Resistance against greenbug, Schizaphis graminum Rond., and Russian wheat aphid, Diuraphis noxia Mordvilko, in tritordeum amphiploids

A collection of tritordeum amphiploids (Hordeum chilense x Triticum turgidu m) and their wheat parents were screened for resistance against the two mai n aphid pests of cereals, the greenbug Schizaphis graminum Rond, and the Ru ssian wheat aphid (RWA) Diuraphis noxia Mordvilko. Antixenosis, antibiosis and tolerance were evaluated in controlled environmental conditions using a clone of greenbug biotype C and a clone of RWA collected on pasta wheat. T ritordeum amphiploids possess genetic resistance against greenbug and RWA; some of the lines tested were more resistant than the parental wheat line. Four principal components explained the resistance against both aphid speci es. The antixenosis shown against both pests was mainly contributed by thei r wheat parents. The antibiosis against both aphid species was obviously de pendent on different plant traits. The highest levels of antibiosis against the two aphids occurred in different amphiploids. Different genes are invo lved in the antibiotic reaction against the two aphids. The Tritordeum resi stance to RWA is based on antixenosis and antibiosis since the tolerance tr aits were not independent of the other types of resistance. The level of to lerance shown to the greenbug was variable and appears to be controlled by different mechanisms. The tolerance to aphids shown by H. chilense is expre ssed in the amphiploids, but with some genomic interaction. Genes conferrin g resistance to aphids in H. chilense could be incorporated into new cultiv ars of wheat to broaden their genetic base of resistance against greenbug a nd RWA.