DC-EPG assisted comparison of European spittlebugs and sharpshooters feeding behaviour on grapevine |
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Authors: | Anna Markheiser Giacomo Santoiemma Alberto Fereres Sanela Kugler Michael Maixner Daniele Cornara |
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Affiliation: | 1. Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plant, Institute for Plant Protection in Fruit Crops and Viticulture, Siebeldingen, Germany;2. Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padova, Padova, Italy;3. Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Cientificas (ICA-CSIC), Madrid, Spain;4. Department of Soil, Plant and Food Science, University of Bari, Bari, Italy |
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Abstract: | Xylem-feeding is apparently the only requirement making an insect a competent vector of the bacterium Xylella fastidiosa, an organism responsible for the devastation of the Southern Italian olive forest and nowadays considered one of the most feared threats to agriculture and landscape in Europe, including vineyards. Here, we used the direct current-electrical penetration graph (DC-EPG) technique to compare and describe the feeding behaviour on grapevine of four xylem-feeding species considered candidate vectors of X. fastidiosa widespread in Europe, namely two spittlebugs (the meadow spittlebug Philaenus spumarius and the spittlebug Neophilaenus campestris) and two sharpshooter leafhoppers (the rhododendron leafhopper Graphocephala fennahi and the green leafhopper Cicadella viridis). We created a standard for the analysis of EPG waveforms recorded with a DC-EPG device, describing feeding activities performed by these insects from stylet insertion into the plant to withdrawal. This standard, along with freely available software, has been developed to harmonize the calculation of feeding behavioural parameters in xylem-feeders. The most relevant differences between the two vector taxa were the probing frequency and the dynamics of xylem ingestion. Sharpshooters tended to perform significantly more probes than spittlebugs. In contrast, the latter spent longer times in low-frequency xylem ingestion, characterized by scattered contractions of the cibarial dilator muscle interspersed with periods of pump inactivity. Cicadella viridis was the species displaying the highest frequency of the electrical pattern found to be associated with X. fastidiosa inoculation in spittlebugs (Xe). Feeding behavioural data presented here represent an important step forward for deepening our knowledge of xylem-sap feeding insects' interaction with both the host plants and the bacterium they transmit. |
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Keywords: | feeding behaviour host-plant selection Pierce's disease plant preference stylet penetration xylem-sap feeders |
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