Whole Genome QTL Search for Root System Architecture in Tetraploid Wheat

Linkage and association mapping for root system architecture (RSA) traits evaluated in seedlings of two recombinant inbred line populations and one association mapping panel of durum wheat (Triticum turgidum L. var. durum Desf.) evidenced 20 clusters of quantitative trait loci (QTL) for root length and number and 30 QTLs for root growth angle (RGA). QTLs were projected on a high-density tetraploid consensus map based on transcript-associated Illumina 90K SNPs developed for bread and durum wheat, thus allowing for an accurate cross-referencing of RSA QTLs between durum and bread wheat. Among the main QTL clusters for root length and number highlighted in this study, 15 overlapped with QTLs for multiple RSA traits reported in bread wheat while out of 30 QTLs for RGA, only six showed colocation with previously reported QTLs in wheat. RSA QTLs have been prioritized based on their relative additive effects, allelic distribution in the AM panel and co-location with QTLs for kernel weight and yield. Three major QTL clusters for root length and number (RSA_QTL_cluster_5#, RSA_QTL_cluster_6#, and RSA_QTL_cluster_12#) and five QTL clusters for root growth angle (QRGA.ubo-2A.3, QRGA.ubo-2B.2/2B.3, QRGA.ubo-4B.4, QRGA.ubo-6A.2 and QRGA.ubo-7A.2) appear particularly valuable for further  investigation towards positional cloning / marker-assisted selection.