Cherry green ring mottle virus (CGRMV; a member of the genus Foveavirus in the family Flexiviridae) has a single-stranded, positive-sense RNA genome of approximately 8.4 kb (4). The viral infection on several Prunus spp. has been mainly reported in Japan, New Zealand, and some countries in Africa, Europe, and North America (3). The virus can cause leaf yellowing on sour and tart cherry. Sweet cherry plants are symptomless hosts of the virus. During the growing season of 2010, leaf samples were collected randomly from one ornamental cherry (Prunus serrulata L.) and 26 sweet cherry (P. avium (L.) L.) plants grown in Shangdong and Henan provinces in northern China and 64 peach (P. persica L. Batsch) plants grown in Hubei Province in central China and tested for the presence of CGRMV by reverse transcription (RT)-PCR. Total RNA was extracted from leaves using the CTAB protocol reported by Li et al (2). Primer set, CGRMV1/CGRMV2 (1), was used for the amplification of a 949-bp fragment, which contains the complete CP gene of 807 bp. PCR products with the expected size were identified in one ornamental cherry, seven sweet cherry, and eight peach plants. Although some of sampled plants showed leaf chlorosis, we did not find the specific association between the symptom and CGRMV infection. The obtained PCR products were cloned into the vector pMD18-T (TaKaRa, Dalian, China). Three independent clones from each isolate were sequenced by Genscript Corp., Nanjing, China. Results showed that CP sequences from the Chinese CGRMV isolates shared 87.7 to 99.8% nucleotide and 93.3 to 100% deduced amino acid similarities, and clones intra each isolate shared more than 99% nt similarities. The CP gene sequences of two representative isolates from cherry (YT-Ch-1) and peach (Pe-HB-18) were submitted to GenBank with Accession Nos. HQ539656 and JF810672, respectively. The neighbor-joining phylogenetic trees generated with nucleotide and amino acid sequences of CP genes by Clustal X v1.8 revealed that all Chinese CGRMV isolates fell into two well-resolved clades. Most of the Chinese CGRMV isolates (12 of 16 isolates, including the isolate YT-Ch-1) were grouped in a large clade represented by isolate ITA5 (GenBank Accession No. AF533159). Four isolates from peach (including the isolate Pe-HB-18) clustered into another clade represented by isolate ITA6 (GenBank Accession No. AF533160). In July 2010, peach GF305 seedlings were inoculated by side grafting with budwoods from two CGRMV positive cherry plants. In May 2011, some newly developed leaves from all inoculated plants showed vein yellowing. The CGRMV infection in these inoculated peach GF305 plants was detected by RT-PCR and protein A sandwich-ELISA using antiserum raised against the recombinant CP of CGRMV isolate YT-Ch-1 (unpublished data). These results further confirmed the CGRMV infection on field cherry plants as detected by RT-PCR. To our knowledge, this is the first record of the presence of CGRMV in ornamental and sweet cherry and peach plants in China, which provides valuable information for further evaluating the sanitary status of the virus in sweet cherry and peach orchards in China.
References: (1) R. Li and R. Mock. J. Virol. Methods 129:162, 2005. (2) R. Li et al. J. Virol. Methods 154:48, 2008. (3) K. G. Parker et al. USDA. Agric. Handb. No. 437:193, 1976. (4) Y. Zhang et al. J. Gen. Virol. 79:2275, 1998.