Abstract
Durum wheat (Triticum turgidum L. 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 of qCR-6B and a major QTL for root angle QTL qSRA-6A using yield datasets from six rainfed environments, including two environments with high CR disease pressure. In the absence of CR, the favorable allele for qSRA-6A provided an average yield advantage of 0.57 t·ha−1, whereas in the presence of CR, the combination of favorable alleles for both qSRA-6A and qCR-6B resulted in a yield advantage of 0.90 t·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.
Highlights
Durum is typically grown under rainfed conditions in the semiarid regions of the world [1]
In Australia, several Fusarium species associated with crown rot (CR) have been detected in cereal hosts [6], including Fusarium pseudograminearum, which is common throughout eastern Australia, and Fusarium culmorum, which is less common but frequent in high-rainfall regions in Victoria and South Australia
In the 2017 yield trial conducted in the CR screening nursery, the panel displayed a wide range of disease responses
Summary
Durum is typically grown under rainfed conditions in the semiarid regions of the world [1]. Increased variability in rainfall is predicted for most durum growing regions worldwide, the Mediterranean region, suggesting that drought will continue to have an impact on production into the future [2]. In Australia, several Fusarium species associated with CR have been detected in cereal hosts [6], including Fusarium pseudograminearum, which is common throughout eastern Australia, and Fusarium culmorum, which is less common but frequent in high-rainfall regions in Victoria and South Australia. The pathogen is prevalent in other growing regions of the world affecting production of winter cereals in the Pacific Northwest of the USA [7,8], Italy, North Africa, and The Middle East [9,10] and recently in China [11]
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