ORIGINAL PAPER Endophytic bacterial community living in roots of healthy and ‘Candidatus Phytoplasma mali’-infected apple (Malus domestica, Borkh.) trees Daniela Bulgari • Adem I. Bozkurt • Paola Casati • Kadriye C ¸ ag ˘layan • Fabio Quaglino • Piero A. Bianco Received: 5 April 2012 / Accepted: 14 June 2012 / Published online: 30 June 2012 Ó Springer Science+Business Media B.V. 2012 Abstract ‘Candidatus Phytoplasma mali’, the causal agent of apple proliferation (AP) disease, is a quaran- tine pathogen controlled by chemical treatments against insect vectors and eradication of diseased plants. In accordance with the European Community guidelines, novel strategies should be developed for sustainable management of plant diseases by using resistance inducers (e.g. endophytes). A basic point for the success of this approach is the study of endophytic bacteria associated with plants. In the present work, endophytic bacteria living in healthy and ‘Ca. Phy- toplasma mali’-infected apple trees were described by cultivation-dependent and independent methods. 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. Moreover, differences in OTUs number and in CFU/g suggested that phytoplasmas could modify the com- position of endophytic bacterial communities associ- ated with infected plants. Intriguingly, the combination of culturing methods and cloning analysis allowed the identification of endophytic bacteria (e.g. Bacillus, Pseudomonas, and Burkholderia) that have been reported as biocontrol agents. Future research will investigate the capability of these bacteria to control ‘Ca. Phytoplasma mali’ in order to develop sustainable approaches for managing AP. Keywords 16S rDNA Á Plant endophytes Á Apple proliferation Á Operational taxonomic units Introduction Phytoplasmas are obligate parasitic symbionts of plants and insects belonging to the class Mollicutes that are transmitted by phloem-feeding insects (IR- PCM Phytoplasma/Spiroplasma Working Team— Phytoplasma Taxonomy Group 2004). Apple prolif- eration (AP) is one of the most important phytoplasma diseases in Europe and it is associated with ‘Candid- atus Phytoplasma mali’, a quarantine pathogen. AP induces a broad range of symptoms such as witches’- brooms, rosettes, enlarged stipules, foliar reddening, growth suppression, and undersized fruits (Seemu ¨ller and Schneider 2004). Because of its economic impor- tance, scientific efforts are focused on the study of Electronic supplementary material The online version of this article (doi:10.1007/s10482-012-9766-3) contains supplementary material, which is available to authorized users. D. Bulgari Á P. Casati Á F. Quaglino Á P. A. Bianco (&) Dipartimento di Scienze Agrarie e Ambientali – Produzione, Territorio, Agroenergia, Universita ` degli Studi, via Celoria 2, 20133 Milan, Italy e-mail: piero.bianco@unimi.it A. I. Bozkurt Á K. C ¸ ag ˘layan Plant Protection Department, Mustafa Kemal University, 31034 Antakya, Hatay, Turkey 123 Antonie van Leeuwenhoek (2012) 102:677–687 DOI 10.1007/s10482-012-9766-3