Quantification of components contributing to rate-reducing resistance in a plant virus pathosystem

Abstract

In fungal pathosystems, it has been shown that rate-reducing resistance can be separated into components to mechanistically explain why epidemics are fast or slow, as affected by host genotype. Components of resistance to plant viruses may be quantified in a similar fashion but with several subcomponents added to account for alternative weed hosts and/or infected volunteers that are of primary importance to initiate epidemics and for vectors which are essential for transmission. Epidemiological principles and operational definitions were developed and utilized to identify and quantify components contributing to rate-reducing resistance in the Capsicum annuum L./weed hosts/tobacco etch virus (TEV)/aphid pathosystem. Pepper genotypes which could be infected with TEV, but delayed symptom appearance and slowed the rate of virus antigen accumulation over time, were also found to have a rate-reducing affect on TEV epidemics in the field compared to fully susceptible genotypes. Rate-reducing genotypes were found to have lower receptivities, represent smaller lesions (epidemiologically), had longer latent periods, and produced fewer viruliferous aphids over time, compared to susceptible pepper genotypes. Insect vector(s) and weed hosts were found to be important subcomponents of the pathosystem and these have also been quantified and related to the development of TEV epidemics in time and space. Substantial yield benefits were realized when rate-reducing resistance was deployed to control TEV. The use of resistant cultivars to reduce the apparent infection rate should increase the effectiveness of disease control tactics that reduce initial inoculum.

Journal Paper No. J-14826 of the Iowa Agriculture and Home Economics Experiment station, Ames, Iowa.