Analysis and mapping of Rhizoctonia root rot resistance traits from the synthetic wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) line SYN-172

The prevalence of root disease after planting in cold spring soils has hindered the adoption of reduced or no-tillage cereal cropping systems in the Pacific Northwest. In particular, R. solani AG8, a necrotrophic root pathogen, can cause significant damage to wheat stands under these conditions. In previous efforts to find root rot resistance, a CIMMYT synthetic wheat line, SYN-172, was found to have little to no seedling stunting from disease and lower root disease scores. To identify trait-maker associations, a population consisting of 150 BC₁F₅ recombinant inbred lines from a cross of “Louise,” a typically susceptible Pacific Northwest (PNW) cultivar, and SYN-172 was created. A total of 689 polymorphic markers were used to identify trait-marker associations for seedling stunting in field green bridge and growth chamber environments. In total, five quantitative trait loci (QTL) were found on chromosome arms 1AL, 2AL, 5BL, 7DS, and 7DL. One QTL, on chromosome 2AL, was consistently detected in all four of the environments tested, and originated from SYN-172. A second QTL on 7DL, originating from the susceptible parent Louise, was found consistently in all three of the field environments, but not in soils artificially infested with R. solani AG8. These QTL have not been previously reported and will be useful root rot resistance genes when transferred into the PNW spring wheat germplasm.