Laboratory of Functional Ecology, University of Neuchâtel, Rue Emile-Argand 11, 2000, Neuchâtel, Switzerland.
Institute of Environmental Processes and Pollution Control, School of Environmental and Civil Engineering, Jiangnan University, Wuxi, 214122, China.
Sci Rep. 2020 Dec 4;10(1):21316. doi: 10.1038/s41598-020-78307-0.
Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climate-controlled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity.
昆虫病原线虫 (EPNs) 已被广泛研究作为防治根食性作物害虫的潜在生物防治剂。已发现受到根虫攻击的玉米根会释放挥发性有机化合物，如 (E)-β-石竹烯 (Eβc)，它可引导 EPNs 找到对玉米有害的幼虫。然而，目前尚不清楚地下生态工程师（如蚯蚓）如何通过改变根 Eβc 介导的三营养级相互作用来影响 EPNs 的生物防治能力。我们在这里想知道，蚯蚓的存在是否以及如何影响 EPNs 发现甜菜夜蛾幼虫的能力。首先，我们在两个不同的耕作系统中进行了田间中尺度实验，结果表明蚯蚓的存在增加了玉米根附近幼虫的 EPN 感染潜力。随后，我们使用气候控制的、基于嗅觉计的生物测定法，证实 EPN 对单独释放的 Eβc（从分配器中释放）的反应在蚯蚓耕作土壤中比在无蚯蚓土壤中高两倍。总之，我们的研究结果表明，内生蚯蚓通过挖掘和筑巢活动，不仅以改善土壤肥力的方式改变土壤性质，还可能增强 EPNs 对根食性害虫的生物防治潜力。为了在农田中实现生态上合理的害虫减少，我们提倡有利于蚯蚓群落结构和多样性的农业实践。
