ARS | Publication request: Resistance evolution to the first generation of genetically modified Diabrotica-active Bt-maize events by western corn rootworm: management and monitoring considerations

Submitted to: Transgenic Research
Publication Type: Review Article
Publication Acceptance Date: September 7, 2012
Publication Date: April 15, 2013
Citation: Devos, Y., Meihls, L.N., Kiss, J., Hibbard, B.E. 2013. Resistance evolution to the first generation of genetically modified Diabrotica-active Bt-maize events by western corn rootworm: management and monitoring considerations. Transgenic Research. 22:269-299.

Technical Abstract: Western corn rootworm (Diabrotica virgifera virgifera; WCR) is a major coleopteran maize pest in North America and the EU, and has traditionally been managed through crop rotation and broad-spectrum soil insecticides. Genetically modified (GM) Bt-maize offers an additional means of control against WCR and has been valuable in reducing insecticide use and increasing farm income. However, there is a concern that the widespread, repeated and exclusive deployment of the same Bt-maize will result in the rapid evolution of resistance in WCR. Field-selected resistance of WCR to Cry3Bb1 is documented in the USA, where an increasing number of cases of unexpected WCR damage to Bt-maize MON 88017 has been reported. This review paper explores the potential of WCR to evolve resistance to plant-produced Cry proteins, and what risk management strategies can be put in place to delay and monitor resistance evolution. In 12 of the 12 artificial selection experiments reported, resistant WCR populations were yielded rapidly under conditions of continuous exposure. Insect resistance management strategies to delay resistance evolution are optimal using a high dose/refuge (HDR) strategy. Evidence suggests that several conditions contributing to the success of the HDR strategy are not met for WCR and Bt-maize MON 863 & MON 88017, DAS-59122-7 and MIR604: (1) the Cry3Bb1, Cry34Ab1/35Ab1 and mCry3A proteins are expressed heterogeneously at a low-to-moderate dose in roots; (2) resistance alleles may be present at a higher frequency than initially assumed; (3) WCR may mate in a non-random manner; (4) resistance traits could have non-recessive inheritance; and (5) fitness costs are not necessarily associated with resistance evolution. Model predictions, however, indicate that a 20% refuge of non-Diabrotica-active Bt-maize can delay resistance evolution in WCR. Further research is needed to resolve the remaining scientific uncertainty related to the appropriateness of the HDR in delaying resistance evolution in WCR, and monitoring is recommended to check the adequacy and efficacy of the HDR strategy. The deployment of an integrated pest management approach reliant on multiple tactics is advocated to ensure effective long-term corn rootworm management and the sustainable use of Bt-maize.