Multifunctional properties of Bacillus thuringiensis bacteria strains and a new approach in struggle with a cotton bollworm

Abstract

1. thuringiensis (Bt) strains showed 40.0 to 83.3% insecticidal activity against to cotton bollworm Helicoverpa armigera. High insecticidal activity occurred mainly on seventh day of experiment. When grown in medium containing different concentrations of NaCl, it was found that Bt1 and Bt31 strains were tolerant upto 600 mM, and 800 mM NaCl, respectively, while the rest were tolerant up to 1000 mM NaCl. All of B. thuringiensis strains synthesize gibberellic acid (GA). On the 1st day of the growth dynamics, the amount of GA synthesized was from 1.05 mg / l to 1.8 mg / l, on the third day of cultivation, the lowest (4.8 mg / l) and the highest (8 , 5 mg / l) GA synthesis was observed in the strains Bt31 and Bt26, respectively. In the first year of treatment with B. thuringiensis 94 strain against cotton bollworm, the biological efficiency was 20.8%, while the treatment before seeding in the second year led to 34.4% biological efficiency. Cotton yield increased by 2.4% compared to the control.