Deciphering variations, identification of marker-trait associations and candidate genes for seed oil content under terminal heat stress in Indian mustard (Brassica juncea L. Czern & Coss) germplasm stock

This research paper investigates the variability in seed oil content (SOC) in Indian mustard (Brassica juncea L.) under terminal heat stress (THS) conditions. A genetic stock of 488 genotypes of B. juncea was evaluated over two years and grouped into five classes based on the reduction in oil content under THS compared to normal sown crop. Based on heat susceptibility index (HSI), a diverse panel of 96 genotypes was selected and evaluated under THS. Twenty-two heat-tolerant donor genotypes were identified, including introgression lines derived from B. tournefortii, B. carinata and Erucastrum cardaminoides. This study is the first to report on marker-trait associations for SOC in B. juncea under THS using a GWAS approach. Furthermore, candidate genes associated with abiotic stress tolerance and lipid metabolism were identified near the significant SNPs, emphasizing their role in SOC regulation under stress. Notable candidate genes include BjuA003240 (encoding for alcohol-forming fatty acyl-CoA reductase), BjuA003242 (involving in lipid biosynthesis), BjuA003244 (associated with mitochondrial functions and stress tolerance), and BjuA003245 (related to MYB transcription factors regulating lipid biosynthesis). This study provides valuable insights into the genetic basis of SOC variation under THS in B. juncea, highlighting potential breeding targets for improved heat stress resilience in Indian mustard cultivation.