First Report of Clover yellow vein virus on Glycine max in Korea

Glycine max (Soybean) is the most important edible crop in Korea. In Korea, eight viruses have been reported to infect soybean, including Alfalfa mosaic virus (AMV), Cowpea mosaic virus (CPMV), Cucumber mosaic virus (CMV), Soybean dwarf virus (SbDV), Soybean mosaic virus (SMV), Soybean yellow common mosaic virus (SYCMV), Soybean yellow mottle virus (SYMMV), and Peanut stunt virus (PSV) (1). In 2012, Glycine max were observed in Daegu, South Korea, with mosaic and mottling symptoms on leaves. Samples with virus-like symptoms (n = 151) were collected from Daegu including legume genetic resource field. Virus particles were filamentous rod shaped, average length 760 nm, and were analyzed by RT-PCR using specific primers for several Potyviruses and previously reported viruses infecting soybean. Only two samples showing mosaic and mottling symptoms were identified as Clover yellow vein virus (ClYVV) based on RT-PCR using primers specific for ClYVV (5'-GTTGGCTTGGTTGACACTGA-3' and 5'-CTTCGATCATGGATGCACA-3'). The sequences of amplified fragments were 97 to 98% similar with ClYVV. ClYVV is a distinct species in the genus Potyvirus and family Potyviridae. ClYVV is transmitted by several species of aphids and by mechanical inoculation (2). ClYVV was first reported on Gentiana scabra, and the disease has never been reported in soybean fields in Korea. The biological properties and full genome sequence of the selected ClYVV isolate of apparent virus symptoms between two samples were analyzed. The ClYVV isolate was inoculated to local lesion plants, re-isolated from local lesions three times, and propagated in Nicotiana benthamiana, and then named ClYVV-Gm. The ClYVV-Gm induced local lesions on inoculated leaves of N. tabacum cv. Xanthi-nc, Tetragonia expansa, and systemic symptoms on upper leaves of Chenopodium amaranticolor, C. quinoa, and N. clevelandii. The ClYVV-Gm caused mosaic and mottling symptoms on Glycine max cv. Kwangan and Phaseolus vulgaris. The genome of ClYVV-Gm was determined to be 9,584 nucleotides in length (GenBank Accession No. KF975894), and it shared 83% to 97% nucleotide identity with the sequences of 27 previously reported ClYVV isolates including Vicia fava and Pisum sativum. Despite low occurrence of ClYVV in Glycine max, ClYVV has a broad host range including tobacco, weed species, and soybean, which can lead to spreading of the virus. Our results indicate that emergence of ClYVV could become a problem to Leguminosae in Korea. To our knowledge, this is the first biological and molecular report of ClYVV infecting Glycine max in Korea. References: (1) Y. H. Lee et al. Korea Soybean Digest 29:7, 2012. (2) T. Sasaya et al. Phytopathology 87:1014, 1997.