Improving Rooting at Depth in Wheat with Introgression from Wild Emmer (Triticum dicoccoides)

Improving the allocation of crop biomass to higher densities of deeper roots in wheat can increase access to subsoil water, which directly affects yield when water is limited late in the season. The critical root length density (RLD) needed for uptake of water is 1 cm/cm³. Modern wheat crops commonly do not reach this critical value below 40 cm depth. The wheat cultivar Shamrock was previously shown to have significantly greater RLDs below 40 cm at anthesis over multiple seasons, compared to other UK wheat cultivars. Shamrock contains material recently introgressed from wild emmer (Triticum dicoccoides) and inherited a non-glaucous trait, the reduction of epicuticular wax. The non-glaucous trait has been mapped to the short arm of 2B (2BS), where the non-glaucous gene Iw1 is located. A doubled haploid (DH) population of Shamrock x Shango, which segregates for this trait, was used to investigate the genetic basis for improved rooting at depth of Shamrock.

Shamrock had significantly greater RLD compared to Shango below 50 cm in the field post-anthesis in the 2013/14 season. The 89 lines of the DH population differed significantly for RLD at 50-80 cm depth in the field post-anthesis in the 2014/15 season. No association was found between RLD and the non-glaucous trait in the field. The distribution of RLD with soil depth within the 50-80 cm layer interacted significantly with the presence of the glaucous trait and a QTL for this variation was identified on 2BS. A select number of DH lines were grown in rhizotrons to the end of tillering. Lines which exhibit the non-glaucous trait had significantly greater root length at 40-80 cm depth, compared to glaucous lines. To confirm the association of wild emmer introgression on 2BS and greater RLDs at depth a group of near isogenic lines (NILs) with and without Iw1 were studied in metre tall rhizotrons. Root distribution within the soil profile of the different NILs will be presented.