Köhl Jürgen, Kolnaar Rogier, Ravensberg Willem J
Wageningen Plant Research, Wageningen University & Research, Wageningen, Netherlands.
Linge Agroconsultancy B.V., Oosterhout, Netherlands.
Front Plant Sci. 2019 Jul 19;10:845. doi: 10.3389/fpls.2019.00845. eCollection 2019.
Microbial biological control agents (MBCAs) are applied to crops for biological control of plant pathogens where they act via a range of modes of action. Some MBCAs interact with plants by inducing resistance or priming plants without any direct interaction with the targeted pathogen. Other MBCAs act via nutrient competition or other mechanisms modulating the growth conditions for the pathogen. Antagonists acting through hyperparasitism and antibiosis are directly interfering with the pathogen. Such interactions are highly regulated cascades of metabolic events, often combining different modes of action. Compounds involved such as signaling compounds, enzymes and other interfering metabolites are produced at low concentrations during interaction. The potential of microorganisms to produce such a compound does not necessarily correlate with their antagonism. Understanding the mode of action of MBCAs is essential to achieve optimum disease control. Also understanding the mode of action is important to be able to characterize possible risks for humans or the environment and risks for resistance development against the MBCA. Preferences for certain modes of action for an envisaged application of a MBCA also have impact on the screening methods used to select new microbials. Screening of MBCAs in bioassays on plants or plant tissues has the advantage that MBCAs with multiple modes of action and their combinations potentially can be detected whereas simplified assays on nutrient media strongly bias the selection toward production of antimicrobial metabolites which may not be responsible for antagonism. Risks assessments for MBCAs are relevant if they contain antimicrobial metabolites at effective concentration in the product. However, in most cases antimicrobial metabolites are produced by antagonists directly on the spot where the targeted organism is harmful. Such ubiquitous metabolites involved in natural, complex, highly regulated interactions between microbial cells and/or plants are not relevant for risk assessments. Currently, risks of microbial metabolites involved in antagonistic modes of action are often assessed similar to assessments of single molecule fungicides. The nature of the mode of action of antagonists requires a rethinking of data requirements for the registration of MBCAs.
微生物生物防治剂（MBCAs）被应用于农作物，用于对植物病原体进行生物防治，它们通过一系列作用方式发挥作用。一些MBCAs通过诱导植物抗性或引发植物反应来与植物相互作用，而无需与目标病原体进行任何直接相互作用。其他MBCAs则通过营养竞争或其他调节病原体生长条件的机制发挥作用。通过超寄生和抗生作用的拮抗剂直接干扰病原体。这种相互作用是高度调控的代谢事件级联，通常结合了不同的作用方式。在相互作用过程中，所涉及的化合物如信号化合物、酶和其他干扰性代谢产物以低浓度产生。微生物产生此类化合物的潜力并不一定与其拮抗作用相关。了解MBCAs的作用方式对于实现最佳病害防治至关重要。同样，了解其作用方式对于能够确定对人类或环境的潜在风险以及对MBCAs产生抗性的风险也很重要。对于MBCA的设想应用而言，对某些作用方式的偏好也会影响用于筛选新微生物的方法。在植物或植物组织上进行生物测定来筛选MBCAs具有这样的优势，即具有多种作用方式及其组合的MBCAs有可能被检测到，而在营养培养基上进行的简化测定则强烈偏向于选择产生抗菌代谢产物的微生物，而这些代谢产物可能与拮抗作用无关。如果MBCAs在产品中含有有效浓度的抗菌代谢产物，则对其进行风险评估是有必要的。然而，在大多数情况下，抗菌代谢产物是由拮抗剂直接在目标生物体有害的现场产生的。这些参与微生物细胞和/或植物之间自然、复杂、高度调控相互作用的普遍存在的代谢产物与风险评估无关。目前，参与拮抗作用方式的微生物代谢产物的风险评估通常类似于对单分子杀菌剂的评估。拮抗剂作用方式的性质需要重新思考MBCAs登记的数据要求。
