Isolation, Characterization and Development of Bacillus thuringiensis Formulations Against Diamond Back Moth (Plutella xylostella L.)
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Date
2011
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UAS Dharwad
Abstract
Total of 80 B. thuringiensis isolates were obtained from 396 samples collected
from the Western Ghats of Karnataka, out of which 44, 27 and 9 isolates were
obtained from the samples collected in Uttara Kannada, Dakshina Kannada and Udupi
districts respectively. All the isolates were subjected for morphological, biochemical
and molecular characterization. Sixty five per cent of the isolates showed spherical
type of crystals and only 3.75 per cent of the isolates had bipyramidal type of crystals.
All the 80 isolates showed positive reaction for nitrate reduction, catalase production,
voges-proskauer reaction and oxidase test, but all were negative for acid and gas
production from glucose, arginine hydrolysis, chitinase activity and esterase activity.
Rep-PCR fingerprinting of 80 isolates indicated that, the isolates grouped into two
major clusters having seven sub-clusters. Bioassay against third instar larvae of
Plutella xylostella showed 100 per cent mortality by the isolates UK-13C and UK-
762D. Efficacy of six different concentrations of crude protein of selected Bt isolates
against DBM showed the mortality ranged from zero to one hundred per cent. The
isolate UK-13C having LC50 value close to that of the reference strain HD1 and least
LC99 was recorded by UK-762D. Thirteen efficient isolates showed good growth in
presence of chemical pesticides Indoxacarb, Novaluron, Chlorofenapyr and Spinosad
and no growth in the presence of Thiodicarb, Profenofos, Captan and Mancozeb.
Three isolates and reference strain HD1 with least LC99 value were selected for
preparation of wettable powder (WP) and water based flowable (WBF) formulations
and were tested for their efficacy against DBM under shade house and field condition
using cabbage as a test crop. In both shade house and field condition, Dipel recorded
the highest mortality of insect larvae followed by HD1 WBF @ double the LC99 and
UK-762D WBF @ double the LC99.