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Mucoromycotina fine root endophytes have similar ecological functions as arbuscular mycorrhizal fungi in assisting plant nutrient uptake. The mechanisms enabling their symbiosis with plants remain largely unexplored. The mechanisms of Mucoromycotina fine root endophyte symbioses may overlap with those regulating arbuscular mycorrhizal fungal symbioses or the plant endophytes Colletotrichum tofieldiae and Serendipita indica. Contrasting colonisation mechanisms between Mucoromycotina fine root endophytes and arbuscular mycorrhiza fungi could provide insights into how ancient fungi facilitated the terrestrialisation of land plants. Investigations into mechanisms of symbiosis will benefit from inclusion of Mucoromycotina fine root endophytes as these fungi are more culturable than arbuscular mycorrhizal fungi under laboratory conditions and can be grown in the absence of a plant host. The most studied plant–fungal symbioses to date are the interactions between plants and arbuscular mycorrhizal (AM) fungi of the Glomeromycotina clade. Advancements in phylogenetics and microbial community profiling have distinguished a group of symbiosis-forming fungi that resemble AM fungi as belonging instead to the Mucoromycotina. These enigmatic fungi are now known as Mucoromycotina 'fine root endophytes' and could provide a means to understand the origins of plant–fungal symbioses. Most of our knowledge of the mechanisms of fungal symbiosis comes from investigations using AM fungi. Here, we argue that inclusion of Mucoromycotina fine root endophytes in future studies will expand our understanding of the mechanisms, evolution, and ecology of plant–fungal symbioses. [ABSTRACT FROM AUTHOR]

The existing literature on symbioses involving microorganisms is biased towards describing the larger of the partners, even though it is often the microbial partner that determines fitness. It is possible to address size asymmetries between mutualistic partners through the scale-independent parameters, z and c, of species–area relationships (SARs). Some general questions and gaps in understanding which can be addressed with SARs are the spatial scales where spatial aggregation is observed whether SAR parameters are determined by environmental settings, and formulating null expectations for global diversity of endosymbionts. We highlight how SARs can be used to address key questions in arbuscular mycorrhizal symbioses, such as the relationship between fine-scale diversity of fungal symbionts on roots and plant fitness. Symbioses involving microorganisms prevail in nature and are key to regulating numerous ecosystem processes and in driving evolution. A major concern in understanding the ecology of symbioses involving microorganisms arises in the effectiveness of sampling strategies to capture the contrasting size of organisms involved. In many mutualisms, including mycorrhizas and gut systems, hosts interact simultaneously with multiple smaller sized mutualists, the identity of which determines success for the host. This complicates quantifying the diversity of mutualisms because sampling techniques fail to capture effectively the diversity of each partner. Here we propose the use of species–area relationships (SARs) to explicitly consider the spatial scale of microbial partners in symbioses, which we propose will improve our understanding of the ecology of mutualisms. [ABSTRACT FROM AUTHOR]

