Abstract
Western corn rootworm (WCR) is a major maize (Zea mays L.) pest leading to annual economic losses of more than 1 billion dollars in the United States. Transgenic maize expressing insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are widely used for the management of WCR. However, cultivation of Bt-expressing maize places intense selection pressure on pest populations to evolve resistance. Instances of resistance to Bt toxins have been reported in WCR. Developing genetic markers for resistance will help in characterizing the extent of existing issues, predicting where future field failures may occur, improving insect resistance management strategies, and in designing and sustainably implementing forthcoming WCR control products. Here, we discover and validate genetic markers in WCR that are associated with resistance to the Cry3Bb1 Bt toxin. A field-derived WCR population known to be resistant to the Cry3Bb1 Bt toxin was used to generate a genetic map and to identify a genomic region associated with Cry3Bb1 resistance. Our results indicate that resistance is inherited in a nearly recessive manner and associated with a single autosomal linkage group. Markers tightly linked with resistance were validated using WCR populations collected from Cry3Bb1 maize fields showing significant WCR damage from across the US Corn Belt. Two markers were found to be correlated with both diet (R2 = 0.14) and plant (R2 = 0.23) bioassays for resistance. These results will assist in assessing resistance risk for different WCR populations, and can be used to improve insect resistance management strategies.
Highlights
Western corn rootworm (WCR) is a major maize (Zea mays L.) pest leading to annual economic losses of more than 1 billion dollars in the United States
The western corn rootworm (WCR)—Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae)—is a major maize pest causing more than 1 billion dollars of economic losses annually (Gray et al 2009)
We develop a genotyping system and construct a genetic map for WCR, and use these tools to identify and validate genetic markers associated with Cry3Bb1 resistance among fieldcollected populations
Summary
Western corn rootworm (WCR) is a major maize (Zea mays L.) pest leading to annual economic losses of more than 1 billion dollars in the United States. Transgenic maize expressing insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are widely used for the management of WCR. Two markers were found to be correlated with both diet (R2 = 0.14) and plant (R2 = 0.23) bioassays for resistance These results will assist in assessing resistance risk for different WCR populations, and can be used to improve insect resistance management strategies. In 2003, transgenic maize expressing the Cry3Bb1 insecticidal protein from the bacterium Bacillus thuringiensis (Bt maize) was introduced to control WCR (Ward et al 2005). Field-evolved resistance to Bt maize was first reported in Iowa among WCR populations collected in 2009 from fields with a history of continuous cultivation of maize expressing the Cry3Bb1 Bt toxin (Gassmann et al 2011). Genetic markers can be used to predict where field failures may occur and in the design of future products for WCR control
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