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Résumé :
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The Russian wheat aphid, Diuraphis noxia (Mordvilko), is an introduced pest that is an economic threat to wheat, Triticum aestivum L., and barley, Hordeum vulgare L., production. Crested wheatgrass, Agropyron cristatum (L.) Gaertner, is an important alternative summer host that provides a food source for Russian wheat aphid populations between spring harvest and fall planting of cereal crops. Greenhouse experiments were conducted to identify accessions of crested wheatgrass plant introductions (PI) resistant to Russian wheat aphids. Four accessions, PI 281862, 297869, 325180, and 439912, were highly resistant to leaf chlorosis and leaf rolling caused by aphid feeding. Further tests were done to characterize the plant components (antibiosis, antixenosis [nonpreference], and tolerance) contributing to resistance of these PI. Resistant PI had high levels of antibiosis, demonstrated by Russian wheat aphid's reduced rates of fecundity when compared with fecundity on susceptible genotypes. When infested with Russian wheat aphids, the resistant PI had reduced dry mass foliage loss compared with susceptible PI, but the losses were not significantly different among entries indicating no measurable tolerance. We detected strong antixenosis (nonpreference) resistance components in the resistant PI when D. noxia were given a choice of several genotypes. PI 281862, 297869, 325180, and 439912 may be new sources of resistance for germplasm enhancement efforts.
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