Impact of Drought and Virus Infection on Plant Traits, Virus Transmission Rate, and Aphid Feeding Behavior

Climate change is projected to increase the intensity and frequency of drought in several regions, potentially impacting aphid-virus-plant relationships. Here, we investigated the combined effects of water regime and virus infection on plant traits, virus transmission, and aphid feeding behavior. Two factorial experiments were established that combined (i) four virus treatments-single infection with cucumber mosaic virus (CMV; non-persistent), single infection with cucurbit aphid-borne yellows virus (CABYV; persistent), double infection, and mock control-with (ii) five water regimes on melon cultivar Bazán (experiment 1) or two water regimes on melon cultivar Piel de Sapo (experiment 2). Virus and drought reduced plant dry weight, number of leaves, and leaf area. In experiment 1, drought reduced the symptom severity on CMV-infected plants. Severe drought did not affect the CMV inoculation rate, but transient, moderate water stress reduced the transmission rate of CABYV. In experiment 2, drought and virus infection altered the feeding behavior of Aphis gossypii. On well-watered but not on droughted plants, both CABYV and double infection with CABYV and CMV reduced passive phloem sap ingestion (E2 waveform), critical for transmission of persistent viruses, in comparison with mock-inoculated controls. On droughted plants, aphids produced shorter intracellular punctures (potential drop waveform), associated with transmission of non-persistent viruses. However, potential drop duration was not reduced for aphids that fed on droughted plants infected with CMV or with both CMV and CABYV. Despite the significant impact of drought on the plant phenotype, drought combined with virus infection had no impact on aphid feeding behavior related to virus transmission.