Frequency and Molecular Characterization of Watermelon Mosaic Virus from Serbia

Watermelon mosaic virus (WMV) is widespread in cucurbit crops, most commonly occuring in temperate and Mediterranean regions. In Serbia WMV has been detected in single and mixed infections with Zucchini yellow mosaic virus and Cucumber mosaic virus in field-grown pumpkin and squash crops. Among pumpkin-affecting viruses WMV is the most frequent one, both by the number of localities and its incidence at each location. During the growing season of 2009, samples from 583 plants of Cucurbita pepo cvs. Olinka, Belgrade zucchini and Tosca (Zucchini group), as well as from C. maxima and C. moschata showing symptoms of virus infection were collected from 12 commercial fields at eight localities and analyzed by DAS-ELISA using polyclonal antisera specific to six most important cucurbit viruses. Interestingly, WMV was detected at fewer sites and had lower ncidence rate than in two previous years. In single infections, WMV was found in 11% of tested plants in three fields; in mixed infections with ZYMV, it was recorded in 9.9% of plants in five fields and with CMV in only 0.2% in one field. The partial coat protein gene and 3’ non-translated region from two representativeisolates of WMV originating from different localities and host plant species were amplified by RT-PCR, sequenced, and compared with the sequences available in GenBank database. The PCR-amplified fragment of predicted size of approximately 1017 bp was obtained. The sequences of isolates 137-08 (Acc. No. GQ259958) and 159-08 (GU144020) proved to be 94-99% identical at the nucleotide level with those from other parts of the world. The sequences of these two isolates differed from each other only at two nucleotide positions, without any amino acid substitution. Phylogenetic analysis of 57 isolates based on 750 bp sequences of the coat protein gene showed no correlation between isolates and their geographic origin, and italso indicated that these isolates fell into three molecular groups of strains. Serbian WMV isolates belong to group I, the most widespread group of isolates of this virus in the world