Detecting partial mycoheterotrophy in green plants remains challenging, particularly in associations with arbuscular mycorrhizal (AM) or rhizoctonia fungi, because natural-abundance stable isotope patterns often provide limited diagnostic resolution in these systems. We tested whether fatty acid composition, widely used to infer trophic relationships in animal and soil ecology, provides complementary evidence of fungal carbon acquisition by plants. We characterized fatty acid profiles of 21 autotrophic reference plants, six partially mycoheterotrophic plants, and 17 fully mycoheterotrophic plants associated with AM, ectomycorrhizal, or saprotrophic fungi. In expanded analyses, we additionally examined three individuals each of the rhizoctonia-associated orchid Goodyera biflora and the presumed autotrophic AM plant Trillium camschatcense with marked 13C enrichment, together with six co-occurring autotrophic reference plants. Fatty acid composition differed significantly among the three nutritional groups. Increasing mycoheterotrophic dependence was associated with decreasing relative abundance of 18:3n-3 and increasing relative abundance of 18:2n-6, which is widely used as a fungal biomarker in soil ecology. Partially mycoheterotrophic plants occupied an intermediate position in ordination space, and all pairwise group comparisons were significant. Differentiation remained significant after exclusion of 18:3n-3 and 16:3n-3 and renormalization of the remaining components, indicating that chloroplast-associated fatty acids alone did not drive the pattern. Goodyera biflora resembled partially mycoheterotrophic orchids, whereas T. camschatcense resembled autotrophic references. Fatty acid profiling may therefore complement stable isotope analysis in assessments of partial mycoheterotrophy. The profiles likely reflect metabolic remodeling, incorporation of fungal-derived carbon into newly synthesized plant lipids, or both, although some retention of intact fungal lipids cannot be excluded.
The influence of the plant cover on the composition of an arbuscular mycorrhizal (AM) fungal synthetic community (SynCom) was studied in a time-course experiment. A mesocosm system was designed to mimic the environmental conditions of a semi-arid Mediterranean ecosystem, allowing the assessment of changes in AM fungal establishment, persistence, and sporulation within the SynCom. The mesocosm system included soil, AM fungi and plant species characteristic of the target region from Southern Spain. Retama sphaerocarpa, Lavandula latifolia, Thymus mastichina and Rosmarinus officinalis were selected and cultivated either in monoculture or in pairwise combinations, covering all possible dual associations. The initial AM SynCom was composed of six species (Rhizophagus clarus, Septoglomus constrictum, Funneliformis coronatum, R. intraradices, F. mosseae and S. viscosum), all isolated from southern Spain. Changes in the AM SynCom, both colonizing plant roots and the spores in the rhizosphere, were monitored every three months over three years. Fungi colonizing roots were identified through nested PCR-TTGE of the SSU rDNA, while AM fungal spores were quantified based on morphotype. Results indicate that plant species composition exerted only a limited influence on the AM fungal community structure, whereas pronounced species-specific differences in establishment, persistence, and sporulation shaped community trajectories over time. Septoglomus constrictum showed increasing spore abundance and specific density across all plant cover types, while other species (R. clarus, F. coronatum) became undetectable in the spore pool or maintained a low spore density (F. mosseae, S. viscosum). Qualitative root-detection patterns were generally consistent with rhizospheric sporulation trends, although the pooled PCR-TTGE approach did not allow quantitative comparison between intraradical occurrence and spore abundance. Overall, these results suggest that S. constrictum showed the most consistent persistence and sporulation under semi-arid Mediterranean conditions, identifying it as a candidate for further validation in AM fungal consortia intended for semi-arid Mediterranean environments, particularly for further testing in restoration-oriented applications under increasing aridity.
