BIOLOGICAL, SEROLOGICAL, AND MOLECULAR VARIABILITIES OF CLOVER YELLOWVEIN VIRUS

A comparative study was made on the host reactions, serological proper ties, and nucleotide sequences of the coat protein (CP) gene of 10 clo ver yellow vein virus (C1YVV) isolates and one bean yellow mosaic viru s (BYMV) isolate collected from different host plant species and locat ions in Japan. Two strains of C1YVV isolates, grouped on the basis of host reactions on Chenopodium amaranticolor, C. quinoa, Nicotiana clev elandii, N. benthamiana, Vicia faba, and Trifolium repens, corresponde d to two serotypes determined by double-antibody sandwich-and triple-a ntibody sandwich-enzyme-linked immunosorbent assay using three polyclo nal and nine monoclonal antibodies. These results were also confirmed by nucleotide sequence analysis of the CP gene. The CP gene of C1YVV i solates of strain 1, including the Australian isolate C1YVV-B, had 93 to 98% nucleotide identities and 97 to 99.6% amino acid identities. Th e CP of C1YVV isolates of strain 2, including the New Zealand isolate C1YVV-NZ had 92 to 98% nucleotide identities and 95 to 98% amino acid identities. The nucleotide identities and the amino acid identities be tween the two C1YVV strains were 82 to 84%, and 90 to 94%, respectivel y. When compared with the CP sequences of 12 C1YVV isolates, the CP se quence of the BYMV isolate had 71 to 73% nucleotide identity and 73 to 77% amino acid identity. Amino acid sequence differences among C1YVV isolates from strains 1 and 2 were located mostly at the N-terminal re gions of the CP Our results indicated that the C1YVV isolates studied could be separated into two strains on the basis of host reactions, se rology, and the nucleotide sequence of the CP gene.