Arbuscular Mycorrhizal Fungi Root Colonization Research Articles

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi.

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Inoculation of Native Arbuscular Mycorrhizae and Bacillus subtilis Can Improve Growth in Vegetable Crops

Arbuscular mycorrhizal fungi (AMF) and some rhizobacteria are known as plant growth-promoting microorganism (PGPM) as they play significant roles in improving soil fertility structure, plant nutrition, growth, and health. However, little is known about the PGPM potential of AMF and rhizobacteria native to the Rift Valley and highland regions of Ethiopia. Hence, this study aimed to investigate the PGPM effect of single and co-inoculation of AMF and the Bacillus subtilis ALCR46 strain, on tomato (Lycopersicum esculentum L.), onion (Allium cepa L.), and squash (Cucurbita pepo L.) plants. The experimental setup was a randomized complete block design with three replications of the following treatments: (i) inoculation with a consortium of AMF, (ii) co-inoculation with a consortium of AMF and the Bacillus subtilis, (iii) inoculation with Rhizophagus clarus, (iv) co-inoculation with R. clarus and B. subtilis, (v) inoculation with B. subtilis, (vi) plants without inoculation (negative control), and (vii) plants treated with chemical fertilizer (positive control). Plants were maintained in a greenhouse for 60 days, and after harvest, plant growth parameters, percentage of AMF root colonization, and spore number were analyzed. The result shows that the growth of crops significantly increased by co-inoculation with the consortium of AMF and B. subtilis. AMF spore density and root colonization rate were also increased in co-inoculated plants. Highest root colonization, spore number, and mycorrhizal dependency were observed in A. cepa. Our results suggest that there is a synergistic effect between the AMF and B. subtilis ALCR46, and between AMF inoculants. However, the application of present findings under field conditions is required to be confirmed by further studies.

Tripartite interactions among free‐living, N‐fixing bacteria, arbuscular mycorrhizal fungi, and plants: Mutualistic benefits and community response to co‐inoculation

AbstractInteractions between arbuscular mycorrhizal (AM) fungi and free‐living nitrogen fixers (FLNF) occur in the rhizosphere where they can enhance plant nutrient acquisition, impact plant growth, and affect soil processes. Tripartite mutualism commonly occurs between nodule‐forming plants, symbiotic diazotrophs, and AM fungi, and can occur between non‐nodulating plants, FLNF, and AM fungi. However, information on the extent of, and controls on, tripartite mutualism in non‐nodulating plant systems is limited to a small number of crop plants and culturable microbial inoculum, mostly in greenhouse growing conditions. We conducted a systematic literature review to synthesize the current understanding of the responses of plants, AM fungi, and FLNF to co‐inoculation, as well as the conditions affecting tripartite mutualism and the magnitude and range of benefits conferred. Our review shows that plants generally benefit from co‐inoculation with AM fungi and FLNF taxa, but benefits are highly variable and context dependent, ranging from 94% reduction in plant shoot biomass to 255% increase in total plant biomass. Additionally, the presence of AM fungi can increase abundance of FLNF and the presence of FLNF can increase AM fungal root colonization, but these responses also vary widely. Major factors influencing variation in response to co‐inoculation by all organisms include plant phenology/age, soil type and nutrient availability, and partner pairing. There is potential for leveraging these tripartite mutualisms to improve plant productivity and soil microbial function, but successful application is more likely with a thorough understanding of the environmental and mechanistic controls on these relationships and testing of field‐scale implementation.

Morpho-Physiological Responses of Malabayabas (Tristaniopsis decorticata (Merr.) Peter G. Wilson & J.T. Waterh.) Seedlings Inoculated with Arbuscular Mycorrhizal Fungi