The functioning of temperate forests is based on a symbiosis linking trees to a vast diversity of ectomycorrhizal (EM) fungi. Although disturbance is a major driver of biodiversity patterns in these ecosystems, its effects on the fine-scale distribution and the short-term dynamics of EM fungal communities are still largely unknown. We used an in situ experiment combined with the analysis of the ITS rDNA region of EM root tips to compare the composition of fungal communities before and one year after small-scale soil disturbance simulating animal bioturbation. Disturbance induced a transient increase in EM root tip abundance, a 56.3
Tropical Africa encompasses several biodiversity hotspots, yet knowledge of ectomycorrhizal (EcM) fungi, key organisms for forest ecosystem functioning, remains fragmented. This study provides the first comprehensive synthesis of EcM fungi across the region, aiming to (i) establish a species checklist as a basis for estimating gamma diversity, (ii) analyze spatial turnover across countries, and (iii) assess the functional effects of EcM fungi on tree seedling growth. We conducted a systematic literature search following PRISMA guidelines, retaining 158 publications published between 1927 and 2025. Species occurrence records were extracted from publications and complemented with data from GlobalFungi and GBIF databases. Statistical analyses in R were used to estimate species richness (Chao2, Jackknife 1 and Jackknife 2), analyze spatial turnover (Jaccard dissimilarity, Mantel correlogram, Generalized Dissimilarity Modelling), and assess the overall effect on tree seedling growth (cross-classified random-effects meta-analysis). We recorded 711 EcM fungal species from 59 genera and 20 families. Russula (169 species), Amanita (81), and Lactifluus (71) were the most represented. Estimated richness reached 1,226 species, indicating substantial undocumented diversity. Community composition showed extremely high heterogeneity among countries (95
Pines and oaks are ecologically and economically important taxa that co-occur in several forest and woodland systems across the northern hemisphere and that have been severely affected by diverse disturbances (e.g., wildfire, drought). Despite their relevance, the value of co-planting pines, that regenerate from seeds, and oaks, which are able to resprout, to improve forest restoration following disturbance has only recently been appreciated. An important consideration with this strategy is whether pines and oaks share root-associated fungal symbionts (ectomycorrhizas -EcM-, arbuscular mycorrhizas -AM- and dark septate endophytes -DSE-) that can be key to tree re-establishment following disturbance. However, the degree of overlap in fungal communities between pines and oaks is poorly understood. To address this knowledge gap, we conducted a systematic literature review of 948 studies published from 1969 to 2024. We hypothesized that both plant taxa would host DSE in addition to EcM, and that ectomycorrhizal fungal (EcMF) assemblages would differ in pines and oaks but that both host genera would share a limited subset of generalist taxa. We found that oaks and pines were mainly colonized by different EcMF species but also shared some taxa (26
Arbuscular mycorrhizal fungi (AMF) can improve plant performance under salinity, but their contribution to phenolic-based antioxidant responses in traditional tomato landraces remains unclear. We evaluated the effects of Diversispora celata and Funneliformis mosseae on growth, nutrition, gas exchange, oxidative status, and phenolic metabolism in Chilean tomato landraces Limachino and Maulino (Solanum lycopersicum L.) exposed to 0 or 150 mM NaCl. A 3 × 2 × 2 design included three inoculation treatments, two salinity levels, two landraces, and four replicates per combination. Biomass, shoot N and P contents, gas exchange, pigments, proline, lipid peroxidation, antioxidant capacity, and individual phenolics were quantified. Salinity reduced biomass, shoot N and P contents, and net photosynthesis, while non-mycorrhizal plants showed the highest lipid peroxidation. Responses depended on landrace and fungal identity. Under salinity, D. celata-inoculated Limachino plants showed higher biomass, shoot N content, and net photosynthesis than non-mycorrhizal plants, together with greater proline accumulation, higher concentrations of several hydroxycinnamic acids, anthocyanins, quercetin derivatives, total phenolics, and antioxidant capacity, and lower lipid peroxidation. In Maulino, both isolates improved gas exchange; F. mosseae was more closely associated with photosynthetic pigments and TEAC/DPPH capacity, and D. celata with phenolic derivatives and CUPRAC capacity. Overall, AMF responses depended on the host–fungus combination, with phenolic-associated non-enzymatic antioxidant responses emerging as a prominent feature of the Limachino–D. celata association.
