Genetic architecture of drought resilience in barley (Hordeum vulgare L.) revealed by genome-wide association study.

Drought stress is a major constraint to barley (Hordeum vulgare L.) production worldwide, with recurrent and variable drought episodes challenging yield stability. Understanding the genetic basis of drought adaptation across different drought history treatments is essential for breeding resilient cultivars. A genome-wide association study (GWAS) was conducted using high-density SNP genotyping across multiple drought history scenarios, including control and combinations of early- and late-generation drought exposure. Drought priming across generations enhanced yield and biochemical traits, with the strongest biochemical gains in the second generation, while continuous drought produced the most consistent improvements in both yield stability and defense responses. GWAS identified multiple highly significant and stable loci across the barley genome, with recurrent association hotspots on chromosomes 4H, 5H, 6H, and 7H. Notable SNPs such as chr4H:439308083:G:A, chr5H:621040118:C:T, and chr7H:493258982:C:T influenced multiple traits across treatments, suggesting pleiotropic effects. Candidate genes included members of the protein kinase family, aldehyde dehydrogenases, and other stress-responsive regulators involved in signal perception, ABA signaling, osmotic adjustment, and oxidative stress detoxification. Protein kinases, particularly MAPKs, SnRKs, and CDPKs, likely mediate rapid and efficient drought signal transduction, while aldehyde dehydrogenases contribute to sustained protection against reactive aldehydes generated during water deficit. The recurrence of specific SNPs across environmental contexts highlights their robustness as potential breeding targets. This study provides novel insights into the genomic architecture of drought tolerance in barley under variable drought histories, identifying key loci and candidate genes with functional relevance to stress adaptation.