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Background: Arbuscular mycorrhizal fungi (AMF) can regulate metal(loid) tolerance in plants and their capacity for phytoremediation. These effects can vary depending on the host plant and the AMF species. The impact of different AMF species on the ability of safflower (Carthamus tinctorius L.) for arsenic (As) phytoremediation is still largely unknown. Therefore, this study aimed to assess the effect of two AMF species, Rhizophagus irregularis, and Funneliformis mosseae, on the tolerance and accumulation of As in safflower in soils spiked with varying arsenate concentrations (0, 25, 50, and 100 mg kg−1). Results: The results indicated that both AMF species established effective symbiotic relationships with safflower. However, plants inoculated with R. irregularis exhibited higher mycorrhizal dependency and root colonization, especially under 100 mg kg−1 As. Both AMF species significantly improved plant growth parameters, chlorophyll content, and phosphorus (P) nutrition, which resulted in increased P/As ratio and enhanced tolerance index in safflower plants. In addition, AMF inoculation reduced As-induced lipid peroxidation by enhancing catalase and peroxidase activity in leaves and roots. While the mycorrhizal symbiosis didn't affect As availability in soils, it significantly reduced shoot As concentration and the translocation factor under all As levels. Furthermore, mycorrhizal inoculation, especially with R. irregularis, increased As concentration and modified-bioconcentration factor in the roots and enhanced total As uptake per plant. Conclusions: Based on the results and multivariate analyses, both AMF species, particularly R. irregularis, enhanced safflower's As tolerance by retaining As in roots, improving phosphorus nutrition, and increasing antioxidant enzyme activity, showcasing their potential to enhance phytostabilization in safflower plants. [ABSTRACT FROM AUTHOR]

Mucoromycotina "fine root endophyte" (MFRE) fungi are an understudied group of plant symbionts that regularly co-occur with arbuscular mycorrhizal fungi. The functional significance of MFRE in plant nutrition remains underexplored, particularly their role in plant nitrogen (N) assimilation from the variety of sources typically found in soils. Using four 15N-labeled N sources to track N transfer between MFRE and Plantago lanceolata , applied singly and in tandem, we investigated N source discrimination, preference, and transfer to host plants by MFRE. We traced movement of 14C from plants to MFRE to determine the impact of N source type on plant carbon (C) allocation to MFRE. We found that MFRE preferentially transferred N derived from glycine and ammonium to plant hosts over that derived from nitrate and urea, regardless of other N sources present. MFRE mycelium supplied with glycine and ammonium contained more plant-derived carbon than those supplied with other N sources. We show that the MFRE directly assimilates and metabolizes organic compounds, retaining C to meet its own metabolic requirements and transferring N to plant hosts. Our findings highlight diversity in the function of endomycorrhizal associations, with potentially profound implications for our understanding of the physiology and ecology of plant-fungal symbioses. [Display omitted] • MFRE preferentially transfer 15N from glycine and ammonium to plants • MFRE supplied with glycine and ammonium received most plant carbon • MFRE fungi use organic compounds, retaining C and transferring N to plants • Plants benefits from MFRE symbiosis depend on substrate nutrient availability Mucoromycotina fine root endophytes (MFRE) are symbiotic fungi that transfer soil nutrients to plants, gaining carbon (C). Howard et al. show that MFRE prefer nitrogen (N) from glycine and ammonium over nitrate and urea, transferring N to the plant and retaining C; N availability influences this, highlighting the importance of MFRE in plant nutrition. [ABSTRACT FROM AUTHOR]

Mycoheterotrophs are non‐photosynthetic plants that obtain all of their carbon requirements through parasitizing mycorrhizal fungi. They originated from the autotrophic ancestors and usually have more specific relationships with fungi than that of green plants, for reasons that are largely unknown. Determining the factors that lead to specificity in mycoheterotrophs could provide insights on the constraints to mycoheterotrophic evolution. Here we assess the fungal diversities in mycoheterotrophic plants and their co‐occurring plants to determine the roles of ecological factors on the specific fungal associations in mycoheterotrophic plants. We investigated mycorrhizal fungal communities in 16 populations of seven Burmannia species with different trophic modes and their co‐occurring plants using high‐throughput sequencing to assess the tripartite relationships of fungi, mycoheterotrophs and co‐occurring autotrophs. We found that mycoheterotrophic species have similar fungal richness to their chlorophyllous relatives, indicating that they are not associated with a reduced set of fungal partners. The preference of mycoheterotrophic species toward specialized fungal assemblages is consistent with the pattern found in the green autotrophic plants within forest habitats, suggesting a coupling of the fungal phylogenetic constraints between mycoheterotrophs and their co‐occurring autotrophs. We furthermore show that the turning to fungal communities having closer phylogenetic relationships during habitat shifts from open grasslands to shaded forests might provide the basis for the specialization of mycorrhizal associations in mycoheterotrophic species of Burmannia. Our findings suggest that fungal niche shifts may have promoted fungal partner changes and specialization in mycoheterotrophic plants. Our results provide new insights into the ecological factors leading to the specialized interactions between mycoheterotrophic plants and their fungal partners, expanding our understanding of the evolutionary trajectories followed by mycoheterotrophs. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The high dependence on chemical fertilizers in the farming systems especially in the arid regions has become a serious challenge that threatens the stability and sustainability of crop production. Therefore, determining alternative nutrition systems based on the organic and biological sources is a critical issue of crops management. The objective of this study is to assess the response of the roselle (Hibiscus sabdariffa L.) to chemical, organic and biological nutrient systems. A two-year field experiment was conducted with a split-plot based on randomized complete blocks design with three replications. The main plots consisted of control (CL), vermicompost (VP), poultry manure (PM), and chemical fertilizer (NPK) (CF), while the sub-plots involved control (AM0), application of Glomus mosseae (AM1), and Rhizophagus intraradices arbuscular mycorrhiza (AM2). The results showed that PM and CF treatments led to the highest increase in fresh calyx yield (58.6%) compared to the control. While PM treatment showed the highest increase in dry calyx yield (23.9%) and seed yield (32.0%). AM inoculation resulted in a 27.3, 26.8, and 22.3% increase in mentioned traits, respectively compared to the control. PM treatment showed the highest values of dry calyx and seed water productivity (13.5 and 15.5 kg m−3, respectively). Also, AM2 treatment showed the highest values for these indices (13.5 and 14.5 kg m−3, respectively). The highest increase in calyx ascorbic acid (20.1%) was obtained from PM treatment, while the highest value of calyx anthocyanin content (0.307 and 0.292 µmol g−1) in the first and the second year was found in PM and CF treatment, respectively. VC treatment resulted in the highest increase in seed oil content (12.8%), while the highest increase in seed protein content (22.8%) belonged to the CF treatment. The average improvements in the calyx ascorbic acid, calyx anthocyanin content, seed oil content, and seed protein content due to AM inoculation were 11.2, 5.0, 9.2, and 7.8%, respectively. According to our findings, the use of mycorrhiza (especially Rhizophagus intraradices) in combination with poultry manure is recommended to achieve proper economic yields and improve water productivity and quality indices of the roselle in order to replace the chemical fertilizers in the cultivation of this plant in the study area. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal (ECM) fungi are important tree symbionts within forests. The biogeography of ECM fungi remains to be investigated because it is challenging to observe and identify species. Because most ECM plant taxa have a Holarctic distribution, it is difficult to evaluate the extent to which host preference restricts the global distribution of ECM fungi. To address this issue, we aimed to assess whether host preference enhances the endemism of ECM fungi that inhabit dipterocarp rainforests. Highly similar sequences of 175 operational taxonomic units (OTUs) for ECM fungi that were obtained from Lambir Hill's National Park, Sarawak, Malaysia, were searched for in a nucleotide sequence database. Using a two‐step binomial model, the probability of presence for the query OTUs and the registration rate of barcode sequences in each country were simultaneously estimated. The results revealed that the probability of presence in the respective countries increased with increasing species richness of Dipterocarpaceae and decreasing geographical distance from the study site (i.e. Lambir). Furthermore, most of the ECM fungi were shown to be endemic to Malaysia and neighbouring countries. These findings suggest that not only dispersal limitation but also host preference are responsible for the high endemism of ECM fungi in dipterocarp rainforests. Moreover, host preference likely determines the areas where ECM fungi potentially expand and dispersal limitation creates distance–decay patterns within suitable habitats. Although host preference has received less attention than dispersal limitation, our findings support that host preference has a profound influence on the global distribution of ECM fungi. [ABSTRACT FROM AUTHOR]

Root nitrogen (N) reallocation is a conservative N-use strategy involving root N remobilization for shoot growth, reproduction, and other metabolic processes, but a critical framework for how it varies among plants is missing. Community-level root N reallocation increases with richness of plant species and N-acquisition strategies because of complementarity in N uptake and storage. Root N reallocation is a conservative trait opposite to competitive root traits along the major axis of the fast–slow spectrum of the root economics space. Root N reallocation declines with more abundant soil microbial K -strategists, hyphosphere/rhizosphere microbial recruitment, and mycorrhizal colonization due to acceleration of N release from recalcitrant organic matter and facilitation of plant efficiency in N foraging. Root nitrogen (N) reallocation involves remobilization of root N-storage pools to support shoot growth. Representing a critical yet underexplored facet of plant function, we developed innovative frameworks to elucidate its connections with key ecosystem components. First, root N reallocation increases with plant species richness and N-acquisition strategies, driven by competitive stimulation of plant N demand and synergies in N uptake. Second, competitive root traits and mycorrhizal symbioses, which enhance N foraging and uptake, exhibit trade-offs with root N reallocation. Furthermore, root N reallocation is attenuated by N-supply attributes such as increasing litter quality, soil fungi-to-bacteria ratios, and microbial recruitment in the hyphosphere/rhizosphere. These frameworks provide new insights and research avenues for understanding the ecological roles of root N reallocation. [ABSTRACT FROM AUTHOR]

