Identification and sequence analysis of Liaoning isolate of Pepper mild mottle virus.
Reaction of indicator plants, serological test, RT-PCR detection, sequencing analysis and sequence homogeneity were conducted to identify the virus isolate obtained from diseased peppers collected in Huludao, Liaoning Province. The results showed that the virus isolate was able to infect Capsicum frutescens with partial necrosis lesions on inoculated leaves and systemic mild mottle or mosaic on new leaves. Necrosis dry spot in Nicotiana tabacum, Nicotiana glutinosa, Nicotiana tabacum var. samsun and Petunia hybrida; Chlorotic lesion in Datura stramonium, Physalis pubescens and Chenopodium amaranticolor. While the virus isolate could not infect Lycopersicon esculentum, Chenopodium amaranticolor, Cucumis melo, Cucumis saticus, Gomphrena globosa, Brassica pekinensis, Zinnia elegans, Vicia faba and Zea mays. Diseased pepper leaves and fruits from field, and seeds from seed company, as well as the inoculated indicator plants leaves with symptoms, were all positive identified with PMMoV by DAS-ELISA. The CP gene of the isolate was successfully cloned by RT-PCR and the homology analysis showed that the homology of CP gene and corresponding amino sequences was over 94% compared with 13 reported PMMoV isolates from GenBank. The phylogenetic tree figure demonstrated that the virus isolate had a close relationship with other Asian PMMoV isolates, and might have the same evolutionary ancestors with the domestic isolates. On conclusion, the virus isolate is identified as PMMoV Liaoning isolate (PMMoV-LN), which is the first report in pepper fields in Liaoning Province. As a typical seed-borne virus, it still has not yet listed as a quarantine object which may cause a rapid extension of PMMoV in China. More attention should be paid to the dangers of the virus and its potential threat to pepper production, and the disease-resistant breeding, inspection and quarantine work for controlling the virus disease should be strengthened.