Characterization of toxins of Bacillus thuringiensis isolated from rice genotypes and their virulence assessment against leaf folder Cnaphalocrocis medinalis Guenee

Abstract

Today the central concern is the environment that needs to be protected from all the newlinechemicals that are being indiscriminately used in various spheres of earth i.e. air, soil and newlinewater. They have immense bad impact on each and every microbial forms associated with newlineit thereby disturbing the ecological scenario. The deteriorating soil condition due to the newlinechemicals are now being replaced by biological formulations (biocides, biofertilizers, newlineplant growth promoters etc.) that can not only be an asset to protect environment but also newlineadd to the productivity and growth of the plant as well. The most potent biocide i.e. newlineentomopathogen is Bacillus thuringiensis(Bt) which has been isolated mainly from soil newlineand its potential has been well studied, and put to use in field condition. Therefore, this newlineinvestigation was designed to study the structural and functional dynamics/diversity of newlineecto-/endospheric phytonic (phyton = plant) microbes, especially the entomopathogen Bt newlinein six wild and cultivar (cv.) rice (Oryza spp., Poaceae) genotypes susceptible and newlinetolerant/resistant to rice leaf folder (LF), Cnaphalocrocis medinalis Guenee. The study newlinerevealed the population dynamics of microbial pool revealing the varied diversity among newlinethe endophytic microbes. The decreasing order of Bt population in the six rice genotypes newlinewas O. sativa cv. Tapaswini gt O. brachyantha gt O. sativa cv.IR-36 gt O. nivara gt O. newlinesativa cv. Naveen gt O. sativa cv. PTB-12. The heterotrophic population count (cfu/g) was newlinehigher in rhizosphere followed by phyllosphere and root endophyte confirming the fact newlinethat these microbes would migrate more towards the roots to draw nutrition from their newlineimmediate niche and play a greater role in determining the community functionalities. newline newline