A Candidate Gene Analysis of QTL for Root Growth Angle in Durum Wheat

Different RSAs are required to maximize the efficiency of the plant in water uptake/coping with drought stress, nutrient foraging and adaptation to different sowing density/managements. Therefore, optimization of RSA traits is an important goal for cereal and modern wheat breeding. In this study, genetic variation in elite tetraploid wheat germplasm has been investigated using two recombinant inbred line populations and one association mapping panel of 183 cultivars. These resources were searched for RSA QTL at seedling stage (seminal roots). QTL were mapped on a high-density tetraploid consensus map based on a transcript-associated Illumina 90K SNP assay, thus allowing for an accurate cross-referencing of RSA QTL. In total, 20 main QTL clusters for root length and/or number as well as 30 QTL for root growth angle (RGA) were identified. Based on their relative additive effects, allelic distribution in the AM panel and co-location with QTL for yield and kernel weight, the RSA QTL have been prioritized in terms of breeding value. Seven main RGA QTL were selected for investigating of gene content in the assembled wheat genomes: Chinese Spring Triticum aestivum (Release: 30/11/2015) assembly and the TriAnnot v4.3 gene prediction and annotation pipeline (Leroy et al. 2011) and the Zavitan T. dicoccoides genome assembly for integration and comparison (Avni et al. 2017). The chromosome regions ranged from 2.1 to 17.0 Mb and contained on average 146 predicted genes. The annotated genes are involved in auxin pathways, PIN-formed protein family of auxin transporters and MYB transcription factors. The comparison between the T. aestivum and T. dicoccoides local gene content and the nature of the genes related to auxin biosynthesis or auxin signaling, and genes most likely involved in the RGA determinism, will be reported. A detailed study of functions, functional domains and tissue expression of the candidate genes is underway.