Does Xylella fastidiosa occur on grapevine in Kosovo (YU)?
Studies were carried out in USA on samples of diseased grapevines collected from Kosovo (YU). Electron microscopy, ELISA, PCR (using specific primers) revealed the presence of Xylella fastidiosa (EPPO A1 quarantine pest), the causal agent of grapevine Pierce's disease. This Kosovo isolate was inoculated to young healthy grapevines and typical symptoms were obtained. The same bacterium was then reisolated from these plants and was able to produce symptoms again on inoculated plants (thus fulfilling Koch's postulates). The Kosovo isolate was compared with US isolates of X. fastidiosa from grapevine and was found to be closely related to them.
EPPO note: If this were to be confirmed, it would be the first report of Pierce's disease in Europe and this would be a very serious threat for the European grapevine industry. But it must be stressed that in this paper many questions remain unanswered, and the authors were not able to provide further details to the EPPO Secretariat when consulted.
The suspect grapevine material (twigs with leaves attached, kept at 4°C) was collected from Cermjan (near Gjakova, a city in western Kosovo near Albania). Two isolations were made from this material, but it is not clear where and when this was done, and what was the total number of samples studied. We understand that the scientist who collected the material left Kosovo 7 years ago.
No data is given on the possible extent of the disease in this region of Kosovo. It is only reported that since the mid-80s symptoms were observed in Cermjan grapevines that did not resemble those caused by fungi which can be found in this region (e.g. Phomopsis viticola). The symptoms were described as follows: 'chlorotic spots and enlarged discoloration and necroses on leaf blades during the dry summer period. Burning or scald and scorch appeared later and spread rapidly in the inner areas. When high temperature was followed by rainfall, leaves shrivelled and died.' The authors have no idea on the possible means of introduction and spread (potential vectors).
EPPO remains doubtful about this report, in view of the ambiguities about when the material was collected, and when and where the isolations were made. We believe that research published in a country other than that where a pest is newly reported should meet high standards of 'good laboratory practice', especially if the report is of high phytosanitary significance. Further research, in Yugoslavia, is clearly needed.
Sources
Berisha, B.; Chen, Y.D.; Zhang, G.Y.; Xu, B.Y.; Chen, T.A. (1998) Isolation of Pierce's disease bacteria from grapevines in Europe.
European Journal of Plant Pathology, 104(5), 427-433.