The self-regulatory potential of agro-ecosystems: Using nematodes as indicators for legume disease suppressive soils

自1974年以来，豆科植物对根腐病的易感性在很大程度上导致了其在欧洲的生产面积下降。这影响了生物固氮作用以及农业生态系统的整体可持续性。由于农药在控制土壤传播疾病方面的作用有限，从长远来看，建立和维持抑制疾病的土壤更有希望。为了发展可持续农业系统，有必要确定从长远来看提高疾病抑制能力的方法。此外，需要确定可靠且易于应用的土壤抑制疾病的指标。在卡塞尔大学（2010年和2011年开始）的两个长期试验中，与犁耕（25-30 cm）结合矿质钾和磷施用相比，四年的最小耕作（<12 cm）结合堆肥施肥对豌豆根腐病病原体的抑制作用已经增强。此外，特定覆盖作物抑制植物寄生线虫。此外，少耕还增加了在病害抑制中起重要作用的自由生活线虫。然而，人们对利用自由生活的线虫营养类群作为土壤抑制疾病的指标知之甚少。在取得这些初步结果的五年后，卡塞尔大学的长期实验是研究土壤抑制疾病的发展和稳定性以及自由生活的线虫在疾病抑制中的作用的重要资源。我们假设。线虫的特定功能群与土壤的抑病性有关；少耕和堆肥提高了土壤的抗病性。覆盖作物培育特定的线虫功能群，从而抑制土壤病害。在工作包1 （WP1）中，将使用形态学和分子（NGS/OTUs）方法在长期实验的四种不同管理土壤中识别和量化自由生活的线虫。物种组成和丰度将与各自土壤的养分含量、微生物生物量和活性有关。在温室试验（WP2）中，将在豌豆上测试土壤对植物寄生线虫的特异性抑制作用，并将其与在WP1中鉴定的线虫功能基团的丰度联系起来。在WP3中，将测试土壤对土壤传播的豌豆真菌病原体的一般抑制作用，而在WP4中，将通过qPCR确定覆盖作物对与疾病抑制相关的线虫分类群（WP1-3）的影响。将使用多元统计方法分析土壤管理历史、土壤物理化学性质、特定和一般抑制性以及线虫功能群之间的相互关系，以便获得新的和易于应用的抑病土壤指标。

The susceptibility of legumes to root-rot diseases has massively contributed to the decline of their production area in Europe since 1974. This affects the biological nitrogen fixation as well as the overall sustainability of agroecosystems. As pesticides are of limited use to control soil-borne diseases, in the long term the build-up and maintenance of disease suppressive soils is much more promising. For the development of sustainable agricultural systems, there is a need to identify means by which to increase disease suppressiveness on the long run. Furthermore, robust and easy-to-apply indicators for disease suppressiveness of soils need to be identified.In two long-term experiments of the University of Kassel (since 2010 and 2011), soil suppressiveness to root-rot pathogens of pea was increased already after four years of minimum tillage (<12 cm depth) combined with compost fertilization compared to plough tillage (25-30 cm) combined with mineral potassium and phosphorous fertilization. In addition, specific cover crops suppressed plant-parasitic nematodes. Furthermore, free-living nematodes, which play an important role in disease suppression, were increased by minimum tillage. However, little is known about the use of free-living nematode trophic groups as indicators for disease suppressiveness of soils. Five years after these initial results, the long-term experiments at the University of Kassel are an important resource to investigate the development and stability of disease suppressiveness of soils as well as the role of free-living nematodes in disease suppression. We hypothesize that1. Specific nematode functional groups are linked with disease suppressiveness of soils;2. Minimum tillage and compost enhance disease suppressiveness of soils3. Cover crops foster specific nematode functional groups and thus, soil disease suppressiveness.In work package 1 (WP1), free-living nematodes will be identified and quantified in four differently managed soils of the long-term experiments applying morphological and molecular (NGS/OTUs) methods. Species composition and abundance will be related to nutrient contents as well as microbial biomass and activity of the respective soils. In a greenhouse experiment (WP2), specific suppressiveness of the soils against the plant-parasitic nematode Pratylenchus penetrans will be tested on peas and linked with abundances of nematode functional groups that were identified in WP1. In WP3, soils will be tested for their general suppressiveness against soil-borne fungal pea pathogens while the effects of cover crops on nematode taxa associated with disease suppression (WP1-3) will be determined via qPCR in WP4. Interrelationships of soil management histories, physico-chemical soil properties, specific and general suppressiveness, and nematode functional groups will be analysed using multivariate statistical approaches in order to obtain new and easy-to-apply indicators for disease suppressive soils.