Phenotyping, association analysis and annotation of genes related to leaf wilting of bread wheat (Triticum aestivum L.) at the seedling stage under drought stress conditions

Rapid screening of plant germplasm in the early stages of growth and determining the genetic basis of wheat leaf wilting index at the seedling stage is necessary for wheat breeding programs. In the present research, leaf wilting index for 290 Iranian bread wheat genotypes, including; 90 cultivars and 200 landraces were studied under drought stress conditions at the seedling stage in 2021 in research greenhouse of faculty agriculture of Urmia University, Urmia, Iran. The results showed that there was variation between the studied genotypes for leaf wilting index, and the landraces had significantly 12% more wilting scores than cultivars. This can be attributed to direct or indirect selection by breeders. The leaf wilting index of about 9% of cultivars and 3% of landraces were identified in drought stress tolerant group. GWAS had nearly the same results as general lineare model and MLM methods. Chromosomes 3B, 2A, 7B, 1A, 3A, 4B, 5B, 6A and 6B, respectively, had the highest number of marker-trait associations in the entire population which explained the phenotypic variation of the trait from 6 to 20%. Annotation of significant markers confirmed the results of GWAS analysis and showed that five markers on chromosomes 1A, 2A, 3A and 7B were aligned with different genes involved in drought stress tolerance. An integral component of membrane, protein phosphorylation, methyltransferase activity and zinc ion binding were part of the molecular functions and biological processes of the identified genes. The findings of this research provide a deep insight into the variation of leaf wilting traits in Iranian bread wheat germplasm under drought stress conditions, which can be used as selction criterium in the national bread wheat improvement programs.