title: Fungal endophytes of the obligate parasitic dwarf mistletoe Arceuthobium americanum (Santalaceae) act antagonistically in vitro against the native fungal pathogen Cladosporium (Davidiellaceae) of their host.
abstract: OBJECTIVE
  Endophytic fungi likely occur in all plants, yet little is known about those of parasitic plants, despite their potential to influence parasite success. Arceuthobium americanum is a parasitic angiosperm that greatly compromises the North American timber industry. We hypothesized that (1) A. americanum hosts fungal endophytes, and (2) these endophytes help A. americanum resist infection by fungal pathogens. •
  
  
  METHODS
  Healthy A. americanum stem and fruit tissues were differentially stained for cellulose and chitin and visualized using fluorescence microscopy. Stem sections (sterilized vs. unsterilized) and seeds were incubated on agar plates to cultivate fungi, both to extract DNA for ITS rDNA sequencing and to observe interactions with native fungi from unsterilized specimens. •
  
  
  RESULTS
  Aside from xylem vessel elements, fungal structures were observed in all tissues, including those of the embryo. The ITS sequences of fungi cultured from internal tissues closely matched those of the known endophytes Phoma, Sydowia, and Phacidiopycnis, while those of surface organisms closely matched Cladosporium spp. Cultured fungi from internal tissues (putative endophytes) inhibited the growth of the surface organisms without affecting the other endophytes. •
  
  
  CONCLUSIONS
  Fungal communities are established in A. americanum stems as well as in fruits and seeds, suggesting vertical transmission. These internally derived fungi act antagonistically toward fungi with pathogenic tendencies. As such, native mistletoe endophytes might protect A. americanum against fungal pathogens in nature. In the future, manipulation of endophytes might be a component of mistletoe control programs.
authors.affiliation: Department of Biological Sciences, Thompson Rivers University, 900 McGill Road, Kamloops, British Columbia, Canada.
authors.forename: Lyssa L
authors.initials: LL
authors.lastname: Martin
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Ross Friedman
authors.forename: Lori A
authors.initials: LA
authors.lastname: Phillips
mesh_terms: D001955:British Columbia; D002963:Cladosporium / Q000145:classification / Q000235:genetics* / Q000254:growth & development*; D004271:DNA, Fungal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D060026:Endophytes / Q000145:classification / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D028163:Viscaceae / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer