Isolation Characterization and Development of Bacillus thuringiensis Formulations Against Diamond Back Moth Plutella xylostella L

Abstract

Total of 80 B. thuringiensis isolates were obtained from 396 samples collected from newlinethe Western Ghats of Karnataka, out of which 44, 27 and 9 isolates were obtained from the newlinesamples collected in Uttara Kannada, Dakshina Kannada and Udupi districts respectively. All newlinethe isolates were subjected for morphological, biochemical and molecular characterization. newlineSixty five per cent of the isolates showed spherical type of crystals and only 3.75 per cent of newlinethe isolates had bipyramidal type of crystals. All the 80 isolates showed positive reaction for newlinenitrate reduction, catalase production, voges-proskauer reaction and oxidase test, but all were newlinenegative for acid and gas production from glucose, arginine hydrolysis, chitinase activity and newlineesterase activity. Rep-PCR fingerprinting of 80 isolates indicated that, the isolates grouped newlineinto two major clusters having seven sub-clusters. Bioassay against third instar larvae of newlinePlutella xylostella showed 100 per cent mortality by the isolates UK-13C and UK-762D. newlineEfficacy of six different concentrations of crude protein of selected Bt isolates against DBM newlineshowed the mortality ranged from zero to one hundred per cent. The isolate UK-13C having newlineLC50 value close to that of the reference strain HD1 and least LC99 was recorded by UK-762D. newlineThirteen efficient isolates showed good growth in presence of chemical pesticides newlineIndoxacarb, Novaluron, Chlorofenapyr and Spinosad and no growth in the presence of newlineThiodicarb, Profenofos, Captan and Mancozeb. Three isolates and reference strain HD1 with newlineleast LC99 value were selected for preparation of wettable powder (WP) and water based newlineflowable (WBF) formulations and were tested for their efficacy against DBM under shade newlinehouse and field condition using cabbage as a test crop. In both shade house and field newlinecondition, Dipel recorded the highest mortality of insect larvae followed by HD1 WBF at newlinedouble the LC99 and UK-762D WBF at double the LC99. newline