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A suspension of nonpathogenic Xanthomonas campestris ( nXc) strain AZ98101 or AZ98106 was sprayed on peach trees in biological control tests against bacterial spot caused by Xanthomonas arboricola pv. pruni. Treatment with each strain reduced the number of leaves with spots. Meta-analysis of the results from seven field trials showed an integrated risk ratio (the ratio of leaf spot incidence on inoculated leaves to incidence on control leaves) of 0.46 by treatment with AZ98101 and 0.54 by AZ98106, indicating that leaf spot incidence was significantly reduced by each strain. Each also significantly reduced the incidence of fruit spot. The risk ratio with AZ98101 was significantly lower than that with AZ98106. The population of AZ98101R-1, a rifampicin-resistant mutant of AZ98101, was 6.3 × 10 CFU/g (fresh mass) on leaves and 8.0 × 10 CFU/g on fruit at 12 days after inoculation, but was undetectable (<10 CFU/g) by 24 days. This is the first report that nXc strains AZ98101 and AZ98106 effectively control bacterial spot on peach. [ABSTRACT FROM AUTHOR]

In 2005, characteristic symptoms of crown gall on grapevines ( Vitis vinifera L. cv. Muscat of Alexandria, and cv. Seto Giants) were observed in a commercial greenhouse-orchard in Okayama Prefecture, Japan. Isolations from diseased tissues consistently yielded bacterial colonies that were white, glistening, and produced abundant polysaccharide on potato semi-synthetic agar (PSA) medium. Ten representative isolates were chosen for further characterization. A multiplex polymerase chain reaction (PCR) assay showed these strains were not Rhizobium vitis but did possess a Ti plasmid. The bacteriological characteristics of the isolates corresponded well with R. radiobacter. The almost complete 16S ribosomal DNA sequences of isolates AT06-1 and AT06-2, selected from 10 grapevine isolates, were determined and corresponded to sequences of R. radiobacter. The pathogenicity of the isolates was tested on young grapevine and tomato ( Lycopersicon esculentum Mill.) plants. Gall symptoms developed on both plant species after inoculation, and bacteria with the same colony morphology as those inoculated were reisolated. Based on these results, the isolates were identified as R. radiobacter (Ti). This report is the first of the occurrence of R. radiobacter (Ti) on grapevine in Japan. Phylogenetic analyses using the partial nucleotide sequences of virC operon located on a Ti plasmid showed that the isolate of R. radiobacter (Ti) isolated from grapevine and some strains of R. vitis (Ti) belonged to the same monophyletic group, which differed from the groups of R. radiobacter (Ti) isolated from plants other than grapevine and of the majority of R. vitis (Ti) strains isolated from grapevine. [ABSTRACT FROM AUTHOR]

A virus that caused a distinct yellow mosaic was isolated in Okayama, Japan from Chinese cabbage ( Brassica rapa L., Pekinensis group). The virus, with spherical particles ca. 28 nm in diameter, was mechanically transmissible only to cruciferous species. From the host range, characteristic morphology of virus particles, serology and sequence analysis of coat protein gene, the causal virus was identified as Turnip yellow mosaic virus (TYMV). Seed transmission of TYMV at 0–2.2% in Chinese cabbage was confirmed. This report is the first of TYMV from Chinese cabbage and in Japan. [ABSTRACT FROM AUTHOR]

In Vitis labruscana ‘Pione’ and ‘Kyoho’, 57 grapevines with rugose wood (RW) symptoms and 31 asymptomatic grapevines were obtained from vineyards in Hiroshima and Okayama prefectures. We surveyed vines for RW-associated viruses and other viruses by reverse transcription-polymerase chain reaction with virus-specific primers and degenerate primers for simultaneous detection of viruses associated with RW or leafroll disease. Rupestris stem pitting-associated virus (RSPaV) was detected from all grapevines with RW symptoms and from eight asymptomatic grapevines. Grapevine leafroll-associated virus-1, -2, -3, Grapevine virus B, Grapevine fleck virus, and Grapevine asteroid mosaic-associated virus were detected from some of the grapevines tested. RSPaV isolates detected were clustered in four groups by phylogenetic analysis using the nucleotide sequences of coat protein gene. These results suggest that RSPaV with diverse genetic variants is highly related to RW in Japanese grapevine cultivars Pione and Kyoho. [ABSTRACT FROM AUTHOR]

