A comparison of sensitivity to inhibitor among acetylcholinesterase (ache) molecular forms of resistant and susceptible strains in helicoverpa armigera*

Abstract The sensitivity of 2.8s and 8.7s acetylcholinesterase (AChE) to eserine sulfate is significantly lower in resistant (R) strain than in susceptible (S) strain in five AChE forms isolated by sucrose gradient centrifugation from cotton bollworm, Helicoverpa armigera. There are 186 and 85 times of difference in heads of adults and 10¹⁰ and 10⁵ times of difference in heads of larvae based on a comparison of I₅₀ values for 2.8s and 8.7s forms respectively. The sensitivity of 5.3s form of AChE to eserine sulfate shows 123 times of difference between R and S strains in larvae, however no difference in adults. The above results indicate that insensitive 2.8s, 8.7s and 5.3s forms of AChE may play an important role in the resistance of cotton boll-worm to organophosphate and carbamate insecticides.