• This review states the isolation, culture, characterization and application of OMF. • Major bottlenecks of traditional identification of OMF and its elucidation are discussed. • States the application OMF for bio-hardening and growth promotion of seedlings. • Provides insights for mass cultivation and conservation of orchids. In nature all orchids develop a mutualistic association with specialized group of fungi called orchid mycorrhiza. In natural environment, orchids are exclusively reliant on mycorrhizal fungi for seed germination, establishment, growth and development. In the early developmental stages, all orchids are mycoheterotrophic, and in most cases the association subsists throughout their lifespan. The significance of orchid mycorrhizal fungi (OMF) for seed germination, nourishment, growth promotion, and survival has been established more than a century ago and tremendous advancements were made in recent decades. Till date, understanding the mode of interaction between orchids and mycorrhizal fungi and determining the architecture of interaction networks are major challenges in ecology and evolutionary biology. The development of molecular techniques has empowered us to unscramble the fungal diversity comprised in the symbiosis and has facilitated us to overcome the difficulties associated with the conventional identification of OMF and orchid-fungal interactions. In addition, the application of modern biotechnological approaches resolved many controversial issues of OMF. Recently, OMF are used for biological hardening and growth promotion of in vitro raised seedlings, early flowering and quality improvement of flowers, and diseases and pests management. The aim of this communication is to update and summarize orchid mycorrhizal research including isolation, culture, and characterization of OMF, understanding the mechanisms of orchid-fungus symbiosis, and application of OMF in seed germination, growth promotion, and survival of asymbiotically raised seedlings and conservation of orchids. This appraisal will convey valuable insights to orchidologists engaged in biology, propagation, and conservation of orchids. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microfliuidcs based green and scalable technology for encapsulating biofertilizer mycorrhizae. • Sporulating MHB co-encapsulation improves spore shelf life by ∼>1.3 times. • The internal grooved pattern of the biofibre improves colonization and evolve tripartite ecology. • Enhances the rhizospheric enzyme activity for nutrient uptake, growth promotion, and boost the yield in paddy crop. Plants establish a specific assembly of soil microbiota around them, hence it's our duty to synchronize their preference with the latest technology. In this context, a microfluidic based scalable process has been developed for the assembling of the microbiota in such a way that quick symbiotic partnership happens to result in enhanced productivity. The stable 100 µm soft gel prepared with the reinforcement of nanoparticles, assembles one mycorrhizae with the required bunch of bacteria in a compatible environment for root colonization. Thus, assembled microbeads show significantly enhanced crop production. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) function mostly depends on their colonization to roots. However, it has not been systematically clear how arbuscular mycorrhiza (AM) formation is affected by organic contaminants. In this study, a meta-analysis was performed to estimate the effects of three groups of organic contaminants (polycyclic aromatic hydrocarbons (PAHs), crude oil, and pesticide) in soil on mycorrhizal colonization rates (MCRs) from various moderators, such as AMF (genus, species, and inoculation mode), contaminant (level, type, and source), and experimental conditions (plant type, duration, and soil sterilization). Our results showed that all MCRs (total, vesicular, arbuscular and hyphal) significantly decreased under the stresses of three contaminants. Generally, pesticide caused larger decrease in all MCRs than PAHs and crude soil except for vesicular MCRs. Mixed AMF showed larger decrease in the total and vesicular MCRs than single AM fungus, but contrary trends in the arbuscular and hyphal MCRs. Moreover, man-made contaminant seemed to produce larger negative effects on the total, vesicular, and arbuscular MCRs than industry contaminant. The inhibitive effects of three contaminants on the total and vesicular MCRs increased with increasing experimental duration, and were larger in the non-sterilized soil than in the sterilized soil. Hyphal and spore growth were also inhibited by three contaminants in most cases. Hyphal length and spore number of single AM fungus were lower than those of mixed AMF, and pesticide produced larger inhibition on the hyphal length and spore number than PAHs and crude oil. Similar trend was found in the non-sterilized soil relative to the sterilized soil. This study indicated that AM formation and AM structure were negatively affected by three organic contaminants, whereas the inhibitive degrees varied with AMF, organic contaminant and experimental conditions. [Display omitted] • All MCRs were inhibited by three organic contaminants regardless of moderators. • Hyphal length and spore number declined under three contaminants in most cases. • Moderators produced different effects on MCRs under three contaminant stresses. • Pesticide produced the largest negative effects on all MCRs except for vesicle MCR. [ABSTRACT FROM AUTHOR]

