Azotobacter inoculation can enhance the resistance of Bt cotton to cotton bollworm, Helicoverpa armigera.

The rising trend of cultivation of Bacillus thuringiensis (Bt) transgenic crops may cause a destabilization of agroecosystems, thus increasing concerns about the sustainability of Bt crops as a valid pest management method. Azotobacter can be a biological regulator to increase environmental suitability and ameliorate soil-nitrogen utilization efficiency of crops, especially Bt cotton. A laboratory test investigated the effects on development and food utilization of Helicoverpa armigera fed with different Cry1Ab/Cry1Ac protein expressions and nitrogen metabolism-related substances of cotton (transgenic Variety SCRC 37 vs. non-Bt cotton cv. Yu 2067) inoculated by Azospirillum brasilense (AB) and Azotobacter chroococcum (AC). The findings indicated that the inoculation of azotobacter significantly decreased the partial development and food utilization indexes (as pupal weight, pupation rate, adult longevity, fecundity, RGR, ECD and ECI) of H. armigera fed on Bt cotton, but contrary tendencies were found among these measured indexes of H. armigera fed on non-Bt cotton inoculated by azotobacter due to the different Bt toxin production. Overall results showed that the inoculation of azotobacter had negative effects on development and food utilization of H. armigera fed on Bt cotton, leading to enhance the target insect-resistance. Presumably, azotobacter inoculation can be used to stimulate plant soil-nitrogen uptake to increase the nitrogen metabolism-related substances and promote plant growth for Bt and non-Bt cotton, simultaneously raising Bt protein expression and enhancing resistance efficacy against cotton bollworm for Bt cotton. This article is protected by copyright. All rights reserved.