Evaluation of insecticidal activity of bacillus thuringiensis isolates S6 and cloning of cry1C gene in escherichia coli
Loading...
Date
2007
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
CCSHAU
Abstract
The increased public concerns of the potential adverse environmental effects
of the extensive use of chemical insecticides, together with slow momentum of discovering
second and third generation insecticides, has stimulated research worldover to screen native Bt
population its bioefficacy against target insect pests. During the present investigation, studies
were under taken to optimize conditions for production of biomass of Bt S6 using low cost
substrates. Experiments were conducted to evaluate its bioefficacy against Helicoverpa
armigera under field conditions. Attempts were also made to clone cry 1C of isolate S6 in
E.coil.
To reduce the cost of production medium, agro-byproducts can be used as the major
ingredients for large scale production of B. thuringiensis biomass. Maximum biomass of Bt S6
(cfu) was produced when potato extract at a concentration of 13 % was used as carbon source.
Although tryptone and peptone were found to be best nitrogen sources but because of high cost
other low cost nitrogen sources were evaluated for biomass production. It was observed that
cotton seed meal at 0.75 % level could be used for Bt S6 biomass production (7x109). The Bt
S6 biomass produced in OPM was comparable to standard LB medium. B. thuringiensis isolate
S6 at 1x109 cells/ml showed maximum insect mortality of 95-100 % against H .armigera
under laboratory conditions after 96 h of treatment. However, under field conditions, insect
mortality of about 76 % was observed in cotton when Bt culture was used at a concentration of
1x109 cells/ml. At lower cell concentration (1x108 cells/ml), insect mortality of about 73%
was observed in cotton. The Optimum temperature for biomass production was found to be
350c. There was a significant decrease in the biomass production with increase or decrease in
temp. The optimum pH of the medium for biomass production was found to be 6.00.
To detect the presence of cry1C gene in Bt isolate S6, total genomic DNA was
amplified by PCR using cry 1C gene specific primers. The PCR product of 1.5 kb size was
amplified by using S6 DNA as template and cloned in E.coli. Four plasmid DNA samples out
of 8 showed amplification with cry1C specific primers. However, the size of cry 1C gene is
about 3.8 kb, suggesting that the cry 1C insert is a partial clone only.
Description
Keywords
Inorganic acid salts, Zinc, Fruits, Boron, Planting, Vegetables, Yields, Biological development, Chlorophylls, Developmental stages