Malabayabas (Tristaniopsis decorticata (Merr.) Peter G. Wilson & J.T. Waterh.) of the Myrtaceae family is a vulnerable endemic tree species in the Philippines. Poor development and low regeneration rates of seedlings in their natural habitats have led to a considerable population decline of the species. This study aimed to determine the morphological and physiological growth responses of T. decorticata seedlings in different soil media inoculated with arbuscular mycorrhizal fungi applied once at a rate of 5 g per seedling for the entire duration of the experiment. Morphological parameters were collected using conventional methods, while physiological parameters were measured using LI-6400 XT Portable Photosynthesis System. Results of the study revealed that the morphological growth of seedlings was generally better in Bantay soil regardless of treatments than in Lipa soil. Interestingly, the net photosynthesis, transpiration rate, and water-use efficiency were generally higher in Lipa unsterilized soil inoculated with arbuscular mycorrhizal fungi. However, this study can not yet confirm the percentage of Arbuscular Mycorrhizal Fungi (AMF) root colonization. Thus, further research must be conducted to determine the AMF root colonization and identify potential indigenous mycorrhizal fungi in both soil media. Keywords: arbuscular mycorrhizal fungi, endemic, net photosynthesis, transpiration rate, Tristanipsis decorticata

Effect of Cinnamon Leaf Compost on Selected Soil Properties in Cinnamon (Cinnamomum zeylanicum Blume) Growing Soils

Integrated nutrient-management programs incorporating organic and inorganic fertilizers have been suggested to increase crop yields and reduce adverse environmental impacts in intensive agriculture. This study was conducted to investigate the effect of long-term cinnamon leaf compost (CLC) application on some selected physical, biological and chemical soil properties and the horizontal and vertical distribution of some selected soil properties in cinnamon-growing soils. The study was conducted in the National Cinnamon Research and Training Center, Palolpitiya, from January to April 2022. The experimental design was Randomized Complete Block Design (RCBD) with six treatments (T1-Control, T2-Current recommendation (CR), T3-3/4 CR with 5 t/ha/yr CLC, T4-1/2 CR with 10 t/ha/yr CLC, T5-1/4 CR with 15 t/ha/yr CLC, T6-20 t/ha/yr CLC) and three replicates. Soil samples were collected considering three horizontal distances (15, 30 and 45 cm) and with three depths (10, 20 and 30 cm). Soil physical properties (aggregate stability, bulk density, soil moisture), chemical properties (soil organic carbon (SOC), pH, electrical conductivity (EC)), and biological properties (arbuscular mycorrhizal root colonization) were determined. Water stable aggregate (WSA), SOC, and soil pH were significantly affected by the treatments, and all the variables except EC were significantly affected by the soil depth (p<0.05). Soil pH was the only variable that was significantly affected by the horizontal distance (p<0.05). Only SOC and pH have shown a significant interaction effect among treatments and depth. The application of CLC (20 t/ha/yr) significantly increases the WSA and SOC. Arbuscular mycorrhizal fungi root colonization was increased with the incorporation of CLC. Continuous application of inorganic fertilizers (T2) caused soil compaction and acidification. WSA, soil pH, and SOC were significantly improved within the 0-10 cm soil depth. The best performances of WSA, pH, and EC were shown in 30-45 cm and SOC in 15–30 cm horizontal distance from the plant base and 0-10 cm soil depth with the application of 1/2 CR and 10 t/ha/yr CLC comparison to other fertilizer combinations. 
 Keywords: Aggregates, Mycorrhizae, pH, Soil organic carbon

Comparing dry farming of tomatoes across varieties and soil management history

Farmers faced with increasingly limited access to freshwater for irrigation are utilizing dry farming techniques to produce fruit, vegetable, and grain crops. Defined as crop production during a dry season using little or no irrigation, dry farming relies on water stored in the soil and requires specialized soil management, healthy soil biology, and careful selection of crop varieties. We investigated these three factors in a dry-farmed tomato (Solanum lycopersicum) field trial with three indeterminate varieties (Early Girl, Momotaro, and Zapotec) and two determinate genotypes (76R and rmc), the latter serving as a model system for studying the role of arbuscular mycorrhizal (AM) fungi. While five prior years of contrasting surface tillage practices changed soil properties, they did not affect marketable tomato yields or quality, nor affect plant physiology, including plant water use efficiency [intrinsic (WUEi) and long-term (δ13C)], gas exchange, stem water potential (Ψstem), and leaf relative water content (RWC). Early Girl produced a greater number of fruits and fewer non-marketable fruits than Momotaro and Zapotec. Although AM fungi root colonization was very low for both wildtype mycorrhizal genotype 76R and its reduced mycorrhizal mutant rmc, it differed significantly depending on genotype and tillage treatment. 76R produced slightly greater marketable fruit, but physiological responses did not differ significantly between genotypes. This study does not provide field-based evidence that soil chemical and biological changes resulting from no-till influence dry-farmed tomato productivity, while genotype had a clear impact on tomato yield and quality. Field-scale tillage experiments may better capture soil physical changes that affect water availability, especially at depth, and should be examined.

