Evaluation of biological control agents against Ralstonia wilt on ginger

Abstract

Of the 420 bacterial strains isolated from rhizosphere soil and the plant surface as well as the stem, leaf, and root tissue of ginger, 85 were selected for amplified ribosomal DNA restriction analysis (ARDRA) fingerprint analysis based on their antagonistic activity in vitro against Ralstonia solanacearum and on their ability to produce certain enzymes and metabolites. Of these 85, 19 antagonists from different clusters were assessed for their antagonism in greenhouse against Ralstonia wilt of ginger and biocontrol efficacies of these strains were 26.09–69.17%. In order to find out the relationship between potential and practical biocontrol ability we established an assessment system that evaluated their in vitro activity. The correlation coefficient between the assessments in vitro and biocontrol efficacies was 0.87, which indicates that this selection strategy can be used in screening biocontrol agents against plant diseases. In the greenhouse, the following strains showed biocontrol efficacies greater than 50%: Bacillus subtilis strain 1JN2, Myroides odoratimimus 3YW8, Bacillus amyloliquefaciens 5YN8, and Stenotrophomonas maltophilia 2JW6. This is the first report of using Myroides sp. and Stenotrophomonas sp. as biocontrol agents against ginger wilt caused by R. solanacearum, and these strains show promise as commercial biocontrol agents.