GENOME WIDE ASSOCIATION ANALYSIS OF AGRONOMIC TRAITS IN DURUM WHEAT (Triticum turgidium var. durum) FOR SEEDLING DROUGHT TOLERANCE

Abstract

Drought is one of the leading abiotic stresses reducing the production and productivity of durum wheat in Sub-Saharan Africa, in particular Ethiopia. Thus, genome-wide association analysis of agronomic traits associated with seedling drought tolerance provides a basis for the development of drought-tolerant cultivars in durum wheat. The study aimed to examine the effects of water stress on agronomic traits in durum wheat, asses trait correlations under varied water conditions, and detect marker trait associations (MTAs) and quantitative trait loci (QTLs) under varied water conditions at the seedling stage. A total of 150 durum wheat genotypes were evaluated in the greenhouse at the National Agricultural Biotechnology Research Center, Holeta, using a completely randomized design under well-watered and water stress conditions with three replications. Genome-wide association (GWA) analysis was conducted using 9396 SNP markers and best linear unbiased estimator values of nine agronomic traits. The analysis of variance revealed highly significant variation among genotypes for all the studied traits under both well-watered and water-stress conditions, suggesting that genotypes were genetically diverse. Broad sense heritability ranged from 44% for root length to 73% for leaf chlorophyll content under well-watered condition, and from 17% root dry weight to 71% leaf chlorophyll content under water-stress condition. Results revealed that water stress significantly reduced shoot fresh weight (SFW) (60.66%), flag leaf area (FLA) (32.37%), root fresh weight (RFW) (31.25%), shoot dry weight (SDW) (23.81%), leaf chlorophyll content (LCC) (18.55%), shoot length (SL) (15.29%), and root dry weight (RDW) (12.9%) compared with the well-watered condition, but increased root length (RL) (20.53%) and root to shoot dry weight ratio (RS) (14.85%). Pearson’s correlation analysis unveiled significant and positive associations among the majority of the studied traits in both well watered and water stress conditions, except for negative correlations observed between SL and LCC in well-watered condition, and between LCC and SL, SFW as well as between RS and SDW, SFW in water stress condition. These findings suggest that selecting for one trait may enhance the performance of another. Principal component analysis identified that the first three components, each with eigenvalues greater than 1, explained 76.38% and 62% of the total variation under well-watered and water stress conditions, respectively. Traits such as RDW, SFW, FLA, LCC, and SL significantly contributed to overall variations under both well-watered and water stress conditions. This highlights the significance of these traits as key indicators for breeding programs aimed at improving drought tolerance in durum wheat. The GWA analysis identified a total of 114 significant MTAs, comprising 54 under well-watered condition and 60 under water stress condition. Furthermore, a total of 52 QTLs were detected, with 24 under well-watered condition, and 28 under water stress condition. The identified MTAs and QTLs included previously discovered and novel loci/genomic regions associated with various studied traits. The MTAs and QTLs discovered in this study hold promise for marker-assisted selection in breeding programs aimed at developing drought-tolerant durum wheat cultivars after further validation using larger and more diverse populations.