A yellowing of buttercup squash (Cucurbita pepo L. var. oleifera Pietsch) leaves was observed on plants in southern Moravia, the main squash-growing area of the Czech Republic. Forty leaf samples were collected in September 2009 and examined for the presence of possible cucurbit viruses by double-antibody sandwich-ELISA. Thirty-three samples were infected with Zucchini yellow mosaic virus and five with Cucurbit aphid-borne yellows virus (CABYV). The positive samples of CABYV originated near the villages of Josefov and Prušánky (one per sample) and Rakvice (three samples), and the virus isolates were named Jos-5, Pr-15, Rak-1, Rak-4, and Rak-5, respectively. CABYV was immediately transmitted from leaves collected in the field to summer squash (Cucurbita pepo L. convar. giromontiina Grebenšcikov) plants by aphids in a persistent manner. Green peach aphids, Myzus persicae (Sulzer), were used to inoculate squash plants with acquisition and inoculation feeding times of 2 and 5 days, respectively. Twenty-one plants were inoculated with 20 aphids per plant. Transmission was successful in 25% of the plants as assessed by ELISA. Infected plants showed very mild yellowing 2 weeks after transmission and were shorter compared with noninoculated controls. Leaf samples of newly infected plants were examined by electron microscopy and isometric particles of approximately 25 nm in diameter, corresponding in size and shape to described particles of CABYV (3), were observed. The presence of CABYV was verified by reverse transcription (RT)-PCR using a primer pair specific to the CABYV coat protein gene (2). The amplicons were sequenced (GenBank Accession Nos. HM771269–HM771273) and 100% sequence identity was found between isolates Jos-5 and Pr-15 and among the isolates Rak-1, Rak-2, and Rak-3. Sequence identity between these two groups was 99.3%. Blast analysis (4) showed that the Czech CABYV isolates are closely related to the Slovak isolates SK-1 (Accession No. FJ428797) and IR-3 (Accession No. FJ428800) with nucleotide sequence identities of 99.6 and 99.1%, respectively. These results indicate a similar origin between the Czech and Slovak isolates. To our knowledge, this is the first report of the natural occurrence of CABYV in the Czech Republic. CABYV is a widespread virus that reduces the yield of cucurbit vegetables (1). Protection against epidemics should be based on the control of aphid vectors, protecting plants with very fine mesh netting, keeping the cultivation area free of weeds, or planting cultivars resistant to CABYV.
References: (1) Anonymous. Research Report 1995-1996, 117. Vegetable Breeding Station, INRA, Montfavet, France, 1998. (2) M. Juarez at al., Plant Dis. 88:907, 2004. (3) H. Lecoq et al. Plant Pathol. 41:749, 1992. (4) Z. Zhang Z. et al. J. Comput. Biol. 7:203, 2000.