Arbuscular mycorrhizal fungi (AMF) are symbionts that are ubiquitous in natural ecosystems. They are crucial in maintaining plant communities by enhancing the uptake of nutrients and water as well as acting as major drivers of seedling recruitment. This study established the mycorrhizal colonization status of common tree species and the diversity of AMF communities across three forest fragments of the Taita Hills. Fine roots of seedlings and rhizosphere soils were sampled across circular plots in forest fragments (Chawia, Fururu and Ngangao) representing low, moderate and high levels of disturbances, respectively. The AMF colonization status was significantly different across tree species ranging between 43.3
Elevated CO2 (eCO2) and arbuscular mycorrhizal fungi (AMF) positively influence plant defense under heavy metal exposure individually, however, the combination of them and the contribution of eCO2 were still unclear. The pot experiment was employed to explore the combined effect of eCO2 (700 ppm) and Funneliformis mosseae on the defense of black locust (Robinia pseudoacacia L.) grown in cadmium (Cd)-polluted soils by 13C isotope tracer. Elevated CO2 significantly caused an increase in Cd content, decreases in contents of malonaldehyde, carotenoids, soluble sugars and proteins, metallothioneins (MTs) and proline and activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione peroxidase and increases in ascorbic acid (AsA), glutathione (GSH), cysteine (Cys) and phytochelatins (PCs) in leaves under F. mosseae colonization. Additionally, the indirect contributions of eCO2 to AsA, GSH, Car, proline, soluble sugars and proteins, Cys, PCs and MTs under eCO2 + F. mosseae were lower than that under eCO2 alone. Overall, eCO2 enhanced the defense of black locust colonized by F. mosseae under Cd exposure by stimulating AsA, GSH, PCs and Cys synthesis, which will provide some insights into the effect of global change on the resistance mechanism of plants colonized by AMF to heavy metals. Elevated CO2 (eCO2) reduced malondialdehyde in black locust colonized by AMF. Ascorbic acid (AsA) and cysteine played a key role in the defense of plants to Cd. The eCO2 raised AsA, glutathione, cysteine and phytochelatin upon AMF inoculation. The eCO2 significantly positively affected leaf antioxidants, such as AsA and GSH. The combination of eCO2 and AMF stimulated antioxidants and chelates against Cd.
Soil fungi, as key players in maintaining ecological functioning and stability, have been widely studied in alpine ecosystems. However, prior studies focused mainly on their spatial patterns and temporal dynamics, as well as their driving factors. In-depth research on community assembly mechanisms, particularly how biotic interactions influence this, is lacking. In this study, we collected root samples of an ectomycorrhizal plant, Bistorta macrophylla, and bulk soil around them, along a 4300–4750 m gradient in alpine meadows of Baima Snow Mountain, northwestern Yunnan, China, and obtained ITS2 sequences using high-throughput sequencing, which were subjected to bioinformatic processing and statistical analyses, including differential abundance analyses, inference of community assembly mechanisms and interpretation of co-occurrence networks. Our results reveal that fungal community assembly in soil is influenced more by stochastic processes with the increase of elevation, but homogeneous selection consistently acts as the predominant process in shaping root-associated communities. This helps keep a stable core mycobiota dominated by Cenococcum and Phialocephala, both being melanized fungi, in the root systems of B. macrophylla. Nevertheless, members of the order Helotiales and certain EcM genera consistently act as key nodes in fungal co-occurring networks in both soil and root samples. Further, we find that the elevational change trend of positive correlations between ectomycorrhizal and saprotrophic fungi matches with the theoretical expectation by the stress gradient hypothesis. Our results emphasize the pivotal role of compartment filtering by plant roots in selecting symbiotic partners and shaping fungal correlation networks, and highlight that the stress gradient hypothesis could be applicable in harsh alpine environments.
