Vitis sp. response to Xylella fastidiosa strain CoDiRO
Following a request from the European Commission, the EFSA Panel on Plant Health assessed a scientific report submitted by the Italian Authorities to the European Commission to support a request to delist Vitis sp. from Annex I ('specified plants') of the Commission Implementing Decision (EU) 2015/789 of 18 May 2015 to prevent the introduction into and the spread within the Union of Xylella fastidiosa (Wells et al.). The report comprised (i) surveys to detect X. fastidiosa in vineyards located in the epidemic zone of CoDiRO with high numbers of diseased olive trees; (ii) inoculation experiments to infect grapevine with a X. fastidiosa isolate 'De Donno' from CoDiRO diseased olives; and (iii) vector transmission experiments with X. fastidiosa infective Philaenus spumarius. The Panel acknowledges the difficulties in providing evidence about this hitherto unknown pathogen/vector/host interaction to support the hypothesis that a plant species cannot be infected with a pathogen. Although field surveys to detect X. fastidiosa in grapevine were negative, there was no supporting information on infective vector populations present in the vineyards. Hence absence of infection pressure cannot be excluded. Furthermore the failure to infect grapevine plants either by artificial inoculation or by vector transmission might be due to inoculation conditions not appropriate to induce infections in grapevine. The detection of X. fastidiosa DNA in inoculated grapevine plants even 12 months after inoculation, although localised at the inoculation points, cannot exclude that the DNA amplified by qPCR was from viable cells. The results presented are coherent and provide converging lines of evidence that grapevine (Vitis vinifera) is not a major susceptible host of X. fastidiosa strain CoDiRO. However, from the experimental evidence it is premature to exclude that systemic infections of V. vinifera and Vitis sp. occur and that infections at limited foci could serve as a source of inoculum.