Summary: To evaluate the nutritional modes of orchids associated with 'rhizoctonia' fungi, analyses of hydrogen (δ2H), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios are usually adopted. However, previous studies have not fully accounted for exchangeable hydrogens, which could affect these evaluations.Here, we performed standard δ13C, δ15N, and δ2H analyses on bulk samples. Additionally, we conducted δ2H analysis on α‐cellulose and cellulose nitrate samples to investigate whether the heterogeneity of exchangeable hydrogens among plant species influences the assessment of nutritional modes.The δ2H of orchids were consistently higher than those of surrounding autotrophic plants, irrespective of the three pretreatments. Although the rhizoctonia‐associated orchid exhibited lower δ13C, its δ2H was higher than those of the autotrophs. Notably, among all response variables, δ15N and δ2H exhibited high abilities for discriminating the nutritional modes of rhizoctonia‐associated orchids.These results indicate that a time‐efficient bulk sample analysis is an effective method for evaluating plant nutritional modes, as the heterogeneity of exchangeable hydrogens does not significantly impact the estimation. Using δ15N and δ2H benefits the assessment of partial mycoheterotrophy among rhizoctonia‐associated orchids. [ABSTRACT FROM AUTHOR]

Melon (Cucumis melo) is the most popular fruit with indisputable socio-economic and nutritional value, as evidenced by its significant acreage (1 Mha) and production (28 Mt) worldwide. However, melon farming is facing the triple challenge of producing enough to meet growing consumer demand, improving the concentration of human wellness compounds, while minimising chemical inputs. This scientific research was carried out to assess the effectiveness of two arbuscular mycorrhizal fungi (AMF), Rhizophagus irregularis (Ri), R. fasciculatus (Rf), and their complex, in improving yield and quality attributes in melon variety ‘Ananas’ grown in greenhouse. Results showed that production and fruit quality were significantly improved in mycorrhizal plants (M-plants) compared to non-mycorrhizal (NM-plants) ones, regardless of AMF treatments. M-plants performance varied according to AMF strains. Indeed, Ri-plant exhibited the highest increases in yield (54%), fresh weight (65%), longitudinal (20%) and equatorial (33%) perimeters, Brix degree (20.6%), polyphenols (315.4%), carotenoids (353%), proteins (209.1%), flavonoids (114.38%), ascorbic acid (31.3%), reducing power (77.04%), DPPH radical inhibition (16.43%), and the highest decrease in titrable acidity (62.5%). In addition, Ri-plant fruits were highly rated by participants in the sensory evaluation test. Therefore, R. irregularis application could be recommended for the sustainable production of high-quality fruits of melon. [ABSTRACT FROM AUTHOR]

One of the most prevalent symbioses on Earth is that formed between the majority of land plants and arbuscular mycorrhizal (AM) fungi. Through these intimate associations, AM fungi transfer soil nutrients to their plant hosts in exchange for photosynthetically fixed carbon resources. It has been hypothesised that this nutritional mutualism is evolutionarily stable because both partners are in control of the exchange of resources and can discriminate between partners according to whichever offers the highest returns. However, in nature, plant–AM symbioses are exposed to a wealth of additional biotic and abiotic interactions which can affect the regulation of carbon‐for‐nutrient exchange between symbionts. Moreover, the extraradical hyphae of AM fungi make up underground networks that may be interactive or physically connected, known as common mycorrhizal networks (CMNs). These can link neighbouring plants, potentially further influencing resource distribution across the network. How these layers of complexity interact to influence resource regulation and allocation between plants and AM fungi is not often considered by experimental designs. Here, we review resource allocation in AM symbioses, scaling up from evidence from reductionist experimental systems using axenic root organ cultures to complex systems incorporating multiple neighbouring plants dealing with other, co‐occurring symbionts. As experimental designs increase in scale and ecologically relevant complexity, the carbon‐for‐nutrient exchange between plants and their AM symbionts is increasingly subject to disruption associated with the wider ecological context, such as the intricacies of the plant‐fungal interactions in a CMN or the presence of co‐occurring organisms. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The use of arbuscular mycorrhizal fungi (AMF) offers promising benefits to agriculture in the Amazon regions, where soils are characteristically acidic and nutrient-poor. The purpose of this research was to investigate the potential effects of two recently described species of AMF (Nanoglomus plukenetiae and Rhizoglomus variabile) native to the Peruvian Amazon for improving the plant growth of Plukenetia volubilis (inka nut or sacha inchi) and protecting the roots against soil pathogens. Two assays were simultaneously conducted under greenhouse conditions in Peru. The first focused on evaluating the biofertilizer effect of AMF inoculation, while the second examined the bioprotective effect against the root knot nematode, Meloidogyne incognita. Overall, the results showed that AMF inoculation of P. volubilis seedlings positively improved their development, particularly their biomass, height, and the leaf nutrient contents. When seedlings were exposed to M. incognita, plant growth was also noticeably higher for AMF-inoculated plants than those without AMF inoculation. Nematode reproduction was significantly suppressed by the presence of AMF, in particular R. variabile, and especially when inoculated prior to nematode exposure. The dual AMF inoculation did not necessarily lead to improved crop growth but notably improved P and K leaf contents. The findings provide strong justification for the development of products based on AMF as agro-inputs to catalyze nutrient use and uptake and protect crops against pests and diseases, especially those that are locally adapted to local crops and cropping conditions. [ABSTRACT FROM AUTHOR]

The tiny terrestrial orchids (plant height less than 8 cm) in the genus Corybas dependent on mycorrhizal fungal (OMF) partners for seed germination and seedling development. The OMF community of the Corybas remains poorly understood, although the relevant knowledge is very important for in situ and ex situ conservation of these orchids. In this study, we characterized OMF richness and compositions of three helmet-orchid species, i.e., Corybas geminigibbus, C. himalaicus, and C. shanlinshiensis, from their natural habitats by using Illumina sequencing of the internal transcribed spacer 2 region. We found that fungal colonization was restricted in the rhizomes of the helmet-orchids instead of their tuberoids, and serendipitoid fungi were predominant, while tulasnelloid were absent in the three investigated Corybas species regardless of their altitude. The three Corybas species shared 27 serendipitoid operational taxonomic units that are different to those of their related orchids, the genera of Cyrtostylis and Stigmatodactylus. Corybas shanlinshiensis alone had a range of ectomycorrhizal fungi (mainly russuloid and thelephoroid) broader than C. himalaicus and C. geminigibbus. Our study provides new information about terrestrial orchid–fungi associations and may further contribute to orchid conservation. [ABSTRACT FROM AUTHOR]

Climate change will likely shift plant and microbial distributions, creating geographic mismatches between plant hosts and essential microbial symbionts (e.g., ectomycorrhizal fungi, EMF). The loss of historical interactions, or the gain of novel associations, can have important consequences for biodiversity, ecosystem processes, and plant migration potential, yet few analyses exist that measure where mycorrhizal symbioses could be lost or gained across landscapes. Here, we examine climate change impacts on tree-EMF codistributions at the continent scale. We built species distribution models for 400 EMF species and 50 tree species, integrating fungal sequencing data from North American forest ecosystems with tree species occurrence records and long-term forest inventory data. Our results show the following: 1) tree and EMF climate suitability to shift toward higher latitudes; 2) climate shifts increase the size of shared tree-EMF habitat overall, but 35% of tree-EMF pairs are at risk of declining habitat overlap; 3) climate mismatches between trees and EMF are projected to be greater at northern vs. southern boundaries; and 4) tree migration lag is correlated with lower richness of climatically suitable EMF partners. This work represents a concentrated effort to quantify the spatial extent and location of tree-EMF climate envelope mismatches. Our findings also support a biotic mechanism partially explaining the failure of northward tree species migrations with climate change: reduced diversity of co-occurring and climate-compatible EMF symbionts at higher latitudes. We highlight the conservation implications for identifying areas where tree and EMF responses to climate change may be highly divergent. [ABSTRACT FROM AUTHOR]

This article explores the significance of mycorrhizal symbioses, which are complex relationships between plants and fungi that have a profound impact on ecosystem dynamics and functions. It delves into the different types of mycorrhizal symbioses and examines the molecular, physiological, and ecological aspects of these interactions. The article also discusses the role of mycorrhizas in nutrient cycling and the exchange of resources between plants and fungi. It emphasizes the importance of community ecology and functional guilds in understanding mycorrhizal interactions and their implications for ecosystem resilience and biodiversity conservation. The article presents various research studies on mycorrhizal symbioses and their ecological implications, including the effects of global change on plant-mycorrhizal interactions, the characteristics of invasive mycorrhizal fungi, the mycorrhizal microbiome, and the role of arbuscular mycorrhizal fungi in agroecosystems and urban environments. The research underscores the need for interdisciplinary collaboration, the significance of comprehending molecular signaling pathways and ecosystem-scale dynamics, and the potential practical applications of mycorrhizal research in sustainable agriculture and ecosystem management. The article concludes by emphasizing the importance of ongoing research and collaboration to unlock new frontiers in mycorrhizal ecology. [Extracted from the article]

