FIRST REPORT OF CUCUMBER LEAF SPOT VIRUS IN BULGARIA

Cucumber leaf spot virus (CLSV), family Tombusviridae, genus Aureusvirus (Martelli et al., 1998) was detected in glasshouse cucumber plants in two areas of southern Bulgaria in 1999. Samples from 18 plants showing symptoms were collected, dried under vacuum in Bulgaria, brought to Torino and tested by ELISA for Cucumber mosaic virus (CMV) and for common cucurbit potyviruses. Three samples, positive for CMV, gave an unusual necrotic systemic disease when sap inoculated to Nicotiana benthamiana and N. clevelandii. In such plants, electron microscopy indicated the presence of CMV and tombusvirus-like particles. The CMV was inactivated by heating the infected sap for 10 min at 75 degree C. The surviving virus was increased in N. benthamiana and tested by agar gel diffusion with antisera to the cucumber fruit streak strain of CLSV (from D. Gallitelli, Bari), closely serologically related to type CLSV (Gallitelli et al., 1986; Weber, 1986), Cucumber necrosis virus, genus Tombusvirus (from S. Winter, Braunschweig), Cucumber soil-borne virus, genus Carmovirus (from R. Koenig, Braunschweig) and Tobacco necrosis virus, genus Necrovirus, from the Torino Institute collection. The virus reacted only with the serum to CLSV, up to a serum dilution 1:32. The reaction of indicator plants sap-inoculated with our isolate what is reported for CLSV (Gallitelli et al., 1983; Weber, 1986). Cucumber cv. `Marketer' was systemically infected by our isolate, without showing symptoms. CLSV had previously been reported in Germany, Greece, U.K. and Jordan. This is the first report CLSV in Bulgaria.