Resistance to tobacco etch virus in Capsicum annuum: inhibition of virus RNA accumulation

Resistance to tobacco etch potyvirus (TEV) in Capsicum annuum cv, Dempsey is conferred by the recessive gene et(a), When Dempsey pepper plants were inoculated with either of two TEV isolates, virus did not accumulate in inoculated or noninoculated leaves, In contrast, each TEV isolate replicated to high levels in C. annuum cv, Jupiter, a susceptible parent of Dempsey pepper, To determine the basis of the resistance, Dempsey and Jupiter pepper plants were inoculated with a TEV isolate (TEV-HAT) engineered to express the beta-glucuronidase gene (TEV-GUS), TEV-GUS moved cell-to-cell and systemically in infected Jupiter pepper plants. In contrast, there was no evidence of any single-cell infection foci induced by TEV-GUS in Dempsey pepper plants. Northern blot analysis of protoplasts inoculated with TEV-HAT RNA indicated that virus RNA did not accumulate in Dempsey pepper protoplasts, whereas TEV-HAT did replicate and accumulate in protoplasts from Jupiter pepper plants. Thus, the resistance to TEV conferred by the et(a) gene is due to interference with virus RNA accumulation.