Selecting an appropriate method to quantify arbuscular mycorrhizal fungi (AMF) colonization in plants can be challenging, particularly for non-experts, due to the wide diversity of available techniques, some of which date back to the 1980s. Despite rapid methodological advances, comprehensive reviews focusing specifically on recent image analysis approaches for AMF root quantification are still scarce in the scientific literature. Given the growing potential of image-based methods to improve the accuracy, reproducibility, and high throughput of AMF root colonization assessment, this review synthesizes conceptual structure and thematic map of studies focusing on AMF colonization from 2001 to 2026. In addition, we examine widely used traditional approaches, such as the gridline intersect method, and emerging tools, including Visual Basic for Application–Arbuscular Mycorrhizal Fungi (VBA-AMF), MycoPatt, WinRHIZO, ImageJ-based workflows, Zeiss Intellesis, and deep learning approaches such as Automatic Mycorrhizal Finder (AMFinder), “Tool for Analysing root images to calculate the Infection rate of arbuscular Mycorrhizal fungi” (TAIM) and Mask Region-based Convolutional Neural Network (Mask R-CNN). By critically comparing their principles, capabilities, and limitations, this review aims to guide researchers in selecting the most appropriate image analysis methods for AMF quantification according to their experimental objectives and technical constraints.
Orchids provide an ideal system for examining the evolution of heterotrophy because all species depend on fungal carbon during germination, whereas adult nutritional modes range from autotrophy to full mycoheterotrophy. The subtribe Calypsoinae illustrates this diversity through repeated shifts in fungal partners and nutritional strategies. Recent phylogenomic analyses place the Dactylostalix–Ephippianthus clade as sister to the Corallorhiza clade, which includes several heterotrophic lineages, raising questions about adult nutrition in Ephippianthus. Here, we combined fungal metabarcoding with δ¹³C and δ¹⁵N analyses to investigate the physiological ecology of the two known Ephippianthus species, which are restricted to Japan and the adjacent Russian Far East. We found that Ephippianthus schmidtii was primarily associated with Tulasnellaceae (Cantharellales). Its δ¹³C and δ¹⁵N values showed no significant positive enrichment relative to co-occurring autotrophic plants, providing no evidence for substantial fungal nutrient gain based on these isotope markers. By contrast, Ephippianthus sawadanus was mainly associated with saprotrophic Cyphellaceae (Agaricales), representing, to our knowledge, the first documented case in which a member of this family was detected as the dominant mycorrhizal associate of a green orchid. Moreover, E. sawadanus exhibited elevated δ¹³C and δ¹⁵N values relative to autotrophic plants, consistent with substantial fungal contributions to its carbon and nitrogen budgets. Together, these findings reveal divergent mycorrhizal strategies and nutritional modes in the East Asian orchid genus Ephippianthus.
Fully mycoheterotrophic orchids rely entirely on fungal symbionts for carbon acquisition, are often highly specialized in their fungal associations, and exhibit stable isotope signatures distinct from autotrophic plants. Danxiaorchis yangii is a rare, leafless orchid endemic to subtropical China whose nutritional ecology has not been previously examined. We combined high-throughput fungal community profiling with multi-element stable isotope natural abundance analyses (δ¹³C, δ¹⁵N, δ²H, δ¹⁸O) to investigate fungal associations and nutrient acquisition in D. yangii. Mycorrhizal rhizomes were dominated by a single operational taxonomic unit affiliated with the wood-decaying saprotroph Candolleomyces candolleanus (Psathyrellaceae), with additional low-abundance taxa related to Ramariopsis (Clavariaceae). Stable isotope signatures showed strong enrichment in ¹³C, ¹⁵N, and ²H relative to co-occurring autotrophic plants, confirming a fully mycoheterotrophic nutritional mode. Notably, the magnitude of nitrogen isotope enrichment differed from that reported for other Psathyrellaceae-associated orchids, suggesting greater complexity in nitrogen acquisition within saprotroph-based mycoheterotrophic systems.