• Seed and aerial biomass enhanced in response to vermicompost and mycorrhiza. • Phenolic content increased by moderate drought stress and mycorrhizal inoculation. • Rutin and quercetin increased with moderate drought stress and mycorrhizal inoculation • In 75% FC and mycorrhiza application lowest HPPH IC50 and highest FRAP recorded • In interactions, M and V increased NPK uptake chlorophyll and osmolyte contents. The use of root symbionts and vermicompost as powerful natural tools is advised in stress conditions. To study the effect of vermicompost and mycorrhizal fungi on some phytochemicals and functional traits of buckwheat under drought stress, a greenhouse experiment was conducted. Three levels of drought stress: D0 (100% Field Capacity: FC), D1 (75% FC), and D2 (50% FC), two levels of mycorrhizal inoculation: M0 (without) and M1(with), and two levels of vermicompost V0 (without) and V1 (with) were used. Vermicompost significantly enhanced seed yield and aerial parts biomass. The highest grain yield (4.97 g dry weight per pot) and aerial parts biomass (40.3 g fresh weight per pot) were obtained in D0V1. The use of mycorrhiza was mainly effective on phytochemical parameters. Moderate levels of drought stress (D1: 75% FC) increased total phenols (33.6 mg gallic acid/g dry weight) and flavonoids (38.3 mg rutin/g Dry weight). Rutin content ranged from 16.24 to 32.5 mg/g dry weight that the highest content being in D1V1M0. Phenolic, flavonoid, and rutin content are correlated with higher antioxidant properties. This increase showed that mycorrhiza and vermicompost act as moderators and elicit to produce metabolites. Simultaneous use of M and V increased nitrogen, phosphorus, and potassium uptake. Cluster analysis classified the treatments into three groups with a higher impact of drought stress. According to Principal component analysis (PCA) FWH, Rutin, TFC, TPC, SS, and IC50 were affecting dimensions. The results showed that drought stress up to 75% FC (D1) can be used in buckwheat. [Display omitted]. [ABSTRACT FROM AUTHOR]

Aloe vera (Aloe barbadensis Miller) is a perennial drought tolerant medicinal species. This research study investigates the influence of biofertilizers on mycorrhizal fungi colonization, leaf number and width, plant height, offset number, leaf relative elongation rate (RER), leaf dry weight and leaf gel weight, water productivity (WP) for the gel, and aloin content in Aloe vera plants. The experiments were carried out in the warm and dry climate of Bushehr Province, Iran during 2016–2018. Treatments are reported to include irrigation regimes and biofertilizers at four levels. In terms of irrigation regimes, 25%, 50%, 75%, and 100% of water requirement accompanied the following treatments for biofertilizers, phosphorus-solubilizing bacteria (PSB), mycorrhizal fungi (MF), PSB+MF , and control (without any biofertilizers). The PSB includes Pseudomonas putida strain P 13 and Pantoea agglomerans strain P 5, in addition to Glomus mosseae as MF. The biofertilizer benefits (remarkably PSB+MF) on investigated traits were observed in three harvests. The results confirm the positive impacts of biofertilizers on important traits such as offset number (an economical part of Aloe vera planting), water productivity with less water consumption, and root colonization, which is the main reason of increasing the mentioned traits. Considering the minimal difference between 100%, 75% and 50% of water requirement in terms of gel fresh weight and more aloin content in 50% of our experiments, Aloe vera is reported as a high drought tolerant plant which merely requires an acceptable gel yield and aloin content. Moreover, better water productivity and consumption is possible in warm and arid regions by applying 50% of Aloe vera water requirement as well as biofertilizers. [Display omitted] [ABSTRACT FROM AUTHOR]

Traits are inherent properties of organisms, but how are they defined for organismal networks such as mycorrhizal symbioses? Mycorrhizal symbioses are complex and diverse belowground symbioses between plants and fungi that have proved challenging to fit into a unified and coherent trait framework. We propose an inclusive mycorrhizal trait framework that classifies traits as morphological, physiological, and phenological features that have functional implications for the symbiosis. We further classify mycorrhizal traits by location – plant, fungus, or the symbiosis – which highlights new questions in trait-based mycorrhizal ecology designed to charge and challenge the scientific community. This new framework is an opportunity for researchers to interrogate their data to identify novel insights and gaps in our understanding of mycorrhizal symbioses. Applying trait-based approaches to ecological research on mycorrhizal symbioses broadens ecological inferences, but there is no single unified framework to unite disparate language, terminology, and methods across the many multidisciplinary scientists studying mycorrhizas. We propose an inclusive framework for trait-based mycorrhizal ecology aimed to stimulate scientists around the world to collect and use more mycorrhizal trait data, particularly in understudied areas. This would widen our understanding regarding the ecological role of mycorrhizal symbioses at individual, species, community, and ecosystem scales. Analyzing how mycorrhizal symbioses fit within existing trait definitions highlights significant theoretical and empirical knowledge gaps, novel questions, and new research directions to improve our understanding of trait-based mycorrhizal ecology. [ABSTRACT FROM AUTHOR]

