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QTL mapping and candidate gene analysis for drought tolerance at the seedling stage in sorghum using BSA-SEQ
Abstract
To elucidate the genetic basis of drought tolerance at the seedling stage in sorghum, we used the drought‑tolerant restorer line LNR‑6 and the drought‑sensitive restorer line LR‑2381 as parents to construct an F₂ segregating population. Drought stress was carefully applied at the six‑leaf seedling stage, and two extreme phenotype bulks (highly tolerant and highly sensitive) were established based on phenotypic evaluation. Bulked segregant analysis (BSA) combined with high‑throughput sequencing was then employed to map quantitative trait loci (QTL) associated with seedling drought tolerance. The results showed that two significantly associated genomic regions were detected on chromosomes 9 and 10, designated qKH9 (29.677 kb) and qKH10 (400.118 kb), respectively. The qKH9 region contained 231 variant sites involving 17 transcripts, whereas qKH10 harbored 4,039 variant sites involving 144 transcripts. Functional annotation indicated that qKH9 includes candidate genes related to zinc finger proteins and protease‑mediated protein degradation, while qKH10 contains putative drought‑responsive genes involved in peroxidase activity and kinase‑mediated signal transduction. These QTL provide key genomic intervals for dissecting the molecular mechanisms underlying seedling drought tolerance in sorghum and lay an important foundation for fine mapping, marker development and molecular breeding for drought tolerance