Plant roots employ diverse strategies to acquire soil nutrients, including direct nutrient uptake through absorptive fine roots and root hairs, scavenging nutrients by forming symbioses with mycorrhizal fungi, and mining nutrients by releasing root exudates. However, whether these three strategies are differently coordinated among phylogenetically closely related tree species and how this coordination shifts with stand development remains largely unclear.To fill these knowledge gaps, we measured 13 root morphological, architectural, physiological and mycorrhizal traits tightly related to nutrient‐acquisition of three Pinus species (P. sylvestris var. mongolica, P. densiflora and P. tabuliformis) at young (20‐year‐old) and mature (50‐year‐old) stages planted in nutrient‐impoverished sandy soils, in Northeast China.We found that young trees had thinner absorptive fine roots and a higher specific root length than mature trees across three Pinus species, indicating that roots become morphologically less efficient in 'do it yourself' scavenging nutrients during stand development. Moreover, young stands had greater root length density and root area index, and mature stands had faster root‐exudation rates, suggesting that young stands rely more on expanding soil volumes to scavenge nutrients and mature stands depend more on root exudation to 'mine' nutrients. The three Pinus species exhibited different nutrient‐acquisition strategies at the mature stage; P. densiflora had higher root length density and root area index, and the other two Pinus species had greater ectomycorrhizal colonization rates.Synthesis. Our findings highlight that phylogenetically closely related tree species may exhibit different nutrient‐acquisition strategies and suggest a shift from an extensive nutrient‐acquisition mode depending more on absorptive fine roots to an intensive nutrient‐acquisition mode relying more on root exudation during stand development. [ABSTRACT FROM AUTHOR]

Since the long-term sustainability of garden ecosystems is dependent on maintaining the soil quality, knowing the condition of the soils and investigating the effects of the activities on the soil properties is very important and effective in ecosystem management. To investigate the soil quality index of almond (Prunus dulcis) orchards under different managed methods in ChaharMahal va Bakhtiari province, soil samples were collected from three points in each orchard and finally classified into 6 groups (Saman, Ben, Shahrekord, Kiar, Ardel, and Farsan). To determine the soil quality index, soil characteristics including pH, EC, total and water-soluble organic carbon, basal and substrate-derived respiration, rhizosphere microbial population, and available soil P and K were analyzed. The results showed that almond orchard management in different regions affected the soil characteristics and the processes evaluated in this study. The monitoring of soil properties showed that pH 7.05 - 8.48, EC 0.23 - 2.91 dS/m, microbial respiration 0.44 - 8.57 mg CO2.100 g-1 .day-1, organic carbon 2.09 - 44.79 g/kg, available phosphorus 1.5 - 122.3 mg/kg, and available potassium were between 91.2 - 3038 mg/kg. Soil quality index components including chemical components, microbial activity, microbial population, and soil organic carbon were determined. The contribution of soil salinity to soil quality obtained using factorial analysis was the highest (31%), followed by microbial carbon mineralization coefficient (27%), rhizosphere microbial population (24%), and water-soluble organic carbon (18%). The soil quality index values for Saman, Ben, Shahrekord, Kiar, Ardal, and Farsan almond orchards were 0.46, 0.40, 0.51, 0.67, 0.54, and 0.37, respectively. These values showed that the evaluated soils are suitable for almond production in Shahrekord, Kiar, and Ardal, and for Saman, Ben, and Farsan, there is a need for serious management measures to improve soil quality and increase the sustainability of these agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Key message: Arbuscular mycorrhizal fungi generated systemic acquired resistance in cucumber to Zucchini yellow mosaic virus, indicating their prospective application in the soil as a sustainable, environmentally friendly approach to inhibit the spread of pathogens. The wide spread of plant pathogens affects the whole world, causing several plant diseases and threatening national food security as it disrupts the quantity and quality of economically important crops. Recently, environmentally acceptable mitigating practices have been required for sustainable agriculture, restricting the use of chemical fertilizers in agricultural areas. Herein, the biological control of Zucchini yellow mosaic virus (ZYMV) in cucumber (Cucumis sativus L.) plants using arbuscular mycorrhizal (AM) fungi was investigated. Compared to control plants, ZYMV-infected plants displayed high disease incidence (DI) and severity (DS) with various symptoms, including severe yellow mosaic, mottling and green blisters of leaves. However, AM fungal inoculation exhibited 50% inhibition for these symptoms and limited DS to 26% as compared to non-colonized ones. The detection of ZYMV by the Enzyme-Linked Immunosorbent Assay technique exhibited a significant reduction in AM-inoculated plants (5.23-fold) compared with non-colonized ones. Besides, mycorrhizal root colonization (F%) was slightly reduced by ZYMV infection. ZYMV infection decreased all growth parameters and pigment fractions and increased the malondialdehyde (MDA) content, however, these parameters were significantly enhanced and the MDA content was decreased by AM fungal colonization. Also, the protein, proline and antioxidant enzymes (POX and CAT) were increased with ZYMV infection with more enhancements due to AM root colonization. Remarkably, defence pathogenesis-related (PR) genes such as PR-a, PR-b, and PR-10 were quickly expressed in response to AM treatment. Our findings demonstrated the beneficial function of AM fungi in triggering the plant defence against ZYMV as they caused systemic acquired resistance in cucumber plants and supported their potential use in the soil as an environment-friendly method of hindering the spread of pathogenic microorganisms sustainably. [ABSTRACT FROM AUTHOR]

Background: Increasing nitrogen (N) use efficiency (NUE) can enhance cereal yields, improve grain quality and reduce agrochemical inputs. However, several challenges are associated with achieving enhanced NUE, e.g., a frequently poor synchronization between N supply and demand; low grain yields per unit of N input; and inherent trade-offs between grain yield and quality. Scope: To address these challenges, we focus on the temporal perspective of NUE related processes at different growth stages, and propose the utilization of beneficial microbes, e.g. arbuscular mycorrhizal fungi (AMF) for their roles in affecting aspects of NUE particularly at the later development stages. Conclusion: Some evidence suggests that AMF can directly promote N uptake and use in cereals, by regulating N transporters, but the indirect effects of AMF on NUE related processes at different growth stages are poorly known. Here we explore AMF and their potential roles in promoting NUE related processes that enhance crop P and N uptake post-anthesis, when nutrient supply often is low. In order to fully exploit the opportunities for beneficial root-fungal symbiosis, we propose approaches for plant breeding and crop management, and consider the potential of plant-microbe interactions post-anthesis to promote NUE and the sustainable production of especially cereals. [ABSTRACT FROM AUTHOR]

The associations of arbuscular mycorrhizal (AM) or ectomycorrhiza (EcM) fungi with plants have sequentially evolved and significantly contributed to enhancing plant nutrition. Nonetheless, how evolutionary and ecological forces drive nutrient acquisition strategies of AM and EcM woody plants remains poorly understood. Our global analysis of woody species revealed that, over divergence time, AM woody plants evolved faster nitrogen mineralization rates without changes in nitrogen resorption. However, EcM woody plants exhibited an increase in nitrogen mineralization but a decrease in nitrogen resorption, indicating a shift towards a more inorganic nutrient economy. Despite this alteration, when evaluating present‐day woody species, AM woody plants still display faster nitrogen mineralization and lower nitrogen resorption than EcM woody plants. This inorganic nutrient economy allows AM woody plants to thrive in warm environments with a faster litter decomposition rate. Our findings indicate that the global pattern of nutrient acquisition strategies in mycorrhizal plants is shaped by the interplay between phylogeny and climate. [ABSTRACT FROM AUTHOR]

Summary: Root hair is regarded as a pivotal complementary survival tactic for mycorrhizal plant like Abies beshanzuensis when symbiosis is disrupted. Relatively little is known about the mechanism underlying root hair morphogenesis in plant species that are strongly dependent on mycorrhizal symbiosis. Many of these species are endangered, and this knowledge is critical for ensuring their survival.Here, a MYB6/bHLH13‐sucrose synthase 2 (AbSUS2) module was newly identified and characterized in A. beshanzuensis using bioinformatics, histochemistry, molecular biology, and transgenesis.Functional, expression pattern, and localization analysis showed that AbSUS2 participated in sucrose synthesis and was involved in root hair initiation in A. beshanzuensis. Additionally, the major enzymatic product of AbSUS2 was found to suppress root hair initiation in vitro. Our data further showed that a complex involving the transcription factors AbMYB6 and AbbHLH13 directly interacted with the promoter of AbSUS2 and strengthened its expression, thereby inhibiting root hair initiation in response to exogenous sucrose.Our findings offer novel insights into how root hair morphogenesis is regulated in mycorrhizal plants and also provide a new strategy for the preservation of endangered mycorrhizal plant species. [ABSTRACT FROM AUTHOR]

