Microscopic evidence of Nectriaceae and other microbes in infected fine root tissue of replant diseased apple plants

felder Sämling' showing symptoms of apple replant disease (ARD) were histologically examined to clarify the relationships of microbial endophytes to tisin Northern Germany or cultivated in greenhouse these three locations.Based on the previous microscopic detection of characteristic ARD symptoms in whole roots, thin sections of selected root segments crosis and blackening and for microbial colonization with a focus on fungi and Actinobacteria.Nectriaceae ing cell necrosis in cortical tissue were frequently present in all tested root samples of ARD-affected tatives of and Rugonectria.In this work, their cellular infection, intracellular development as well as plant reactions to this attack were clearly demonstrated by series of thin sections.shaped and coccoid bacteria and the colonization of mycorrhizal fungi revealed new insights into early stages of ARD development in root tissue.Other fungi and Oomycetes, which differ in their hyphal structure, in propagules or in their spread from Nectriaceae and arbuscular mycorrhizal fungi, were only rarely those gained from biotest plants and emphasize the importance of Nectriaceae and Actinobacteria in further research on the etiology of ARD and in developing counter-measures.