Adaptive Traits to Improve Durum Wheat Yield in Drought and Crown Rot Environments

Durum wheat (Triticum turgidumL. ssp.durum) production can experience significant yield losses due to crown rot (CR) disease. Losses are usually exacerbated when disease infection coincides with terminal drought. Durum wheat is very susceptible to CR, and resistant germplasm is not currently available in elite breeding pools. We hypothesize that deploying physiological traits for drought adaptation, such as optimal root system architecture to reduce water stress, might minimize losses due to CR infection. This study evaluated a subset of lines from a nested association mapping population for stay-green traits, CR incidence and yield in field experiments as well as root traits under controlled conditions. Weekly measurements of normalized difference vegetative index (NDVI) in the field were used to model canopy senescence and to determine stay-green traits for each genotype. Genome-wide association studies using DArTseq molecular markers identified quantitative trait loci (QTLs) on chromosome 6B (qCR-6B) associated with CR tolerance and stay-green. We explored the value ofqCR-6Band a major QTL for root angle QTLqSRA-6Ausing yield datasets from six rainfed environments, including two environments with high CR disease pressure. In the absence of CR, the favorable allele forqSRA-6Aprovided an average yield advantage of 0.57 t center dot ha(-1), whereas in the presence of CR, the combination of favorable alleles for bothqSRA-6AandqCR-6Bresulted in a yield advantage of 0.90 t center dot ha(-1). Results of this study highlight the value of combining above- and belowground physiological traits to enhance yield potential. We anticipate that these insights will assist breeders to design improved durum varieties that mitigate production losses due to water deficit and CR.