Mining Agricultural Soils for Bacteria Antagonistic to Plant Pathogens

บทคัดย่อ

Microbial biological control agents have been isolated from numerous substrates, but the reservoir of potential useful organisms has not been evaluated in soils that are exposed to herbicides during cropping practices. Therefore, we screened bacteria from soils from under field crops that had been routinely sprayed with herbicides for their ability to reduce the in vitro growth of two plant pathogens. Simple dual plate and paper disc diffusion assays were used to identify potential biocontrol agents. Among 115 bacterial isolates, 8 isolates showed antifungal activity against Rhizoctonia solani 1406 and 6 isolates had >50% inhibition. The most suppressive isolate was M59 (68% inhibition). From the 16S rRNA gene sequence, M59 had 100% identity to Pseudomonas aeruginosa strain JCM 5962^T. Results from antibacterial screening against Xanthomonas axonopodis pv. citri (Xac) revealed that isolate M93 has the potential to produce antibacterial compounds that can inhibit growth of the citrus canker pathogen in vitro. From a nucleotide BLAST search of the 16S rRNA gene sequence, M93 had 99.9% identity with Bacillus subtilis strain IAM 12118^T. Further research is necessary to identify candidate compounds and their antimicrobial efficacy in greenhouse trials.