Investigating root system architectural traits in durum wheat to improve adaptation to drought and crown rot conditions

Abstract

Durum wheat (Triticum turgidum L. ssp. durum) producers can experience significant yield and grain losses due to crown rot (CR) disease, caused primarily by a fungal pathogen Fusarium pseudograminearum. Losses due to CR are 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. Deploying physiological traits for drought adaption (e.g. deeper roots), to reduce stress due to water deficit may, therefore, potentially minimise losses due to CR infection. The rapid generation advance technology, ‘speed breeding’, was used to rapidly develop recombinant inbred lines (RIL) populations (F6) derived from crosses between Australian cultivars and ICARDA elite breeding lines pre-selected for drought adaptation in Syria and Morocco. Populations were evaluated in the field and under controlled conditions for several physiological traits, including seminal root angle and number and CR severity. This provided the genetic predisposition of lines for rooting behaviour and CR susceptibility in the absence of water stress. Field experiments were established in Queensland, Australia, which allowed an examination of the value of root development traits to improve adaptation to each of the stresses. NDVI measurements were recorded weekly, which enabled modelling of the senescence pattern and calculation of stay-green traits for each genotype. Genome-wide association studies using DArT markers identified key genomic regions underpinning the traits. Our genetic analyses highlighted the genetic relationships between yield as well as above- and below-ground physiological traits. Through this study, we have provided new insights into the genetic controls and value of these traits, which we anticipate will assist breeders to design improved durum varieties that may mitigate production losses due to water deficit and CR.