Characterizing the inheritance of resistance to the Bacillus thuringiensis Gpp34Ab1/Tpp35Ab1 insecticidal protein in western corn rootworm, Diabrotica virgifera virgifera LeConte

Yield losses and management costs for western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte, exceed approximately 2 billion dollars annually for corn producers in the US. Corn hybrids developed through genetic engineering produce insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt). Since 2003, several Bt insecticidal proteins are available in commercially released hybrids, which reduce root-feeding injury caused by WCR. One such plant-incorporated protectant (PIP), a Bt protein previously referred to as Cry34/35Ab1 but revised to Gpp34Ab1/Tpp35Ab1, was first registered with the Environmental Protection Agency (EPA) in 2005. Gassmann et al. (2016) published the first report of resistance to Gpp34Ab1/Tpp35Ab1 corn in a field-collected WCR population. In this study, our objective was to assess the inheritance of a field-derived Gpp34Ab1/Tpp35Ab1 resistance trait in WCR. Bioassays with larvae of Bt-susceptible, Gpp34Ab1/Tpp35Ab1-resistant, and heterozygous strains were conducted using seedling mats containing Gpp34Ab1/Tpp35Ab1 or non-Bt corn.  Data on survival to adulthood were collected and analyzed using a mixed model analysis of variance (ANOVA). Our data indicate that Gpp34Ab1/Tpp35Ab1 resistance in these strains is inherited in a non-recessive manner. These data on heritability of Gpp34Ab1/Tpp35Ab1 resistance in WCR are important for practical decision-making and use in modeling for insect resistance management (IRM). Utilizing IRM strategies to delay the spread of resistance traits in populations will remain essential to preserve current and future technologies for the management of insect pests.