Mucoromycotina fine root endophytes (M-FRE), although commonly present in cultivated crops, represent a largely overlooked symbiosis, and their diversity and ecological functions under field conditions remain poorly understood. The co-occurrence of M-FRE and Glomeromycotina arbuscular mycorrhizal fungi (G-AMF) was assessed in field-grown durum wheat (Triticum turgidum subsp. durum), testing the effects of combined water and nitrogen stress on root colonization and fungal community diversity in roots, rhizosphere, and extra-radical hyphae. The M-FRE colonization was reduced under combined stress but was unaffected by wheat genotype. In contrast, G-AMF colonization varied among genotypes and was insensitive to this combined stress. While G-AMF colonization correlated with root traits, M-FRE abundance was rather determined by soil properties and the applied stress. Colonization by M-FRE but not by G-AMF correlated with nitrogen and phosphorus uptake in plant shoots. Partial 18 S metabarcoding detected 74 G-AMF taxa and 12 M-FRE taxa, some shared across compartments, revealing active growth of M-FRE extra-radical hyphae. Stress had contrasting effects on diversity: G-AMF alpha diversity remained stable, whereas M-FRE diversity declined, with stress driving distinct community structures for both groups. Collectively, our results suggest that M-FRE and G-AMF are structured by distinct ecological drivers, supporting functional differentiation between these morphologically similar symbioses.
Brassicaceae cover crops are widely adopted in agroecosystems, yet their legacy effects on arbuscular mycorrhizal fungi (AMF) remain context-dependent and mechanistically unresolved. In this study, we assessed how a standing white mustard (Sinapis alba L.) cover crop interacts with tillage intensity to influence AMF colonization, community composition, diversity, and abundance in volunteer barley (Hordeum vulgare L.) roots. AMF responses were quantified using complementary approaches, including microscopic assessment of root colonization, 18S rRNA gene amplicon sequencing, and taxon-specific real-time PCR (qPCR). Roots were sampled before white mustard termination, thereby avoiding tissue disruption and isothiocyanate release, to distinguish host-mediated filtering from biofumigation-associated chemical disturbance. Colonization intensity was primarily determined by tillage, with significantly higher colonization under no-tillage compared to conventional tillage. Community-level responses, however, were dependent on taxonomic resolution. At the amplicon sequence variant (ASV) level, white mustard reduced AMF richness, whereas diversity and evenness were unaffected. At the genus level, richness remained stable, but diversity and evenness declined under the combined effects of cover cropping and conventional tillage, indicating that tillage modulated the impact of cover crop legacy. Dominant Glomeraceae lineages remained stable across treatments, and total AMF abundance showed no consistent response to management, although Rhizophagus irregularis was more abundant under no-tillage. Colonization intensity correlated with ASV richness rather than with individual taxa, suggesting that early symbiotic dynamics were linked to community diversity rather than to the dominance of specific lineages. These findings suggest that white mustard cover cropping, despite its well‑recognized agronomic benefits, may also carry context‑dependent shifts in AMF communities, highlighting a potential ecological trade‑off that should be considered when designing cover crop–tillage management combinations.
Grasses, including major cereal crops, associate with arbuscular mycorrhizal (AM) fungi to varying degrees depending on environmental conditions. Understanding mechanisms driving this environment-induced variation in mycorrhization, i.e. plant AM plasticity, is necessary to predict grass-mycorrhizal responses to global change factors, such as nutrient enrichment, and to resolve the role of AM symbiosis in cereal crop production. We compared AM plasticity in four cereal crops by testing the effect of nitrogen (N) fertilization on AM colonization and root PLFA 16:1ω5 concentration. To assess whether mycorrhization patterns reflect root functional traits, we compared specific root length among species. To determine whether plants regulate AM colonization qualitatively (by selectively associating with certain AM taxa) or quantitatively (by collectively suppressing colonization across taxa), we investigated directional shifts and variability in AM community structure in response to N fertilization. AM colonization varied between cereal species and was reduced by N fertilization, but we found limited evidence for interspecific differences in AM plasticity. Winter wheat appeared less AM responsive and associated more with uncultured AM fungi compared to the three spring-sown cereal species, oat, spring wheat and spring barley. Fertilization did not affect AM community composition, and within-species variation in AM community β-dispersion did not covary with variation in AM colonization or PLFA 16:1ω5 concentration. These results support the view that host plants regulate arbuscular mycorrhization quantitatively rather than through taxonomic selectivity. We propose AM plasticity as a plant-mycorrhizal trait to be used for more accurate predictions of plant environmental responses in eco-physiological and agroecological research.
