NUCLEOTIDE-SEQUENCES OF THE 3'-TERMINAL REGION OF ONION YELLOW DWARF VIRUS ISOLATES FROM ALLIUM PLANTS IN JAPAN

The 2032 nucleotide sequence of the 3' terminal region of onion yellow dwarf virus (OYDV) isolated from Allium wakegi, bearing the genes for viral coat protein (CP) and a truncated RNA-dependent RNA polymerase, has been determined. Respecive homologies of the nucleotide sequence in the corresponding region and the deduced amino acid sequence of CP with the equivalents of leek yellow stripe virus (LYSV) from garlic we re 68.0 and 59.3%. Variation in the nucleotide sequence is concentrate d in the boundary region between the putative RNA-dependent RNA polyme rase gene and the CP gene as well as in the 3' noncoding region, These sequence divergencies, including the deletion of 79 nucleotides, resu lted both in alterations to the amino acid sequence and the absence of 28 amino acid residues in the amino terminal region of OYDV CP in com parison with LYSV CP, In addition, the lenght of the 3' noncoding sequ ence of OYDV was one-third that of LYSV. Comparison of the 3' terminal 1197 nucleotides sequence of OYDV with sequences of the respective cD NAs cloned by RT-PCR directly from the total RNA of infected Allium pl ants that included two varieties of A. fistulosum, ''Wakenegi' and ''S himonita-negi'', and A. chinense, showed 90.7% overall identities, eve n though they have long been cultivated in locally restricted area in Japan. These findings appear to suggest that a single strain of OYDV i nvaded Japanese Allium plants long ago and spread throughout them.