• Habenaria barbertoni and H. epipactidea's mycorrhizal communities were compared. • Orchid species shared mycorrhizae from the orders Cantharellales and Sebacinales. • Mycorrhizae identified in orchids included both overlapping and distinct taxa. • Mycorrhizae from rust lineage Atractiellales were only detected in H. barbertoni. Southern Africa is a biodiversity hotspot for a variety of orchids, including Habenaria. However, we know very little about the orchid mycorrhizae that are associated with these orchids. To bridge this gap, we compared the community of orchid mycorrhizae that are associated with two indigenous Habenaria species, H. barbertoni and H. epipactidea , using a high-throughput sequencing platform. We selected these two orchids because their distribution zones overlap in South Africa. Furthermore, H. barbertoni is endangered, whereas H. epipactidea is not. We hypothesised that the mycorrhizal diversity and composition linked with the roots of these two orchids would overlap, but that some distinct fungal taxa would exist, and these distinct fungi would include unusual taxa. Analyses of the DNA sequence data revealed that the two orchids shared 35 fungal OTUs. Twenty-four and seventeen OTUs were exclusively detected in the roots of H. barbertoni and H. epipactidea , respectively. Mycorrhizal fungi from the rust lineage Atractiellales (Atractiellomycetes, Pucciniomycotina) were only detected in the roots of the endangered H. barbertoni , which represents the first report of these fungi associated with orchids outside of the Andean rainforest. Our findings increase knowledge of the diversity of mycorrhizae associated with indigenous orchids on the African continent. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi improve plant growth, nutrition, fitness and stress tolerance while AM fungi obtain carbohydrates and lipids from the host. This whole process of mutual benefit requires substantial alterations in the structural and functional aspects of the host root cells. These modifications ultimately culminate in the formation of arbuscules, which are specialized intraradical and highly branched fungal structures. Arbuscule-containing cells undergo massive reprogramming to hosting arbuscule and members of the GRAS transcription factor family have been characterized as AM inducible genes which play a pivotal role in these process. Here, we show a functional analysis for the GRAS transcription factor SCL3/SlGRAS18 in tomato. SlGRAS18 interacts with SlDELLA, a central regulator of AM formation. Silencing of SlGRAS18 positively impacts arbuscule development and the improvement in symbiotic status, favouring flowering and therefore progress in the formation and development of fruits in SlGRAS18 silenced plants which parallel to a discernible pattern of mineral nutrient redistribution in leaves. Our results advance the knowledge of GRAS transcription factors involved in the formation and establishment of AM symbiosis and provide experimental evidence for how specific genetic alterations can lead to more effective AM symbiosis. • The tomato transcription factor SlGRAS18 is a negative regulator of Arbuscular Mycorrhiza (AM). • Tomato SlGRAS18 interacts with SlDELLA, a central regulator of AM formation. • Silencing of SlGRAS18 positively impacts the symbiotic effectiveness. [ABSTRACT FROM AUTHOR]