Drought is an increasingly important constraint on plant productivity, affecting agricultural yields, forest dynamics, and ecosystem functioning worldwide. Mycorrhizal symbioses formed by arbuscular (AM) and ectomycorrhizal (EcM) fungi are key regulators of plant responses to water limitation, influencing water acquisition, transport, and maintenance of plant water status at the soil–plant interface. This review synthesizes current knowledge of the mechanistic pathways through which mycorrhizal associations enhance plant drought tolerance. We distinguish between direct hydraulic contributions, including expanded soil exploration via extraradical hyphal networks, hyphal water uptake, redistribution, and modifications of rhizosphere hydraulic properties, and indirect physiological and biochemical effects, such as changes in root system architecture, regulation of aquaporins, osmotic adjustment, antioxidant capacity, and phytohormonal signaling. Particular emphasis is placed on structural and functional differences between AM and EcM symbioses. We examine how contrasting intraradical interfaces (i.e., arbuscules versus Hartig net) and extraradical networks influence water movement, plant hydraulic conductance, and whole-plant performance under drought. We assess the implications of these processes for agriculture and forestry, highlighting context-dependent fungal–plant compatibility, maintenance of diverse mycorrhizal communities, and management practices that preserve soil structure and mycorrhizal networks. Despite substantial evidence that mycorrhizal fungi improve plant performance under water deficit, their quantitative contributions to plant water transport and growth remain insufficiently resolved, particularly in EcM-dominated systems. Addressing these knowledge gaps will require integrative, multi-scale approaches linking molecular regulation, root and hyphal hydraulics, and ecosystem-level water fluxes. Such advances are critical for predicting vegetation responses to intensifying drought conditions under global change.
Fully mycoheterotrophic orchids depend on fungus-derived carbon. Associations with wood- and litter-decaying saprotrophic (SAP) fungi have been reported mainly in fully mycoheterotrophic orchids from warm, humid forests, whereas ectomycorrhizal (ECM) fungi commonly support fully mycoheterotrophic orchids in boreal and temperate forests. For example, the subtropical and tropical Epipogium roseum associates with wood-decaying Psathyrellaceae fungi, whereas the cool-temperate E. aphyllum associates with ECM fungi, including Inocybe. Field observations suggest possible SAP associations in E. japonicum in cool-temperate to subalpine forests in Japan, based on its frequent occurrence near decaying logs and coarse woody debris. Here, we characterized the fungal associates and carbon sources of E. japonicum from moist ravines and compared them with those of nearby E. aphyllum from ECM-dominated coniferous forests. We combined high-throughput ITS2 metabarcoding with δ13C and δ15N measurements from plants collected on Mount Kitadake. Sequencing showed that mycorrhizal rhizome tissues of E. japonicum were dominated by Psathyrellaceae, particularly Coprinopsis, whereas those of E. aphyllum were dominated by Inocybe. Epipogium japonicum showed stronger 13C enrichment relative to co-occurring autotrophic plants than did E. aphyllum, consistent with carbon acquisition through deadwood-associated SAP fungi. These results indicate that two fully mycoheterotrophic congeners exploit contrasting fungal guilds within the same cool-temperate mountain landscape.
