Distinct bacterial communities associated with healthy and apple proliferation apple trees

Bacterial endophytes are plant-associated bacteria that affect the plant life cycles in different manners such as the nitrogen fixation or the biocontrol of plant pathogens. A basic point for the success of sustainable management of plant diseases based on biocontrol agents is the study of endophytic bacterial community associated with plants. In the present work, endophytic bacteria living in healthy and ‘Candidatus. Phytoplasma mali’-infected apple trees were described by cultivation-dependent and independent methods. Moreover, the isolates were tested for the production of indolacetic acid and siderophores, and the solubilization of phosphate. 16S rDNA sequence analysis showed the presence of the groups Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Chlamydiae, and Firmicutes. In detail, library analyses underscored 24 and 17 Operational Taxonomic Units (OTUs) in healthy and infected roots, respectively, with a dominance of Betaproteobacteria. Furthermore, differences in OTUs number and in CFU/g suggested that phytoplasmas could modify the composition of endophytic bacterial communities associated with infected plants. Intriguingly, the combination of culturing methods and cloning analysis allowed to identify endophytic bacteria (e.g. Bacillus, Pseudomonas, and Burkholderia) that have been reported as biocontrol agents. Future researches will investigate the capability of these bacteria to control ‘Ca. Phytoplasma mali’ in order to develop sustainable approaches for apple proliferation managing.