title: Interactions between 'Candidatus Phytoplasma mali' and the apple endophyte Epicoccum nigrum in Catharanthus roseus plants.
abstract: OBJECTIVE
  We investigated the ultrastructural and molecular interactions between 'Candidatus Phytoplasma mali' and the apple endophyte Epicoccum nigrum in the experimental host Catharanthus roseus to determine whether inoculation of endophyte could trigger defence reactions in the host.
  
  
  RESULTS
  Apple proliferation (AP) symptom severity was evaluated in AP-grafted plants that were treated by E. nigrum and compared with untreated controls. Phytoplasma concentration was quantified by real-time PCR in treated and untreated plants. Ultrastructural observations revealed that in endophyte-treated periwinkles, modifications to phytoplasmas, such as irregular shape and cytoplasm confined to the periphery of the cell, and plant cytological changes, such as abundant callose depositions and P-protein aggregations in the sieve elements, occurred. AP-grafted plants that were treated by the endophyte (E. nigrum) showed a reduction in symptom severity; in particular, flowers appeared normal in shape and size, when compared with uninfected controls. Real-time PCR indicated that phytoplasma concentration in AP-grafted plants treated with E. nigrum was about 2·8 times lower than that in untreated ones.
  
  
  CONCLUSIONS
  These results demonstrated that the inoculation with E. nigrum influenced phytoplasma infection in C. roseus plants; plant ultrastructural modifications allowed us to hypothesize an enhancing host defence response.
  
  
  CONCLUSIONS
  At present, curative protocols against this phytoplasma are not available. Alternative approaches are thus required to reduce disease spread. Our study might represent a first step in the clarification of plant-phytoplasma-endophyte relationships to find possible strategies for the control of phytoplasma diseases.
authors.affiliation: Dipartimento di Biologia e Protezione delle Piante, Università di Udine, Udine, Italy. rita.musetti@uniud.it
authors.forename: R
authors.initials: R
authors.lastname: Musetti
authors.forename: S
authors.initials: S
authors.lastname: Grisan
authors.forename: R
authors.initials: R
authors.lastname: Polizzotto
authors.forename: M
authors.initials: M
authors.lastname: Martini
authors.forename: C
authors.initials: C
authors.lastname: Paduano
authors.forename: R
authors.initials: R
authors.lastname: Osler
mesh_terms: D001203:Ascomycota / Q000502:physiology*; D030008:Catharanthus / Q000382:microbiology*; D027845:Malus / Q000382:microbiology; D045582:Phytoplasma / Q000235:genetics / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology / Q000648:ultrastructure; D016133:Polymerase Chain Reaction