Arbuscular mycorrhizal fungi (AMF) play a crucial role in crop productivity and agroecosystem processes. However, the composition of soil AMF communities and the factors associated with their diversity and distribution in Ohio remain poorly understood. We profiled both soil AMF and physico-chemical characteristics in 18 soybean fields across agricultural regions in Ohio. AMF sequences were recovered through amplicon sequencing of the 18S ribosomal gene coupled with PacBio technology. We detected 14 genera belonging to six families of the Glomeromycota. The family Glomeraceae accounted for 39
Many photosynthetic orchids combine photosynthesis with fungal carbon acquisition, yet the isotopic relationships between orchids and their fungal partners remain poorly resolved. Direct stable isotope analysis of pelotons and extraradical fungal tissues can refine fungal baselines and clarify nutritional dynamics in orchid mycorrhizas. We investigated Cremastra appendiculata, a photosynthetic orchid with contrasting mycorrhizal states, by comparing fungal communities between individuals with and without coralloid rhizomes and analyzing the δ13C and δ15N values of leaves, protocorms, coralloid rhizomes, pelotons, Psathyrellaceae rhizomorphs, dead wood, and autotrophic reference plants. Psathyrellaceae-associated individuals were strongly enriched in 13C relative to autotrophic reference plants, indicating substantial acquisition of fungal carbon, whereas rhizoctonia-associated individuals exhibited little 13C enrichment and appeared predominantly autotrophic. Leaf δ15N values exceeded those of the associated fungal tissues in both states, suggesting plant-mediated 15N enrichment during nitrogen assimilation and allocation to leaves. Coralloid rhizome pelotons did not differ detectably in δ13C or δ15N between digestion stages. Pelotons resembled extraradical Psathyrellaceae rhizomorphs in δ15N but had higher δ13C values, indicating tissue-specific carbon isotope baselines. Psathyrellaceae tissues were less 13C enriched than fungal tissues reported from fully mycoheterotrophic orchids associated with wood-decaying fungi. These results support contrasting nutritional states in C. appendiculata: a predominantly autotrophic, rhizoctonia-associated state and a more fungus-dependent, Psathyrellaceae-associated state. The fungal isotope pattern raises the possibility that bidirectional carbon transfer persists even in the latter state. Determining whether the orchid transfers carbon to its fungal partners requires controlled culture or tracer experiments.
Variation in arbuscular mycorrhizal fungal (AMF) root colonization and associated root traits among plant species plays a crucial role in determining plant community responses to environmental change. However, species mean trait values often obscure substantial variation among individuals within a species. Because trait-based ecology has focused predominantly on interspecific differences, the intraspecific responses of AMF-associated traits to resource limitations remain poorly understood. To address this gap, we examined intraspecific variation in AMF-associated traits among genetically diverse individuals of alfalfa (Medicago sativa) and sainfoin (Onobrychis viciifolia) under drought and nutrient limitation. Drought induced the greatest intraspecific variation in plant performance and AMF-associated traits. In both species, baseline levels of hyphae and arbuscule colonization predicted subsequent responses to drought stress. However, species-specific patterns emerged following stress. In alfalfa, plant individuals with lower shoot mortality were associated with greater vesicle colonization and increased average root diameter, indicating a shift toward carbon storage and altered root morphology during stress recovery. Conversely, despite higher overall arbuscule and hyphae colonization in sainfoin, intraspecific variation in drought tolerance was primarily linked to root tissue density, highlighting the importance of root structural investment rather than AMF abundance. These findings highlight that, while AMF-associated trait responses to stress are species-specific, substantial variation exists among individuals within a species, and this variation strongly influences plant performance under stress. Our results underscore the importance of incorporating intraspecific variation into trait-based frameworks for understanding plant community responses to environmental change and for integrating AMF-associated traits into cultivar selection for sustainable agricultural systems.
Orchid seed germination is generally considered to be obligatorily dependent on mycorrhizal fungi. However, some terrestrial orchids are capable of asymbiotic germination in water agar under laboratory conditions, raising questions about the degree of fungal dependency during germination in nature. Here, we investigated in situ germination and fungal associations of the terrestrial orchid Bletilla formosana in Taiwan using seed packet experiments, high-throughput sequencing, ink staining, and stable isotope analyses. B. formosana exhibited rapid germination and a relatively high germination percentage under natural conditions, with seeds germinating within one month and median germination reaching 43.4
Soil pH is among the most consistent abiotic axes structuring arbuscular mycorrhizal (AM) fungal communities, yet the pH dependence of individual taxa has not been turned into an interpretable instrument that resolves preference at the genus level and maps globally. HESI (Hydrogenic Edaphic Suitability Index) is a fuzzy-set trapezoidal pH-membership function for twelve Glomeromycotina genera whose four parameters are read from binned presence-rate profiles in GlobalFungi by an explicit rule rather than fitted, then scored on an independent SoilGrids pH surface. Under spatial block cross-validation, which tests transfer to unsampled regions, the mean binned Boyce index was + 0.19; in-sample across the whole GlobalFungi pool, it was positive for eleven of twelve genera (mean + 0.52), eight with bootstrap intervals above zero and five distinguishable from a label-permutation null. The flexible pH spline matched or exceeded machine-learning models, most clearly at the species level, where the learners fell below zero while the unfitted function remained positive. The genus with a negative index and the one with no discriminating window mark the diagnostic limits of a single-axis model. Species-level pH optima estimated independently in GlobalAMFungi agreed in rank with those from GlobalFungi (ρ = +0.46, p = 0.030), and family-level optima with small-subunit virtual-taxon optima (ρ = +0.79 across eight families), so the niches track an independent marker; whether the scored surface transfers is unresolved at these sample sizes. Soil pH sorted which genera occur, a signal distinct from the temperature-dominated richness of published global maps. The per-genus surfaces are offered as spatially explicit, testable hypotheses.
