Updated project metadata. The lower needs for chemical fertilisers make the Pisum Sativum well suited for sustainable agricultural systems. During the past decades, yield losses were mainly due to pathogenic infestation, with Ascochyta blight as the most severe disease. In this fungal disease complex Didymella pinodes, as the most aggressive pathogen, has been examined intensively. Despite the great number of varieties, no resistance was yet found and several strategies were developed to avoid infestation. In recent years enhanced resistance to pathogens due to previous infestation by symbiotic microorganisms was discovered in several plants. However, only little attention was drawn on the implications of P. Sativum´s symbionts (Rhizobia, Mycorrhiza) on the disease severity as well as the effects of the pathogen on the symbiotic interactions. Hence, here the implications of the pathogenic infestation on the tripartite symbiosis of P. Sativum on a molecular (proteomics, metabolomics) and physiological level, and moreover, the potential of the root symbionts to enhance resistance against Didymella pinodes are investigated.