Effects of elevated ozone on transmission and symptom severity of a generalist plant virus

Background/Question/Methods Elevated concentrations of tropospheric ozone are an impact of increasing concern in the modern global climate, as detrimental effects of ozone on both plant and human health are well-established.   However, potential impacts of elevated ozone on plant disease and epidemiology are still being evaluated. In particular, more work is needed on the impacts of elevated ozone on the spread and severity of viral plant diseases. To study these impacts, we used Avena fatua and Barley Yellow Dwarf Virus (BYDV), a generalist grass virus obligately transmitted by aphids.  1-2 weeks after germination, Avena fatua plants were fumigated with 100 ppbv ozone for four hours a day. A control subset of plants were grown in the greenhouse and exposed to only ambient levels of ozone (approx 10-15 ppbv).  A week after fumigations had begun, half of the plants in each ozone treatment were infected with Barley Yellow Dwarf Virus (BYDV) through aphid feeding, and half were left uninfected. Fumigations were continued for a period of four weeks.
Results/Conclusions
Preliminary results indicate that ozone had no detectable effect on the percent of plants infected, perhaps because Avena is so easily infected.  The experimental conditions did not allow aphids to select plants, so it is still possible that differences in infection rates could appear under more natural conditions due to different aphid preferences for fumigated vs. non-fumigated plants.  A followup study is being conducted which will address aphid preference. As expected, BYDV strongly reduced biomass in the ambient ozone treatment.  In contrast, elevated ozone completely eliminated the effect of BYDV on biomass.  This could be mediated by a a reduction in virus concentration within the host. Work to evaluate the effects of elevated ozone on within-host virus concentrations is ongoing.