During April 2003, four young cucumber plants with slight stunting and delay of flowering were found in two commercial greenhouses in the Wielkopolska Region in Poland. Sporadically, chlorotic spots, sometimes with necrotic centers, were observed on the leaves of plants. Later, symptoms were less recognizable or they disappeared completely. Crude sap from symptomatic leaves of Cucumis sativus was used for mechanical inoculation of various plant species. The virus caused local and systemic infections on Cucumis sativus, Nicotiana benthamiana, and N. clevelandii and induced local necrotic lesions only on Chenopodium quinoa, C. amaranticolor, C. ficifolium, C. murale, Petunia hybrida, Cucurbita melo, Zinnia elegans, and Spinacia oleracea. No symptoms were seen in inoculated N. tabacum, N. glutinosa, Lycopersicon esculentum, Capsicum annuum, Physalis floridana, Phaseolus vulgaris, and Cucurbita pepo. Symptoms and host range were similar to those described for infection by Cucumber leaf spot virus (CLSV) (1). Electron microscopic examination of negatively stained leaf-dip preparation from infected plants showed spherical virus particles (approximately 30 nm). Total RNA extracted from symptomatic C.sativus and N. benthamiana plants, and RNA extracted from purified virus preparations were tested using reverse transcription-polymerase chain reaction (RT-PCR) with specific primers designed to amplify a fragment of the RNA-dependent RNA polymerase gene (4). RT-PCR products were sequenced with CEQ DTCS dye terminator cycle sequencing kit and the CEQ 2000 DNA Analysis System (Beckman Coulter, Inc., Fullerton, CA). The 664-nt amplicon sequence (GenBank Accession No. AY571334) had 95% nucleotide and 98% amino acid sequence identity with the Spanish CLSV isolate (GenBank Accession No. AY038365) (4) and 98 and 99% identity, respectively, with another CLSV isolate (3). The nucleic acid sequence of the Polish CLSV isolate was 81 to 84% identical to the equivalent region of two isolates of Pothos latent virus, another aureusvirus (GenBank Accession No AJ243370 and X87115) and had 86% identity with the amino acid sequence of both isolates. To our knowledge, this is the first report of CLSV in Poland. The virus was previously reported in Germany, Great Britain, Jordan, Greece, Saudi Arabia, Spain, and Bulgaria (1,2,4). CLSV is a member of the genus Aureusvirus, formerly Carmovirus (family Tombusviridae). In the first half of 2004, no cucumber plants testing positive for CLSV were found. This incidental occurrence of CLSV indicates that the virus is not a significant threat to cucumber in Poland at this time.
References: (1) A. Brunt et al. Cucumber leaf spot virus. Viruses of Plants.Descriptions and Lists from the VIDE Database. CAB International, 1996. (2) D.Kostova et al. J. Plant Pathol. 83:147, 2001. (3) J. S. Miller et al. Virus Res. 52:51, 1997. (4) E. Segundo et al. Plant Dis. 85:1123, 2001.