Growth compensation and faster development of Colorado potato beetle (Coleoptera : Chrysomelidae) feeding on potato foliage expressing oryzacystatin I

Feeding, growth, development, and food conversion efficiency of Colorado po tato beetle larvae reared on foliage from a "Kennebec" potato line expressi ng oryzacystatin I (OCI) at about 1% of its total soluble proteins were com pared to those of larvae feeding on untransformed foliage from the same lin e. During stages L1 to L3, larvae feeding on OCI consumed leaf material 14% faster, gained weight 28% faster, and weighed 20% more at the end of the L 3 stage, compared to controls. Continued exceptional performance on OCI dur ing the final L4 stage was expressed as faster development than controls, a n effect that persisted during pupal development and resulted in emergence of similar weight adults 1 day earlier than controls. Larvae initially main tained on control foliage and switched to OCI foliage during L4 did not ove rcompensate as those on OCI foliage throughout development, but performed s imilarly to larvae on control foliage throughout. Total azocaseinase activi ty in midgut extracts from these 4th instars 1 d after switching to OCI fol iage was sensitive to inhibition by a recombinant form of OCI expressed in Escherichia coli, but was no longer sensitive 4 d after switching, indicati ng a gradual adaptation of the insect digestive protease system, based on t he production of OCI insensitive proteases. Despite OCI potato foliage bein g consumed faster by small larvae using it for food, there was no indicatio n that it was less efficient than untransformed foliage as food protein. (C ) 1999 Wiley-Liss, Inc.