Fungal endophytes are fungi that live part of their life cycles within plant tissues, without causing obvious negative effects on the plant. Endophytic fungi span the spectrum from latent pathogens to mutualists and may alter plant resistance to biotic and abiotic stressors. Most previous research has been on endophytes of crops rather than native plant species. Pinus ponderosa is the most widespread pine species in North America, but little is known about the composition of its fungal endophyte community. Our objective was to determine the diversity of P. ponderosa foliar fungal endophyte communities between different trees, between branches within a tree, and between needles of different ages. We selected three trees from a single location, five branches from each tree, and collected needles from 2015 and 2016 from each branch. Needles were surface sterilized and plated on culture media. After emergence, endophytes were distinguished by microscopy into distinct morphotypes. Mean number of fungal morphotypes per needle age was analyzed using a T-test. The frequency of each morphotype between branches within a tree, and between trees was compared using a chi-squared test.
A total of 22 fungal morphotypes were isolated from needle samples. Of these morphotypes, only eight were found on all three trees. Five were found exclusively in 2016 needles and eight were found exclusively in 2015 needles. There was not a significant difference in distribution of fungal morphotypes between branches within a tree. These results suggest that fungal endophyte community composition changes with needle age and that fungal endophyte communities can be distinct between trees, but are more uniform between branches within a tree. Future research should focus on how these endophyte communities affect P. ponderosa response to stress. Because many fungi are unable to be grown in culture, next generation sequencing technology should be incorporated to determine if patterns found in culturable endophyte communities are representative of overall community composition.