Negotiating soil water deficit in mycorrhizal trifoliate orange plants: A gibberellin pathway

Gibberellins (GAs), an important endogenous hormone, serve a crucial regulatory role in plants’ resistance to environmental stress, whereas it is unclear whether and how arbuscular mycorrhizal fungi (AMF) regulate the profile of GAs in plants exposed to soil water deficit (SWD). This study aimed to analyze how Rhizoglomus intraradices inoculation affected plant growth performance, antioxidant enzyme activities, and the composition, synthesis, metabolism, and signaling pathways of GAs in the roots of trifoliate orange (Poncirus trifoliata) under a 10-week SWD. Although the SWD decreased both root AMF colonization and soil hyphal length, mycorrhizal plants nevertheless outperformed non-mycorrhizal plants in terms of growth performance, as well as peroxidase (70.0%) and catalase (149.2%) activities, indicating greater drought tolerance. A total of nine GAs compositions were detected in the roots, with bioactive GA4 exclusively found in AMF roots. AMF colonization significantly reduced bioactive GA3 levels by 37.9%, while it increased inactive GA8, GA9, and GA15 levels under SWD by 522.2%, 100.0%, and 2500.0%. Inoculation with AMF also up-regulated the expression of PtCPS, PtPKS, and PtKO in GA synthesis pathways of roots and the expression of PtGA20ox, PtGA3ox, and PtGA2ox in GA metabolisms under SWD. In addition, the expression of DELLA genes PtGaipb and PtGai associated with GA signaling pathways was further up-regulated under SWD by AMF inoculation. It is concluded that AMF regulated the composition, synthesis, and deactivation of GAs in roots to promote plant growth, along with an increase in PtGaipb and PtGai expression to possibly initiate mycorrhizal signaling pathways in response to SWD.

Toxic effect of mercury on arbuscular mycorrhizal fungi colonisation and physiological status of three seed-based Miscanthus hybrids

BackgroundCurrently, mercury pollution is a widespread problem in the world. As mercury is difficult to remove from the environment, it has long-term negative effects on soil health and human life. One of the techniques to stabilise Hg is phytostabilisation, which can be supported by arbuscular mycorrhizal fungi (AMF). MethodsIn a 4-month pot experiment, we investigated the suitability of three seed-based Miscanthus hybrids (GNT3, GNT34, GNT43) for growth on soils heavily polluted with mercury (6795.7 mg kg-1). During the experiment, the effects of high soil contamination with mercury on physiological parameters and colonisation of roots of seed-based Miscanthus hybrids by indigenous AMF from Hg-contaminated and uncontaminated soils were investigated. ResultsA high pseudo-total Hg concentration (6795.75 mg kg-1) in soil was found. The Hg content in the aerial part of GNT34 grown on Hg-contaminated soil was 1.5 times and 3 times higher than GNT3 and GNT43, respectively. The Hg content in the roots of GNT3 on Hg-contaminated soil was 25% and 10% lower than that of GNT34 and GNT43, respectively. The N content in the aboveground part of GNT34 in the Hg variant was 13.5% lower compared to the control soil. The P and K content in the shoots of the Miscanthus hybrids was lower in the plants grown on Hg-contaminated soil. The P content in GNT43 in the Hg variant was 33% and 19% lower than in GNT34 and GNT3, respectively. The K content in GNT34 in the Hg variant was 24.7% and 31.4% higher than in GNT43 and GNT3, respectively. The dry weight of the shoots and roots as well as the shoot height of the Miscanthus hybrids were lower in Hg-contaminated soil. Lower values of AMF root colonisation parameters (F, M) were observed in the plants in the Hg variant. In the Hg variant, a lower photosynthetic rate and a decrease in chlorophyll content were observed in the leaves of the Miscanthus hybrids. In the Hg variant, an increase in the content of flavonols was observed. The strongest toxic effect of mercury on the light phase of photosynthesis was measured in GNT34. ConclusionSoils heavily contaminated with mercury negatively affected the physiological parameters of Miscanthus, as evidenced by a decrease in photosynthetic rate and biomass. The ability of indigenous AMF from Hg-contaminated soils to colonise the roots of seed-based Miscanthus hybrids was limited.

