Development and practice of a glasshouse screening technique for resistance of wheat to the aphid Sitobion avenae

Differences in resistance to S. avenae were confirmed amongst eight spring wheat stocks in glasshouse tests. Taking these stocks as standards, a glasshouse screening technique was developed in which 15 plants of each entry were arranged randomly in one block and aphids were scattered over the whole at the stem-extension phase. When the infestation of individual plants was scored about 2 wk later, resistant and susceptible stocks were well differentiated. Provided that scoring was completed before or at ear emergence, separation of resistant entries was more efficient with older plants. Ranking of the standard stocks was little influenced by other variations of technique or environment. Twenty-six out of 91 previously untested spring wheat breeding lines appeared to be moderately resistant to S. avenae, suggesting that progress in the selection of resistant cultivars will depend more on the further development of suitable techniques than on the availability of heritable resistance.