Marker assisted introgression of stay green QTLs and identification of stable high yielding stay green genotypes using AMMI based selection indices in rabi sorghum (Sorghum bicolor L. Moench)

Sorghum is a key cereal crop in Asia and African regions, valued for its resilience in dryland regions and used for food, fodder, and biofuel. However, in the post-rainy season, sorghum production is impacted by terminal drought stress. The stay-green trait enhances its adaptability to drought, making it a vital focus in breeding efforts. This study aimed to identify stable, high-yielding stay-green sorghum lines through marker-assisted backcross breeding. Three farmer-preferred, non-stay-green varieties viz., SPV2217, BJV44, and SVD0806 were crossed with stay-green donors K260 and K359w, which carry the stg3A and stg3B QTLs, respectively. Analysis of the BC₂F₂ populations of six crosses revealed high heritability, variability and genetic advance for yield traits. Foreground selection with 10 SNP markers confirmed the presence of stay-green alleles. Further evaluation in the BC₂F₃ and BC₂F₄ generations validated consistent stay-green expression. In BC₂F₄ generation, positive significant correlations were seen between most of the stay-green traits and grain yield, except rate of leaf senescence, which had a negative correlation. Field trials at four locations in the northern zones of Karnataka i.e., Dharwad, Bailhongal, Hukkeri, and Vijayapura identified genotype STG 1 as the most stable, high-yielding line, based on AMMI stability indices ASTABi and ssiASTABi, making it promising for drought-prone regions in Karnataka.