Relations of Gramine Contents and Aphid Populations on Barley Lines

Four species of aphids, Rhopalosiphum padi (L.), R.maidis(F.), Schizaphis graminum (ROND.)and Sitobion akeviae(SHINJI), are important barley pests. There is a large variance in susceptibilities of lines. Selected lines were compared for aphid susceptibility. Gramine contents were analyzed by liquid chromatography. Resistant lines had larger amounts of gramine, and always gave lower aphid indices. Susceptible lines had little amounts gramine, showed higher aphid indices, and indicated variability with time and sampling site. Decreases of gramine were followed by increases in aphid populations. Toxicant or deterrent action of gramine to aphids was also observed by adding gramine to an artificial rearing solution.