First Report of Cucumber mosaic virus in Agastache rugosa in China.

Agastache rugosa (family Lamiaceae) is one of the most common herbs of traditional Chinese medicine in China, and the species increasingly gains popularity on the international market. In June 2012, typical mosaic symptoms were observed on many A. rugosa plants in a field in Shanxi Province. The incidence of this disease reached more than 60% in a 2.6-ha field. Seven symptomatic plants were tested by DAS-ELISA using monoclonal antibodies specific for Tobacco mosaic virus (TMV), Cucumber mosaic virus (CMV), and Tomato mosaic virus (ToMV); all antisera used in DAS-ELISA were generated and validated in our laboratory. CMV was found in all seven samples tested, but not TMV and ToMV. Double-stranded RNAs (dsRNA) extracted from infected leaves were used as templates in the subsequent two-step RT-PCR reaction (1). In order to further confirm the presence of CMV, a pair of specific primers (forward: 5'-ACGTCGACCATGGACAAATC-3', and reverse: 5'-TACCCGGGTCAGACTGGTAGCACC-3') based on the coat protein gene sequence of CMV were used to amplify PCR products of the expected size (657 bp) from ELISA-positive samples (2). These PCR products were cloned into pUCm-T Vector (Sangon Biotech, Shanghai) and sequenced. Five independent clones have been sequenced to obtain the consensus sequence. This consensus sequence (GenBank Accession No. JQ403529) was compared with other CMV sequences available in GenBank using DNAMAN. The partial CMV coat protein sequence showed the highest 97.9% nucleotide identity with a subgroup IB CMV isolate from China (DQ459481). To our knowledge, this is the first report of the natural occurrence of CMV on A. rugosa. References: (1) M. Krajacić et al. J. Chromatogr. A. 1144:111, 2007. (2) F. Li et al. J. Zhejiang Univ. 26:261, 2000.