Genetic Analysis of Tetraploid Wheat Root Traits

Durum wheat (Triticum turgidum L. var. durum) is a very important crop in the Mediterranean basin. Intense breeding activities are carried out to improve its productivity, quality and resistance, and new genomic tools are essential to speed up the breeding progress. A segregating population of 136 recombinant inbred lines (RILs) derived from a cross between the durum wheat cv. Simeto and the T. dicoccum accession Molise Colli was genotyped with the wheat 90k iSelect Infinium SNP assay and DArTseq assay. Out of 174,396 wheat SNP and silico DArT markers (81,587 derived from 90k SNP assay and 92,809 from DArTseq), a total of 44,652 were polymorphic between the parents (10,680 and 33,972 respectively). A linkage map was developed with 31,756 SNP markers (9,040 derived from 90k SNP assay and 22,716 from DArTseq) and twenty one linkage groups which covered all of the chromosomes. Simeto and Molise Colli were characterized by a quite different development of the root apparatus, and in particular Molise Colli showed more a larger root system in terms of root length and diameter. The root measurements were performed with the Win-RHIZO system which is an interactive scanner-based image analysis system for the scanning, digitising and analysis of root samples. A total of 18 QTL were identified on chromosomes 1B, 2A, 3A, 4B, 6A, 6B and 7B. A part of the phenotypic variability for root apparatus size was explained by the 4B QTL corresponding to Rht region. Most of the QTL were contributed by Molise Colli, but for some QTL on chromosomes 6B and 7B a positive effect was found for the Simeto allele. Wild and domesticated relatives of wheat represent a valuable source of alleles useful for improving durum wheat, which can be transferred to varieties of elite with crosses. The parents of the genetic map herein represented differ for a number of traits of agronomic importance for durum wheat. Therefore the SNP-based Simeto x Molise Colli linkage map represents a useful tool for the genetic improvement of durum wheat.