Genetic dissection of the root system architecture QTLome and its relationship with early shoot development, breeding and adaptation in durum wheat

Root system architecture (RSA), shoot architecture, and shoot-to-root biomass allocation are critical for optimizing crop water and nutrient capture and ultimately grain yield. Nevertheless, only a few studies adequately dissected the genetic basis of RSA and its relationship to shoot development. Herein, we dissected at a high level of details the RSA-shoot QTLome in a panel of 194 elite durum wheat (Triticum turgidum ssp. durum Desf.) varieties from worldwide adopting high-throughput phenotyping platform (HTPP) and genome-wide association study (GWAS). Plants were grown in controlled conditions up to the seventh leaf appearance (late tillering) in the GROWSCREEN-Rhizo, a rhizobox platform integrated with automated monochrome camera for root imaging, which allowed us to phenotype the panel for 35 shoot and root architectural traits, including seminal, nodal, and lateral root traits, width and depth, leaf area, leaf, and tiller number on a time-course base. GWAS identified 180 quantitative trait loci (QTLs) (-log p-value ≥ 4) grouped in 39 QTL clusters. Among those, 10, 11, and 10 QTL clusters were found for seminal, nodal, and lateral root systems. Deep rooting, a key trait for adaptation to water limiting conditions, was controlled by three major QTLs on chromosomes 2A, 6A, and 7A. Haplotype distribution revealed contrasting selection patterns between the ICARDA rainfed and CIMMYT irrigated breeding programs, respectively. These results provide valuable insights toward a better understanding of the RSA QTLome and a more effective deployment of beneficial root haplotypes to enhance durum wheat yield in different environmental conditions.