Assessment Strategies For Screening Effective Bacteria As Biological Control Agents And Elucidating The Mechanisms Of Biological Control For Rice Blast(Magnaporthe Grisea)

Rice blast disease is an important disease but effective biological control agents(BCAs)for controlling the causal organism Magnaporthe grisea,are currently unavailable.The research is aiming to establish an assessment system for screening effective bacteria as biological control agents using molecular techniques against M.grisea on rice and assess the potential biological control agents in the greenhouse.935 bacterial isolates were obtained from the surface and interior of stems,phyllosphere,rhizosphere,endorhiza,and endosphere of field-grown rice plants and bulk soil and biological control potential according to in vitro and vivo activities of their extracellular metabolites(chitinase,cellulase,glucanase,protease,and siderophores)was studied.Amplified ribosomal DNA restriction analysis and BOX-PCR analysis were also performed to examine the genetic diversity of 30 isolates with at least one point of assessed biological control potential.The thirty isolates achieved positive biological control efficacy ranging from 18.08%to 77.50%at 45 days post pathogen inoculation(dpi).I acquired 10 well-performed potential BCAs,especially Bacillus cereus H-S in 24,Bacillus subtilis D-L in 76 displayed good biological control capacity against M.grisea diseases on rice.This demonstrated that H-S in 24 and D-L in 76 in both greenhouse and molecular techniques tests(examining of infectious growth and appressorium penetration on the rice leaf)showed high positive results by limiting the effects of M.grisea on the plant.Pearson correlation analyses of assessment scores and antagonistic test in greenhouse show 0.87 and 0.73 against M.grisea suggesting that the BCAs screening and assessing system developed is adaptable for controlling rice blast disease.