CORESTA Meeting, Agronomy/Phytopathology, Suzhou, 1999, AP07 (adjourned)

Incidence of viruses in tobacco crops in Greece

Aristotle University of Thessaloniki, Greece
An extensive two years (1997-98) survey was carried out in tobacco seedbeds and crops of the most important tobacco growing areas of Greece. From seedbeds 1821 plants were collected during 1998 and more than 6.000 samples from field plants showing virus-like symptoms (stunting, mosaic, leaf distortion and necrotic patterns) during 1997 and 1998. Samples were tested for virus presence either by ELISA, electron microscopy (EM) and/or mechanical inoculation onto indicator plants. In seedbeds, average infection ranged from 0% to 80% for cucumber mosaic cucumovirus (CMV), from 0% to 55.5% for potato virus Y potyvirus (PVY) and from 0 % to 42,2% for tomato spotted wilt tospovirus (TSWV). Alfalfa mosaic alfamovirus (AMV) infections were detected in five out of the 45 seedbeds where infection rates ranged from 2% to 12%. In field surveys, the aphid-borne viruses CMV and PVY appeared the most widespread as they were detected in all sampling areas and in all tobacco types and varieties. CMV infections ranged from 0% to 100% whereas those of PVY from 0% to 80% but in individual fields was occasionally detected even in 100% of infected plants. TSWV identified in most areas in Northern Greece with incidence ranging from 2-100%. AMV infections were not found in Drama, Karditsa, Komotini whereas in the other areas usually lower infection percentages (0,8-51%) compared to the other aphid transmitted viruses were detected. TRV and its nematode vectors were only detected in a small number of tobacco fields. TMV was detected in high percentages, up to 100%, especially in oriental varieties in all areas. EMDV incidence was in all cases very low (<0,001%). A new semi-persistently transmitted aphid-borne closterovirus isolated from the oriental type variety Basma in Macedonia (Drama) was also partially characterized.