The complete nucleotide sequence of the RNA genome of turnip mosaic virus Japanese strain (TuMV-J) has been determined from five overlapping cDNA clones and by direct sequencing of viral RNA. The RNA sequence was 9833 nucleotides in length, excluding a 3' terminal poly(A) tail. An AUG triplet at position 130-132 was assigned as the initiation codon for the translation of the genome size viral polyprotein which would consist of 3164 amino acid residues. Interestingly, a different amino acid sequence (continuous twenty amino acids) within the cytoplasmic inclusion protein between TuMV-J and Canadian strain of TuMV was observed, caused by an insertion and a deletion of nucleotides.

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Unfamiliar necrotic symptoms on or within potato tubers of cultivars Nishiyutaka and Dejima were observed in Nagasaki prefecture, Japan, in 1992. Symptoms were typically on the surface of the tuber, which either protruded at first and then became sunken, or showed necrotic spots, with necrosis within the tubers. Symptoms sometimes appeared at harvesting but more often appeared after storage for several months. Investigations revealed that the causal agents of the disease were isolates of Potato virus Y necrotic strain (PVYNTN) and the disease was potato tuber necrotic ringspot disease (PTNRD), previously reported in Europe and Lebanon. Five potato cultivars were inoculated with an isolate from necrotic tubers. The highest percentage of progeny tubers showing PTNRD was found in cv. Nishiyutaka (23.3%). In contrast, cvs. Shima-bara, Mayqueen, and Danshaku showed a low percentage of PTNRD. Additional potato tubers with PTNRD were also observed after storage of the tubers. To investigate the relatedness between isolates of PVYNTN and of necrotic strain PVYN, previously isolated in Japan, Nishiyu-taka was inoculated with an isolate of PVYN, which also induced PTNRD. Nucleotide sequences of coat protein (CP) genes of six PVYNTN isolates were determined. The CPs were 267 amino acids in length, with a substitution of one or no amino acid among each of the six isolates. The phylogenetic relationship based on nucleotide sequences of CP genes showed that these six PVYNTN isolates clustered together with PVYN isolates. This is the first report of PTNRD caused by PVYNTN isolates in Asia.

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Two kinds of biphenyl phytoalexins accumulated in leaves of Photinia glabra Maxim