Bio-protection of brown spot disease of rice and insight into the molecular basis of interaction between Oryza sativa, Bipolaris oryzae and Bacillus amyloliquefaciens

The aim of the study is to evaluate the efficacy of Bacillus amyloliquefaciens strain BS5 against brown spot disease of rice and to understand the molecular mechanism of host-pathogen-bioagent interactions through a proteomic approach. We tested the antagonistic potential of forty Bacillus spp. against Bipolaris oryzae under in vitro. Based on their antagonism, ten effective strains were selected and characterized at the molecular level. The antibiotic biosynthetic genes producing bacillomycin, bacilysin, iturin, surfactin, subtilin, mersacidin, subtilosin, ericin, mycosubtilin and fengycin from the effective strains were detected by PCR analysis. Among the strains, BS5 exerted higher mycelial growth inhibition (76.66%) of the pathogen and possesses the maximum number (9) of antibiotic genes as well. We also evaluated the efficacy of liquid formulation of the Bacillus strains BS5, BS6 and BS39 against brown spot disease under glasshouse and field conditions. The results indicated a significant reduction in the intensity of brown spot disease with the combined application of seed treatment + seedling dip + foliar spray of BS5 liquid formulation under glasshouse and field conditions. Furthermore, a 2D-PAGE analysis revealed a total of nine proteins with differential expressions using MALDI-TOF Mass spectrometry (MS). The Mascot algorithm demonstrated homology among proteins such as ribulose 1, 5 bisphosphate carboxylase, 2-cys-peroxiredoxin, ATP synthase, trehalose-phosphate phosphatase, serine/threonine protein kinase and 50s ribosomal protein. The functions of the proteins were mainly related to plant metabolism, defense response and disease resistance. The three ways synergy associated with the host-pathogen-bioagent of rice plants will be provided in this study.