Arable - Are chitin amendments to soil a means to control potato cyst nematodes?

摘要：植物寄生线虫每年给全球农业造成约800亿美元的损失，并威胁许多地区的粮食安全。马铃薯孢囊线虫(PCN)是一种寄生在茄科植物上的植物寄生线虫，主要危害马铃薯类作物。仅在英国，PCN每年造成的损失就超过3100万GB。从历史上看，PCN一直是通过使用杀线虫剂来管理的。然而，由于潜在的环境问题，这些化学品已受到严格监管。目前，英国市场上只剩下一种颗粒状杀线虫，随着2024年即将进行的法规审查，这一点的未来并不确定。苏格兰是马铃薯种子的主要生产国和出口国。目前的法规规定，如果在一块田里检测到PCN，那块地就不能再用于种薯了。PCN正在种子种植区蔓延，最近的预测表明，如果没有改进的PCN管理工具，这个行业将在2050年崩溃。甲壳素是一种丰富的生物分子，存在于昆虫、真菌和贝类中。甲壳素也存在于PCN蛋壳中，它通过为蛋壳提供刚性和抗拉强度来保护发育中的幼虫。几丁质土壤改良剂此前曾被提议用于控制植物寄生线虫。将甲壳素添加到土壤中可能有助于选择降解甲壳素的微生物种群，从而自然地提高这些微生物在该环境中的流行率。微生物随后可能利用土壤中已有的甲壳素来源，如PCN蛋壳，作为能源，允许将PCN数量抑制到不再对马铃薯作物构成威胁的水平。目前，我们不知道几丁质土壤改良剂是否适合苏格兰的生长条件，或者它们对有益的、含有甲壳素的土壤生物的影响。在这项工作中，我们将调查几丁质土壤改良剂是否控制了英国土壤中的PCN，以及这种控制是如何实现的。将收集使用或不使用几丁质土壤改良剂处理的田间地块的土壤样本。这些样本将用于鉴定不同真菌、细菌和自由生活线虫种群的存在，并量化PCN数量和甲壳素降解活性。通过比较处理和未处理的样本，可以了解PCN种群的变化，哪些微生物负责，以及是否对更广泛的土壤生物多样性产生负面影响。在受控温室环境中的测试将确认土壤改良剂中的甲壳素是否对通过蛋壳降解减少PCN种群具有积极作用，并将确认哪些微生物应对此负责。项目成果将包括确定使用或不使用富含甲壳素的土壤改良剂处理的田间样本中微生物和线虫种群的差异。对土壤样本中负责降解几丁质的几丁质酶的增加的分析将证实用于降解PCN蛋壳的途径。此外，对PCN蛋壳的结构研究将验证蛋壳是否被充分降解以防止PCN孵化。将在处理和未处理的样本中识别潜在有益的自由生活线虫种群，以调查以甲壳素为基础的土壤改良剂潜在的更广泛的杀线虫效果。

Summary:Plant parasitic nematodes cause an estimated $80 billion of annual damage to global agriculture and threaten food security in many regions. The potato cyst nematode (PCN) is a plant parasitic nematode that infects solanaceous species and causes significant damage, primarily to potato crops. In the UK alone, PCN causes more than £31 million in damage annually. Historically, PCN has been managed by using nematicides. However, due to potential environmental concerns, these chemicals have become tightly regulated. Currently there is only one granular nematicide left on the UK market and this has an uncertain future with an upcoming regulation review in 2024. Scotland is a large producer and exporter of seed potatoes. Current regulations state that if PCN has been detected in a field, that field can no longer be used for seed potato production. PCN is spreading in seed growing areas and recent predictions suggest that without improved PCN management tools this industry will collapse by 2050.Chitin is an abundant biomolecule which is found in insects, fungi and shellfish. Chitin is also present in PCN eggshells where it protects the developing juvenile by providing the eggshell with rigidity and tensile strength. Chitinous soil amendments have previously been proposed for control of plant parasitic nematodes. Addition of chitin to soils may help select for chitin-degrading microbial populations, naturally raising the prevalence of these organisms in that environment. The microbes may subsequently use sources of chitin already present in the soil, such as PCN eggshells, as an energy source, allowing the suppression of PCN numbers to a level where they are no longer a threat to the potato crop.We currently do not know if chitinous soil amendments are suitable for Scottish growing conditions or the impact they have on beneficial, chitin-containing, soil organisms. In this work we will investigate whether chitinous soil amendments control PCN in UK soils and how this control is achieved. Soil samples from field plots treated either with or without chitinous soil amendments will be collected. These samples will be used to identify the presence of different fungal, bacterial and free-living nematode populations and to quantify PCN numbers and chitin degrading activity. Comparing treated and untreated samples will allow understanding of changes in PCN populations, which microorganisms are responsible and if there is a negative impact on wider soil biodiversity. Testing in a controlled greenhouse environment will confirm whether the chitin within the soil amendment has a positive effect towards reducing PCN populations through eggshell degradation and will confirm which microorganisms are responsible.The project outcomes will include identifying differences in microbial and nematode populations in field samples treated with or without a chitin-rich soil amendment. Analysis of the increased presence of chitinase, the enzyme responsible for chitin degradation, in soil samples will confirm the pathway utilised to degrade PCN eggshells. Additionally, structural investigation of PCN eggshells will validate whether eggshells are degraded sufficiently to prevent PCN hatching. Populations of potentially beneficial free-living nematodes will be identified in treated and untreated samples to survey for potential wider nematocidal effects of chitin-based soil amendments.