December 3, 2004
Source: American Phytopathological Society, Plant Disease Notes [edited]

First report of cucumber leaf spot virus in Poland
H. Pospieszny and M. Cajza, Institute of Plant Protection, Department of Virology and Bacteriology, Miczurina 20, 60-318 Poznan, Poland; and R. Plewa, Adam Mickiewicz University in Poznan, Department of Experimental  Biology, Animal Physiology, Fredry 10, 61-701 Poznan, Poland. Plant Dis. 88:1381, 2004; published on-line as D-2004-0928-01N, 2004. Accepted for publication 25 Aug 2004.

During April 2003, 4 young cucumber plants with slight stunting and delay of flowering were found in 2 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 percent nucleotide and 98 percent amino acid sequence identity with the Spanish CLSV isolate (GenBank Accession No. AY038365) (4) and 98 and 99 percent identity, respectively, with another CLSV isolate (3). The nucleic acid sequence of the Polish CLSV isolate was 81-84 percent identical to the equivalent region of 2 isolates of Pothos latent virus, another aureusvirus (GenBank Accession No AJ243370 and X87115) and had 86 percent identity with the amino acid sequence of both isolates.

To our knowledge, this is the 1st 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 1st 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.

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[Aureusvirus is a new genus of plant viruses typified by Pothos latent virus (PoLV) and comprising cucumber leaf spot virus (CLSV), previously classified as definitive species in the genus Carmovirus. Aureusviruses are soil-borne viruses readily transmitted by sap inoculation to a moderate range of hosts. Natural transmission of CLSV is by the chytrid fungus _Olpidium bornovanus_ [Ob], (previously _O. radicale_), whereas PoLV infects the host without the apparent intervention of a vector. A bulk culture of _Olpidium radicale_ (now classified as Ob) from melon roots collected at Montfavet, France did not transmit CLSV or the cucumber fruit streak strain of CLSV (CLSV-FS). CLSV is sap-transmitted, and is seed-borne (c.1 percent) and soil-borne. Found naturally only in cucumber. Reported from Germany, Greece, Great Britain and Jordan (Weber et al., 1982, 1986; Gallitelli et al., 1983) and Spain. CLSV is most likely related to Melon necrotic spot carmovirus (MNSV), red clover necrotic mosaic dianthovirus (RSNMV) and cucumber necrosis tombusvirus (CNV). CLSV is an Aureusvirus in the family _Tombusviridae_ and is most closely related to Pothos latent virus. The scientific name for pothos is  _Epipremnum aureum_; its common name is devil's ivy.

Links:
Brunt, A.A., Crabtree, K., Dallwitz, M.J., Gibbs, A.J., Watson, L. and
Zurcher, E.J. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions
and Lists from the VIDE Database. Version: 20th August 1996. <http://biology.anu.edu.au/Groups/MES/vide/> 

<http://www3.res.bbsrc.ac.uk/webdpv/web/adpv.asp?dpvnum=319>
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- Mod.DH]