Combining Ability and Heterotic Responses Among Newly Developed Elite Stay-Green Sorghum Inbred Lines

Sorghum [Sorghum bicolor (L) Moench], a crop grown in arid and semi-arid environments, can be enhanced with the stay-green trait to improve post-flowering drought tolerance. Previous studies on stay-green sorghum hybrids have noted a positive association between stay-green and grain yield in low potential environments but did not assess the combining ability or heterotic responses of individual genotypes. In this study, stay-green seed parents developed at Purdue University were crossed with three elite pollinators, and their combining ability and heterotic responses were assessed in multiple locations which represented both stress and non-stress environments. Results showed greater variation in general and specific combining ability estimates in stress environments compared to non-stress environments, with a higher proportion of additive genetic variance compared to non-additive variance in both types of environments. Levels of heterosis for grain yield, 1000 seed weight, and plant height varied across locations and between R-lines. Several experimental hybrids derived from the stay-green inbred lines outyielded commercial hybrid checks in the Ethiopian environments while showing good hybrid seed production potential, with high seed parent yield and good nicking.