AN OVERVIEW - RESISTANCE TO THE RUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE) WITHIN THE PERENNIAL TRITICEAE

Introgression of valua le gene(s) for insect resistance has been achie ved bv interspecific hybridization between the perennial Triticeae spe cies and the cultivated cereals. We relate Russian wheat aphid, Diurap his noxia (Mordvilko), resistance to the newly defined and realigned g enera of the perennial Triticeae based on genomic composition. Possibl e sources of Russian wheat aphid resistance in the perennial Triticeae are reported for the first time. We could not correlate the degree of Russian wheat aphid resistance with the genomic system of classificat ion. However, genera within the tribe Triticeae can be loosely grouped into three categories: (1) moderately resistant: Leymus and Elytrigia ; (2) tolerant to moderately suseeptible: Agropyron, Pseudoroegneria, Elymus, and Pascopyrum; and (3) susceptible: Hordeum and Thinopyrum. W ithin the tribe Triticeae, the genera Leymus and Elytrigia are the bes t sources of resistance. However, within each species, extensive varia tion for resistant types occurs.