Defense responses and symbiotic functional initiation in trifoliate orange‒arbuscular mycorrhizal fungi interaction

Arbuscular mycorrhizal fungi (AMF) trigger beneficial effects on their hosts, but it is unknown how plants modulate their defense responses during root colonization of AMF and the symbiotic benefits are initiated. The purpose of this study was to analyze the root mycorrhizal colonization process of trifoliate orange and the responsive patterns of plant growth, root peroxide hydrogen (H2O2), antioxidant enzymes and their encoding gene expression, and sugar, lipid and phosphate transporter protein gene expression at 7‒56 days of inoculation (doi) with Funneliformis mosseae (Fm). Fm developed appressoriums on the root surface at 7 doi, followed by abundant arbuscules in root cortical cells at 28 doi, intracellular vesicles at 42 doi, and root mycorrhizal colonization rate of 41.54% at 56 doi. Plant growth improvement by Fm started at 28 doi. The immune defense response of roots was initiated at 7 doi, as evidenced by the increase of H2O2 levels and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity, as well as the up-regulation of PtMn-SOD, PtCu/Zn-SOD, PtPOD, and PtCAT expression, which lasted until 14 doi. Starting at 28 doi, a sugar transporter gene (PtSWEET), a lipid transporter gene (PtSTR), and a phosphate transporter gene (PtPT6) were initiated to be up-regulated, followed by the up-regulation of PtSTR2, PtPT3, and PtPT5 at 42 doi and PtFe-SOD at 56 doi. Arbuscule formation and plant growth improvement together at 28 doi suggested that arbuscules trigger improved growth responses of host plants. This study also reveals the initiation of host immune defense response and function in early root AMF colonization.Graphical

Arbuscular Mycorrhizal Fungi, Especially Rhizophagus intraradices as a Biostimulant, Improve Plant Growth and Root Columbin Levels in Tinospora sagittata

Tinospora sagittata is a columbin-rich medicinal plant, but its columbin levels are reduced under artificial cultivation conditions. The objective of this study was to analyze the effects of inoculations with Diversispora versiformis (Dv), Funneliformis mosseae (Fm), Rhizophagus intraradices (Ri), and mixed inoculation (Dv + Fm + Ri) (Mix) on growth performance, root morphology, leaf photosynthetic physiology, and root columbin levels in T. sagittata. These arbuscular mycorrhizal fungi (AMF) were able to colonize the roots, as evidenced by a root mycorrhizal colonization rate ranging from 17% to 48% and soil hyphal lengths ranging from 17.51 cm/g to 32.02 cm/g, with the Mix treatment being the greatest. AMF inoculations improved plant height (16–151%), leaf number (119–283%), shoot (37–211%), and root biomass (22–318%) to varying extents, with Ri and Mix treatments being the most prominent. AMF-treated plants presented relatively greater root total length, projected area, surface area, volume, and average diameter, especially those treated with Ri and Mix. AMF inoculations also significantly improved the leaf nitrogen balance index, transpiration rate, and stomatal conductance, while the photosynthesis rate and chlorophyll index varied by AMF species, along with a decrease in intercellular CO2 levels. Root columbin levels ranged from 0.524 mg/g to 5.389 mg/g, and AMF inoculation significantly increased root columbin levels by 228–928%, with Ri being the most significant. Root columbin levels were significantly positively correlated with soil hyphal length, root total length, root projected area, root surface area, root volume, and root average diameter, but not root AMF colonization rate. This study demonstrates for the first time that AMF, especially Ri, can be employed as a biostimulant to promote growth as well as root columbin levels in T. sagittata, where AMF-triggered improvement in root morphology is an important reason for promoting root columbin levels.

