Screening of fungal endophytes isolated from eastern white pine needles

Foliar endophytes of white pine were isolated from trees at a site in New Brunswick (Canada) and grown in liquid culture. Oxford disk bioassays of the resulting extracts against yeast showed that, of the 86 strains tested, 22 produced antifungal extracts. The resulting extracts were screened by LC-MS and showed variability in metabolite production, but the majority produced pyrenophorol and a number of related derivatives, all of which are known to be antifungal. DNA sequencing of these strains determined that the majority were Lophodermium nitens . A strain of white pine blister rust was isolated in liquid culture from young seedlings infected with the pathogen for toxicity testing. Bioassays performed with 5 μM pyrenophorol showed that it significantly reduced the cell dry weight of the pathogen compared to controls. These data support the hypothesis that pyrenophorolproducing L. nitens endophytes may increase the tolerance of the host tree to white pine blister rust