Biocontrol Mechanisms Of Tomato Bacterial Wilt By Mitsuaria Sp.TWR114 And Ralstonia Sp.TCR112

The aim of this study was to determine the potential importance of competition for nutrients in the biocontrol of tomato bacterial wilt by the antagonistic bacteria Mitsuaria sp.TWR114 and Ralstonia sp.TCR112.Firstly,we compared the resource utilization patterns of both the antagonistic bacterial isolates and the bacterial wilt pathogen on representative 51 compounds(19 amino acids,17 organic acids,11 sugars,and 4 others)found in tomato root exudates.As a result,it was found that the antagonistic bacteria showed utilization pattern similar to that of the pathogen.In the subsequent co-culturing experiment,we examined the competitive interactions between each antagonistic bacteria and the pathogen in one-quarter strength M63 minimal medium supplemented with the nutrients that could be utilized by both bacteria.The results showed that TYWR114 significantly inhibited growth of the pathogen in co-culture with four(glutamine,galactose,galacturonic acid,and inosine)of seven tested compounds.Likewise,TCR112 significantly inhibited the pathogen growth in co-culture with four(glutamine,glutamic acid,galactose,and glucose)of seven tested compounds.Finally,we assess the effect of the nutrient amendment on the biocontrol efficacy of the antagonistic bacteria against tomato bacterial wilt in a tomato seedling bioassay.Accordingly,it was found that the biocontrol effect of TWR114 was remarkably reduced by the amendment of vermiculite with glutamine,glutamic acid,galacturonic acid,and inosine,while that of TCR112 was remarkably reduced by the amendment with glutamine,glutamic acid,and inosine.These results clearly indicated that the competition for various nutrients within the rhizosphere is one of the important biocontrol mechanisms of TWR114 and TCR112.