First report of fungal endophyte communities and non-defensive phytochemistry of biocontrol-inoculated whitebark pine seedlings in a restoration planting

Plant-associated endophyte communities influence plant health and vary with host plant genetics. Evidence suggests that microfungi of plant interiors (i.e. endophytes) vary with host genetics due to genetic variation in plant defense phytochemistry. We examined correlations between fungal endophyte communities, the application of an endophytic fungal inoculum, and non-defensive phytochemistry of six-year-old seedlings of whitebark pine (<i>Pinus albicaulis</i>) in a field trial using a culture-free approach. Fungal communities in whitebark pine foliage were investigated four years after an experimental inoculation of seedlings with <i>Myrothecium roridum</i>, an endophytic fungus hypothesized to modify host microbiomes and potentially defend against white pine blister rust. Foliar fungal endophyte richness, Shannon diversity, and endophyte community composition varied across genetic maternal trees, although these effects were potentially confounded with spatial location. Foliar carbon and nitrogen isotopes, and carbohydrate composition were each unassociated with endophytic diversity or community composition after controlling for spatial effects. Endophytic communities did not vary with the inoculation treatment, nor was the inoculant detected systemically in inoculated seedlings. We draw two conclusions from this work: (1) fungal microbiomes of whitebark pine seedlings across our study site did not vary with host phytochemistry indicative of ecophysiological status, (2) the inoculation of <i>P. albicaulis</i> seedlings with <i>M. roridum</i> did not lead to persistent systemic changes in seedling foliar microbiomes.<br>