First Report of Cucumber mosaic virus in Sweet Cherry in the People's Republic of China.

From the spring of 2003 to the summer of 2006, sweet cherry (Prunus avium) trees in orchards near Lvshun City, in the northeast People's Republic of China, had symptoms suggestive of those caused by Cucumber mosaic virus (CMV; genus Cucumovirus, family Bromoviridae). Symptoms included chlorotic patches or mottling on leaves that were also deformed (4). In April 2006, 20 symptomatic leaves sampled from 10 trees in each of four orchards were assayed for CMV with a CMV-specific antiserum (Agdia Inc., Elkhart, IN) in a double-antibody sandwich-ELISA. Of the 80 symptomatic leaf samples, 27 tested positive for the presence of CMV. CMV was detected in all four orchards, within which incidence varied between 0.5 and 4%. Viral nucleoproteins were purified by differential centrifugation and sucrose density gradient fractionation from symptomatic leaves. Transmission electron microscopy of nucleoproteins revealed isometric particles approximately 30 nm in diameter, which is also typical of CMV. Total RNA was also extracted from 100 mg of symptomatic tissue following a Trizol-based protocol (1). A reverse transcriptase-PCR assay with nucleocapsid gene-specific primers was then used (forward primer 5'-ATGGCGACGTCCTCGTTCA-3'; reverse primer 5'-CATCGTTCCCTTCAAAATAG-3') (3). A PCR product of approximately 633 bp was obtained. The PCR product was cloned and sequenced. The sequence (GenBank Accession No. HM996559) had 95% identity with the RNA-1 sequence from CMV 'Fny' strain in GenBank (Accession No. D00356.1). The People's Republic of China is one of the major producers of sweet cherry in Asia and the spread of CMV in China may cause significant economic losses. Thus, virus-infected material should not be used for propagation and surveys should be undertaken to determine if the aphid vectors capable of transmitting CMV are present (2).To our knowledge, this is the first report of CMV occurring in sweet cherry orchards in the People's Republic of China. References: (1) P. Chomczynski and K. Mackey. Biotechniques 19:942, 1995. (2) F. E. Gildow et al. Phytopathology 98:1233, 2008. (3) T. M. Rizzo and P. Palukaitis. J. Gen. Virol. 70:1, 1989. (4) J. Shang et al. Z. Naturforsch. C 65:73, 2010.