A Major Root Architecture QTL Responding to Water Limitation in Durum Wheat

Abstract

The optimal root system architecture (RSA) of a crop is context dependent and critical for efficient resource capture in the soil. Narrow root growth angle promoting deeper root growth is often associated with improved access to water and nutrients in deep soils during terminal drought. RSA, therefore is a drought-adaptive trait that could minimize yield losses in regions with limited rainfall. Here, GWAS for seminal root angle (SRA) identified seven marker-trait associations clustered on chromosome 6A, representing a major quantitative trait locus ( qSRA-6A ) which also displayed high levels of pairwise LD ( r 2 = 0.67). Subsequent haplotype analysis revealed significant differences between major groups. Candidate gene analysis revealed loci related to gravitropism, polar growth and hormonal signaling. No differences were observed for root biomass between lines carrying hap1 and hap2 for qSRA-6A , highlighting the opportunity to perform marker-assisted selection for the qSRA-6A locus and directly select for wide or narrow RSA, without influencing root biomass. Our study revealed that the genetic predisposition for deep rooting was best expressed under water-limitation, yet the root system displayed plasticity producing root growth in response to water availability in upper soil layers. We discuss the potential to deploy root architectural traits in cultivars to enhance yield stability in environments that experience limited rainfall.

Durum Wheat Seminal Root Traits within Modern and Landrace Germplasm in Algeria

“…For example, root spread angle is an additional feature whose variation can influence how crops cope with water-limited conditions and/or other environmental constraints, such as high pH, toxic ions, or low nutrient availability [45,46]. The root angular spread at an early growth stage can be used to predict the partitioning of root biomass in the soil profile at the adult plant stage [5,27,28], a feature relevant for water use efficiency in wheat [21,47]. Therefore, artificial systems are efficient at revealing phenotypic (and presumably genetic) variability, but its implications on agronomic performance must be validated later under field conditions.…”

“…Indeed, several studies have found useful associations with traits in adult plants of wheat species [23][24][25][26]. For instance, the seminal root angle was correlated with nodal root angle [5,27], and with grain yield under drought conditions [28]. The seminal root number was correlated with thousand kernel weight (TKW) under stress, while the primary root length at the seedling stage was correlated with TKW under wetter conditions [25].…”

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

“…A panel comprising 168 genotypes was evaluated in this study. The panel included 151 durum lines from the NAM population developed at the University of Queensland [39]. The NAM population was generated by crossing eight lines from ICARDA's durum breeding program in Morocco with two Australian cultivars.…”

“…To investigate the relationship between root biomass and yield under CR conditions, a subset of the panel (40 genotypes) was selected according to the haplotype at the major QTL for root angle qSRA-6A (i.e., hap1 = narrow, n = 20; and hap2 = wide, n = 20) [39]. The 40 genotypes were evaluated for root biomass using the method reported by Voss-Fels et al [57] with slight modifications.…”

“…A number of quantitative trait loci (QTLs) for root traits have been reported in durum wheat [37,38], including the major QTL for seminal root angle (SRA) qSRA-6A [39]. The study of qSRA-6A identified two main haplotypes: hap1 (associated with narrow SRA) and hap2 (associated with wide SRA), which were found to be independent of root biomass.…”