Journal of Pure and Applied MicrobiologyVol. 9 No. Special Edition Nov. 2015

Biocidal Activity of Bacillus thuringiensis on Plutella xylostella L.

Y. Srujana1, P.S. Hugar2 and P.U. Krishnaraj3

1Department of Agricultural Entomology, College of Agriculture, Dharwad, University of Agricultural Sciences, Dharwad-580 005, Karnataka, India. 2Senior Information Specialist, Directorate of Extension, University of Agricultural Sciences, Dharwad-580 005, Karnataka, India. 3Professor in Ag. Microbiology, college of Agriculture, Bijapur, University of Agricultural Sciences, Dharwad-580 005, Karnataka, India.

Received on 15 July 2015 and accepted on 26 September 2015

 

ABSTRACT

Fifty native Bacillus thuringiensis isolates of Dharwad were evaluated for their insecticidal activity against third instar larvae of Plutella xylostella. Toxicity of these isolates ranged from nill to 92.00 per cent. Most promising ones are DBT-388 (92.00%) and DBT-772 (86%) comparable with reference strain HD1 (84%). Crude protein extraction was done from DBT-388 and DBT-772 isolates along with HD-1. LC50 values were 1738, 2113 and 2427 ppm for DBT-388, DBT-772 and HD-1 respectively. Spore crystal complex count also taken from DBT-388 and HD-1 to calculate the International Unit (IU) /ml and to to find out its potency. DBT-388 and HD-1 had a count of 42,000 and 32,000 IU/ml, respectively when measured on P. xylostella. DBT-388 produced more spores than the HD-1. Effective isolates (mortality greater than 75%) were screened to know the spectrum of cry1, cry2, cry8, cry9 and cry20 genes present in them. cry1 gene was amplified in eleven isolates, cry2 in eight isolates whereas cry8 and cry9 in three and six isolates, respectively. cry20 was not amplified in any of the twelve isolates.

Keywords : Bacillus thuringiensis, Plutella xylostella, toxicity, LC50 values and cry genes.