Fitness costs and inheritance of Cry2Ab2 resistance in Spodoptera frugiperda (JE Smith)

Cry2Ab2 is a Bacillus thuringiensis (Bt) protein expressed in transgenic corn and cotton targeting above-ground lepidopteran pests including the fall armyworm, Spodoptera frugiperda (J.E. Smith). The objective of this study was to characterize fitness costs and inheritance of Cry2Ab2 resistance in S. frugiperda. To determine if fitness costs were associated with the resistance, life history parameters (larval survival, growth, development and egg production) of Cry2Ab2-resistant,-susceptible, and two reciprocal Fl colonies of S. frugiperda were assayed on non-toxic diet and non-Bt corn leaf tissue. The results showed that there were no significant differences among the four insect colonies for all the biological parameters measured with few exceptions, suggesting that the resistance in the colony was not associated with significant fitness costs in the test conditions. To examine the inheritance of resistance, susceptibilities of the resistant and susceptible parents, as well as eight additional colonies generated from various genetic crosses, were assayed using Cry2Ab2-treated diet and Cry2Ab2 corn leaf tissue. The Cry2Ab2 resistance in S. frugiperda in the colony was inherited as a single autosomal recessive or incompletely recessive gene. The results of the study suggest a potential risk of resistance development in S. frugiperda to the Cry2Ab2 protein and thus effective management strategies should be implemented for the sustainable use of the Bt corn technology for pest management.