Quantitative trait loci for soil-penetrating ability of roots in durum wheat

Increasing root penetration (RP) ability into hard soil is important to improve drought resistance in durum wheat. Traits related to RP ability were evaluated in 110 recombinant inbred lines (RILs) derived from a cross between 'Jennah Khetifa' and 'Cham1' using paraffin-Vaseline (PV) discs. QTL analyses were made for the number of roots penetrating the PV disc (PVRN), total number of seminal and crown roots (TRN), RP index (PVRN/TRN) and root dry weight (DW). 'Jennah Khetifa' had higher PVRN, RP index and root DW values than 'Cham1', and the RILs showed significant differences for these traits. Two closely-linked markers, Xgwin6l7a and Xgwm427b, on the long arm of chromosome 6A were associated with PVRN and RP index. For root DW, a QTL was linked to marker Xgwm11 on chromosome 11B. Alleles of 'Jennah Khetifa' were associated with increased PVRN, RP index and root DW. No QTL was detected for TRN in this mapping population. The absence of co-located QTLs suggested that RP ability was controlled separately from TRN and root DW. Although the population size and number of replications were small, this study helps in understanding the complexity of root growth and the potential of marker-assisted selection for selecting genotypes with high RP ability in durum wheat populations.