Title : Genetic improvement of durum wheat under drought stress: Exploring QTLs from wild relatives to enhance resilience and yield
Abstract:
Drought is one of the most severe climatic stresses affecting global durum wheat (Triticum durum Desf.) production. Wild relatives of this crop offer a valuable reservoir of adaptive alleles that can enhance drought tolerance. To explore these genetic resources, Nested Association Mapping (NAM) panel was developed using the Moroccan variety ‘Nachit’ a T.dicoccoides-derived line known for its large grain size as the recurrent parent. This was crossed with three high-performing lines originating from T. dicoccoides, T. araraticum, and Ae. speltoides resulting in 426 progenies. which was evaluated across 12 environments in Syria, Lebanon, and Morocco over four seasons 2018-19 till 2021-22, each experiencing varying levels of moisture stress using Augmented Design, the additive main effects and multiplicative interaction (AMMI) was performed to analyze GGE interactions, stability for the traits was estimated using (AWAI) index. Our results showed that grain yield was the most affected trait by drought stress and 1000-keel weight (TKW) was the most important trait for adaptation to it. The analysis of genotype-environment interactions revealed highly significant differences among genotypes, environmental, and their interactions effects across all traits. For grain yield, the most promising genotypes were N:86, N:59, and N:114, which carry genes from T.dicoccoides. Additionally, N:253 and N:307, which derived from T. araraticum and T. dicoccoides. In a noteworthy finding, genotypes containing genes from Ae.speltoides exhibited the highest values for the thousand-grain weight trait, highlighting their contribution to enhanced kernel size under varying environmental conditions. Genotyping with a 25K TraitGenetics array produced a Consensus Map containing 1,678 polymorphic SNPs, spanning 1,723.4 cM and aligned to the Svevo genome assembly. Kinship analysis grouped progenies into three distinct clades corresponding to their parental origin. A total of 22 stable quantitative trait loci (QTLs) were identified across multiple traits, independent of flowering time. The most significant genomic regions Q.DR.002-1B, Q.DR.015-6A, and Q.DR.021-7B were strongly associated with traits under drought stress. Haplotype analysis using a second germplasm panel confirmed that genotypes carrying the positive alleles at these three loci exhibited a 25% increase in TKW under drought conditions. To facilitate molecular breeding, the underlying SNPs were converted into Kompetitive Allele Specific PCR (KASP) markers and successfully validated in a third germplasm set. These markers explained up to 15% of the phenotypic variation in TKW under moisture stress, demonstrating their effectiveness in selecting drought-tolerant genotypes. Overall, these findings underscore the importance of wild genetic resources in breeding programs aimed at improving durum wheat resilience under arid conditions. The identified loci and validated markers now provide valuable tools for accelerating molecular breeding efforts toward more drought-adaptive, high-yielding varieties.
Keywords: Durum Wheat, Wild Relatives, Drought Tolerance, Quantitative Trait Loci (QTLs), KASP Markers.
