GENES FOR RESISTANCE TO RUSSIAN WHEAT APHID IN PI294994 WHEAT

Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a major eco nomic pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in several western U.S. states. Genetic resistance is an effectiv e strategy for protecting the wheat crop from RWA while minimizing the use of pesticides. The study was conducted to determine the number of genes conferring resistance in the seedling and adult growth stages i n the wheat line PI294994 and to establish whether greenhouse and fiel d resistances were related. The resistant line PI294994 was crossed wi th the club wheat cultivars Moro and Hyak. F2 and F3 seedlings and F, adult plants from the two crosses were artificially infested with RWA and evaluated for their reactions in the greenhouse and field, respect ively. Seedling and adult plant reactions indicated that the resistanc e in the line PI294994 is controlled by two genes. Resistance is confe rred by a dominant allele at one locus and by a homozygous recessive a llele at the second locus. PI294994 is an effective source of genetic resistance in the field to RWA in the Pacific Northwest.