Combining Ability Analysis for Yield and Associated Traits in Sunflower (Helianthus annuus L.) F₁ Hybrids under Normal and Heat Stress Conditions

Abstract

Heat stress is one of the highest environmental restraints limiting sunflower productivity worldwide by adversely affecting flowering, seed development, and oil accumulation. The present study was conducted to estimate the general combining ability (GCA) and specific combining ability (SCA) of sunflower parental lines and their F₁ hybrids under normal and heat stress environments using the Line × Tester mating design. Analysis of variance revealed highly significant differences among genotypes, parents, crosses, and line × tester interactions for most of the traits studied, indicating the presence of substantial genetic variability. Significant GCA and SCA variances suggested that both additive and non-additive gene effects contributed to the inheritance of the evaluated characters, although the magnitude of SCA variance was comparatively higher for several economically important traits, demonstrating the predominance of non-additive gene action. Several parental lines exhibited desirable GCA effects for seed yield and related traits, whereas several cross combinations expressed high positive SCA effects under both normal and heat stress conditions, indicating their potential for hybrid development. Heat stress considerably reduced the overall performance of most genotypes; however, selected hybrids maintained comparatively superior performance, suggesting improved adaptation to elevated temperature. The findings provide valuable information for sunflower breeding strategies targeting improved productivity and heat stress tolerance under changing climatic conditions.