The western corn rootworm (WCR) decimates maize crops worldwide. One potential way to control this pest is treatment with entomopathogenic nematodes (EPNs) that harbor bacterial symbionts that are pathogenic to insects. However, WCR larvae sequester benzoxazinoid secondary metabolites that are produced by maize and use them to increase their resistance to the nematodes and their symbionts. Here we report that experimental evolution and selection for bacterial symbionts that are resistant to benzoxazinoids improve the ability of a nematode–symbiont pair to kill WCR larvae. We isolated five Photorhabdus symbionts from different nematodes and increased their benzoxazinoid resistance through experimental evolution. Benzoxazinoid resistance evolved through multiple mechanisms, including a mutation in the aquaporin-like channel gene aqpZ. We reintroduced benzoxazinoid-resistant Photorhabdus strains into their original EPN hosts and identified one nematode–symbiont pair that was able to kill benzoxazinoid-sequestering WCR larvae more efficiently. Our results suggest that modification of bacterial symbionts might provide a generalizable strategy to improve biocontrol of agricultural pests.

西部玉米根虫 (WCR) 摧毁了全世界的玉米作物。控制这种害虫的一种潜在方法是用含有对昆虫致病的细菌共生体的昆虫病原线虫 (EPN) 进行处理。然而，WCR 幼虫会隔离由玉米产生的苯并恶嗪类次级代谢物，并使用它们来增加它们对线虫及其共生体的抵抗力。在这里，我们报告了对苯并恶嗪类具有抗性的细菌共生体的实验进化和选择提高了线虫-共生体对杀死 WCR 幼虫的能力。我们分离出五个Photorhabdus来自不同线虫的共生体，并通过实验进化增加了它们对苯并恶嗪类的抗性。苯并恶嗪类耐药性通过多种机制演变，包括水通道蛋白样通道基因aqpZ的突变。我们将耐苯并恶嗪类的Photorhabdus菌株重新引入其原始 EPN 宿主，并确定了一对能够更有效地杀死苯并恶嗪类螯合 WCR 幼虫的线虫-共生体对。我们的研究结果表明，细菌共生体的修饰可能为改善农业害虫的生物防治提供一种普遍的策略。