A nonpathogenic strain of Agrobacterium vitis VAR03-1 was tested as a biological control agent against crown gall of grapevine ( Vitis vinifera L.). A mixture of the nonpathogenic strain VAR03-1 and a tumorigenic strain G-Ag-27 of A. vitis at cell ratios of 1 : 1, 3 : 1, 9 : 1, and 99 : 1 significantly inhibited gall formation and size on stems of tomato ( Lycopersicon esculentum Mill.). Strain VAR03-1 also inhibited gall formation on stems of both tomato and grapevine at a 1 : 1 cell ratio with several tumorigenic A. vitis strains isolated from different fields of grapevine in Japan. In biological control tests, when roots of grapevine and tomato seedlings were soaked in a cell suspension of strain VAR03-1 for 24 h before a 1-h soaking in a cell suspension of the pathogen and subsequent planting in pots of infested soil, strain VAR03-1 significantly reduced the incidence of gall formation on both plants. [ABSTRACT FROM AUTHOR]

Graft unions of nursery stock of grapevine ( Vitis vinifera L.) collected in Japan yielded pathogenic and nonpathogenic strains of Agrobacterium. On the basis of classical diagnostic tests, a sequence analysis, and a multiplex polymerase chain reaction method previously reported, the pathogenic strain was identified as Agrobacterium tumefaciens biovar 3, whereas the nonpathogenic strains were assigned to Agrobacterium radiobacter biovar 3. Stems of tomato ( Lycopersicon esculentum Mill.) seedlings were inoculated with both A. tumefaciens biovar 3 strain G-Ag-27 as a pathogen and one of the control strains isolated from grapevine or A. radiobacter biovar 2 strain K84 as competitors to assay the suppression of gall formation caused by the pathogen. In a test with a 1 : 1 pathogen/nonpathogen cell ratio, all A. radiobacter biovar 3 strains reduced gall incidence and size compared to that of the positive control inoculated only with the pathogen. Strain VAR03-1 was especially effective in reducing the incidence of gall formation on grapevine and reduced gall size by 84%–100% of those on the positive control. Many tested nonpathogenic biovar 3 strains were bacteriocinogenic, causing an inhibition zone against A. tumefaciens biovar 3 strains on YMA medium. Strain VAR03-1 was the most effective against indicator strains and appears to be a promising agent for controlling crown gall of grapevine. [ABSTRACT FROM AUTHOR]

The distribution of plants with tomato bacterial canker within a greenhouse was analyzed using Morisita's binomial index of dispersion, I, to assess spatial distribution patterns. The distribution patterns of diseased plants were similar in four commercial greenhouses. The degree of clustering of added together diseased plants based on the I index did not increase with time, but the statistical significance of the cluster distribution did increase, suggesting that new independent cluster points had formed during the investigation. Therefore, a scattered pattern of potentially or apparently diseased plants caused by primary inoculum from residual plants in the soil emerged with time. [ABSTRACT FROM AUTHOR]

A nonpathogenic strain of Rhizobium vitis, VAR03-1, was tested as a biological control agent for crown gall of apple. When apple tree roots were soaked in a cell suspension of antagonists before planting in the field, treatment with VAR03-1 significantly reduced the number of plants with tumors and the disease severity. The inhibitory effects of treatment with VAR03-1 and the nonpathogenic R. rhizogenes strain K84, which is commercially used as a biological control agent throughout the world, on apple crown gall were almost identical. VAR03-1 was bacteriocinogenic, producing a halo of inhibition against two species of tumorigenic Rhizobium isolated from galled apple trees. Moreover, VAR03-1 established populations on roots of apple tree rootstock and persisted on roots for 437 days. This is the first report that the nonpathogenic R. vitis VAR03-1 effectively controls crown gall of apple. [ABSTRACT FROM AUTHOR]