Identification of genetic factors regulating pollen viability in wheat under heat stress environment

Rising global temperature threaten wheat productivity, particularly during reproductive phase. Improving pollen viability (PV) under heat stress is critical for sustaining yields in high-temperature environments. This study presents the first genome-wide association study (GWAS) of historical Pakistani wheat accessions for pollen viability (PV) under terminal heat stress. A panel of 194 accessions was evaluated over two years under normal and heat stress environments. Pollen exposure to high temperatures resulted in a significant reduction in pollen viability (PV). Using the FarmCPU model, 18 and 19 quantitative trait loci (QTLs) were detected under normal condition, while 25 and 3 QTLs were identified under heat stress in the respective years 2020–21 and 2021–22. Annotation of these 28 QTLs under heat stress revealed 11 possible putative candidate genes. Further, transcriptome profiling of reproductive tissues identified six differential genes. Whereas five genes showed differential expression under heat and drought stress in a transcriptome profiling study. Based on both studies, four genes were selected as candidate gene expression including, TraesCS2B01G579800.1 (UBX domain-containing protein), TraesCS4D01G062100.1 (Homeobox protein BEL1-like protein), TraesCS5D01G383300.1 (Serine/threonine-protein phosphatase), TraesCS6D01G153900.1 (Chaperone protein) considered as putative candidate genes. The differential gene expression of these four genes in spike tissues under stress conditions suggest the complex and variable nature of stress-responsive genetic regulation in wheat. These genomic resources provide putative candidate genes which need functional validation to understand the molecular mechanisms underlying pollen grain viability under heat stress.