CATEGORIES OF RESISTANCE IN PLANT INTRODUCTIONS OF WHEAT RESISTANT TO THE RUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE)

Wheat cultivars previously identified as resistant to the Russian wheat aphid, Diuraphis noxia (Mordvilko), in South Africa and in Idaho were evaluated in the greenhouse to determine the categories of resistance in operation. All test entries tested possessed a significant level of tolerance to D. noxia feeding, based on percentage reductions in plant height. Twenty-one days after infestation, D. noxia maintained on the three plant introductions from South Africa displayed reduced reproductive rates indicative of low-level antibiosis. However, none of the test entries reduced overall fecundity during the total (84-d) reproductive period of the experiment. None of the test entries displayed antixenosis.