Does cotton bollworm show cross-resistance to the Bacillus thuringiensis toxins Cry1Ac and Cry2Ab? A mini review

Abstract

Since 1996, transgenic Bacillus thuringiensis (Bt) cotton has been commercially grown in numerous countries in an effort to stem the losses caused by key lepidopteran pests. However, the development of pest resistance to Bt toxins has jeopardized the continued utilization of Bt cotton. As a strategy designed to circumvent the development of resistance, Bt cotton varieties expressing two or more toxins targeting the same pest have been introduced. Nevertheless, from the perspective of long-term planting of Bt cotton, the potential risk of cross-resistance to these Bt toxins is a threat that cannot be ignored. In this paper, we review current research (including that based on the analysis of protein binding sites and resistance genes) on the resistance of cotton bollworm (Helicoverpa armigera) to the Bt toxins Cry1Ac and Cry2Ab and the interrelationship between these toxins. On the basis of existing evidence, we assume that the actions of Cry1Ac and Cry2Ab against cotton bollworm are not completely independent, and then propose the ''resistance-associated gene mutation potential hypothesis''. Although the mechanisms underlying the resistance of pests to Bt toxins are yet to be comprehensively elucidated, this hypothesis could undoubtedly have important implications for adopting ''pyramid'' strategy in the future. Further research is recommended to devise strategies to retard the development of H. armigera resistance to Bt cotton, either using different Bt toxins or their various combinations.

Effect of Urea Spray on Boll Shell Insecticidal Protein Content in Bt Cotton

“…Bacillus thuringiensis transgenic cotton (Bt cotton) is the cotton cultivar with insect resistance, which is obtained by transferring Bt toxin gene from B. thuringiensis into cotton (Ma et al, 2020). In the whole process of growth and development of Bt cotton, all tissues and organs can express insecticidal protein, which can effectively reduce the harm of cotton bollworm and other related pests (Chen et al, 2005(Chen et al, , 2018Zhang et al, 2019;Zhou et al, 2019).…”