Molecular characterization of Lepidopteran specific Bacillus thuringiensis strains isolated from Hilly Zone Soils of Karnataka, India

Abstract

Bacillus thuringiensis (Bt) strains pathogenic to Lepidopteran insects and native to hilly zone soils of Karnataka (India) were explored. 19 strains were isolated from the soils and identified by morphological and microscopic characters. Toxicity level of the Bt isolates was tested by treating third Instar larvae of silkworm (Bombyx mori L.) and mulberry leaf roller (Diaphania pulverulentalis). Mortality rate of the insect larvae treated with Bt isolates was ranged from 20 to 80%. A few isolates namely, Bt2, Bt6, Bt8, and Bt14 strains were more virulent (caused >50% death) than others. Detection of cry genes using cry gene specific primers by polymerase chain reaction (PCR) revealed the presence of at least one of the cry genes. In one of the isolates (Bt9), the cry gene was not detected. The Cry1Ac gene was abundant and it was detected in 13 isolates. Cluster analysis for genetic diversity showed two major groups and four sub groups.

Keywords: Molecular characterization, Bacillus thuringiensis, bioassay, genetic diversity, Cry genes, hilly zone

African Journal of Biotechnology Vol. 12(20), pp. 2924-2931