Watermelon mosaic virus reported for the first time in Poland

Watermelon mosaic virus (WMV) is a member of the genus Potyvirus (family Potyviridae) and consists of flexuous, filamentous particles, approximately 750 nm long. The virus can cause economically important diseases in several horticultural crops, mostly cucurbits and legumes, resulting in quality and yield losses. WMV can experimentally infect more than 170 plant species belonging to 27 families, including many weeds that can host the virus between crops. The geographical occurrence of the virus is patchy and depends on climatic conditions. So far in Europe it has been only detected in southern countries, i.e. Croatia, France, Italy and Slovakia (Desbiez et al., 2007). In 2008, fifteen samples of zucchini plants with mosaic symptoms on the leaves were collected from three fields in Poland. All samples were analyzed by DAS-ELISA with commercial antisera for the detection of WMV, Zucchini yellow mosaic virus (ZYMV) and Papaya ringspot virus (PRSV) (DSMZ, Braunschweig, Germany). WMV was found in every sample tested. There were no positive reactions using antisera to ZYMV and PRSV. WMV in samples testing positive by ELISA was confirmed by RT-PCR. Total RNA was extracted by a phenol-chloroform method from fresh, infected zucchini leaves. RNA samples were tested for the presence of WMV using specific primers designed to amplify a fragment of the coat protein gene (Sharifi et al., 2008). PCR products were cloned into the pGEM-T Easy Vector (Promega) and sequenced. Sequences were compared to data available in GenBank. An 822-nt amplicon was obtained (GenBank Accession No. FJ628395). This had 98% nt sequence identity with WMV sequences from China and Korea (EF127832 and AB369278, respectively) and only 93% nucleotide sequence identity with WMV sequences from France and Pakistan (AY437609 and AB127934, respectively) (Desbiez & Lecoq, 2008). This is the first report of the natural occurrence of WMV in Poland.