First Report of Moroccan watermelon mosaic virus in Zucchini Crops in Greece

Abstract

In the summer of 2012, zucchini (Cucurbita pepo L.) plants of F1 hybrid Rigas showing very severe malformation and blisters in leaves and fruit were observed in the prefectures of Ilia and Messinia, Peloponnese, southwestern Greece. Over 100 samples were collected and only a few were found by double antibody sandwich (DAS)-ELISA to be singly or mixed infected with the commonly encountered Cucumber mosaic virus (CMV, genus Cucumovirus), Zucchini yellow mosaic virus (ZYMV, genus Potyvirus), and Watermelon mosaic virus (WMV, genus Potyvirus), to which Rigas is known to be tolerant. All affected plants were also tested by DAS-ELISA and RT-PCR (2) for the presence of Moroccan watermelon mosaic virus (MWMV; genus Potyvirus), a virus not previously reported in Greece, and were consistently found positive by both methods. Sap from plants in which MWMV was solely detected was used to mechanically inoculate Chenopodium quinoa Willd. and cucurbit species (zucchini, cucumber, melon, and watermelon). C. quinoa produced chlorotic local lesions, while cucurbits showed very severe mosaic and malformation of leaves. Zucchini plants of F1 hybrids Rigas, Golden (tolerant to WMV and ZYMV), and Elion (not exhibiting any tolerance) grown in a screenhouse produced equivalent severe symptoms on leaves and fruits. Furthermore, transmission experiments in a non-persistent manner using a clone of Myzus persicae Sulz. and zucchini plants of F1 hybrid Boreas as donor and test plants were carried out. Ten plants were used in each experiment (one aphid/plant) and this was repeated five times (50 plants in total). The transmission rate was high ranging from 75 to 90%. RT-PCR obtained amplicons of 627 bp were subjected to direct sequencing (GenBank Accession No KF772944), which revealed 99% sequence identity to the corresponding region of a MWMV Tunisian isolate (EF579955). In 2013, in addition to zucchini plants found MWMV positive, watermelon (Citrullus lanatus Thunb.) plants from the same region of Peloponnese showing leaf malformation and mosaic symptoms were found MWMV positive (4/30) by DAS-ELISA and RT-PCR, revealing the virus establishment and further spread. In the Mediterranean basin, the virus has already been reported in Morocco, Italy, France, Spain, Tunisia, and Algeria, where it has emerged recently from a common source, has quickly become established through rapid dissemination and is considered as an important emerging threat (4). Isolates from these countries, including the present one from Greece, are very closely molecularly related to each other, contrary to isolates from sub-Saharan Africa (South Africa, Sudan, Congo, Zimbabwe, Niger, Cameroon, Nigeria) that are much more divergent (1,3). To our knowledge, this is the first report of MWMV in Greece. References: (1) H. Lecoq et al. Plant Dis. 85:547, 2001. (2) H. Lecoq et al. New Dis. Rep. 16:19, 2007. (3) A. T. Owolabi et al. Int. J. Virol. 8:258, 2012. (4) S. Yakoubi et al. Arch. Virol. 153:775, 2008.