Arbuscular Mycorrhizal Fungi Taxa Show Variable Patterns of Micro-Scale Dispersal in Prairie Restorations

Uncovering Diversity within the Glomeromycota: Novel Clades, Family Distributions, and Land Use Sensitivity

Arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) are essential to plant community diversity and ecosystem functioning. However, increasing human land use represents a major threat to native AMF globally. Characterizing the loss of AMF diversity remains challenging because many taxa are undescribed, resulting in poor documentation of their biogeography and family-level disturbance sensitivity. We survey sites representing native and human-altered ecosystems across the American continents-in Alaska, Kansas, and Brazil-to shed light on these gaps. Using a recently developed pipeline for phylogenetic placement of eDNA, we find evidence for three putative novel clades within the Glomeromycota, sister to Entrophosporaceae, Glomeraceae, and Archaeosporaceae, with evidence for geographic structuring. We further find that taxa in the Diversisporaceae, Glomeraceae, and Entrophosporaceae relatively high families are overrepresented and more diverse in temperate samples. By contrast, the diversity of taxa that cannot be placed into a family is higher in tropical samples, suggesting that tropical sites harbor relatively high undescribed AMF diversity. Moreover, we find evidence that Entrophosporaceae is more tolerant, while Glomeraceae is more sensitive to disturbance. These results underscore the vast undescribed diversity of AMF while highlighting a way forward to systematically improve our understanding of AMF biogeography and response to human disturbance.

Arbuscular mycorrhizal fungi travel the world with harvested underground crops

In recent years, the dispersal of potentially invasive plants, animals, and pathogens via international trading routes for fresh agricultural goods has been the subject of intensive research and risk assessment. Comparatively little is known about the potential impact of global food trade on the spreading of symbiotic soil microorganisms, such as arbuscular mycorrhizal (AM) fungi. The present study thus assessed whether internationally traded underground crop harvest products carry AM fungal propagules. Twenty batches of tubers, corms or bulbs originating from eight different countries were sampled and used to inoculate Sorghum bicolor (L.) Moench plants grown in a heat-sterilized, sandy dune soil from the United Arab Emirates (UAE). Results revealed that most of the underground crop harvest products contained AM fungal propagules able to establish AM symbioses in a pot experiment under greenhouse conditions. Though it is likely that most AM fungal propagules attached to harvest products will ultimately be eliminated in the waste or sewage stream, it is well possible that a certain portion would find its way into agricultural or natural ecosystems, e.g., via organic waste disposal or use of kitchen greywater for irrigation. Given the large volumes of underground crops traded worldwide, their impact on AM fungal dispersal and distribution deserves further investigation and assessment of associated risks of adulteration of soil microbial communities.

Environmental heterogeneity structures root-associated fungal communities in Daphne arbuscula (Thymelaeaceae), a shrub adapted to extreme rocky habitats

Rocky habitats, globally distributed ecosystems, harbour diverse biota, including numerous endemic and endangered species. Vascular plants thriving in these environments face challenging abiotic conditions, requiring diverse morphological and physiological adaptations. Their engagement with the surrounding microbiomes is, however, equally vital for their adaptation, fitness, and long-term survival. Nevertheless, there remains a lack of understanding surrounding this complex interplay within this fascinating biotic ecosystem. Using microscopic observations and metabarcoding analyses, we examined the fungal abundance and diversity in the root system of the rock-dwelling West Carpathian endemic shrub, Daphne arbuscula (Thymelaeaceae). We explored the diversification of root-associated fungal communities in relation to microclimatic variations across the studied sites. We revealed extensive colonization of the Daphne roots by diverse taxonomic fungal groups attributed to different ecological guilds, predominantly plant pathogens, dark septate endophytes (DSE), and arbuscular mycorrhizal fungi (AMF). Notably, differences in taxonomic composition and ecological guilds emerged between colder and warmer microenvironments. Apart from omnipresent AMF, warmer sites exhibited a prevalence of plant pathogens, while colder sites were characterized by a dominance of DSE. This mycobiome diversification, most likely triggered by the environment, suggests that D. arbuscula populations in warmer areas may be more vulnerable to fungal diseases, particularly in the context of global climate change.

Crop Productivity Boosters: Native Mycorrhizal Fungi from an Old-Growth Grassland Benefits Tomato (Solanum lycopersicum) and Pepper (Capsicum annuum) Varieties in Organically Farmed Soils

This paper investigates the response of five tomato and five pepper varieties to native arbuscular mycorrhizal (AM) fungal inoculation in an organic farming system. The field experiment was conducted across a growing season at a working organic farm in Lawrence, KS, USA. The researchers hypothesized that native AM fungi inoculation would improve crop biomass production for both crop species, but that the magnitude of response would depend on crop cultivar. The results showed that both crops were significantly positively affected by inoculation. AM fungal inoculation consistently improved total pepper biomass throughout the experiment (range of +2% to +8% depending on the harvest date), with a +3.7% improvement at the final harvest for inoculated plants. An interaction between pepper variety and inoculation treatment was sometimes observed, indicating that some pepper varieties were more responsive to AM fungi than others. Beginning at the first harvest, tomatoes showed a consistent positive response to AM fungal inoculation among varieties. Across the experiment, AM fungi-inoculated tomatoes had +10% greater fruit biomass, which was driven by a +20% increase in fruit number. The study highlights the potential benefits of using native AM fungi as a soil amendment in organic farmed soils to improve pepper and tomato productivity.