Genome-wide association mapping in safflower (Carthamus tinctorius L.) for genetic dissection of drought tolerance using DArTseq markers

Understanding the genetic basis of drought tolerance in safflower (Carthamus tinctorius L.) is essential for developing resilient varieties. In this study, we performed a genome-wide association study (GWAS) using DArTseq markers to identify marker-trait associations (MTAs) linked to drought tolerance across 90 globally diverse safflower genotypes. These genotypes were evaluated under both rainfed (drought) and irrigated conditions over three consecutive years (2016-2018). Significant variation in seed yield and morphological traits was observed between genotypes and across environments, with notably reduced performance under rainfed conditions. A total of 66 MTAs were identified for key agronomic traits, including seed yield, 1000-seed weight, number of heads per plant, and days to maturity, with 45 MTAs showing significant associations with the stress-tolerance index (STI). Twelve MTAs were consistently detected across both stress and non-stress conditions, suggesting stable loci for breeding applications. BLAST searches indicated that several identified markers corresponded to genes involved in abiotic stress response, including biotin carboxylase, serine/threonine-protein kinase, and zinc finger domain proteins. The clustering of genotypes based on drought-tolerance coefficient (DC) and STI values grouped genotypes into drought-susceptible and drought-tolerant categories, with no strong correlation to geographic origin. These findings provide valuable insights into the genetic architecture of drought tolerance in safflower and highlight candidate loci for marker-assisted selection, supporting the development of drought-resilient varieties.