LAUSR

Nematocidal properties of spore crystal mixtures of six Bacillus thuringiensis (Bt) strains (KAU 49, 50, 52, 61, 99 and 424) collected from Western Ghats, a biodiversity hot spot of India, were analysed against Haemonchus contortus larvae isolated from goats. One dose nematocidal assay dose response to lyophilised spore-crystal mixtures (SCM) of the six Bt strains were determined by adding 200 μg/mL of each SCMs to culture plate wells containing aqueous suspension of H. contortus larvae. Out of the strains screened, KAU 50 and 424 were found to possess nematocidal properties. Maximum nematocidal properties were exhibited 7 days post-inoculation of the lyophilised SCMs. The 50 per cent lethal concentrations deduced by log probit analysis for KAU 50 was found to be 130.59 μg/mL, whereas that of KAU 424 was found to be 144.536 μg/mL at 95 per cent confidence level. This is the first report on the nematocidal propery of Bt strains against Haemonchus contortus larvae isolated from goats. Further studies are needed for identification and characterisation of the toxin.