title: The strange case of a biofilm-forming strain of Pichia fermentans, which controls Monilinia brown rot on apple but is pathogenic on peach fruit.
abstract: A biofilm-forming strain of Pichia fermentans proved to be most effective in controlling brown rot on apple fruit when coinoculated into artificial wounds with a phytopathogenic isolate of Monilinia fructicola. Culture filtrates and autoclaved cells had no significant influence on the disease. When sprayed onto the apple fruit surface, this yeast formed a thin biofilm but failed to colonize the underlying tissues. When inoculated into wounds artificially inflicted to peach fruit or when sprayed onto the surface of peach fruit, the same strain showed an unexpected pathogenic behaviour, causing rapid decay of fruit tissues even in the absence of M. fructicola. Both optical and scanning electron microscopy were used to evaluate the pattern of fruit tissue colonization by P. fermentans. While on apple surface and within the apple wound the antagonist retained its yeast-like shape, colonization of peach fruit tissue was always characterized by a transition from budding growth to pseudohyphal growth. These results suggest that pseudohyphal growth plays a major role in governing the potential pathogenicity of P. fermentans, further emphasizing the importance of a thorough risk assessment for the safe use of any novel biocontrol agent.
authors.affiliation: Dipartimento di Protezione delle Piante - Center for Biotechnology Development and Biodiversity Research and Unità di ricerca Istituto Nazionale Biostrutture e Biosistemi, University of Sassari, Via E. De Nicola, Sassari, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Giobbe
authors.forename: Salvatore
authors.initials: S
authors.lastname: Marceddu
authors.forename: Barbara
authors.initials: B
authors.lastname: Scherm
authors.forename: Giacomo
authors.initials: G
authors.lastname: Zara
authors.forename: Vittorio L
authors.initials: VL
authors.lastname: Mazzarello
authors.forename: Marilena
authors.initials: M
authors.lastname: Budroni
authors.forename: Quirico
authors.initials: Q
authors.lastname: Migheli
mesh_terms: D000898:Antibiosis / Q000502:physiology*; D001203:Ascomycota / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology; D018441:Biofilms / Q000254:growth & development; D027845:Malus / Q000382:microbiology*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010843:Pichia / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology*; D027861:Prunus / Q000382:microbiology*