Inoculation with arbuscular mycorrhizal fungi (AMF) has allowed for controlled development and growth in different species. However, its effect on some tropical species such as Swietenia mahagoni has not been evaluated. This study evaluated the growth and photosynthetic development of S. mahagoni produced in substrates inoculated with AMF. Using a completely randomized design, the combinations of two factors were evaluated: substrate (cocoa husk + coconut fiber + composted pine sawdust in proportions 6:2:2 and 2:6:2, and a control composed of soil + cocoa husks in a 9:1 ratio) and mycorrhizal strains (Glomus cubense, Rhizoglomus irregulare and Funneliformis mosseae). From 30 to 120 days after the seed's germination in the nursery, the leaf surface and the total dry mass were evaluated, and growth analysis was carried out using the relative growth rate and the net assimilation rate. At 120 days, the photosynthetic rate, stomatal conductance, transpiration and internal CO2 concentration were evaluated. Significant interactions between the different factors were found for all the variables evaluated. The Glomus cubense and Rhizophagus intraradices strains, in the substrate made up of 20 % cocoa husk + 60 % coconut fiber + 20 % sawdust, produced significant increases in the growth and photosynthetic development of S. mahagoni. The importance of the mycorrhizal association is evident, as it provides S. mahagoni seedlings with more efficient photosynthetic mechanisms, improving their establishment in plantations. [ABSTRACT FROM AUTHOR]

Background: Panax quinquefolius L. is one of the most important foods and herbs because of its high nutritional value and medicinal potential. In our previous study we found that the ginsenoside content in P. quinquefolius was improved by arbuscular mycorrhizal fungi (AMFs). However, little research has been conducted on the molecular mechanisms in P. quinquefolius roots induced by AMFs colonization. To identify the metabolomic and transcriptomic mechanisms of P. quinquefolius induced by AMFs, non‐mycorrhized (control) and mycorrhized (AMF) P. quinquefolius were used as experimental materials for comparative analysis of the transcriptome and metabolome. Results: Compared with the control, 182 metabolites and 545 genes were significantly changed at the metabolic and transcriptional levels in AMFs treatment. The metabolic pattern of AMFs was changed, and the contents of ginsenosides (Rb1, Rg2), threonine, and glutaric acid were significantly increased. There were significant differences in the expression of genes involved in plant hormone signal transduction, glutathione metabolism, and the plant–pathogen interaction pathway. In addition, several transcription factors from the NAC, WRKY, and basic helix–loop–helix families were identified in AMFs versus the control. Furthermore, the combined analysis of 'transcriptomics–metabolomics' analysis showed that 'Plant hormone signal transduction', 'Amino sugar and nucleotide sugar metabolism' and 'Glutathione metabolism' pathways were the important enriched pathways in response to AMFs colonization. Conclusion: Overall, these results provide new insights into P. quinquefolius response to AMFs, which improve our understanding of the molecular mechanisms of P. quinquefolius induced by AMFs. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Orchid mycorrhiza forms unique symbiotic associations between members of the Orchidaceae and multiple ecological guilds of fungi. Because orchids associate with a wide variety of fungi with different ecological functions, they represent an ideal study system to address fundamental questions about the evolution and ecophysiology of mycorrhizal symbiosis. Although it is well established that shifts in mycorrhizal associations are linked to transitions in plant trophic mode, it remains unclear what ecological drivers promote these evolutionary changes.Here, we investigated mycorrhizal communities and isotope signatures across six populations of the terrestrial orchid Neottia ovata growing under contrasting light conditions in temperate Europe. We hypothesized that plants growing in forests would associate with different mycorrhizal fungi than plants occurring in grasslands and that the limited light availability in forests leads to a higher contribution of fungi to the carbon budget of orchids.Our results showed that N. ovata predominantly associated with rhizoctonia fungi of the family Serendipitaceae in both habitats, but plants in forests also recruited ectomycorrhizal fungi. Root communities highly resembled soil communities and variation in root communities was significantly related to habitat type and edaphic factors. In contrast, isotope signatures (13C, 15N, 2H and 18O) and N concentration showed no significant relationship with habitat type. In addition, both 13C and 2H were not significantly correlated to habitat's light availability.Although it has been suggested that the presence of a wide variety of ectomycorrhizal fungi in root communities of orchids can serve as a precursor for evolutionary shifts to partial mycoheterotrophy (mixotrophy), the presence or absence of ectomycorrhizal fungi did not substantially influence the isotope signatures of N. ovata. These results indicate that rhizoctonia fungi played the major functional role in C and nutrient supply and that ectomycorrhizal fungi did not substantially contribute to the carbon budget of the plants. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

SUMMARY: Plant responses to environmental change are mediated via changes in cellular metabolomes. However, <5% of signals obtained from liquid chromatography tandem mass spectrometry (LC‐MS/MS) can be identified, limiting our understanding of how metabolomes change under biotic/abiotic stress. To address this challenge, we performed untargeted LC‐MS/MS of leaves, roots, and other organs of Brachypodium distachyon (Poaceae) under 17 organ–condition combinations, including copper deficiency, heat stress, low phosphate, and arbuscular mycorrhizal symbiosis. We found that both leaf and root metabolomes were significantly affected by the growth medium. Leaf metabolomes were more diverse than root metabolomes, but the latter were more specialized and more responsive to environmental change. We found that 1 week of copper deficiency shielded the root, but not the leaf metabolome, from perturbation due to heat stress. Machine learning (ML)‐based analysis annotated approximately 81% of the fragmented peaks versus approximately 6% using spectral matches alone. We performed one of the most extensive validations of ML‐based peak annotations in plants using thousands of authentic standards, and analyzed approximately 37% of the annotated peaks based on these assessments. Analyzing responsiveness of each predicted metabolite class to environmental change revealed significant perturbations of glycerophospholipids, sphingolipids, and flavonoids. Co‐accumulation analysis further identified condition‐specific biomarkers. To make these results accessible, we developed a visualization platform on the Bio‐Analytic Resource for Plant Biology website (https://bar.utoronto.ca/efp%5fbrachypodium%5fmetabolites/cgi‐bin/efpWeb.cgi), where perturbed metabolite classes can be readily visualized. Overall, our study illustrates how emerging chemoinformatic methods can be applied to reveal novel insights into the dynamic plant metabolome and stress adaptation. Significance Statement: The inability to identify a vast majority of peaks detected in untargeted metabolomics studies creates a bottleneck in understanding how plants respond metabolically to stress. Here, using Brachypodium distachyon as a model, we employed information theory and machine learning to assess how leaf and root metabolomes and specific chemical structural classes change under stress, revealing novel insights. [ABSTRACT FROM AUTHOR]

Mycorrhizas are widespread below‐ground symbioses formed between plant roots and soil fungi. This plant–fungal partnership impacts terrestrial ecosystems by mediating plant performance and biogeochemical processes. The influence of mycorrhizas on plant and ecosystem functioning is ultimately driven by the biological processes that regulate plant–mycorrhizal interactions. Although convergent patterns in morphological and genetic traits of mycorrhizas have been well‐documented and reflect key selection forces that shape the biology of mycorrhizas, generalizable traits of mycorrhizal‐associated root metabolome, which are more intimately linked to plant and ecosystem functioning, remain unexplored.Here, we compared mycorrhizal‐associated metabolome alterations across multiple plant–mycorrhizal fungus combinations. Specifically, we inoculated a phylogenetically diverse set of temperate tree species with either arbuscular mycorrhizal or ectomycorrhizal fungi (the two major mycorrhizal lifestyles). Using comprehensive metabolomics approaches, we then assessed the metabolome in mycorrhizal and non‐mycorrhizal roots and the corresponding leaves.Comparing across multiple plant–mycorrhizal fungus combinations, our data revealed metabolite alterations unique to mycorrhizal lifestyle as well as those common across plant–fungus combinations irrespective of lifestyles. Roots colonized by arbuscular mycorrhizal and ectomycorrhizal fungi accumulated different sets of carbohydrates, reflecting unique carbon allocation strategies for mycorrhizas. Arbuscular mycorrhizal roots accumulated cyclic polyols (e.g. inositols) inaccessible to their fungal partners, suggesting tight regulation of carbon partitioning. Such accumulation did not occur in ectomycorrhizal‐colonized roots, which instead accrued acyclic polyols (e.g. mannitol and arabitol) that were undetected in non‐mycorrhizal roots and likely of fungal origin. Mycorrhizas also altered specialized metabolism, featuring frequent increases in flavan‐3‐ols (e.g. catechins, gallocatechins, and their oligomers) but decreases in flavanols irrespective of mycorrhizal lifestyles, suggesting tactical reconfiguration of specialized metabolites to both facilitate and restrain the symbiont. These characteristic metabolite alterations were largely root specific and were not mirrored in leaves.Synthesis. Using multiple plant–mycorrhizal systems and metabolomics approaches, our study demonstrates that part of the metabolite alterations occurring during root–mycorrhizal interactions were relatively common across plant–mycorrhizal systems, with implications for both carbon partitioning and tissue protection strategies important for successful symbiosis. These generalizable patterns appear robust to the phylogenetic history of host plants and thus may be widespread in land plants. [ABSTRACT FROM AUTHOR]

