First Report of Moroccan Watermelon Mosaic Potyvirus in Zucchini in Italy

Unusual symptoms were observed in summer 1997 in field zucchini of several cultivars grown in central Italy. Symptoms included reduction in growth, severe mosaic, blistering and deformation of leaves, and malformation on fruits. Plants gave negative results in enzyme-linked immunosorbent assay (ELISA) for cucumber mosaic cucumovirus, squash mosaic comovirus, papaya ringspot, zucchini yellow fleck, zucchini yellow mosaic, and watermelon mosaic 2 potyviruses. Positive reactions were obtained in ELISA with a monoclonal antibody that reacts with many potyviruses (from J. Vetten, Braunschweig) and with polyclonal antibodies (Sanofi, France) to Moroccan watermelon mosaic potyvirus (MWMV). Field symptoms were reproduced in zucchini cvs. Genovese and Striato d'Italia by mechanical inoculation of samples from symptomatic field plants. Chenopodium amaranticolor, C. quinoa, and Gomphrena globosa gave local lesions, while Citrullus lanatus cv. Crimson Sweet, Cucumis melo cv. Top Mark, C. metuliferus, C. sativus cvs. Marketer, MM76, and Sweet Slice, and Cucurbita maxima reacted with systemic mosaic. C. melo cv. Doublon formed necrotic local lesions followed by systemic necrosis. No infection occurred in Nicotiana benthamiana, N. clevelandii, N. glutinosa, Phaseolus vulgaris cv. Black Turtle, Pisum sativum cv. Alaska, tobacco White Burley, and Vigna unguiculata. These data are in agreement with the known host range of MWMV. MWMV is a tentative species in the genus potyvirus, widely present in Africa and occasionally found in Spain (1,2). Further spread of this virus in the Mediterranean area will create new problems for commercial cucurbit production and breeding, and for diagnosis. References: (1) E. Kabelka and R. Grumet. Euphytica 95:237, 1997. (2) N. M. McKern et al. Arch. Virol. 131:467, 1993.