Contribution of awns and hairy glumes in spring wheat to resistance against wheat midge, Sitodiplosis mosellana

The wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), poses a threat to spring wheat in North America. Larvae feed on the developing kernels, causing decreased grain quality and yield loss. The resistance gene Sm1, a single, naturally occurring gene that results in larval mortality, is important for managing this pest. However, relying on a single resistance gene may result in the evolution of virulent pest biotypes. To identify possible alternative mechanisms of resistance, mechanical deterrence against wheat midge oviposition was evaluated using doubled haploid spring wheat lines (DH lines) with different combinations of awns and hairy glumes. Adult wheat midges were introduced to cages containing 12 preanthesis wheat spikes consisting of combinations of the presence or absence of awns with either hairy or smooth glumes, and oviposition on these phenotypes was recorded. In addition, kernel damage of five lines per phenotype was assessed under field conditions. The presence of awns on wheat spikes reduced oviposition in the laboratory choice cages, but not all wheat lines with awns reduced damage in the field. Hairy glumes did not reduce midge oviposition or grain damage. Independent of the awned and hairy-glumed phenotypes, egg numbers and damage varied among the DH lines. Four wheat lines exhibited wheat midge deterrence and are promising candidates as sources of novel resistance to combine with Sm1 to pyramid resistance.