Understanding the genetic basis of heat stress tolerance in wheat (Triticum aestivum L.) through genome-wide association studies.

Heat stress can reduce the production potential of wheat (Triticum aestivum L.) by affecting the various developmental stages of wheat including the seedling stage. Understanding the genetic basis of heat stress tolerance can help in breeding resilient wheat cultivars with improved productivity. Here, evaluation of a diverse panel of spring wheat landraces and cultivars under non-heat stress (23°C) and heat stress (36°C) treatments in a controlled environment revealed large phenotypic and genetic variations. Heat stress negatively affected all seedling traits with the maximum reduction in root length (85.6%) and the least reduction in coleoptile length (15.44%). Moreover, based on seedling performance, we identified six highly heat tolerant (PI 366905, Kzyl Sark, Rang, Perico S, Bohr Gamh, and PI 620689) and six highly heat susceptible (CItr 17470, CItr 13270, Coeruleum, Shashi, Hallany, and Currawa) genotypes. Genome-wide association analysis using 302,524 single nucleotide polymorphisms identified 23 marker-trait associations (MTAs), of which 16 were associated with various seedling traits under heat stress. Gene annotation and expression analysis indicated 35 differentially expressed genes, of which 13 were considered as high-confidence genes with functional relevance to heat stress including protein kinase, basic-leucine zipper, UDP-glucosyltransferase, pyrophosphate-energized proton pump, fatty acid hydroxylase, and other classes of proteins. The MTAs and candidate genes identified in this study hold promise for developing heat-resilient wheat cultivars through the selection of favorable alleles with gene-specific molecular markers.