First Report of Cucurbit chlorotic yellows virus Infecting Melon in China.

In October 2007, symptoms of chlorosis on the upper leaves and a bright yellow color on the lower leaves were observed sporadically on hami melon (Cucumis melo cv. Xuelihong) in a high tunnel in Nanhui of Shanghai, China. Disease progresses from initial mottling of leaves into leaves that are completely yellow with the veins remaining green. The oldest leaves develop symptoms first, so these leaves have a pronounced even yellow color. In October 2009, these symptoms were found in all melons produced in the suburbs of Shanghai. These symptoms were similar to those caused by Cucurbit yellow stunting disorder virus (CYSDV) and Cucurbit chlorotic yellows virus (CCYV) (1-3). Twelve samples from symptomatic melons were collected in the Jiading, Nanhui, Fengxian, and Chongming districts of Shanghai for virus diagnosis. Large populations of whiteflies were observed in association with the diseased cucurbit crops. Total RNA was extracted with Trizol reagents (Invitrogen, Carlsbad, CA). We used random primers (9-mer) for reverse transcription-PCR. Extracts were for CYSDV using specific primers CYSDV-CP-F (5'-ATGGCGAGTTCGAGTGAGAA-3') and CYSDV-CP-R (5'-TCAATTACCACAGCCACCTG-3') to amplify a 756-bp fragment of coat protein gene and CCYV using specific primers CCYV-HSP-F1 (5'-TGCGTATGTCAATGGTGTTATG-3') and CCYV-HSP-R1 (5'-ATCCTTCGCAGTGAAAAACC-3') to amplify a 462-bp fragment of the HSP gene (1). CYSDV was not found in all samples. The expected 462-bp target fragment of CCYV was obtained in all samples but not from any of the healthy controls. All the 462-bp PCR products were cloned to pGEM-T vector (Promega, Madison, WI) and sequenced. All sequences obtained were homologous. A comparison of the submitted sequence (GenBank Accession No. HQ148667) with those in GenBank showed that the sequence had 100% nucleotide identity to the Hsp70h sequences of (CCYV) isolates from Japan (Accession Nos. AB523789 and AB457591) (1,4), Taiwan (Accession No. HM120250) (2), and mainland of China (Accession Nos. GU721105, GU721108, and GU721110). CCYV is a new member of the genus Crinivirus, first discovered in Japan in 2004 (4) and reported in Taiwan in 2009 (2). To our knowledge, this is the first report of CCYV on melon in China. References: (1) Y. Gyoutoku et al. Jpn. J. Phytopathol. 75:109, 2009. (2) L.-H. Huang et al. Plant Dis. 94:1168, 2010. (3) L. Z. Liu et al. Plant Dis.94:485, 2010. (4) M. Okuda et al. Phytopathology 100:560, 2010.