Characterization of a tea pest specific Bacillus thuringiensis and identification of its toxin by MALDI-TOF mass spectrometry

Tea, Camellia sinensis (L.) O'Kuntz is a cash crop, cultivated in tropical and subtropical climatic countries throughout the globe. The tea ecosystem hosts several species of arthropods, of them many species attack different parts of tea plants during their growth phases resulting in huge economical loses. Buzura suppressaria (Bs), Hyposidra talaca (HT), Hyposidra infixaria (HI) are members of order Lepidoptera, which are the most notorious tea pests, found in North-East India and make huge destruction of tea plantation due to their voracious eating habit and short life span. A potent indigenous strain of Bacillus thuringiensis (Bt) against the tea looper (TL) was isolated from Danguajhar Tea Garden, Goodricke Group Ltd. India, and characterized based on morphological, biochemical and genetic traits (16S rRNA gene NCBI GenBank Accession. No. JF966358). Virulence assay, to itemize the entomopathogenic nature of Bt against TL, was determined in laboratory and field conditions to enumerate its LC50 (1.11 x 10(7) spores/mL) and LT50 (54.64 h) values with a TL mortality rate of 99.43% in field. For large scale production, Bt was screened with four different mediums (based on barley, wheat, rice flour and nutrient broth) and was found to produce a maximum of 4.6 x 10(7) spores/mL, when barley was considered as a sole source of carbon. Highly expressive sporulation associated toxins was identified as an immune inhibitor A of Bt (NCBI Accession No.gi vertical bar 9858110 vertical bar AAG00998.1) by MALDI-TOF mass spectrometry which is an extra cellular bacterial protein known for putrefaction of host tissue proteins with a wide-range of substrate specificity. The results were quite encouraging which can be adapted as a greener way of pest control.