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Occurrence of Ourmia melon virus in the Guilan Province of Northern Iran

A survey was conducted in 2005 and 2006 in the major cucurbit-growing areas in Guilan Province (northern Iran). Leaf samples were collected from plants of melon (Cucumis melo L.) (n = 119) and squash (Cucurbita sp.) (n = 150) showing various virus-like symptoms (mosaic, yellowing, chlorotic spot, and irregular ring spot) on leaves. All samples collected from 16 different regions were screened for the presence of 10 cucurbit viruses by double-antibody sandwich (DAS)-ELISA using polyclonal antibodies provided by H. Lecoq (INRA, Avignon, France) and V. Lisa (CNR, Torino, Italy). Virus-free cucurbits (melon, squash, and cucumber) grown in insect-proof cages were used as negative controls. Positive and negative controls were included in all tests. Ourmia melon virus (OuMV, genus Ourmiavirus) was the most prevalent virus in melon and was detected in 59% of the samples. OuMV was also detected in 20 of 150 (13%) squash samples. OuMV was detected in 4 of the 16 areas surveyed (Rasht, Somehsara, Masal, and Rood-Bar). The identification of OuMV was confirmed through differential host range reaction. Crude sap from symptomatic leaves was used to inoculate Chenopodium quinoa and Gomphrena globosa as local lesion hosts. Squash, melon, and cucumber were subsequently inoculated by using a single local lesion. Typical yellowing and chlorotic spot symptoms were observed after 40 to 45 days on melon and squash and leaf curling was observed on Nicotiana rustica. The OuMV presence in these symptomatic test plants was confirmed by DAS-ELISA and the tests were negative with Cucurbit aphid-borne yellows virus (CABYV) and Zucchini yellow mosaic virus (ZYMV) antisera. No symptoms were observed on Datura stramonium, Capsicum annum, Phaseolus vulgaris, Pisum sativum, Raphanus sativus, and Beta vulgaris, and OuMV was not detected by DAS-ELISA in these plants. Although showing no symptoms, OuMV-inoculated Vicia faba plants reacted positively in DAS-ELISA. The number of multiple infections of OuMV with other common cucurbit viruses was relatively high (46%), most frequently with ZYMV and CABYV. Since the first report of OuMV from melon in Azerbaijan-E-Gharbi Province, western Iran (1), there has been no report of OuMV occurrence in any other region of Iran or any other country in the world, and the sequence of OuMV remains to be determined. Our results show that OuMV is naturally spreading into other regions of Iran.

Reference: (1) V. Lisa et al. Ann. Appl. Biol. 112:291, 1988.