Genetic dissection and genomic prediction of drought indices in bread wheat (Triticum aestivum L.) genotypes

Drought constitutes the main obstacle to agricultural productivity in the Central and West Asia and North Africa (CWANA) region, notably leading to substantial reductions in wheat yields due to terminal water stress. The adoption of drought-resistant wheat varieties appears to be a vital strategy to maintain wheat production in the face of climatic challenges. In this context, a study was conducted utilizing a set of 198 elite bread wheat genotypes developed at the International Center for Agricultural Research in the Dry Areas (ICARDA). This set of elite genotypes was evaluated at the Sidi Al-Aidi station in Morocco over two years (2021–2022), under rain-fed and irrigated conditions. Phenotypic assessments for grain yield and drought indices were performed, alongside genotyping the population using 15k SNP markers. These preparatory steps facilitated a genome-wide association study (GWAS) and genomic prediction, leveraging the Mixed Linear Model (MLM) to pinpoint marker-trait associations (MTAs) and candidate genes pertinent to grain yield and drought indices. The results manifested substantial variations in both grain yield and drought indices among the genotypes tested. Grain yield performance ranged from 0.34 to 2.57 ​t/ha under rain-fed conditions and 1.12 to 4.57 ​t/ha under irrigated scenarios. The comprehensive analysis identified 39 significant MTAs (p ​< ​0.001) and 14 putative genes associated with drought indices and grain yield. Noteworthy is the marker “wsnp_Ex_c12127_19394952” on chromosome 5B, which displayed a significant correlation with grain yield in rain-fed environments. Furthermore, the most prominent marker linked to tolerance index (TOL) was “BobWhite_c42349_99”, situated on chromosome 5A and associated with the TraesCS5A02G498000 gene. This gene plays a critical role, encoding for catalase protein crucial for response to hydrogen peroxide. These markers could be used for marker-assisted selection in wheat breeding programs targeting drought tolerance.