Scientists from the Chinese Academy of Agricultural Sciences and partners
conducted a study to investigate the performance of an insecticidal protein
that has the potential to be used in combating cotton pests. The result is
published in Transgenic Research.

The researchers developed a chimeric protein of Vip3Aa1 and Vip3Ac1, named
Vip3AcAa, which exhibits a broader insecticidal spectrum. Then in a more
recent study, they investigated the cross resistance and interactions
between Vip3AcAa and Cry1Ac with three strains of cotton bollworm, one that
is susceptible and two that are Cry1Ac-resistant, to determine if Vip3AcAa
can be pyramided with Cry1Ac protein in cotton.

Results showed that progression of insect resistance to Cry1Ac toxin did not
affect the sensitivity of Cry1Ac-resistant strains to Vip3AcAa. Mortality
was found to be comparable to the expected mortality for all the
combinations of Vip3AcAa and Cry1Ac tested, which indicate independent
activity between these two insecticidal proteins. When the vip3AcAa and
cry1Ac genes were both introduced into cotton, mortality rates of Cry1Ac
resistant bollworms (larvae) that fed on this new cotton increased
significantly compared with larvae fed on non-Bt cotton and cotton producing
only Cry1Ac.

Based on the findings, Vip3AcAa protein is a good choice for a "pyramid"
strategy for pest resistance management in cotton.

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