Characterization of possible bacterial biocontrol agents, isolated from various plants in Indonesia, against bacterial wilt and damping-off of tomato

抄録

One hundred bacterial strains isolated from various plants grown organically in Indonesia were assessed for their potential biocontrol ability. Phylogenic analysis based on the 16S rRNA analysis showed that Gram positive and negative bacteria were distributed in the host plants. About 43% of them belonged to Bacillus spp. and the other genera were Achromobacter, Acinetobacter, Agrobacterium, Alcaligenes, Brevibacterium, Enterobacter, Leucobacter, Microbacterium, Paenibacillus, Pseudomonas, Serratia, and Stenotrophomonas. The screening results showed that strains EB13, EB45, and EB53 isolated from Brassica chinensis, Fragaria vesca, and Ipomea aquatica, which were identified as B. amyloliquefaciens, B. cereus, and Alcaligenes sp., increased the survivability of tomato in bacterial wilt (BWT) significantly (P<0.05) by 67%, 83%, and 72%, respectively. Two strains, EB13 and EB45, also increased the survivability of tomato in damping-off significantly (P<0.05) by 45%, while EB53 and EB87 identified as Enterobacter gergoviae showed 23% and 34% disease suppression, respectively, although the differences were not significant. EB13rifkan, EB53rif and EB87rif, spontaneous antibiotics mutants of the parent strains, were confirmed to colonize tomato roots and suppress the population of Rhizoctonia solani in soil and root A seven-day culture broth of strains EB13 and EB87 and its butanol extract showed antibiosis to R. solani and R. solanacearum. HPLC analysis revealed the productions of iturin and surfactin by EB13 and an iturin-like compound by EB87. These results indicate that plant-derived bacteria not only offer potential biocontrol agents for the two tomato diseases but also provide a new source for antibiotics iturin and surfactin.