Differential Reactions of Russian Wheat Aphid to Various Small-Grain Host Plants
There are no standardized procedures for evaluation of host-plant resistance of small grains to Russian wheat aphid (RWA), (Mordvilko), Diuraphis noxia. Research results, therefore, often are ambiguous. One possible source of ambiguity is the host genotype on which aphids are reared prior to being used on test plants. In this study, two collections of RWA were cultured separately on TX78V2290-36-1 wheat (Triticum aestivum L. em Thell), TXGHI0989 wheat, ‘Nora’ oat (Avena sativa L.) and ‘Eronga’ triticale (✕ Triticosecale Wittmack). After a 30-d period on the culture plants, the aphids were removed and placed on tester plants to determine whether the host-plant genotype used for colony maintenance affected aphid performance on testers. The tester plants were the same as those used for colony maintenance. Aphids were placed on testers from source plants in all possible combinations and aphid response to tester genotypes was determined by counting the number of embryos produced per aphid. Results showed that the source genotype had a significant effect on subsequent performance of aphids. The TX78V2290-36-1 wheat provided the best overall rearing environment of the genotypes tested. Aphids originally maintained on TX78V2290-36-1 successfully discriminated wheat from oat and oat from triticale, as well as distinguishing the different levels of resistance of the two wheat genotypes.
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