Oviposition deterrence in spring wheat, Triticum aestivum, against orange wheat blossom midge, Sitodiplosis mosellana: implications for inheritance of deterrence

Some spring wheat lines are known to be antixenotic to ovipositing orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae). The genetic basis of antixenosis, expressed in the plant as oviposition deterrence to S. mosellana , was explored using a population of 92 doubled-haploid wheat lines from a cross between a susceptible parent and a deterrent parent which also had antibiosis resistance. Wheat midge egg densities on wheat spikes were obtained from a standardized laboratory cage test and from the field in 2006 and 2007. Compared to the susceptible parent, egg densities on 55–88% of the lines were reduced by more than half in the laboratory and both years in the field. Twenty-five of the 92 lines were consistently at least as deterrent as the deterrent parent in all three environments. Frequency distribution of egg densities compared to the parents indicated that deterrence was conferred by more than one gene, with complementary interaction among genes. Heritability of deterrence was estimated at 67%, showing that environment had a substantial effect on the phenotypic expression of the trait. Consistently deterrent lines had a larger proportion of eggs laid on the rachis compared to the other lines in all environments, suggesting that the presence of deterrence affects where on the spikelet the females lay their eggs. There was no evidence for linkage between deterrence genes and the antibiosis gene, Sm1 . Oviposition deterrence is a promising means for suppressing wheat midge oviposition in commercial wheat crops; however, the multigenic nature of oviposition deterrence in wheat to S. mosellana and the influence of environment on its expression will provide challenges for incorporating this trait into wheat breeding programs.