MOLECULAR AND INSECTICIDAL CHARACTERISATION OF NOVEL CRY TOXINS FROM Bacillus thuringiensis AGAINST APHIDS
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Date
2019-11-07
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UNIVERSITY OF AGRICULTURAL SCIENCES, GKVK BENGALURU
Abstract
Aphids are the most damaging pests of plants. The present investigation lays
emphasis on isolation and identification of Aphidicidal Bacillus thuringiensis isolates.
600 Bacillus like isolates were obtained from different agro-ecological zones. The
isolates were obtained using standard enrichment technique as described by Travers et
al., (1987). A total of 65 Bacillus like colonies were screened, 15 putative Aphidicidal B.
thuringiensis isolates were identified based on morphological as well as through
microbiological studies including Transmission Electron Microscopy (TEM) & Scanning
Electron Microscopy (SEM). Spherical and amorphous crystal inclusion was
predominantly present in 34.28% of the Bt isolates when compared to other shapes.
Crystal protein profiling of Bt isolates by SDS-PAGE analysis showed the presence 130,
73, 34, 25 and 13 kDa bands, among which 50-66 kDa bands were present abundantly.
The detection of cry gene of these isolates was done by PCR analysis, indicated that cry1,
cry2A, cry3A and cry11A were on plasmid DNA. All cry genes were 80-100%
homologous when aligned on alignment tool NCBI-BLASTn. All isolates of Bt were
tested for their insecticidal activity against aphids. Bioassay results suggest that the Bt
toxins were responsible for the mortality of the exposed aphids and the observed physical
changes were induced by B. thuringiensis infection; these strains had been re-isolated
from the dead aphids, and the presented results fulfilled Koch’s postulates. The present
invention introduced the promising Bt isolates which could specifically create efficient
biocontrol agent for Aphids and in the near future other sucking pests