Characterization of the suppressive effects of the biological control strain VAR03-1 of Rhizobium vitis on the virulence of tumorigenic R. vitis
Rhizobium vitis: strain VAR03-1 is a biological control agent that suppresses grapevine crown gall disease caused by a tumorigenic strain of R. vitis (Ti). Both acetosyringone-induced expression of a virulence gene and the growth of Ti were suppressed in vitro when it was cultivated in the VAR03-1 culture filtrate. These inhibitory effects were reduced by high-temperature treatment or incubation for 72 h. Both activities were detected in the high molecular weight fraction (> 100 kDa) of the filtrate. Our results suggest that the antagonistic effects of VAR03-1 on Ti are mediated by large particle(s) released in the culture media.
KeywordsRhizobium vitis Crown gall disease Biological control agent Antitumorigenic bacterial strain
The bacterial strains were kindly provided by Okayama Prefecture in Japan via the dedicated arrangement of a material transfer agreement by Mr. Koji Tanina. This research was supported by KAKENHI Grant 17H03778 from the Ministry of Education, Culture, Sports, Science and Technology of Japan to A.K. and Y.N., and basic funds from Okayama University to Y.N. We also thank Honokai for providing a scholarship to K.S.
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Conflict of interest
The authors declare no competing financial interests.