Drought is one of the major abiotic stress factors limiting wheat production worldwide, thus threatening food security. The dissection of the genetic footprint of drought stress response offers strong opportunities toward understanding and improving drought tolerance in wheat. In this study, we investigated the genotypic variability for drought response among 200 diverse wheat cultivars (genotypes) using agronomic, developmental, and grain quality traits, and conducted genome-wide association studies (GWAS) to uncover the genetic architectures of these important traits. Results indicated significant effects of genotype, water regime and their interactions for all agronomic traits. Grain yield was the most drought-responsive trait and was highly correlated with kernels number per meter square. GWAS revealed 17 and 20 QTL regions under rainfed and drought conditions, respectively, and identified one LD block on chromosome 3A and two others on 5D associated with breeding progress. The major haplotypes of these LD blocks have been positively selected through breeding and are associated with higher starch accumulation and grain yield under drought conditions. Upon validation, the identified QTL regions caring favorable alleles for high starch and yield will shed light on mechanisms of tolerance to drought and can be used to develop drought resistant cultivars.

Modern bread wheat has a huge genetic potential to adjust its heading date with favorable conditions that has remained largely unexplored so far. In this study, we used an association panel of in Germany adapted cultivars that was tested in multi-location field trials across Germany over three years. The genotypic response to climatic parameters variation depending on location and year uncovered the implication of photoperiod in promoting transition to flowering in higher latitudes, while spring temperature accelerates flowering in lower ones. Spring temperature overdominates other factors in decreasing the days to heading whereas the higher amount of solar radiation is delaying it. Genome wide scan detected a so far unknown stable locus TaHd14 on chromosome 5A. Including non-adapted cultivars, the exotic allele TaHd119 on chromosome 3A could be identified. The later explains up to 33% of the genetic variance and accelerates heading date by 5.63 days. The response to the competition of latitude dependent climatic variables detected fine tuning QTL responding to temperature and photoperiod in lower and higher latitudes, respectively. A novel locus TaHd12 on chromosome 5A showed significant epistatic interactions with 15 known operators of HD regulation when exotic cultivars were included in the analysis