Identification of novel QTL for sawfly resistance in wheat
The wheat stem sawfly (WSS) (Cephus cinctus Nort.) is an important pest of wheat (Triticum aestivum L. em. Thell.) in the Northern Great Plains. This paper reports the genetic analysis of antixenosis for egg-laying WSS females in recombinant inbred lines (RIL) of hard red spring wheat. Female WSS preferentially choose certain wheat genotypes for egg-laying, with the cultivar Reeder being preferred and Conan being less preferred. We measured percent stem infestation and percent stem cutting for 91 RIL from a Reeder–Conan cross in four sawfly-infested locations in Montana. Heritability based on means over environments was h2 = 0.86 for infestation and h2 = 0.75 for cutting. Percent infestation was negatively correlated with heading date (r = –0.57, P < 0.001) and degree of stem solidness (r = –0.31, P < 0.01). A molecular map was created with 431 markers. Quantitative trait loci (QTL) for infestation and cutting were identified as cosegregating with QTL for heading date (controlled by Ppd-D1 on chromosome 2D) and stem solidness (controlled by Qss.msub.3BL). Additionally, significant QTL for infestation and cutting on chromosomes 2D and 4A were present in several environments, and did not cosegregate with heading date, plant height, or solid stems. These QTL may complement the use of solid stems for host plant resistance by developing wheat lines that vary for attractiveness to the wheat stem sawfly.