Abid, A.; Awan, F. S.

Bread wheat is one of the major food crops globally, accounting for one-fifth of global calorie consumption. Global climate change due to growing greenhouse effect has posed a major threat to wheat production. Heat stress reduces wheat production by disrupting essential physiological and biochemical pathways. This experiment aimed at identifying quantitative trait loci (QTLs), associated with single nucleotide polymorphisms linked with several yield-related traits, such as biological yield(B/Y), yield per plant(Y/P), days to maturity(DM), and harvest index(HI), that have a role in heat stress tolerance by evaluating 184 Pakistani wheat accessions. Marker trait associations were identified using Genome wide association study (GWAS) that revealed 59 QTLs related to B/Y, Y/P, HI and DM across all of the 21 chromosomes out of which 32 had high confidence protein coding regions. These QTLs were functionally characterized using wheat databases including ENSEMBL and UNIPROT. Their functional annotation revealed that some of the proteins expressed by these regions including elongation factor alpha and cytochrome p450 on chr5B and chr5D exhibit direct response to heat stress. Several transcription factors on chr5A and 1A help repair damaged DNA or act as chaperones and restore cellular activity, playing a key role in rendering heat tolerance to wheat. 2B was identified as QTL hotspot having 6 significant SNPs that were related to proteins having substantial role in heat tolerance. Haplotype analysis of these SNPs revealed the patterns of inheritance of these SNPs. A single haplotype block influencing multiple yield-related traits and exhibiting pleiotropic effect was identified. 3 haplotypes were identified on 1A, 2B, 3B, 6B and 7B of CB241, CB329, and CB094 wheat accessions associated with BY, Y/P and DM that were referred to as heat tolerant genotypes. This data can be utilized for enhancing heat stress tolerance in wheat by screening wheat genotypes for candidate genes involved or over expressing the genes involved in heat stress response.