Forest Tree Microbiomes and Associated Fungal Endophytes: Functional Roles and Impact on Forest Health

Abstract

Terrestrial plants including forest trees are generally known to live in close association with microbial organisms. The inherent features of this close association can be commensalism, parasitism or mutualism. The term “microbiota” has been used to describe this ecological community of plant-associated pathogenic, mutualistic, endophytic and commensal microorganisms. Many of these microbiota inhabiting forest trees could have a potential impact on the health of, and disease progression in, forest biomes. Comparatively, studies on forest tree microbiomes and their roles in mutualism and disease lag far behind parallel work on crop and human microbiome projects. Very recently, our understanding of plant and tree microbiomes has been enriched due to novel technological advances using metabarcoding, metagenomics, metatranscriptomics and metaproteomics approaches. In addition, the availability of massive DNA databases (e.g., NCBI (USA), EMBL (Europe), DDBJ (Japan), UNITE (Estonia)) as well as powerful computational and bioinformatics tools has helped to facilitate data mining by researchers across diverse disciplines. Available data demonstrate that plant phyllosphere bacterial communities are dominated by members of only a few phyla (Proteobacteria, Actinobacteria, Bacteroidetes). In bulk forest soil, the dominant fungal group is Basidiomycota, whereas Ascomycota is the most prevalent group within plant tissues. The current challenge, however, is how to harness and link the acquired knowledge on microbiomes for translational forest management. Among tree-associated microorganisms, endophytic fungal biota are attracting a lot of attention for their beneficial health- and growth-promoting effects, and were preferentially discussed in this review.

Why Does Phlebiopsis gigantea not Always Inhibit Root and Butt Rot in Conifers?

“…Functional outcomes and community structure are largely unrelated to abiotic conditions, but taxonomic richness, evenness, and species associations (i.e., co-occurrence patterns) exhibit strong relationships with community function, which affects decomposition rates and fungal activity. A similar pattern was found by Terhonen et al [47], who studied the composition of tree endophytes. Accounting for wood traits, fungal species were much more likely to have positive than negative co-occurrence patterns and competitive exclusion was extremely rare, whereas positive interactions among fungal endophytes were more common than expected.…”

Tree Root Zone Microbiome: Exploring the Magnitude of Environmental Conditions and Host Tree Impact

“…High abundance of Proteobacteria was previously reported within numerous types of ecosystems, such as in grasslands (Singh et al, 2007), croplands (Tian and Gao, 2014), forest-grass ecosystems (Zeng et al, 2016), and natural hardwood forest soils (Lin et al, 2011). Ascomycota were reported dominant in soil fungal communities of semi-arid (Porras-Alfaro et al, 2011) and temperate (Prober et al, 2015;Chen et al, 2017) grasslands, oppositely to forest soils dominated by Basidiomycota (Goldmann et al, 2015;Terhonen et al, 2019).…”

Pathogens Associated to Kiwifruit Vine Decline in Italy

“…Moreover, KVDS plants showed a lower frequency of symbiotic fungal species. Indeed, woody plant decline is often not directly associated with single specific pathogens, but it is related to the dysbiosis of the plant-associated microbiome, resulting in an imbalance in the functions exerted by the microbial community [29,32].…”