RESISTANCE TO SITODIPLOSIS MOSELLANA (DIPTERA: CECIDOMYIIDAE) IN SPRING WHEAT (GRAMINEAE)

Abstract

AbstractCultivars of winter wheat, Triticum aestivum L., previously identified as possible sources of resistance to wheat midge, Sitodiplosis mosellana (Géhin), were crossed with spring wheat to produce lines with a spring growth habit and assure synchrony between insect and plant. Many of the lines showed low levels of infestation by wheat midge in the field, and 21 of these were tested for resistance in the laboratory. All test lines exhibited resistance, ranging from 58 to 100% suppression of larvae and 70 to 100% suppression of seed damage, compared with a susceptible line. Larval development was delayed and survival was reduced on all lines. This antibiosis was associated with a hypersensitive reaction in the seed surface. The hypersensitive reaction, or feeding damage by young larvae before they died, reduced the biomass of some infested resistant seeds by 28% compared with over 60% for infested susceptible seeds. Some lines also reduced the level of infestation either through oviposition deterrence or a resistance which prevented newly hatched larvae from establishing on the seed surface. A few lines also reduced the hatching rate of wheat midge eggs. The resistance was equally effective in field trials during two consecutive summers in Manitoba and Saskatchewan, with at least a 20-times difference in the level of infestation between susceptible and resistant wheats. No larvae could develop to maturity on some resistant lines. Large plots of one resistant line produced less than 1% as many larvae as a typical susceptible wheat, and the larvae that did survive produced few, small adults. This resistance is the first documented case of a high level of true resistance to wheat midge in spring wheat, distinct from asynchrony between the insect and susceptible stage of the plant. The antibiosis component of the resistance is currently being incorporated in cultivars suitable for production in western Canada.