Diversity of Arbuscular Mycorrhizal fungi under different agroforestry practices in the drylands of Southern Ethiopia

The conversion of an agroforestry based agricultural system to a monocropping farming system influences the distribution and composition of arbuscular mycorrhizal fungi (AMF). The aim of this paper was to analyze AMF species diversity, spore density, and root colonization across different agroforestry practices (AFP) in southern Ethiopia. Soil and root samples were collected from homegarden, cropland, woodlot, and trees on soil and water conservation-based AFP. AMF spores were extracted from the soil and species diversity was evaluated using morphological analysis and root colonization from root samples. The AMF spore density, root colonization and composition were significantly different among the AFP (P < 0.05). In this study, 43 AMF morphotypes belonging to eleven genera were found, dominated by Acaulospora (32.56%), followed by Claroideoglomus (18.60%). Home gardens had the highest spore density (7641.5 spore100 g− 1 dry soil) and the lowest was recorded in croplands (683.6 spore100 g− 1 dry soil). Woodlot had the highest root colonization (54.75%), followed by homegarden (48.25%). The highest isolation frequency (63.63%) was recorded for Acaulospora scrobiculata. The distribution of AMF species and diversity were significantly related to soil total nitrogen and organic carbon. The homegarden and woodlot AFP were suitable for soil AMF reserve and conservation.

Increasing diversity gradient in lentil mixtures for intercropping with wheat reveals an increase in lentil biomass with minimal impact on mycorrhizal activity

The management of arbuscular mycorrhizal fungi (AMF) is crucial for sustainable agricultural systems, given its beneficial impacts on soil health and crop productivity. This study aimed to assess the effect of lentil (Lens culinaris Medik.) mixtures for intercropping with durum wheat (Triticum durum Desf.) on mycorrhiza and investigate the role of legume intraspecific diversity in mycorrhizal development and crop biomass production. Since both intraspecific and interspecific diversity (i.e., cultivar mixtures and intercropping) have an effect in shaping soil microbiota in the rhizosphere, we hypothesised that increasing the level of diversification in the system enhances the provision of services (e.g., aboveground biomass accumulation), due to enhanced microbial activity and diversity. Specifically, increasing diversity within lentil cultivar mixtures strengthens the affinity of wheat for mycorrhiza, thereby influencing wheat mycorrhization in wheat-lentil intercrops. To test our hypothesis, we designed three lentil cultivar mixtures with increasing diversity levels using a trait-based approach, drawing from a pool of Italian lentil landraces characterised in a previous study. As an additional factor, we intercropped lentil mixtures with wheat and compared it with sole wheat and sole lentil commercial cultivar. In both experimental years, intercropping lentil mixtures with wheat consistently yielded higher soil mycorrhization levels (46% in 2021 and 52% in 2022) compared to sole wheat cultivation (23% in 2021 and 34 % in 2022). Nevertheless, AMF colonisation in lentil roots was significantly higher in sole crops (55% in 2021 and 70% in 2022, except for the commercial cultivar) compared to intercrops (35% in 2021 and 60% in 2022). This difference could be attributed to the presence of wheat, which might have suppressed the capacity of lentils to establish successful symbiosis with mycorrhiza. On the other hand, AMF colonisation of wheat roots in 2022 was significantly higher (52%) when intercropped with lentils than when cultivated as sole wheat (40%). Concerning biomass production in lentil mixtures in 2022, we observed a positive correlation between lentil biomass and the number of functional groups in the mixtures, both as pure stands (R2 = 0.19, p = 0.06) and intercrops (R2 = 0.29, p = 0.01). Additionally, in 2022, the total biomass of the intercropped system increased with the increase in diversity. Further experiments, incorporating microbial genetic analysis, are necessary to uncover potential associations between functional mixtures and AMF composition.

Arbuscular mycorrhizal colonization of pioneer mangrove species in Mahakam Delta, East Kalimantan

Arbuscular mycorrhizal fungi (AMF) are symbiotic, with more than 80% of plant species in terrestrial and mangrove ecosystems. This study aimed to determine the level of AMF colonization on Avicennia lanata and its correlation with soil chemical properties. Sampling was conducted in Sepatin Village, located in Mahakam Delta. There are four sampling locations, three were mangrove rehabilitation areas (A, B, and C), and one was a mangrove natural forest (MNF). Root samples were taken from four A. lanata seedlings purposively selected at each location. The roots were stained with 0.05% trypan blue, and the mycorrhizal structures of the roots were observed using a compound microscope. The results showed that the percentage of AMF colonization with A. lanata in MNF was higher (97%) than in other locations. Internal hyphae were the dominant structure found in the root of A. lanata in all locations, with a percentage of 76.61%. AMF root colonization negatively correlated with N-total, C-organic, and available P. In contrast, Ca, Mg, K, Na, and CEC positively correlated with AMF root colonization. The colonization of AMF in the root of A. lanata may promote the early growth of seedlings, and the application of AMF can support rehabilitating mangrove degraded.

