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Kawaguchi A.,Research Institute for Agriculture
European Journal of Plant Pathology | Year: 2015

A nonpathogenic strain of Agrobacterium (=Rhizobium) vitis, ARK-1, limits the development of crown gall of grapevine (Vitis vinifera L.). Co-inoculation of grapevine shoots with ARK-1 and the tumorigenic (Ti) strain VAT03-9 at a 1:1 cell ratio resulted in significantly lower expression of the virulence genes virD2 and virE2 of VAT03-9 1 day after inoculation (dai) compared with expression levels when shoots were inoculated only with VAT03-9. In contrast, nonpathogenic A. vitis strain VAR06-30, which does not limit the development of crown gall of grapevine, co-inoculated with VAT03-9 did not affect expression levels of virD2 and virE2 under the same conditions. ARK-1 began to suppress the VAT03-9 population by seven dai, but no such effect was observed with VAR06-30 during the nine dai study period. Thus, the biological control activity of ARK-1 is likely based on the suppression of essential virulence genes. © 2015, Koninklijke Nederlandse Planteziektenkundige Vereniging. Source


Kawaguchi A.,Research Institute for Agriculture
Microbes and Environments | Year: 2013

A nonpathogenic strain of Rhizobium vitis ARK-1 was tested as a biological control agent for grapevine crown gall. When grapevine roots were soaked in a cell suspension of strain ARK-1 before planting in the field, the number of plants with tumors was reduced. The results from seven field trials from 2009 to 2012 were combined in a metaanalysis. The integrated relative risk after treatment with ARK-1 was 0.15 (95% confidence interval: 0.07-0.29, P<0.001), indicating that the disease incidence was significantly reduced by ARK-1. In addition, the results from four field trials from 2007 to 2009 using R. vitis VAR03-1, a previously reported biological control agent for grapevine crown gall, were combined in a meta-analysis. The integrated relative risk after treatment with VAR03-1 was 0.24 (95% confidence interval: 0.11-0.53, P<0.001), indicating the superiority of ARK-1 in inhibiting grapevine crown gall over VAR03-1 under field conditions. ARK-1 did not cause necrosis on grapevine shoot explants. ARK-1 established populations on roots of grapevine tree rootstock and persisted inside roots for two years. Source


Kawaguchi A.,Research Institute for Agriculture
Journal of General Plant Pathology | Year: 2011

Forty-one strains of Rhizobium vitis, either tumorigenic (Ti) or nonpathogenic, were characterized using multilocus sequence analysis (MLSA) of the partial nucleotide sequences of pyrG, recA, and rpoD. The strains separated into seven clades. Rhizobium vitis (Ti) strains isolated from Japan were divided into five genetic groups (A to E), and nonpathogenic R. vitis strains were divided into two genetic groups (F and G). This result suggests that there are new genetic groups of R. vitis in Japan. Among these groups, members of A and B groups are widely distributed throughout Japan. © 2011 The Phytopathological Society of Japan and Springer. Source


Differences in hrpZ sequences determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) were used to investigate the molecular epidemiology of Pseudomonas syringae pv. syringae (PSS) strains that were isolated from diseased barley and wheat plants in Okayama, Japan. PCR-RFLP using HhaI separated PSS strains into two groups (A and B). Although specific PCR-RFLP groups of PSS strains were not always isolated from specific cultivars or seeds produced in a specific area, many strains isolated from barley and wheat belonged to PCR-RFLP groups A and B, respectively. © 2012 The Phytopathological Society of Japan and Springer Japan. Source


A nonpathogenic strain of Rhizobium (=Agrobacterium) vitis, ARK-1, limited the development of grapevine crown gall. A co-inoculation with ARK-1 and the tumorigenic strain VAT07-1 at a 1:1 cell ratio resulted in a higher population of ARK-1 than VAT07-1 in shoots without tumors, but a significantly lower population of ARK-1 than VAT07-1 in grapevine shoots with tumors. ARK-1 began to significantly suppress the VAT07-1 population 2 d after the inoculation. This result indicated that ARK-1 reduced the pathogen population at the wound site through biological control. Although ARK-1 produced a zone of inhibition against other tumorigenic Rhizobium spp. in in vitro assays, antibiosis depended on the culture medium. ARK-1 did not inhibit the growth of tumorigenic R. radiobacter strain AtC1 in the antibiosis assay, but suppressed the AtC1-induced formation of tumors on grapevine shoots, suggesting that antibiosis by ARK-1 may not be the main mechanism responsible for biological control. © 2014 Microbes Environ. All rights reserved. Source

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