A Polish Isolate of Zucchini yellow mosaic virus from Zucchini is Distinct from Other European Isolates

Zucchini yellow mosaic virus (ZYMV) is a member of the Potyvirus genus in the Potyviridae family, the largest group of plant viruses. Different isolates of this virus have been found in infected cucurbits throughout the world, including localities in Europe, America, Australia, and Asia. In August 2005, mosaic and yellowing of leaves, as well as yellow spots on green fruits, were observed on zucchini (Cucurbita pepo cv. giromontiina) growing in commercial fields in the Kujawsko-Pomorskie Region of Poland. Flexuous virus particles (~750 nm long), typical of potyviruses, were observed in leaf-dip preparations from symptomatic zucchini plants. The virus in the sap from symptomatic plants was mechanically transmitted and systemic infections were produced on Citrullus lanatus, Cucumis melo, Cucumis sativus, C. pepo cvs. giromontiina and patissoniana, C. maxima, and Nicotiana benthamiana. Severe symptoms such as severe malformation of leaves and stunting of plants were observed on zucchini plants (cv. giromontiina) infected mechanically with the virus and grown in the greenhouse. Double-antibody sandwich (DAS)-ELISA using an anti-ZYMV polyclonal antiserum (AS-0234; DSMZ, Braunschweig, Germany) identified the presence of ZYMV in mechanically infected C. pepo cv. giromontiina and N. benthamiana plants. Subsequently, a reverse transcription (RT)-PCR using a universal primer, Sprimer, designed from the consensus sequences that code for the conserved sequence GNNSGQP in the NIb region of Potyviridae family members and the M4 primer was performed (1). The 1740-bp PCR fragments were cloned into the pGEM-T vector (Promega, Madison, WI) and three randomly selected clones were sequenced on an ABI automatic sequencer. An 837-bp sequence representing the full length coat protein gene (GenBank Accession No. EF178505) was compared with homologous sequences from other ZYMV isolates using BioEdit and Mega 3.1 softwares. Genetic distances were calculated by Kimura's two-parameter method (2). Surprisingly, the Polish ZYMV isolate (ZYMV-Zug) was more closely related to ZYMV isolates from Asia than those from Europe. Pairwise comparisons of ZYMV-Zug with several other European ZYMV isolates (GenBank Accession Nos. DQ645729, AJ420020, AJ459956, AJ420014, AJ420019, DQ124239, and AJ420018) indicated an 81 to 82% nucleotide and 91 to 92% amino acid identity, while there was a 94% nucleotide and 99% amino acid identity with the Shanxi (GenBank Accession No. AY074808) and Shandong isolates (GenBank Accession No. AF513552) from China. References: (1) J. Chen et al. Arch. Virol. 146:757, 2001. (2) S. Kumar et al. Brie. Bioinform. 5:150, 2004.