Arbuscular Mycorrhizal Fungi Colonization of Jatropha curcas Roots and Its Impact on Growth and Survival under Greenhouse-Induced Hydric Stress

Arbuscular mycorrhizal fungi (AMF) provide benefits to host plants by enhancing nutrition and overall fitness. In this study, AMF species were isolated from the soil rhizosphere of Jatropha curcas and were identified and evaluated for their potential in fostering the development of Jatropha seedlings within a controlled greenhouse environment. The first experiment assessed the interplay between hydric stress and AMF inoculation on mycorrhizal colonization. The next experiment examined the impact of quercetin on mycorrhizal colonization. Out of 204 glomerospores corresponding to 28 species spanning 10 genera, Acaulospora (14) and Scutellospora (5) were the most abundant taxa. Six new records of AMF for Costa Rica are reported. Mycorrhizal colonization was observed in 43.2% of Jatropha plants (34.7% by AMF typical hyphae; arbuscules 8.9%; coils 5.6%; and vesicles 5.4%). Significant survival effects due to AMF inoculation under hydric stress were observed. On day 85, non-mycorrhizal plants subjected to hydric stress showed a mere 30% survival rate, whereas their mycorrhizal counterparts under hydric stress exhibited survival rates of 80% and 100% with and without irrigation, respectively. Furthermore, plants with irrigation and mycorrhizas showed greater hydric stress tolerance and superior growth. The inoculated plants, irrespective of irrigation, demonstrated mycorrhizal colonization rates of 63% and 72%, respectively. Quercetin did not affect Jatropha’s growth, but there were differences in AMF root colonization. In summary, these findings accentuate the viability of a native consortium in augmenting Jatropha survival, warranting consideration as a potent biofertilizer within greenhouse settings. The AMF described can be used for Jatropha propagation programs.

Higher colonization but lower diversity of root-associated arbuscular mycorrhizal fungi in the topsoil than in deep soil

Arbuscular mycorrhizal fungi (AMF) colonizing plant roots play a pivotal role in maintaining soil nutrient cycling and ecosystem stability, and this role may vary in different habitat environments. However, the influence of soil depth on root AMF colonization, diversity, and the complex interactions among AMF taxa is still not well understood. In this study, we investigated the frequency, intensity, and abundance of root AMF colonization, as well as root AMF diversity, composition, and co-occurrence patterns across three soil depths: 0–20 cm, 20–40 cm, and the soil-rock mixing layer. Soil nutrients (e.g., organic matter, nitrogen, and phosphorus) and root biomass were higher in the 0–20 cm layer than in the soil-rock mixing layer, while soil pH showed an opposite relationship. The higher root biomass in the upper soil layer may enhance root secretions and exudates, thereby promoting root AMF colonization. In contrast, the lower soil nutrient content and higher soil pH observed in the 20–40 cm and soil-rock mixing layers may contribute to greater AMF diversity in the deeper soil layers compared to the topsoil. Although no significant differences were observed in the composition of the root AMF community, specific amplicon sequence variants affiliated with Glomus, Racocetra, and unclassified taxa were more enriched in the 20–40 cm and soil-rock mixing layers compared to the 0–20 cm layer. Network analysis revealed that deep soil, compared to topsoil, enhances interactions among root AMF by intensifying competitive relationships. This suggests that the complex interactions among root AMF taxa within deep soil contribute to the resilience of root AMF in resource-scarce conditions, particularly in the 20–40 cm layer and the soil-rock mixing layer. At the genus level, Glomus, Racocetra, and unclassified taxa emerged as keystone taxa due to their prominent linkage with other root AMF groups. Collectively, the results suggest that higher soil nutrient levels and root biomass can promote root mycorrhizal colonization but suppress AMF diversity and weaken interactions among root AMF taxa in the upper soil layer compared to deeper soil layers. Furthermore, the distinct functions of AMF colonization and diversity at different soil depths should be considered when evaluating vegetation reconstruction in karst ecosystems with varied soil depth distribution.

