Effects of transgenic Cry1Ac+CpTI cotton on carboxylesterase activity in Helicoverpa armigera

In order to clarify changes in the carboxylesterase(CarEs) activity of Helicoverpa armigera(Hubner)feeding on transgenic cotton,and the recovery of carboxylesterase activity in H.armigera that fed on non-transgenic cotton after feeding on transgenic cotton for 1 to 3 days,transgenic and non transgenic cotton leaves were fed to some fourth-instar H.armigera larva for 5 days,after which some were fed with non-transgenic cotton leaves for a few days after feeding on transgenic cotton leaves for 1 day or 3 days.Midgut CarEs activity was examined every 24 hours.The results show that CarEs activity in H.armigera fed on non-transgenic cotton leaves increased over time,whereas that of H.armigera fed on transgenic cotton leaves first increased then decreased.The enzyme activity of cotton bollworms fed on non-transgenic cotton leaves after feeding on transgenic cotton leaves for one day decreased gradually over time,whereas that of those fed on non-transgenic cotton leaves after feeding on transgenic cotton leaves for three days remained higher than the control.These results indicate that CarEs activity in H.armigera can be induced by feeding on trangenetic cotton leaves and that this plays a role in the resistance of H.armigera to the Cry1Ac toxin.