Isolation and characterization of oligotrophic bacteria possessing induced systemic disease resistance against plant pathogens

Abstract

Biocontrol microbes have mainly been screened among large collections of microorganisms via. nutrient-rich in vitro assays to identify novel and effective isolates. However, thus far, isolates from only a few genera, mainly spore-forming bacilli, have been commercially developed. In order to isolate field-effective biocontrol microbes, we screened for more than 200 oligotrophic bacterial strains, isolated from rhizospheres of various soil samples in Korea, which induced systemic resistance against the soft-rot disease caused by Pectobacterium carotovorum SCC1; we subsequently conducted in planta bioassay screening. Two oligotrophic bacterial strains were selected for induced systemic disease resistance against the Tobacco Mosaic Virus and the gray mold disease caused by Botrytis cinerea. The oligotrophic bacterial strains were identified as Pseudomonas manteilii B001 and Bacillus cereus C003 by biochemical analysis and the phylogenetic analysis of the 16S rRNA sequence. These bacterial strains did not exhibit any antifungal activities against plant pathogenic fungi but evidenced several other beneficial biocontrol traits, including phosphate solubilization and gelatin utilization. Collectively, our results indicate that the isolated oligotrophic bacterial strains possessing induced systemic disease resistance could provide useful tools as effective biopesticides and might be successfully used as cost-effective and preventive biocontrol agents in the field. ©The Korean Society of Plant Pathology.