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

A collection of tritordeum amphiploids (Hordeum chilense × Triticum turgadum) and their wheat parents were screened for resistance against the two main aphid pesis of cereals, the greenhug. Schizaphis graminum Rond. and ihe Russian wheat aphid (RWA) Diuraphis naxia Mord-vilko. Antixenosis. antibiosis and tolerance were evaluated in controlled environmental conditions using a. clone of greenbug biotypc C and a clone of RWA collected on pasta wheat. Tritordeum amphiploids pos-sess 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 species. The antixenosis shown against both pests was mainly contributed by their wheat parents. The antibiosis againsl both aphid species was obviously dependent on diflerent plant traits. The highest levels of antibiosis against the two aphids occurred in different amphiploids. Different genes are involved in the antibiotic reaction against the two aphids. The Tritordeum resistance to RWA is based on anlixenosis and ant-biosis since the tolerance trails were not independent of the other types of resistance. The level of tolerance shown to the greenbug was variable and appears to be controlled by differeni mechanisms. The tolerance to aphids shown by H. chilense is expressed in the amphiploids. but with some genomic interaction. Genes conferring resistance to aphids in H. chilensee could be incorporated into new cultivars of wheat to broaden their genetic base of resistance against greenbug and RWA.