First report of Pepino mosaic virus in tomato in Italy

Pepino mosaic virus (PepMV) was originally found in pepino (Solanum muricatum) from Peru (Jones et al., 1980). It has been reported affecting tomato crops in France (Anon., 2000); Germany (Lesemann et al., 2000); Spain (Jordáet al., 2000); the Netherlands (van der Vlugt et al., 2000) and the UK (Wright & Mumford, 1999). It is now included on the European Plant Protection Organization (EPPO) Alert List. Unusual virus-like symptoms were noticed in southern Sardinia (Italy) in February and March 2000 on glasshouse tomato cultivars (Camone and Cronos) grafted onto tomato cv. Beaufort rootstocks, obtained from an Italian propagator before transplanting in late summer 2000. Some leaves showed chlorosis and scattered necrotic spots on their distal part; on others there were symptoms of chlorosis and mosaic. The symptoms were first noticeable in October, on only a few plants, but by March 2001 more than 40% of tomato plants were affected by the disease. On stems and young leaves a mild mosaic was sometimes present. On some immature fruits alteration of the colour was seen, and later uneven ripening was noticed. Electron microscopic observation of negatively stained preparations from tomato leaves or fruits revealed the presence of typical potexvirus-like particles. Using immunosorbent electron microscopy (IEM), these particles were decorated using an antiserum (DSMZ AS-0554; IgG at 1 mg mL−1) produced against a Peruvian PepMV isolated from pepino (Jones et al., 1980). A twofold dilution series performed using this antiserum revealed a three-step reduction in the detection limit against a sample of Italian PepMV from tomato (at only 1 : 32), when compared with the original Peruvian isolate (detection limit 1 : 256). van der Vlugt et al. (2000) also reported differences in the decoration titre in IEM when using an antiserum raised against a Peruvian pepino isolate of PepMV (Jones et al., 1980) against a tomato isolate from the Netherlands. However, despite these differences observed in IEM, PepMV from three different glasshouses was easily and reliably detected using this antiserum in DAS–ELISA, with sap dilutions down to 1 : 1000. Finally, on mechanical inoculation to tomato cv. Marmande, one isolate of the virus induced mosaic. This is the first report of PepMV in Italy. Although spread within the glasshouse can be easily explained by the extreme infectivity of the virus, the dissemination route of the virus within European countries remains unclear. The authors wish to acknowledge that their research, conducted at the Istituto di Fitovirologia Applicata, is supported by the National Research Council of Italy. Special Project ‘Diagnosi precoce di malattie nelle piante di interesse agrario e forestale’, paper No. 9.