Characterization and pathogenic evaluation of Bacillus thuringiensis isolates from West Azerbaijan province-Iran

In order to find native strains of Bacillus thuringiensis, toxic to some agricultural pests, a survey was conducted in West Azerbaijan province. B. thuringiensis strains were isolated using acetate selection method with different concentrations. The morphology of crystals was studied using light microscopy. Bioassay tests were conducted on Culex pipiens (L.) as well as Pieris brassica (L.). Biochemical tests performed to identify the isolated strains. Based on the results, 48 B. thuringiensis strains were isolated from 740 samples. The best acetate concentration was determined as 0.25M (56.25%). Soil samples were the main source of B. thuringiensis (66%). Majority of strains (58%) had bipyramidal crystals. There was significant difference in toxicity to insects among B. thuringiensis isolates, 18.74 and 35.41% of the isolates were toxic to larvae of C. pipiens and P. brassicae, respectively, causing more than 50% mortality. B. thuringiensis subsp. kurstaki was the most common biochemical type (12 isolates = 25%). Results indicated that B-t isolates with insecticide activity could be used in integrated pest management to control agricultural and medical pests.