Tree seedling shade tolerance arises from interactions with microbes and is mediated by functional traits

Shade tolerance is a central concept in forest ecology and strongly influences forest community dynamics. However, the plant traits and conditions conferring shade tolerance are yet to be resolved. We propose that shade tolerance is shaped not only by responses to light but also by a species’ defense and recovery functional traits, soil microbial communities, and interactions of these factors with light availability. We conducted a greenhouse experiment for three temperate species in the genus Acer that vary in shade tolerance. We grew newly germinated seedlings in two light levels (2% and 30% sun) and controlled additions of microbial filtrates using a wet-sieving technique. Microbial filtrate treatments included: &amp;lt;20 µm, likely dominated by pathogenic microbes; 40-250 µm, containing arbuscular mycorrhizal fungi (AMF); combination, including both filtrate sizes; and sterilized combination. We monitored survival for nine weeks and measured fine root AMF colonization, hypocotyl phenolics, stem lignin, and stem+root nonstructural carbohydrates (NSC) at three-week intervals. We found that differences in seedling survival between low and high light only occurred when microbes were present. AMF colonization, phenolics, and NSC generally increased with light. Phenolics were greater with &amp;lt;20 µm microbial filtrate, suggesting that soil-borne pathogens may induce phenolic production; and NSC was greater with 40-250 µm filtrate, suggesting that mycorrhizal fungi may induce NSC production. Across species, microbe treatments, and light availability, survival increased as phenolics and NSC increased. Therefore, shade tolerance may be explained by interactions among soil-borne microbes, seedling traits, and light availability, providing a more mechanistic and trait-based explanation of shade tolerance and thus forest community dynamics.

Native Diversity of Endotrophic Mycorrhizal Fungi of Forage Grass Species Occurring in Asan River Basin, Mussoorie Hills, Uttarakhand

Arbuscular Mycorrhizal (AM) fungi colonize more than 80% of plants on land in which grasses are known to have higher endomycorrhizal colonization. AM fungi are a common group of symbiotic fungi in the order, Glomale of Division, Zygomycota. These fungi are known to benefit growth through increased nutrient uptake especially phosphorus. In this study, a total of 21 grass species collected from the Asan river basin, Mussoorie hills, Dehradun, Uttarakhand were screened for AM fungal root colonization and their mycorrhizal diversity. Traditional method of sieving and decanting was used for isolating mycorrhizal spores whereas for studying colonization rapid staining and clearing method was used. The highest root colonization (95±2.9) and AM spore count (234±3.56) were observed in Phalaris minor whereas Saccharum spontaneum exhibited least colonization (30±0.53) and AM spore count (46.7±14.5), respectively. The Andropogoneae (Sorghum tribe) was observed to be the most diverse tribe in association with endomycorrhizal fungi among the studied grasses. This study confirms that the grass species are highly colonized and dependent on endomycorrhizal association. The diversity and colonization patterns of endotrophic mycorrhizal fungi are described in details in this research paper. The AM fungal association with grass species provides new vistas and insight on the functioning of any grass ecosystem and also helps in harnessing the benefits of AM fungi through their usage in waste and abundant land reclamation programmes.

Quantification of arbuscular mycorrhizal fungi root colonization in wheat, tomato, and leek using absolute qPCR

Arbuscular mycorrhizal fungi (AMF) form symbioses with most terrestrial plants and are known to have a positive effect on plant growth and health. Different methodologies have been developed to assess the AMF-plant symbiosis. The most applied method, which involves staining of roots and microscopic observation of the AMF structures, is tedious and time-consuming and the results are highly dependent on the observer. Using quantitative polymerase chain reaction (qPCR) to quantify AMF root colonization represents a reliable, high-throughput technique that allows the assessment of numerous samples. Quantification with qPCR can be performed through two methods: relative quantification and absolute quantification. In relative quantification, the target gene is normalized with a reference gene. On the other hand, absolute quantification involves the use of a standard curve, for which template DNA is serially diluted. In a previous paper, we validated the primer pair AMG1F and AM1 for a relative quantification approach to assess AMF root colonization in Petunia. Here, we tested the same primers with an absolute quantification approach and compared the results with the traditional microscopy method. We evaluated the qPCR method with three different crops, namely, wheat (cv. Colmetta and Wiwa), tomato, and leek. We observed a strong correlation between microscopy and qPCR for Colmetta (r = 0.90, p < 0.001), Wiwa (r = 0.94, p < 0.001), and tomato (r = 0.93, p < 0.001), but no correlation for leek (r = 0.27, p = 0.268). This highlights the importance of testing the primer pair for each specific crop.

