Japanese Journal of Phytopathology

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Bell pepper plants showing vein yellowing and leaf roll symptoms were observed in plastic houses at Kitanakagusuku, Okinawa Prefecture in 1981. The causal agent did not infect plants by mechanical inoculation or through seed but was transmitted by grafting and two species of aphids, Aphis gossypii Glover. collected from pepper and Myzus persicae Sulz. in a persistent manner. The causal agent has limited host range, only infect Capsicum species. In serological tests this agent did not react with antisera to potato leaf roll virus, tobacco necrotic dwarf virus, barley yellow dwarf virus and beet western yellows virus. Partially purified preparations contained spherical particles 25nm in diameter. In ultrathin sections virus-like particles were observed only in the phloem cells of infected pepper plants. Based on these results the causal agent was classified as a new member of the luteovirus group and named pepper vein yellows virus (PeVYV).

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Ethyl acetate (EtOAc) extract of germination fluids of Pyricularia oryzae induced infection by non-pathogenic Alternaria alternata to rice leaves. When spores of A. alternata were inoculated with EtOAc extract to rice leaves, lesions by infection of A. alternata appeared. The higher the concentration of EtOAc extract was, the more the lesions formed. There was no difference in the susceptibility-inducing activity between EtOAc extracts from the compatible race of P. oryzae and the incompatible one to the corresponding rice cultivars. However, the susceptibility-inducing activity of EtOAc extract from P. oryzae was always higher than that from P. grisea at any concentrations tested. From these results we concluded that EtOAc extract from germination fluids of P. oryzae contained susceptibility-inducing factor(s) which were disease determinants of basic compatibility in rice blast disease.

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cDNAs to rice ragged stunt Oryzavirus genome segment 10 (S10) were made by oligo-dT primed 1st strand cDNA synthesis after poly A addition to 3' terminal of viral transcripts and cloned in a bacterial plasmid pBR322. The overlapping cDNA clones were sequenced and the assembled sequence covered the full-length of the genome except for 22 nucleotides from the 5' terminus, which were determined by a direct RNA sequencing method. RRSV S10 is 1162 nucleotide long and an inverted repeat structure containing 6 nucleotides was found in the terminal region. It has a mini ORF in addition to the down stream long ORF. The upstream mini ORF encodes 12 amino acids. Presence of this mini ORF was confirmed by sequencing another full-length cDNA clones generated by reverse transcription coupled with a polymerase chain reaction. The long ORF encodes a polypeptide of 297 amino acids (M_r 32.4K).

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Recently, a disease similar to southern blight has occurred frequently on seedling stock of loquat in Nagasaki Prefecture. One kind of fungus similar to Sclerotium rolfsii Saccardo, the causal fungus of southern blight, was isolated consistently from collar rot lesions of loquat seedling stocks. The isolates were identical to S. rolfsii in all examined characters, such as mycelial growth, colony color, sclerotia formation and pathogenicity against various plants. From these results the isolated fungus was identified to be Sclerotium rolfsii Saccardo. The S. rolfsii isolates from loquat could be grouped into two types according to the size of sclerotia formed on Czapek Agar medium.

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