Mitigation and management of Cry1F resistance in European corn borer in Canada

自20世纪初首次发现欧洲玉米螟以来，玉米螟一直是北美玉米的经济害虫。ECB对玉米的取食危害会造成产量损失、掉穗、折茎和倒伏，影响收成。在引进表达苏云金芽孢杆菌杀虫蛋白的转基因玉米之前，整个北美地区ECB的管理和产生的产量损失估计超过13亿加元。自1996年首次引入以来，Bt玉米已被广泛用于欧洲央行的管理，2017年，加拿大85%的玉米英亩种植了Bt玉米。对Bt蛋白的抗性发展是对Bt玉米可持续利用的主要威胁；然而，在北美密集使用20多年后，ECB仍然对Bt毒素敏感。2018年，我们的研究团队在加拿大新斯科舍省的ECB内部发现了北美第一例实用的田间进化抗Bt玉米的案例。欧洲央行对Bt蛋白的抗性发展对Bt玉米在北美的持续成功具有广泛的影响。拟议研究的主要目标是减轻加拿大欧洲央行对Cry1F的抵抗力。要做到这一点，关键是要了解加拿大东部ECB的物候，表征在NS中发现的Cry1F抗性，确定当前抗Cry1F种群的分布，以及加拿大ECB对剩余Bt蛋白的敏感性，以实现可持续管理。这种情况也为评估行业主导的缓解Cry1F抗性的战略提供了机会，该战略通过将单一事件Bt玉米杂交种替换为用于欧洲央行控制的金字塔产品来缓解。最后，这一事件为评估当前加拿大Bt玉米抗虫性监测(IRM)策略的有效性提供了机会，并探索了利用分子技术改进IRM的潜在方法。

European corn borer (ECB; Ostrinia nubilalis) has been an economic pest of corn throughout North America since its first detection in the early 20th century. Feeding injury by ECB in corn results in yield loss, ear drop, stalk breakage, and lodging, impeding harvest. Management of ECB and incurred yield losses were estimated to exceed $1.3 billion CAD across North America before the introduction of genetically modified corn that expresses insecticidal proteins from the bacterium Bacillus thuringiensis (Bt corn). Since its first introduction in 1996, Bt corn has been widely adopted for ECB management and in 2017, 85% of corn acres in Canada were planted with Bt corn. Resistance development to Bt proteins is a major threat to the sustainable use of Bt corn; however, ECB remained susceptible to Bt toxins after more than 20 years of intensive use in North America. In 2018, our research team discovered the first case of practical field-evolved resistance to Bt corn in North America within ECB in Nova Scotia, Canada. The development of resistance to Bt protein by ECB has wide-ranging implications for the continued success of Bt corn in North America. The principal objective of the proposed research is to mitigate Cry1F resistance in ECB in Canada. To achieve this, it is critical to understand the phenology of ECB in Eastern Canada, characterize the Cry1F resistance discovered in NS, determine the current distribution of Cry1F-resistant populations, and the susceptibility of ECB in Canada to remaining Bt proteins for sustainable management. This situation also provides an opportunity to evaluate the industry-led strategy to mitigate Cry1F resistance by replacing single event Bt corn hybrids with pyramided products for ECB control. Lastly, this occurrence provides an opportunity to evaluate the efficacy of current insect resistance monitoring (IRM) strategies for Bt corn in Canada and to investigate potential ways to improve IRM using molecular techniques.