Nutrient acquisition in plants can be represented by a suite of intercorrelated root traits such as root diameter, nitrogen content, root tissue density and specific root length. However, it is unclear how a plant's ability to precisely forage for nutrients in a heterogeneous soil environment (i.e. the precision of placing roots into nutrient‐rich areas) relates to these traits. Mycorrhizal symbiosis also affects the relationship between the fine root traits and root foraging precision because fungal hyphae may be used for foraging instead of roots. Hypotheses matching high root foraging precision with low mycorrhizal colonization or 'fast' acquisitive strategies of plants have been raised based either on data from tree species or a limited number of herbaceous species. To test these hypotheses, we compiled data quantifying the experimentally measured degree to which root biomass responded to patchy substrate nutrient concentrations (i.e. root foraging precision) for 123 herbaceous grassland species using a partial meta‐analysis. We tested root foraging precision relationship with root traits involved in nutrient acquisition and mycorrhizal symbiosis (root diameter, specific root length, root tissue density, root tissue nitrogen content and mycorrhizal colonization). The root foraging precision data came from four different pot experiments, and the trait data were extracted from publicly available trait databases. We used a phylogenetically informed approach in order to detect the degree of conservation of the relationships. We found that root foraging precision was not significantly correlated with other fine root traits and mycorrhizal colonization. Thus, it appears unrelated to the main dimensions of the nutrient acquisition space of herbaceous species, namely acquisitive–conservative strategy and outsourcing of acquisition to the fungi. Also, we found only a very weak phylogenetic signal in root foraging precision of 123 species. Our results suggest that root foraging precision constitutes another distinct, evolutionarily independent dimension in herbaceous species' trait space. [ABSTRACT FROM AUTHOR]

Rhizosphere effect of nanoscale zero‐valent iron (nZVI) is crucial but little reported. Maize seeds were dressed with four nZVI concentrations (0, 1.0, 1.5, 2 g kg−1) and inoculated with arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). The SEM images illuminated that excessive nZVI particles (2 g kg−1) were agglomerated on the surface of hyphae and spore, causing severe deformation and inactivation of AMF symbionts and thereafter inhibiting water uptake in maize seedlings. This restrained the scavenging effects of enzymatic (superoxide dismutase, peroxidase) and non‐enzymatic compounds (proline & malondialdehyde) on ROS, and leaf photoreduction activity and gas exchange ability (p < 0.05). Interestingly, the inoculation with AMF effectively alleviated above negative effects. In contrast, appropriate dose of nZVI, that is, ≤1.5 g kg−1, can be evenly distributed on the hyphae surface and form the ordered symbionts with AMF. This help massively to enhance hyphae growth and water and nutrient uptake. The enhanced mycorrhizal infection turned to promote rhizosphere symbiont activity and leaf Rubisco and Rubisco activase activity. Light compensation point was massively lowered, which increased photosynthetic carbon supply for AMF symbionts. Particularly, such priming effects were evidently enhanced by drought stress. Our findings provided a novel insight into functional role of nZVI in agriculture and AMF‐led green production. Summary Statement: Proper dose of nZVI can form orderly rhizosphere symbiont with AMF, improve the Rubisco and Rubisco activity for higher assimilation rate, and promote carbon supply for AMF colonization. Yet, excessive nZVI turned to cause severe structural deformation and inactivation of AMF symbionts. [ABSTRACT FROM AUTHOR]

Plant roots associate with diverse microbes (including bacteria, fungi, archaea, protists, and viruses) collectively called the root-associated microbiome. Among them, mycorrhizal fungi colonize host roots and improve their access to nutrients, usually phosphorus and nitrogen. In exchange, plants deliver photosynthetic carbon to the colonizing fungi. This nutrient exchange affects key soil processes, the carbon cycle, and plant health and therefore has a strong influence on the plant and microbe ecosystems. The framework of nutrient exchange and regulation between host plant and arbuscular mycorrhizal fungi has recently been established. The local and systemic regulation of mycorrhizal symbiosis by plant nutrient status and the autoregulation of mycorrhizae are strategies by which plants maintain a stabilizing free-market symbiosis. A better understanding of the synergistic effects between mycorrhizal fungi and mycorrhizosphere microorganisms is an essential precondition for their use as biofertilizers and bioprotectors for sustainable agriculture and forestry management. [ABSTRACT FROM AUTHOR]

Recent studies have indicated that soil contamination with microplastics (MPs) can negatively affect agricultural productivity, although these effects vary greatly depending on the context. Furthermore, the mechanisms behind these effects remain largely unknown. In this study, we examined the impact of two concentrations of polypropylene (PP) fibers in the soil (0.4 % and 0.8 % w/w) on soybean growth, nitrogen uptake, biological nitrogen fixation (BNF), and water use efficiency by growing plants in two soil types, with and without arbuscular mycorrhizal fungi (AMF). PP contamination consistently reduced vegetative growth (–12 %, on average compared to the control), with the severity of this effect varying significantly by soil type (more pronounced in Alfisol than in Vertisol). The extent of BNF progressively reduced with the increase in PP contamination level in both soils (on average, –17.1 % in PP0.4 and –27.5 % in PP0.8 compared to the control), which poses clear agro–environmental concerns. Water use efficiency was also reduced due to PP contamination but only in the Alfisol (–9 %, on average). Mycorrhizal symbiosis did not seem to help plants manage the stress caused by PP contamination, although it did lessen the negative impact on BNF. These findings are the first to demonstrate the effect of PP on BNF in soybean plants, underscoring the need to develop strategies to reduce PP pollution in the soil and to mitigate the impact of PP on the functionality and sustainability of agroecosystems. [Display omitted] • Polypropylene (PP) fibers inhibited soybean growth in two different soil types. • 0.4 % PP in soil reduced biological nitrogen fixation (BNF) and water use efficiency. • Increasing PP contamination to 0.8 % did not significantly change the effects. • Mycorrhiza did not help plants overcome PP stress but mitigated the impact on BNF. [ABSTRACT FROM AUTHOR]

Domestication processes, amplified by breeding programs, have allowed the selection of more productive genotypes and more suitable crop lines capable of coping with the changing climate. Notwithstanding these advancements, the impact of plant breeding on the ecology of plant–microbiome interactions has not been adequately considered yet. This includes the possible exploitation of beneficial plant–microbe interactions to develop crops with improved performance and better adaptability to any environmental scenario. Here we discuss the exploitation of customized synthetic microbial communities in agricultural systems to develop more sustainable breeding strategies based on the implementation of multiple interactions between plants and their beneficial associated microorganisms. Domestication process and breeding programs, focused exclusively on the selection and improvement of specific plant traits, have negatively affected the recruitment and functionality of beneficial associations in agricultural systems. Rhizosphere and root-associated microorganisms play important roles in plant growth and resilience. Breeding programs aiming to rationally manipulate root traits in order to recruit beneficial microorganisms or to deter pathogens need to be developed. The development and application of synthetic communities ('SynComs') represent a sustainable way to improve plant growth and resilience. [ABSTRACT FROM AUTHOR]

Root exudation of carboxylates is a key response to phosphorus (P) limitation for many plant species. However, sampling and quantitative and qualitative determination of root exudates under field conditions faces various challenges. Recently, multiple studies have demonstrated that manganese (Mn) concentration in mature leaves may serve as a proxy for rhizosheath carboxylate concentration. In this issue of Plant and Soil, the paper by Yan and co-authors shows that leaf Mn concentration ([Mn]) was higher in P-limited forests of southern China than in forests of northern China that exhibit higher soil [P]. This study revealed the potential relationships between rhizosheath carboxylates and leaf [Mn] in the studied Chinese flora, and indicates a potential common strategy (i.e. root carboxylate exudation) among plants, including many mycorrhizal plants, in P-limited forests. Despite the fact that there is great variation among plant species, and the molecular basis underlying the positive correlation between plant Mn uptake and root release of carboxylates remains largely unexplored, this study has paved the road for an easy and reliable way to assess rhizosheath carboxylates in forest ecosystems. In combination with the handheld X-ray fluorescence spectroscopy system that enables non-destructive analysis of [Mn] in dried mature leaves (e.g., herbarium specimens), researchers are now able to estimate the patterns of root-released carboxylates for a broad range of plant species under various environmental conditions, in an easy, rapid and low-costs way. [ABSTRACT FROM AUTHOR]

Climate change has intensified drought conditions, aiding the spread of some invasive plant species. However, the impact of drought on invasion control, such as clipping, remains largely unexplored. Therefore, we conducted a greenhouse experiment to investigate the growth of an invasive non-native grass, Johnsongrass (Sorghum halepense), under drought and non-drought conditions, coupled with clipping and non-clipping treatments. We measured above- and belowground biomass and eco-physiological parameters of photosynthesis, plant water and nutrient status, and arbuscular mycorrhizal (AM) fungi-related factors. We also developed a theoretical model simulating the population dynamics of a hypothetical invasive grass species, enabling us to generalize the effects of clipping across a broad gradient of drought conditions. We found that: (1) The differences in aboveground biomass between clipped and non-clipped grasses were significant under the condition of non-drought, but became non-significant under drought; (2) Our model also showed a decrease in the clipping-caused population difference with increasing drought severity; (3) The clipped grasses exhibited a higher carbon assimilation rate and lower water stress compared to non-clipped ones under drought, but these differences were non-significant without drought; (4) The difference in leaf phosphorus concentration and AM fungal abundances between the clipped and non-clipped grasses were consistent across both drought levels. Taken together, the clipping efficacy was diminished under drought likely due to the low water stress experienced by clipped grasses. Furthermore, the AM fungi-related factors are unlikely to drive the reduced clipping efficacy. Therefore, the implementation of control treatment could consider climate conditions to improve the control efficacy. [ABSTRACT FROM AUTHOR]

