RUSSIAN WHEAT APHID REACTION AND AGRONOMIC AND QUALITY TRAITS OF A RESISTANT WHEAT

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has caused significant losses to wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in Canada, Mexico, and the USA during 1986 to 1990. Resistance is not available in adapted cultivars. We conducted this study to determine levels of resistance to the Russian wheat aphid in 19 wheat, 2 barley, 1 oat (Avena sativa L.), 1 triticale (X Triticosecale Wittmack), and 1 Triticum monococcum L. (einkorn wheat) genotype in greenhouse seedling screening tests. All adapted wheat cultivars and advanced breeding lines and barley cultivars were susceptible. The triticale (TX33000) and T. monococcum (PI 266844) genotypes were moderately resistant, while wheat introduction PI 372129 and 'Colorado 37' oat were resistant. Correlations (r) among 7-, 12-, and 17-d rating times for 7 and 24 genotypes in two experiments were highly significant (+ 0.83 to + 0.98). Seedling survival, after RWA removal and with or without 8 wk of vernalization and transplanting, was not correlated with RWA damage ratings. Although vernalization and transplanting reduced survival of most genotypes, survival of PI 372129 seedling was excellent in both tests. PI 372129 is the first wheat genotype showing significant resistance to the U.S RWA populations. PI 372129 ('Trucikum 57') is an introduction from the USSR and possesses several undesirable traits for a hard red winter wheat breeding program, including late maturity, tallness, weak straw, white grain, and soft milling endosperm.