FEEDING DAMAGE OF RUSSIAN WHEAT APHID ON RESISTANT AND SUSCEPTIBLE WHEAT GENOTYPES

Effects of Russian wheat aphid (Diuraphis noxia Mordvilko) feeding on resistant wheat (Triticum aestivum L.) plant introduction line, PI 137 739 (antibiotic line), and a susceptible cultivar, Stephens, were exam ined. Reduction in leaf chlorophyll content was determined after diffe rent densities (0, 40 and 80) of aphids were allowed to feed for 3, 6, 9, and 11 days in leaf cages attached to seedlings. In the non-caged region of infested plants, leaf chlorophyll content was significantly higher in PI 137739 compared with Stephens. Reduction in chlorophyll c ontent was not aphid-density or duration of aphid-feeding dependent in the non-caged regions. In the caged region, increased physical damage to leaves and significant reduction in total chlorophyll content were observed in PI 137739 compared with Stephens. Increased aphid density and prolonged aphid-feeding caused greater reduction in leaf chloroph yll content in caged sections. Increased probing of aphids because of restricted movement in the caged section and tissue unpalatibility of the resistant genotype could have caused severe chlorophyll reduction in the resistant plant introduction line, PI 137739.