With escalating global health challenges, triclocarban (TCC) contamination has reemerged as a critical ecological threat, especially in wetland ecosystems. Yet, the mechanisms by which arbuscular mycorrhizal fungi (AMF) regulate plant root resistance and the rhizosphere environment under TCC exposure remain poorly understood. Here, we established an AMF-Phragmites communis symbiotic system and conducted TCC exposure experiments. Our results demonstrated that TCC exposure significantly inhibited mycorrhizal colonization, root morphology, and the antioxidant system of P. communis. Specifically, under the 5 mg kg− 1 soil TCC exposure, arbuscule abundance decreased by 3.53-fold, root total length declined to 1011.13 cm, and the integrated biomarker response index value of the antioxidant system dropped to 0.25. In contrast, arbuscular mycorrhizal (AM) symbiosis promoted root morphological and physiological growth. Transcriptome analysis revealed that AM symbiosis upregulated genes encoding key enzymes in the Mitogen-Activated Protein Kinase (MAPK) signaling pathway (e.g., MAPKKK and MAPK family members), whereas TCC exposure downregulated their expressions. Furthermore, in the rhizosphere soil, the composition and structure of microbial communities were distinctly influenced by AM symbiosis and TCC exposure. Compared to AM symbiosis, which upregulated soil metabolites associated with metabolism, TCC exposure downregulated soil metabolites across multiple functional categories, including metabolism, environmental information processing, and cellular processes. This research broadens our understanding of how AM symbiosis enhances the resistance of P. communis and maintains the stability of the rhizosphere environment under TCC exposure, and evidences the potential of AMF application in improving the purification capacity of wetland systems.
Aphid-microbe-plant interactions are fundamental to understanding plant responses to combined biotic and abiotic stress. The grain aphid Sitobion avenae is a major pest of wheat, particularly under drought conditions. Although arbuscular mycorrhizal fungi (AMF) can enhance plant tolerance to water deficit, their effects on aphid performance across wheat cultivars differing in drought resistance remain unclear. We examined the influence of Acaulospora delicata on S. avenae performance on two wheat cultivars-Yunhan-618 (drought-resistant) and Xinong-1376 (drought-susceptible)-under well-watered and water-deficit stress conditions. Under water-deficit stress conditions, root colonization by A. delicata was higher in both Yunhan-618 and Xinong-1376 when compared to well-watered conditions. In the absence of mycorrhiza, nymphal developmental time was prolonged, especially on drought-stressed Xinong-1376 plants. AMF inoculation shortened developmental time, increased adult longevity, and enhanced fecundity of S. avenae under both water regimes. On Yunhan-618, AMF association increased intrinsic growth rate and reproductive output of this aphid. Honeydew excretion by S. avenae was greater on AMF-inoculated plants under well-watered conditions. Aphid body mass and water balance traits were generally higher on AMF-associated Yunhan-618 plants under adequate water supply. Aphids also preferentially settled on AMF-inoculated drought-susceptible wheat plants under both water regimes as compared to drought-resistant wheat plants. Overall, A. delicata enhanced plant drought resilience but simultaneously promoted aphid fitness. These findings underscore the complex and context-dependent role of AMF in shaping plant-aphid interactions, with important implications for pest dynamics under climate change.
The ectomycorrhizal (ECM) fungal ecologies of old forests on islands are important to conserve but have been understudied, especially in eastern North America. In this study, we characterize the ECM fungal communities of four 9000-year-old red spruce (Picea rubens) sites and one beech-birch site on a coastal island in Maine, USA, the first such study on a northeastern North American coastal island. By sampling the ECM fungi colonizing seedling roots, mature roots and root-free bulk soil, we show that the ECM communities in red spruce sites are dominated by Cenococcum, Piloderma and Cortinarius. Further, we show extremely limited ECM fungal community overlap between red spruce sites and a beech-birch site suggesting factors affecting ECM fungal communities on this island are like those on mainland. Within red spruce sites, we show substantial overlap between the ECM fungi on seedling, mature tree roots and root-free bulk soil by dominant genera and identify specific ECM fungal sequence variants found widely across these old growth stands.
