QTL mapping for drought tolerance traits in a recombinant inbred line population of sorghum

Abstract:

Sorghum feeds millions across the semi-arid tropics, yet drought routinely slashes yields by 30-60% in rainfed systems. Identifying the chromosomal regions governing drought tolerance would accelerate breeding progress. This research mapped quantitative trait loci (QTL) for drought-related traits in 186 F₇ recombinant inbred lines (RILs) derived from a cross between a drought-tolerant Ethiopian landrace (Meko-1) and a high-yielding but drought-susceptible line (ETS-2752). The population was phenotyped under managed drought stress and well-watered conditions at Bahir Dar during the 2022 and 2023 post-rainy seasons. A genetic linkage map spanning 1,247 cM was constructed from 142 SSR markers across ten chromosomes. Composite interval mapping detected seven QTL for stay-green score, leaf rolling, root length, and grain yield under stress. Three major QTL on chromosomes 3, 7, and 9 individually explained 9.4-16.8% of phenotypic variance. The chromosome-3 QTL co-localised with a previously reported stay-green locus (Stg3), confirming its relevance across genetic backgrounds. These markers can be deployed in marker-assisted selection to accelerate the development of drought-tolerant sorghum varieties for the Ethiopian highlands and similar environments.