RAPD-PCR characterization of Bacillus thuringiensis soil isolates from Mizoram with insecticidal activity against Culex tritaeniorhynchus

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Year 2012 Vol 1 Issue 3
Document Type : original article
¹Zothansanga Ralte1 ² G Gurusubramanian 2 ³ N Senthil Kumar 1
¹Department of Biotechnology1, Mizoram University, Aizawl, Mizoram - 796 004
²Department of Zoology2 ,, Mizoram University, Aizawl, Mizoram - 796 004
³Department of Biotechnology1, Mizoram University, Aizawl, Mizoram - 796 004
Abstract
Vector-borne diseases are one of the major public health problems in developing countries. Culex tritaeniorhynchus (Diptera: Culicidae) could be a vector of filariasis and West Nile encephalitis. The use of entomopathogenic bacteria like Bacillus thuringiensis (Bt) as larvicides is a viable alternative for the biological control mosquitoes with a low environmental impact. Hence, an attempt was made to explore the abundance of Bt in Mizoram soils from different habitats, testing their toxicity against C. tritaeniorhynchus and characterization by following acetate selection, mortality, dissimilarity analysis and RAPD-PCR assay methods.

In this present study, nine soil isolates (Mzubt 2,4,5,6,11,23,25,26 and 29) were identified, characterized and evaluated against C. tritaeniorhynchus. The new isolates were compared with two reference strains - Bt israelensis 4Q1 and Bt aizawai 4J3 obtained from Bacillus Genetic Stock Center, USA
The mzubt 2 and mzubt 6 isolates showed higher larvicidal activity than other isolates, against C. tritaeniorhynchus. RAPD-PCR assay has been optimized that discriminate Bacillus thuringiensis (Bt) isolates from nine different habitats soil covering five districts of Mizoram. All the studied isolates showed a diverse RAPD patterns and were different from each other in relation to habitats, toxicity and type of cry gene present. High polymorphism was observed between Bt isolates which was authenticated through high PIC, RP, EMR and MI values. Further, three major clusters were identified through dissimilarity analysis No relationship found between the type of cry gene in Bt and their toxicity against mosquitoes. The importance of the isolation of native strains of Bt in the mosquito management program in Mizoram is highlighted based on the findings.
Keywords
Bt isolates, toxicity, RAPD-PCR, dissimilarity analysis
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