Soil desertification poses a critical ecological challenge in arid and semiarid climates worldwide, leading to decreased soil productivity due to the disruption of essential microbial community processes. Fungi, as one of the most important soil microbial communities, play a crucial role in enhancing nutrient and water uptake by plants through mycorrhizal associations. However, the impact of overgrazing-induced desertification on fungal community structure, particularly in the Caatinga biome of semiarid regions, remains unclear. In this study, we assessed the changes in both the total fungal community and the arbuscular mycorrhizal fungal community (AMF) across 1. Natural vegetation (native), 2. Grazing exclusion (20 years) (restored), and 3. affected by overgrazing-induced degradation (degraded) scenarios. Our assessment, conducted during both the dry and rainy seasons in Irauçuba, Ceará, utilized Internal Transcribed Spacer (ITS) gene sequencing via Illumina® platform. Our findings highlighted the significant roles of the AMF families Glomeraceae (∼71% of the total sequences) and Acaulosporaceae (∼14% of the total sequences) as potential key taxa in mitigating climate change within dryland areas. Moreover, we identified the orders Pleosporales (∼35% of the total sequences) and Capnodiales (∼21% of the total sequences) as the most abundant soil fungal communities in the Caatinga biome. The structure of the total fungal community differed when comparing native and restored areas to degraded areas. Total fungal communities from native and restored areas clustered together, suggesting that grazing exclusion has the potential to improve soil properties and recover fungal community structure amid global climate change challenges. [ABSTRACT FROM AUTHOR]

Analyses of variance was used to compare plant biomass and I SP i root colonization and DESeq2 (Love I et al i ., 2014) to compare fungal gene expression across drought and control treatments, respectively. Acclimation, climate change, RNA-Seq, stress, mycorrhizal symbiosis Keywords: acclimation; climate change; mycorrhizal symbiosis; RNA-Seq; stress EN acclimation climate change mycorrhizal symbiosis RNA-Seq stress 1910 1913 4 05/25/22 20220615 NES 220615 Acknowledgements Sequencing data was generated on an Illumina HiSeq 4000 that was purchased with funds from National Institutes of Health (NIH) under award number S10OD018220, KGP was supported by NSF CAREER Award DEB #1845544. [Extracted from the article]

Summary: Habitat restoration may depend on the recovery of plant microbial symbionts such as arbuscular mycorrhizal (AM) fungi, but this requires a better understanding of the rules that govern their community assembly.We examined the interactions of soil and host‐associated AM fungal communities between remnant and restored patches of subtropical montane forests.While AM fungal richness did not differ between habitat types, community membership did and was influenced by geography, habitat and host. These differences were largely driven by rare host‐specific AM fungi that displayed near‐complete turnover between forest types, while core AM fungal taxa were highly abundant and ubiquitous. The bipartite networks in the remnant forest were more specialized and hosts more specific than in the restored forest. Host‐associated AM fungal communities nested within soil communities in both habitats, but only significantly so in the restored forest.Our results provide evidence that restored and remnant forests harbour the same core fungal symbionts, while rare host‐specific taxa differ, and that geography, host identity and taxonomic resolution strongly affect the observed distribution patterns of these fungi. We suggest that host‐specific interactions with AM fungi, as well as spatial processes, should be explicitly considered to effectively re‐establish target host and symbiont communities. [ABSTRACT FROM AUTHOR]

Key message: We highlight the newly emerged roles of plant SPX-PHR proteins beyond phosphate starvation responses in controlling arbuscular mycorrhizal colonization success in roots. [ABSTRACT FROM AUTHOR]

Partially mycoheterotrophic plant species obtain organic carbon, via both photosynthesis and mycorrhizal symbiosis. In this study, we investigated the mycorrhizal fungi association and nutritional mode of Cheirostylis liukiuensis, which is suspected to be a partial mycoheterotrophic plant, due to its characteristic reduced underground organs, low-light growth environment, and some fully mycoheterotrophic species in the phylogenetically related genera. Molecular analysis of the dominant mycobiont and stable isotope analysis suggested that C. liukiuensis is a partial mycoheterotrophic plant predominantly associate with non-ectomycorrhizal Ceratobasidiaceae fungi. As examples of partial mycoheterotrophic orchids exploiting non-ectomycorrhizal rhizoctonia are still limited, this study provides valuable information on the nutritional modes of green orchids. [ABSTRACT FROM AUTHOR]

Phospholipase Ds (PLDs) are a heterogeneous group of enzymes that are widely distributed in organisms. These enzymes hydrolyze the structural phospholipids of the plasma membrane, releasing phosphatidic acid (PA), an important secondary messenger. Plant PLDs play essential roles in several biological processes, including growth and development, abiotic stress responses, and plant–microbe interactions. Although the roles of PLDs in plant-pathogen interactions have been extensively studied, their roles in symbiotic relationships are not well understood. The establishment of the best-studied symbiotic interactions, those between legumes and rhizobia and between most plants and mycorrhizae, requires the regulation of several physiological, cellular, and molecular processes. The roles of PLDs in hormonal signaling, lipid metabolism, and cytoskeletal dynamics during rhizobial symbiosis were recently explored. However, to date, the roles of PLDs in mycorrhizal symbiosis have not been reported. Here, we present a critical review of the participation of PLDs in the interactions of plants with pathogens, nitrogen-fixing bacteria, and arbuscular mycorrhizal fungi. We describe how PLDs regulate rhizobial and mycorrhizal symbiosis by modulating reactive oxygen species levels, hormonal signaling, cytoskeletal rearrangements, and G-protein activity. • PLD-PA is a key regulator of signaling cascades during plant responses to pathogens and symbionts. • PLDs and RBOHs are closely related in the early stages of plant response to pathogens. • Hormonal signaling is an essential mechanism for the regulation of the symbiosis in which PLDs may be involved. • PLDα1 is potentially involved in the regulation of the G-protein cycle during symbiosis with rhizobia. [ABSTRACT FROM AUTHOR]

Aims: It is well established that mycorrhizal symbiosis can affect plant-plant interactions. On the other hand, how intraspecific plant interactions influence communities of arbuscular mycorrhizal fungi (AMF) is still very poorly understood. Methods: We applied 454 pyrosequencing to determine the responses of AMF communities to intraspecific shoot and root interactions using Medicago sativa L. as host plant. Results: We found that intraspecific plant interaction caused significant variation in the structure of the AMF community assessed from roots but not from soil. Intraspecific root system interaction resulted in significantly elevated AMF species richness, greater total mycorrhizal and arbuscular colonization, and a larger root:shoot ratio compared to plants experiencing intraspecific shoot interaction or no interaction. Intraspecific shoot interaction resulted in significantly depressed AMF species richness. Conclusions: Our results support two hypotheses. The first is that increased AMF species richness in plants experiencing intraspecific root interaction originates from competitive release provided by high root density. The second is that shoot interaction leads to reduced allocation to root systems, increasing the stringency with which host plants selectively reward the most cooperative fungi. Because intraspecific interactions among host plants can influence the structure of their AMF community, interactions among species in complex plant communities may influence AMF community structure in addition to a plant diversity effect. [ABSTRACT FROM AUTHOR]

Photosynthetic carbon (C) allocated below‐ground can be shared with mycorrhizal fungi in exchange for nutrients, but also added into soil as rhizodeposits that potentially increases plant nutrient supply by supporting microbial nutrient mineralization from organic matter. How water and nitrogen (N) availability affects plant C allocation to the rhizosphere, including both arbuscular mycorrhizal fungi (AMF) symbionts and rhizodeposits, remains largely unknown.We used a 13CO2 pulse labelling experiment to assess the effects of drought and N addition on below‐ground allocation of C to soils and roots (quantified as excess 13C) and tested their relationships with AMF colonization in an Australian grassland. We also examined relationships between AMF and previously reported root respiration and decomposition of rhizodeposits in this study.We found that drought decreased the absolute amount of excess 13C allocated to both soils and roots, likely due to less photosynthetic C fixation. In contrast, proportionally more excess 13C was allocated to soils but less to root biomass with drought, suggesting that relatively more C was allocated to rhizodeposits and to AMF hyphal growth and extension. However, N addition reversed drought effects on below‐ground C allocation by retaining proportionally more excess 13C in roots and less in soils, congruent with higher soil N and phosphorus availability, root biomass and number of root tips compared to drought without N addition. This suggests that the alleviation of nutrient limitation promoted plants to expend relatively more C on root growth and root trait adjustment, but less C on rhizodeposition and mycorrhizal symbiosis.Synthesis. Mycorrhizal colonization related negatively to rhizodeposit decomposition rate but positively to both excess 13C in root biomass and root respiration, suggesting a possible trade‐off in C allocation between mycorrhizal symbiosis and rhizodeposition. We conclude that below‐ground C allocation in this grassland can be mediated by mycorrhizal colonization and is strongly affected by water and nutrient availability. [ABSTRACT FROM AUTHOR]

