Exploring climate variability on vector-plant-pathogen interactions: Effects of elevated CO2 on Barley yellow dwarf virus titer and Rhopalosiphum padi (Hemiptera: Aphididae) vector reproduction on wheat and weed host plants

Current atmospheric CO₂ levels are continuing to rise and are predicted to double in the next 100 years. Understanding the impacts of increased CO₂ on insect vectors, plant pathogens, and vector-plant-pathogen interactions is critical for evaluating its impact on food production. Barley yellow dwarf virus (BYDV) is a pathogen commonly transmitted by cereal aphids, including Rhopalosiphum padi, and it negatively impacts the yield of economically important crops like wheat and barley. We examined the effects of ambient CO₂ (aCO₂) and elevated CO₂ (eCO₂) on BYDV+ R. padi reproduction, plant nutrition, and BYDV titer in three host plants: foxtail barley, green foxtail, and winter wheat. We found that in aCO₂, R. padi had significantly higher reproduction on foxtail barley (x̄=16.80) and winter wheat (x̄=19.25) than on green foxtail (x̄=5.75). Similarly, in eCO₂, R. padi had significantly higher reproduction on foxtail barley (x̄=22.59) and winter wheat (x̄=29.32) than on green foxtail (x̄=4.68). In addition, plants in eCO₂ (x̄=19.15) had significantly higher R. padi reproduction than those in aCO₂ (x̄=13.9). We also found that host plant total carbohydrates was a positive predictor of R. padi reproduction under both CO₂ conditions (P=0.02). While we have yet to analyze BYDV titer of the three hosts plants under aCO₂ and eCO₂, based on previous experiments, we expect plants in eCO₂ to have higher virus titer than those grown in aCO₂. This combination of higher vector populations and higher virus titer could lead to high rates of virus transmission to host plants, and negatively impact crop production.