An assessment system for screening effective bacteria as biological control agents against Magnaporthe grisea on rice

• Production of hydrolytic enzymes and secondary metabolites are proposed.
• ARDRA and BOX-PCR for genetic analysis.
• Correlation coefficient show 0.87 between the assessment and biocontrol efficacy.
• Correlation coefficient show 0.73 between antagonism and biocontrol efficacy.

Rice blast is an important disease but effective biological control agents (BCAs) for controlling the causal organism Magnaporthe grisea, are currently unavailable. In this study, to effectively screen potential BCAs against M. grisea from those substrates, an assessment system was established to screen the biological control potential from 935 bacterial isolates according to amplified ribosomal DNA restriction analysis (ARDRA), BOX-PCR analysis, in vitro activities of their extracellular metabolites (chitinase, cellulase, glucanase, protease, and siderophores) and in vivo biological control activity under greenhouse conditions. The conventional correlation coefficient was 0.87 between the biocontrol efficacy of the selected 30 isolates at 45 days post pathogen inoculation (dpi) and their assessment scores for biological control potential indicates that the established assessment system was effective. The 30 isolates achieved positive biocontrol efficacy ranging from 18.08 to 77.50% at 45 dpi, with 10 accomplishing a biocontrol efficacy over 40% at 45 dpi. Two of them respectively achieved 77.5% and 75% biocontrol efficacy, could be utilized for controlling of rice blast disease in field.