*aschwember@uc.cl

Durum wheat is a fundamental cereal in the Mediterranean region. It provides more than 20% of the nutritional demands in the form of pasta and other semolina-based products for human consumption. Plants have developed different mechanisms to cope with drought stress since water deficit affects the durum grain yields, causing farmers losses of up to 50%.

Therefore, the objectives of this study were to evaluate the yield components on a panel of 225 elite durum wheat genotypes under contrasting water regimes (optimal and water-deficit) and to understand the physiological, molecular, and metabolic aspects of the drought response in durum wheat as a basis for developing resilient and high-yielding cultivars to ensure food security.

The combined analyses of variance showed significant effects (p < 0.05) of genotypes (G), environments (E), and their interactions (G×E) for all traits, except for grains per spike (GPS) and spike per square meter (SPM), in which the G×E factor was not significant. The E effect explained most of the variation for yield (YD; 79.8%) and 1000-grains weight (TKW; 63.22%).

Moreover, the G×E interaction exhibited a more significant contribution to the total variability than the G effect for all traits except for TGW, which had a broad-sense heritability value of 0.882. Seven hundred seventy-two significant marker-trait associations (MTAs) distributed across the 14 chromosomes for five yield-related traits and along the 8 environments studied were identified. Among them, 9 MTAs were detected across all environments and were grouped into three QTLs according to linkage disequilibrium.

These QTL were associated with TGW and GPS and located on chromosomes 2A (QTN_2A_TGW/GPS.1; QTN_2A_TGW/GPS.2) and 2B (QTN_2B_TGW/GPS.1), comprising a total of 630 genes and explaining between a 5.15% and 14.29% of the phenotypic variation. Two contrasting genotypes to drought response, QUC 3678-2016 (drought-tolerant) and BRESCIA (drought-susceptible), were identified. RNA-seq analysis indicated that 697 and 900 genes were regulated in response to water deficit between these two contrasting genotypes in leaf and root, respectively, at 0-, 14-, and 30-days post anthesis (DPA).

The multi-omics integration analysis identified 30 genes and six metabolites in root and 30 genes and ten metabolites in leaf as the primary variable in the drought-tolerant genotype, confirming proline as an important compound involved in drought tolerance and opening an opportunity for the use of new biomarkers (i.e., associated with some specific carbohydrates and amino acids) in durum wheat breeding programs.