Genetic Similarities among Bacillus Thuringiensis Strains From Different Climatic Zones of Nepal

Abstract

Bacillus thuringiensis is a spore forming bacterium showing the unusual ability to produce endogenous crystals during sporulation that are toxic for some pest insects. This work was performed to study the composition, ecological distribution of biochemical types and genetic similarities among the isolates of this entomopathogenic bacterium from high altitude region (Tangboche, Khumbu region), and Terai region (Biratnagar). Using acetate selection methods to screen soil samples, 115 presumptive B. thuringiensis were isolated from 43 soil samples. Of these strains, 64% (74/115) were classified as B. thuringiensis on the basis of their crystal proteins visualized by microscopy. The percentages of samples with B. thuringiensis were 78.9 and 83.4 for the Khumbu region and Biratnagar respectively. The respective B. thuringiensis indexes were 0.7 and 0.61 for the regions. Of the total 64 B. thuringiensis isolates, 13.51% were novel, while rest of the isolates (86.49%) were identified upto subspecies level as evident by the defined biochemical typing. B. thuringiensis subspecies thuringiensis, indiana and type 16 were recovered from both high altitude and Terai region. Randomly amplified polymorphic DNA (RAPD)Polymerase Chain reaction (PCR) was used to study the genetic similarities. Based on the

RAPD patterns obtained with random primer, B. thuringiensis subspecies indiana isolates

from

Khumbu region showed more than 65% genetic similarities, whereas those from Biratnagar showed more diverse among the strains.

Key Words: Bacillus thuringiensis subspecies, RAPD-PCR, genetic similarity, Khumbu, Biratnagar.