In vitro cultivation and biocontrol potential of Botryosphaeria visci against European mistletoe (Viscum album L.)

To improve the biological control of white mistletoe (European mistletoe) additional detailed information on Botryosphaeria visci infection, its basic nutritional requirements, growth, and in vitro growth characteristics is needed. The objectives of this study were to isolate and identify the fungus B. visci associated with Viscum аlbum from Sorbus aucuparia, to provide information on its in vitro introduction and growth characteristics on different media, and to test the pathogenicity of the isolated fungus. To achieve these goals, the morphology of conidiophores from infected parts of mistletoe was evaluated by microscopy. The isolate from fresh collections of V. album was identified as Sphaeropsis visci anamorph of ascomycete Botryosphaeria visci. The morphology of the vegetative mycelium and growth of B. visci varied depending on the media used. The best medium supporting growth and sporulation was oatmeal. Re-infection of European mistletoe in laboratory conditions showed positive result on liquid media, and in field conditions but only after mechanical damage to the mistletoe leaves. Our results expand the knowledge regarding the optimal cultivation of this fungus. This may facilitate further mycological and pathological studies involving B. visci isolates, and the results have a theoretical basis for the implementation of measures for the prevention and control of mistletoe.