AbstractIntroduction The aphid Rhopalosiphum padi L. is a vector of Barley yellow dwarf virus (BYDV) in wheat and other economically important cereal crops. Increased atmospheric CO_2 has been shown to alter plant growth and metabolism, enhancing BYDV disease in wheat. However, the biochemical influences on aphid metabolism are not known. Objectives This work aims to determine whether altered host-plant quality, influenced by virus infection and elevated CO_2, impacts aphid weight and metabolism.Methods Untargeted ~1H NMR metabolomics coupled with multivariate statistics were employed to profile the metabolism of R. padi reared on virus-infected and non-infected (sham-inoculated) wheat grown under ambient CO_2 (aCO_2,400 imol mol~-1) and future, predicted elevated CO)_2 (eCO)_2, 650 imol mol~-1) concentrations. Un-colonised wheat was also profiled to observe changes to host-plant quality (i.e., amino acids and sugars).Results The direct impacts of virus or eCO_2 were compared. Virus presence increased aphid weight under aCO_2 but decreased weight under eCO_2; whilst eCO_2 increased non-viruliferous (sham) aphid weight but decreased viruliferous aphid weight. Discriminatory metabolites due to eCO_2 were succinate and sucrose (in sham wheat), glucose, choline and betaine (in infected wheat), and threonine, lactate, alanine, GABA, glutamine, glutamate and asparagine (in aphids), irrespective of virus presence. Discriminatory metabolites due to virus presence were alanine, GABA, succinate and betaine (in wheat) and threonine and lactate (in aphids), irrespective of CO_2 treatment.Conclusion This study confirms that virus and eCO_2 alter host-plant quality, and these differences are reflected by aphid weight and metabolism.
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