Durum wheat-lentil relay intercropping enhances soil mycorrhizal activity but does not alter structure of arbuscular mycorrhizal fungal community within roots

In intercropping systems, crop species select host-adapted microorganisms and influence the associated plant-microbial interactions like in the case of arbuscular mycorrhizal fungi (AMF). Attempts to assess the impact of intercropping on the activity, diversity, and community composition of AMF remain inconclusive, more so in intercropping systems involving traditional Mediterranean crops such as durum wheat and lentils. We carried out field experiments in Central Italy to assess the impact of relay intercropping durum wheat (Triticum durum Desf. cv. Minosse) and lentil (Lens culinaris Medik. cv. Elsa) on soil mycorrhizal inoculum potential (MIP) (2019 and 2020), AMF root colonization (2019, 2020, and 2021), and root AMF diversity and community composition (2020 and 2021), compared to the respective sole crops. Results showed that relay intercropping enhanced lentil grain yield and durum wheat grain protein concentration but marginally reduced durum wheat grain yield and lentil grain protein concentration. In addition, relay intercropping enhanced soil mycorrhizal activity but differentially influenced mycorrhizal root colonization compared to sole cropping. Sequencing analyses generated a total of 234 amplicon sequence variants belonging to Glomeromycota, which were assigned to 31 virtual taxa using the MaarjAM reference database. Glomeraceae and Claroideoglomeraceae were the most abundant taxa but had contrasting abundances in 2020 and 2021. The overall changes in AMF species diversity and community structure were affected by the interaction between crop species and year, and not by intercropping. Claroideoglomus and Septoglomus showed a strong association with lentil roots while Rhizophagus and Paraglomus were associated with durum wheat roots in 2020, affirming host genotype-AMF preferences. The principal component analysis showed that grain protein concentration was associated with selected mycorrhizal parameters such as community richness and AMF root colonization. Further studies on the functional analysis of the different AMF communities selected by the crop genotype and year may reveal the importance of intercropping in maintaining soil functionality and productivity under low-input systems.

Native mycorrhizal communities in maize roots as affected by plant genotype, starter fertilization and a seed-applied biostimulant

Background and aimsOne of the most promising strategies for sustainable intensification of crop production involves the utilization of beneficial root-associated microorganisms, such as plant growth-promoting bacteria and arbuscular mycorrhizal fungi (AMF). The aim of this study was to investigate whether a seed-applied biostimulant, based on the bacterial strain Bacillus amyloliquefaciens IT-45 and a plant polysaccharide extract, and crop enhancement tools, such as hybrids with contrasting early vigor and nitrogen (N) plus phosphorus (P) starter fertilization, and their interactions, shape the communities of native root-colonizing AMF symbionts in maize.MethodsA factorial growth chamber experiment was set up with two maize genotypes in natural soil. Mycorrhizal colonization was evaluated after root staining. The diversity and composition of AMF communities were assessed by PCR-DGGE of the 18S rRNA gene and amplicon sequencing.ResultsN and P fertilization determined a consistent reduction of AMF root colonization and, in combination of biostimulant, a reduction of AMF richness. The biostimulant alone generally did not affect AMF colonization or the community biodiversity. In addition the effect of the two factors were modulated by maize genotype. In all treatments, predominant AMF were represented by Glomus sp. and Funneliformis mosseae, while populations of the genus Rhizoglomus were rarely detected in biostimulant and NP fertilization treatments.ConclusionThe results of this study increase our understanding of how the biostimulant seed treatment may affect native AMF communities, depending on NP fertilization and maize genotype and may improve the implementation of innovative tools in sustainable and resilient agroecosystems.