Virus infection mediates the effects of elevated CO 2 on plants and vectors

Atmospheric carbon dioxide (CO 2 ) concentration has increased significantly and is projected to double by 2100. To increase current food production levels, understanding how pests and diseases respond to future climate driven by increasing CO 2 is imperative. We investigated the effects of elevated CO 2 (eCO 2 ) on the interactions among wheat (cv. Yitpi), Barley yellow dwarf virus and an important pest and virus vector, the bird cherry-oat aphid ( Rhopalosiphum padi ), by examining aphid life history, feeding behavior and plant physiology and biochemistry. Our results showed for the first time that virus infection can mediate effects of eCO 2 on plants and pathogen vectors. Changes in plant N concentration influenced aphid life history and behavior and N concentration was affected by virus infection under eCO 2 . We observed a reduction in aphid population size and increased feeding damage on noninfected plants under eCO 2 but no changes to population and feeding on virus-infected plants irrespective of CO 2 treatment. We expect potentially lower future aphid populations on noninfected plants but no change or increased aphid populations on virus-infected plants therefore subsequent virus spread. Our findings underscore the complexity of interactions between plants, insects and viruses under future climate with implications for plant disease epidemiology and crop production.