LEVEL AND NATURE OF THE RESISTANCE TO THE CEREAL APHID, SITOBION-AVENAE (F), IN 13 WINTER-WHEAT CULTIVARS

Thirteen winter wheat cultivars were tested under field and greenhouse conditions for resistance to the cereal aphid, Sitobion avenae (F.). Marked differences were recorded between cultivars in nonpreference (a ntixenosis), antibiosis and tolerance to aphids. Nonpreference was sig nificantly (P < 0.001) correlated with antibiosis measured in terms of the biomass of aphids on naturally and nonsignificantly (P > 0.1) on artificially infested ears (criterion for cultivar antibiosis). Over a ll the cultivars, there was no correlation between nonpreference and t olerance and between antibiosis and tolerance to aphids. Five cultivar s expressed high level of resistance to S. avenae. The high resistance of three cultivars was due to high nonpreference and antibiosis, and only in two cultivars all three mechanisms contributed to resistance.