First Report of Cucumber mosaic virus Infecting Pinewood Coneflower (Rudbeckia bicolor) in Korea

Abstract

Department of Plant Medicine, Chungbuk National University, Cheongju 361-763, Korea(Received on December 21, 2009; Accepted on February 15, 2010)A virus isolate causing symptoms of yellow mosaic, fernleaves, malformation and plant necrosis on Rudbeckiabicolor was prevalent around Pyeongchang area inKorea. The causal virus was identified as Cucumbermosaic virus (CMV) using characteristics from bio-logical, serological and molecular analyses and namedas CMV-Rb. CMV-Rb caused mosaic on Nicotianabenthamiana, N. tabacum, Capsicum annuum, and Lyco-persicon esculentum. However, typical local lesions didnot develop on inoculated Pisum sativum, Cucurbitamoschata, Datura stramonium and Tetragonia expansaplants. Full-length genome sequences of CMV-RbRNAs 1, 2 and 3 were obtained using 12 primer pairs byRT-PCR analysis. The genome of CMV-Rb RNA seg-ments 1, 2, and 3 consists of 3363nt, 3049nt, and 2214ntin length, respectively. In order to ascertain their taxo-nomic identity, nucleotide and the deduced amino acidsequence analyses RNAs 1, 2 and 3 of CMV-Rb isolateswere conducted with previously reported sequences ofCMV strains and/or isolates. CMV-Rb RNAs showedabout 90 to 99% sequence identity to those of subgroupI strains suggesting that CMV-Rb is more closely relat-ed to CMV isolates belong to subgroup I. To our know-ledge, this is the first report of CMV on Rudbeckiabicolor in Korea.Keywords : CMV-Rb, phylogenetic analyses, Rudbeckiabicolor, subgroup ICucumber mosaic virus (CMV), the type member of thegenus Cucumovirus, infects more than 1,000 species ofplants and induces the typical mosaic symptoms in manyhost plants. Some of the intermediate symptoms, however,include blight, fernleaf, ringspot, and stunt. In Korea, atleast 109 natural host plant species has been reported, i.e.,20 in upland crops, 20 in vegetable crops, 28 in floral crops,acacia in wood, 40 in wild plants (List of plant disease inKorea, 2004, The Korean Society of Plant Pathology).Recently, CMV infections were also reported on Hydrangeamacrophylla (Lee et al., 2001), water chickweed (Choi etal., 2004), Isodon inflexus Kudo, Jeffersonia dubia Benth,Phryma leptostachya var. asiatica Hara (Lee et al., 2008).However, no natural outbreaks by CMV have been reportedon Rudbeckia bicolor, but Bidens mottle virus (BiMoV)was only identified (Brunt et al., 1996; Choi, 2001; Jin,2003; Lee, 1981; Lee et al., 2003; Logan et al., 1984).The genome of CMV consists of three genomic RNAs(RNA 1, 2 and 3; Roossinck, 2001). In infected host plants,it also produces two subgenomic RNAs (4 and 4A; Palukaitiset al., 1992). Based upon biological, serological, and, mole-cular biological characteristics of CMV isolates, they wereclassified into two subgroups, i.e., subgroup I and II (Owenand Palukaitis, 1988). The nucleotide sequence identitybetween subgroup I and II isolates range from 69 to 77%,while showing above 90% nucleotide sequence identitywithin each subgroup isolates. More detailed nucleotidesequence analyses, especially with the coat protein (CP)and 5' nontranslated region (NTR) of RNA 3 further sug-gested subdivision of subgroup I into subgroups IA and IB(Roossinck et al., 1999). This subgrouping was more clear-ly supported from the analysis of nucleotide sequences of1a and 3a open reading frames (ORFs) than those of the 2aand CP ORFs (Roossinck, 2002). In this paper, we reportthe biological and serological characteristics as well ascomplete nucleotide sequence analyses of CMV-Rb isolate.We believe this is the first report of natural CMV infectionon Rudbeckia bicolor in Korea.Pinewood coneflower (R. bicolor), family Asteraceae, iswidely grown as an ornamental crop and a wildflower. In2005, we could easily observe yellow mosaic, sometimes