Suillus is among the best-known examples of an ectomycorrhizal (ECM) fungal genus that demonstrates a high degree of host specificity. Currently recognized host genera of Suillus include Larix, Pinus, and Pseudotsuga, which all belong to the pinoid clade of the family Pinaceae. Intriguingly, Suillus sporocarps have been sporadically collected in forests in which known hosts from these genera are locally absent. To determine the capacity of Suillus to associate with alternative hosts in both the pinoid and abietoid clades of Pinaceae, we examined the host associations of two Suillus species (S. punctatipes and S. glandulosus) through field-based root tip sampling and seedling bioassays. Root tip collections underneath Suillus sporocarps were molecularly identified (fungi: nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 [ITS barcode]; plant: trnL) to assess the association with multiple hosts. The bioassays contained both single- and two-species treatments, including a primary (Larix or Pseudotsuga) and a secondary (Picea, Pinus, or Abies) host. For the S. punctatipes bioassay, an additional treatment in which the primary host was removed after 8 mo was included to assess the effect of primary host presence on longer-term ECM colonization. The field-based results confirmed that Suillus fungi were able to associate with Abies and Tsuga hosts, representing novel host genera for this genus. In the bioassays, colonization on the primary hosts was detected in both single- and two-species treatments, but no colonization was present when Picea and Abies hosts were grown alone. Removal of a primary host had no effect on percent ECM colonization, suggesting that primary hosts are not necessary for sustaining Suillus colonization once they are successfully established on secondary hosts. Collectively, our results indicate that host specificity is more flexible in this genus than previously acknowledged and help to explain the presence of Suillus in forests where recognized hosts are not present. [ABSTRACT FROM AUTHOR]

Background and aims: Certain plant species release root carboxylates in response to phosphorus (P) limitation; however, the prevalence of root exudate release in species in P-limited forest ecosystems remains unexplored due to challenges in field assessment.Manganese (Mn) accumulation in mature leaves can indicate the presence of root carboxylate exudates in rhizosphere soil. To account for environmental factors such as soil pH, a negative reference species that does not release carboxylates is used for comparison. In this study, we assessed multiple forest stands across soil types and different levels of P availability in northern (Gansu) and southern (Guangxi) China. Leaf and soil samples were collected from 188 plant families representing various life forms, and leaf Mn concentration ([Mn]) was analyzed as a proxy for root carboxylate exudation patterns, using Dryopteridaceae as a negative reference.The results supported our hypotheses that leaf [Mn] was higher in P-limited forests of southern China compared to P-richer forests of northern China, even though the soil [Mn] was higher in the forests of northern China. Additionally, we observed a higher prevalence of species with high leaf [Mn] across various plant families in Guangxi (82%) than in Gansu (42%).Our findings suggest a potential common strategy among plants in Guangxi forests, where root exudates are released in response to P limitation, possibly due to ineffective mycorrhizal symbiosis for nutrient acquisition. The diverse forest systems in China exhibit varying soil P availability, leading to the evolution of plant species with distinct P-acquisition strategies.Methods: Certain plant species release root carboxylates in response to phosphorus (P) limitation; however, the prevalence of root exudate release in species in P-limited forest ecosystems remains unexplored due to challenges in field assessment.Manganese (Mn) accumulation in mature leaves can indicate the presence of root carboxylate exudates in rhizosphere soil. To account for environmental factors such as soil pH, a negative reference species that does not release carboxylates is used for comparison. In this study, we assessed multiple forest stands across soil types and different levels of P availability in northern (Gansu) and southern (Guangxi) China. Leaf and soil samples were collected from 188 plant families representing various life forms, and leaf Mn concentration ([Mn]) was analyzed as a proxy for root carboxylate exudation patterns, using Dryopteridaceae as a negative reference.The results supported our hypotheses that leaf [Mn] was higher in P-limited forests of southern China compared to P-richer forests of northern China, even though the soil [Mn] was higher in the forests of northern China. Additionally, we observed a higher prevalence of species with high leaf [Mn] across various plant families in Guangxi (82%) than in Gansu (42%).Our findings suggest a potential common strategy among plants in Guangxi forests, where root exudates are released in response to P limitation, possibly due to ineffective mycorrhizal symbiosis for nutrient acquisition. The diverse forest systems in China exhibit varying soil P availability, leading to the evolution of plant species with distinct P-acquisition strategies.Results: Certain plant species release root carboxylates in response to phosphorus (P) limitation; however, the prevalence of root exudate release in species in P-limited forest ecosystems remains unexplored due to challenges in field assessment.Manganese (Mn) accumulation in mature leaves can indicate the presence of root carboxylate exudates in rhizosphere soil. To account for environmental factors such as soil pH, a negative reference species that does not release carboxylates is used for comparison. In this study, we assessed multiple forest stands across soil types and different levels of P availability in northern (Gansu) and southern (Guangxi) China. Leaf and soil samples were collected from 188 plant families representing various life forms, and leaf Mn concentration ([Mn]) was analyzed as a proxy for root carboxylate exudation patterns, using Dryopteridaceae as a negative reference.The results supported our hypotheses that leaf [Mn] was higher in P-limited forests of southern China compared to P-richer forests of northern China, even though the soil [Mn] was higher in the forests of northern China. Additionally, we observed a higher prevalence of species with high leaf [Mn] across various plant families in Guangxi (82%) than in Gansu (42%).Our findings suggest a potential common strategy among plants in Guangxi forests, where root exudates are released in response to P limitation, possibly due to ineffective mycorrhizal symbiosis for nutrient acquisition. The diverse forest systems in China exhibit varying soil P availability, leading to the evolution of plant species with distinct P-acquisition strategies.Conclusion: Certain plant species release root carboxylates in response to phosphorus (P) limitation; however, the prevalence of root exudate release in species in P-limited forest ecosystems remains unexplored due to challenges in field assessment.Manganese (Mn) accumulation in mature leaves can indicate the presence of root carboxylate exudates in rhizosphere soil. To account for environmental factors such as soil pH, a negative reference species that does not release carboxylates is used for comparison. In this study, we assessed multiple forest stands across soil types and different levels of P availability in northern (Gansu) and southern (Guangxi) China. Leaf and soil samples were collected from 188 plant families representing various life forms, and leaf Mn concentration ([Mn]) was analyzed as a proxy for root carboxylate exudation patterns, using Dryopteridaceae as a negative reference.The results supported our hypotheses that leaf [Mn] was higher in P-limited forests of southern China compared to P-richer forests of northern China, even though the soil [Mn] was higher in the forests of northern China. Additionally, we observed a higher prevalence of species with high leaf [Mn] across various plant families in Guangxi (82%) than in Gansu (42%).Our findings suggest a potential common strategy among plants in Guangxi forests, where root exudates are released in response to P limitation, possibly due to ineffective mycorrhizal symbiosis for nutrient acquisition. The diverse forest systems in China exhibit varying soil P availability, leading to the evolution of plant species with distinct P-acquisition strategies. [ABSTRACT FROM AUTHOR]

•The signaling process during mycorrhiza establishment involves intense molecular communication between symbionts. It has been suggested that a group of protein effectors, the so-called MiSSPs, plays a broader function in the symbiosis metabolism, however, many of these remain uncharacterized structurally and functionally. •Herein we used three-dimensional protein structure modeling methods, ligand analysis, and molecular docking to structurally characterize and describe two protein effectors, MiSSP13 and MiSSP16.5, with enhanced expression during the mycorrhizal process in Laccaria bicolor. •MiSSP13 and MiSSP16.5 show structural homology with the cysteine and aspartate protease inhibitor, cocaprin (CCP1). Through structural analysis, it was observed that MiSSP13 and MiSSP16.5 have an active site similar to that observed in CCP1. The protein-protein docking data showed that MiSSP13 and MiSSP16.5 interact with the papain and pepsin proteases at sites that are near to where CCP1 interacts with these same targets, suggesting a function as inhibitor of cysteine and aspartate proteases. The interaction of MiSSP13 with papain and MiSSP16.5 with pepsin was stronger than the interaction of CCP1 with these proteases, suggesting that the MiSSPs had a greater activity in inhibiting these classes of proteases. Based on the data supplied, a model is proposed for the function of MiSSPs 13 and 16.5 during the symbiosis establishment. Our findings, while derived from in silico analyses, enable us formulate intriguing hypothesis on the function of MiSSPs in ectomycorrhization, which will require experimental validation. [ABSTRACT FROM AUTHOR]

