Wilt disease on 20 plant species growing in a cabbage field naturally infested with both Verticillium longisporum and V. dahliae (tomato pathotype) was examined. Severe symptoms were noted on cabbage, Chinese cabbage and Japanese radish, and the two pathogens were readily isolated from different plants or a single individual. Concurrent infection by the two pathogens was also observed in udo (Aralia cordata Thunb.) and potato, with moderate and slight symptoms, respectively. Only V. longisporum was isolated from scarlet runner bean, which had slight internal symptoms. These three noncruciferous plants were newly recorded as host species for V. longisporum through natural infection. V. longisporum was most frequently isolated in tissues of cruciferous crops infected with the two pathogens, whereas V. dahliae was most frequently isolated in potato. V. dahliae was the sole pathogen obtained from tomato and cosmos. Neither of the two pathogens were isolated from head lettuce and gramineous crops, namely sweet corn, sorghum, wild oat and sudax. Among weed species, V. longisporum was clearly pathogenic on marshcress (Rorippa islandica Borb.) and was isolated from them, and V. dahliae was isolated from common purslane (Portulaca oleracea L.). These results indicated that the two pathogens were still pathogenic on their hosts with their usual severity without interfering with each other under the concurrent conditions.

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A novel rice disease, characterized by discolored rice grain symptoms, was observed in the southern part of Okayama Prefecture in 1978. Sarocladium sp. was isolated at a high frequency from the discolored rice grains. Rice plants, at the boot and flowering stages, were inoculated with a conidial suspension of the isolated fungal strains. Regardless of the growth stage at the time of inoculation, rice grains became discolored, while no apparent symptoms were induced on leaf blades. Inoculation at the boot stage induced browning leaf sheaths, whereas no symptoms appeared after inoculation at the flowering stage. In a comparative analysis of the strains with S. oryzae, the rice sheath rot fungus, the isolates and the sheath rot fungus were indistinguishable in their pathogenicity on rice plants, or morphological and cultural characteristics. These results clearly indicate that the discolored rice grains in Okayama Prefecture were caused by the sheath rot fungus, S. oryzae.

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The detection of the pathogen of bacterial grain rot of rice, Burkholderia glumae, from agro-environmental water using selective media is difficult, because the water generally contains a very low concentration of the targeting pathogen. A new procedure was devised using membrane filtration and enrichment culture followed by PCR. A PCR primer set, PGF 1 (5'-TGTCTGACACGGAACACCTGGGTAG-3') and PPR1 (5'-AGGTTGAGTTCTCGCATTTGTGCCG-3'), was designed for specific amplification of the 16S-23S rDNA spacer region in B. glumae. The procedure made possible the detection of B. glumae from 1000ml of irrigation water inoculated with approximately 10⁰ cfu of the pathogen. We tested this procedure for various samples of agro-environmental water. B. glumae was detected from some samples of paddy water, irrigation water, river water and lake water from May through November. When the method was used on 30 species of volunteer plants in or around paddy fields with bacterial grain rot, B. glumae was detected from one plant of Monochoria vaginalis.

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Coat protein (CP) of Apple stem grooving virus (ASGV) was obtained from E. coli expressing ASGV-CP gene. Purified CP was injected into a rabbit and antiserum to ASGV-CP was raised. The antiserum reacted with ASGV-CP in both western blots and double antibody sandwich-enzyme linked immunosorbent assays (DAS-ELISA). For DAS-ELISA on ASGV in citrus leaves, extraction buffers with different pH were tested. ELISA values were higher when extraction buffers of higher pH were used. Carbonate-bicarbonate buffer (pH 9.6) containing 0.05% Tween 20 gave the highest reading. This ELISA system was shown to be useful for detection ASGV in our surveys.

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A new disease of quince with fruit spots and brown flecks on leaves was found in Aomori. A species of Cylindrosporium was isolated from the fruit spots, and Mycosphaerella type pseudothecia were obtained from overwintered, affected leaves. Single-spore isolates from the pseudothecia produced a Cylindrosporium anamorph on potato dextrose agar. These isolates caused the same spots on quince and apple fruits and the blown flecks on quince leaves in inoculation tests. Based on morphological and cultural characteristics, the fungus was identified as Mycosphaerella pomi (anamorph: Cylindrosporium pomi). This is the first report of M. pomi on quince in Japan.

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