specific combining ability variances with dominance variances determined the non-additive gene action for all the traits. The best general combining ability effects for most of the traits were displayed by lines FH-Lalazar, NIAB-878 along with testers FH-326 and SILKY-3. Specific combining ability effects and better-parent heterosis were showed by crosses FH-Lalazar×SILKY-3, FH-Lalazar×FH-326, NIAB-878×SILKY-3 and NIAB-878×FH-326 for seed cotton yield and yield contributing traits under high temperature stress. Conclusion Consequently, heterosis breeding for non-additive type of gene action, may utilize the potential parents in different cross combinations to develop high temperature tolerance in local cotton cultivars and hybrids for improving seed cotton yield .