Nacobbus aberrans affects plants growth and development, and decreases the production of numerous horticultural crops. Several investigations have shown that symbiosis with arbuscular mycorrhizae can confer tolerance to pathogens through different action mechanisms, such as nutrient space competition and plant resistance induction. The aim of this study was to analyse the potential of three arbuscular mycorrhizal fungi (AMF): Rhizophagus intraradices B1, Rhizophagus intraradices A2 and Funneliformis mosseae in the control of N. aberrans, and to evaluate the physiological and biochemical responses to inoculation in pepper plants. The experiment was conducted under controlled conditions. Mycorrhization percentages, chlorophyll, carotenes, soluble proteins, proline, phenolic compounds, total and reducing sugar content, relative conductivity of root cell membranes and final nematode population were determined. The mycorrhization percentages were higher in plants parasitised by N. aberrans than in those not parasitised. The final population of nematodes was reduced in the presence of mycorrhizae. In the absence of AMF, parasitism by N. aberrans caused a decrease in the soluble proteins and chlorophyll content. The loss of functionality of infected roots in the plants induced water stress, reflected by the accumulation of proline, sugar and increased the relative conductivity of cell membranes. At the same time, as a product of pathogenesis, phenolic compounds accumulated. Inoculation with AMF decreased the proline, sugars, phenolic compounds content and relative conductivity. These results show the potential for the use of AMF in pepper production to reduce the population of N. aberrans, being the strain R. intraradices B1 as the most promising candidate. [ABSTRACT FROM AUTHOR]

PREMISE: Orchids depend primarily on mycorrhizal fungi to obtain nutrients throughout their life cycle. Epiphytic orchids account for 69% of orchid diversity. The unstable availability of water and nutrients in their arboreal habitats often results in severe water and nutrient stresses. Consequently, mycorrhizal associations may be important for the survival of epiphytic orchids, but our understanding thereof remains limited. Here, we investigated the mycorrhizal community in a single epiphytic orchid species, using more samples than in any previous study. METHODS: We assessed the mycorrhizal communities of Thrixspermum japonicum, one of the most common epiphytic orchids in the temperate region of Japan. In total, 144 individuals were collected from 28 host tree species at 20 sites across 1300 km. The mycorrhizal fungi were identified based on nuclear ribosomal DNA internal transcribed spacer sequences and assigned operational taxonomic units (OTUs) based on 97% sequence similarity. RESULTS: We obtained 24 OTUs; 9 belonged to the Ceratobasidiaceae and 15 to the Tulasnellaceae. These OTUs are widely distributed throughout the phylogenetic trees of the two fungal families. However, a single Ceratobasidiaceae OTU accounted for 49.7% of all fungal sequences and was predominant in samples from 15 host tree species and 12 sites. CONCLUSIONS: Our results imply that despite having a broad range of mycorrhizal partners, T. japonicum was predominantly associated with a single fungal taxon at most of the sites among the host‐tree species investigated. These findings contribute to elucidating mycorrhizal symbiosis in epiphytic habitats. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi, forming symbiotic associations with land plants, are obligate symbionts that cannot complete their natural life cycle without a host. The fatty acid auxotrophy of AM fungi is supported by recent studies showing that lipids synthesized by the host plants are transferred to the fungi, and that the latter lack genes encoding cytosolic fatty acid synthases. Therefore, to establish an asymbiotic cultivation system for AM fungi, we tried to identify the fatty acids that could promote biomass production. To determine whether AM fungi can grow on medium supplied with fatty acids or lipids under asymbiotic conditions, we tested eight saturated or unsaturated fatty acids (C12 to C18) and two β-monoacylglycerols. Only myristate (C14:0) led to an increase in the biomass of Rhizophagus irregularis, inducing extensive hyphal growth and formation of infection-competent secondary spores. However, such spores were smaller than those generated symbiotically. Furthermore, we demonstrated that R. irregularis can take up fatty acids in its branched hyphae and use myristate as a carbon and energy source. Myristate also promoted the growth of Rhizophagus clarus and Gigaspora margarita. Finally, mixtures of myristate and palmitate accelerated fungal growth and induced a substantial change in fatty acid composition of triacylglycerol compared with single myristate application, although palmitate was not used as a carbon source for cell wall biosynthesis in this culture system. Our findings demonstrate that myristate boosts the asymbiotic growth of AM fungi and can also serve as a carbon and energy source. [ABSTRACT FROM AUTHOR]

Colubrina glandulosa has potential for reforestation of disturbed areas. Seedlings inoculated with arbuscular mycorrhizal fungi (AMF) can be produced with biosolids from Sewage Treatment Plants. This study aimed to evaluate the response of Colubrina glandulosa seedlings to isolated or mixed inoculation of different AMF species on a biosolid-based substrate under greenhouse conditions. The experimental design was completely randomized, with 32 replicates (seedlings)/treatment and five treatments: (1) control or absence of inoculation (CT); (2) inoculation with Dentiscutata heterogama (DH); (3) inoculation with Gigaspora margarita (GM); (4) inoculation with Rhizophagus clarus (RC); (5) inoculation with the mixture of the three AMF species (MT). We evaluated height and collar diameter of the seedlings at 30, 60, 90, 120, and 140 days after the experiment installation. We evaluated shoot dry biomass (SDM), root dry biomass (RDM), and total dry biomass; SDM / RDM ratio; Dickson Quality Index; relative increments in height, collar diameter, and shoot biomass; nutrient content (N, P, K) in the shoots and roots; efficiency of absorption and utilization of nutrients; rate of root mycorrhizal colonization, at 140 days. In general, the highest values of growth and nutrition variables occurred in the MT treatment, which was recommended, in comparison with CT, DH, GM, and RC. Colonization rates were low (= 20 %), regardless of the mycorrhizal inoculum, due to the high levels of phosphorus in the biosolid. [ABSTRACT FROM AUTHOR]

Sustainable management of iron (Fe) deficiency through the microbial association is highly desirable to ensure crop yield. This study elucidates whether and how arbuscular mycorrhizal fungi (AMF) ameliorate Fe deficiency symptoms in sorghum. AMF inoculation showed a significant improvement in plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), suggesting its potentiality to diminish Fe deficiency symptoms in sorghum. This AMF-driven prevention of Fe deficiency was further supported by the improvement of biochemical stress indicators, such as cell death, electrolyte leakage, hydrogen peroxide, and superoxide anion. In this study, AMF showed a significant increase in phytosiderophore (PS) release as well as Fe and S concentrations in sorghum under Fe deficiency. Quantitative real-time PCR analysis demonstrated the consistent upregulation of SbDMAS2 (deoxymugineic acid synthase 2), SbNAS2 (nicotianamine synthase 2), and SbYS1 (Fe-phytosiderophore transporter yellow stripe) in roots due to AMF with Fe deficiency. It suggests that the enhancement of Fe due to AMF is related to the mobilization of Fe(III)-PS in the rhizosphere supported by the long-distance transport of Fe by SbYS1 transporter in sorghum. Our study further showed that the elevation of S mainly in the presence of AMF possibly enhances the S-containing antioxidant metabolites (Met, Cys, and GSH) as well as enzymes (CAT, SOD, and GR) to counteract H2O2 and O2− for the restoration of redox status in Fe-deprived sorghum. Moreover, S possibly participates in Strategy II responses revealing its crucial role as a signaling molecule for Fe homeostasis in sorghum. [ABSTRACT FROM AUTHOR]

Water deficit stress is one of the major limiting factors that adversely affect plant growth and yield production. Some rhizosphere bacteria are known to promote plant growth in such stressful conditions. To study the response of quantifying canola growth, yield and yield components, to root colonization by two species of mycorrhizal fungi, a two-year field experiment was conducted at the research farm of Zanjan University. The main plot conditions were irrigation at 85% (S1), 70% (S2) and 55% (S3) of field capacity which were defined as no stress, mild and severe stress. The subplot treatments included three levels of mycorrhizal inoculation: non inoculation (control), G. mosseae and G. intraradices. The results showed that regardless of water deficit stress, colonized plants produced more biomass, seed and oil yield than non inoculated plants. Water deficit stress reduced the RWC and oil percentage of the seeds, although mycorrhizal improved these traits. Water deficit strikingly decreased the linoleic acid content in the seeds in contrast with increased stearic, oleic, arachidic and linolenic acids in the canola seeds. The presence of bacteria increased the seed oil percentage, oleic and linoleic contents. However, it decreased arachidic, particularly when the plants were subjected to water deficit stress. [ABSTRACT FROM AUTHOR]

Background and aims: Exotic invasive plants may have adverse effects on native plant communities and ecosystem functions by altering communities of belowground mutualistic mycorrhizal fungi. However, little is known about how such alterations change over time. The aim of this work was to determine the arbuscular mycorrhizal fungi (AMF) communities colonizing the roots of Nicotiana glauca populations of distinct ages (1 and 20 years old), and of co-occurring native plants, growing at four different Mediterranean semiarid locations. The short-term and long-term effects of the invader on rhizosphere activity and nutrient pools were also determined. Methods: Illumina MiSeq technology was used for high-throughput sequencing of AMF communities and basal respiration and enzymatic activities were determined for assessing rhizosphere activity. Results: The composition and structure of AMF communities differed according to the invasive character of plant and the invaded site. The AMF community belonging to the young invasive plants had a significantly different structure and composition in comparison to the native plants and the adult invasive plants. However, the native plants and the adult invasive plants harboured a similar AMF community. In general, basal respiration, enzymatic activities and nutrients of the rhizospheres of two populations of N. glauca of distinct ages were significantly different from those of the rhizosphere of native plants, but these differences were independent of the time after the invasion. Conclusions: The invasion of semiarid Mediterranean sites by N. glauca mediated temporary changes in mycorrhizal associations, whereas the early effect of this invasive plant decreasing rhizosphere activity remained across time. [ABSTRACT FROM AUTHOR]