DIVERSITY AND DISTRIBUTION OF FUNGAL ENDOPHYTES IN TWO AMAZONIAN HARDWOOD GENERA

Hevea brasiliensis (Euphorbiaceae) is the primary species for tapped natural rubber and an economically important crop since the 1870’s. Plantation-grown trees of H. brasiliensis are susceptible to numerous pathogens, some which are resistant to traditional chemical control. Fungal endophytes obtained from the wild are often considered ideal candidates for developing biological controls for pathogens, however little knowledge of the fungal endophytes associated with wild rubber and related hosts exists. The objectives of this study were the following: 1) determine the composition of the fungal endophyte communities associated with wild H. brasiliensis and its close relatives in Micrandra using cultures and culture-independent methods; 2) determine the species identities of endophytes in the genus Diaporthe associated with the two host genera; and 3) assess the overall utility of automated and manual methods for curating operational taxonomic unit (OTU) characterization of endophytes. To accomplish these objectives, fungal isolates and DNA from 381 seedlings and 144 adults of Hevea and Micrandra from three Amazon Peru locations were characterized using sequences from the internal transcribed spacer regions (ITS) of the ribosomal DNA repeat unit for both cultures and culture-independent samples, the latter using metagenomics methods. To determine the species identities of the Diaporthe isolates, four loci were analyzed using phylogenetic methods. A comparison of the effects of manual and automated operational taxonomic unit (OTU) classification was performed by using four different methods. Trichoderma species were most frequently identified from adult trees while Diaporthe species were the most abundant from seedlings, suggesting host developmental stage may be a key determinant of tropical endophytic community assemblage. Twenty-one distinct Diaporthe lineages were recovered with seven described as new species. Manual OTU curation methods were less error-prone suggesting that algorithm adjustments are needed for currently used automated methods. This study resulted in a greater understanding of the diversity of endophytes, particularly Diaporthe spp., associated with wild rubber. Knowledge of fungal diversity, host life stage associations, and spatial distribution of Hevea and Micrandra endophytes will provide additional tools for integrated disease management approaches and aid development of successful biocontrol methods

Ecological partnership: Restoring Pinyon woodlands on the Navajo Nation, USA

Pinyon woodlands in the semi-arid southwestern United States developed in response to environmental factors and historical human interactions, providing sustenance and traditional ecological benefits to Native Nations, such as the Navajo (Diné). Historically, Diné communities practiced land stewardship through seasonal movements and resource management, ensuring ecosystem resilience. However, the constraints imposed by European colonization led to transformative changes in their livelihoods and environments. Encompassing 71,000 km2, pinyon-juniper woodlands comprise 89 % of forested area on the Navajo Nation reservation, providing crucial ecosystem services and cultural resources. Since reservation establishment in 1868, increased tree density has diminished understory plant communities and elevated woodland susceptibility to wildfires, compromising overall forest health. Recognizing the imperative for ecological restoration, a collaborative effort between Diné College and Northern Arizona University (NAU) was established in 2018 to develop a pinyon woodland research site on the Diné College campus in Tsaile, Arizona, on the Navajo Nation reservation. We assessed the effectiveness of restoration thinning treatments in reinstating historical woodland structure, modifying fuels for fire mitigation, and engaging students in ecological practices. Thinning resulted in a 62 % reduction in tree density and a 25 % reduction in basal area, altering the woodland structure to reflect historical conditions more accurately. This alteration mitigated the risk of high-intensity wildfires while preserving the age structure of older trees (oldest dating back to 1435 C.E.). Forest floor fuels were low throughout the study, as thinned wood was removed, and activity fuels were immediately treated with chipping. The active participation of Diné College and NAU students, interns, and faculty throughout the study contributed to a cohesive approach in advancing our goals. The comprehensive training empowered students to contribute meaningfully to fieldwork and data collection, aligning with Diné College's mission to enhance post-secondary student learning and development for the benefit of the Diné. By integrating contemporary and culturally sensitive perspectives, our study sheds light on the effectiveness of restoration thinning treatments, emphasizing the delicate balance between ecological resilience and cultural preservation for the Navajo Nation

An Integrative View of the Phyllosphere Mycobiome of Native Rubber Trees in the Brazilian Amazon

The rubber tree, Hevea brasiliensis, is a neotropical Amazonian species. Despite its high economic value and fungi associated with native individuals, in its original area in Brazil, it has been scarcely investigated and only using culture-dependent methods. Herein, we integrated in silico approaches with novel field/experimental approaches and a case study of shotgun metagenomics and small RNA metatranscriptomics of an adult individual. Scientific literature, host fungus, and DNA databases are biased to fungal taxa, and are mainly related to rubber tree diseases and in non-native ecosystems. Metabarcoding retrieved specific phyllospheric core fungal communities of all individuals, adults, plantlets, and leaves of the same plant, unravelling hierarchical structured core mycobiomes. Basidiomycotan yeast-like fungi that display the potential to produce antifungal compounds and a complex of non-invasive ectophytic parasites (Sooty Blotch and Flyspeck fungi) co-occurred in all samples, encompassing the strictest core mycobiome. The case study of the same adult tree (previously studied using culture-dependent approach) analyzed by amplicon, shotgun metagenomics, and small RNA transcriptomics revealed a high relative abundance of insect parasite-pathogens, anaerobic fungi and a high expression of Trichoderma (a fungal genus long reported as dominant in healthy wild rubber trees), respectively. Altogether, our study unravels new and intriguing information/hypotheses of the foliar mycobiome of native H. brasiliensis, which may also occur in other native Amazonian trees