Edaphic drought reduces phosphorus (P) diffusivity in soils and arbuscular mycorrhizal fungi (AMF) can compensate for this. We recently showed, along a high-resolution substrate moisture gradient, that AMF effectively deliver P to plants under drought from areas beyond the reach of roots. Here, we investigated how edaphic drought affected the active sites of P exchange between AMF and plants inside the roots using different histochemical stains. Inoculation of dwarf tomato plants (cv. MicroTom) with AMF (Rhizophagus irregularis) slightly increased water retention (decreased the water potential) in substrates, decreased root length, and increased shoot P concentrations compared to non-mycorrhizal plants. Despite their reduced root length, mycorrhizal tomato plants showed a surprisingly congruent physiological drought stress response with their non-mycorrhizal counterparts. However, the activity of alkaline phosphatase (ALP) detected in intraradical fungal structures decreased significantly as soil and xylem water potentials decreased. The decline of ALP activity with increasing drought intensity was accompanied by a reduction of elevated P concentration benefits in shoots of mycorrhizal plants compared to non-mycorrhizal plants. Therefore, we conclude that edaphic drought can restrict the nutritional advantages that plants receive from AMF at the root-fungal interface. This is one of the direct consequences of drought. • Short-term drought hardly showed an effect of colonization of tomato roots by AMF. • Yet, alkaline phosphatase activity in the intraradical hyphae strongly decreased. • Reductions in phosphatase activity correlated with declining shoot phosphorus. • Reduced P transfer from fungus to plant thus seems directly induced by drought. [ABSTRACT FROM AUTHOR]

Alternate wetting-drying (AWD) in rice cultivation controls soil redox conditions and consequently nutrient solubility. Under low redox potential, ferric iron reduction leads to bound phosphate (Fe(III)–P) dissolution, but lack of oxygen retards organic phosphorus (P org) mineralization. Microorganisms accelerate P org mineralization as the redox potential increases during drying, but it is not known which P source will be preferentially taken up by microorganisms and plants. Using double 32/33P labeling, we traced for the first time the P released from inorganic (32P) and organic (33P) sources into microbial biomass P (MBP), phospholipids, and plants under continuous flooding (CF) and AWD. The CF rapidly induced reducing conditions that increased Fe–P dissolution and thus P availability. The AWD had no preference for 32P and 33P incorporation into plants. However, the ratios of 32P in roots to 32P in MBP or to 32P in phospholipids in rooted soil were 4–9 times higher than the respective ratios of 33P. Moreover, the ratios of 33P in roots to 33P in MBP or to 33P in phospholipids were always <0.6. Thus, plants and microorganisms were more competitive for P from Fe–P and from P org , respectively. The AWD increased 32P and 33P incorporation into phospholipids in rooted soil by 53–56% as compared to CF. Also, the ratio of 32P in phospholipids to 32P in MBP was 1.4–2.2 times higher under AWD than under CF. Thus, AWD stimulated microorganisms to allocate more P for cell membrane synthesis as compared to CF. Plants were similarly effective to take up P from inorganic and organic sources. Increased root biomass stimulated arbuscular mycorrhizal symbiosis (represented by 16:1ω5c) and thus 33P recovery in roots under AWD. In turn, the acceleration of microbial P turnover and the microbe-specific preference for P org highlight the importance of arbuscular mycorrhiza for plant P uptake under fluctuating water conditions. [Display omitted] • Continuous flooding increased reductive dissolution of Fe–P and thus P availability. • Microbes allocated more P for cell membrane synthesis under alternate wetting-drying. • Microorganisms in a maintenance state allocated more P for cell compound synthesis. • Rice plants were similarly effective to take up P from inorganic and organic sources. [ABSTRACT FROM AUTHOR]

• AMF inoculation promoted plant height and shoot and root biomass, irrespective of soil P levels. • AMF stimulated taproot length, the number of 2nd- and 3rd-order lateral roots, and root volume in P 0.5 and P 50. • AMF increased root P levels in P 0.5 and P 50 and leaf P levels in P 0.5. • AMF increased soil neutral and total phosphatase but reduced root acid phosphatase. • AMF up-regulated root CsPT1 expression, but down-regulated root CsPT4 expression. Tea (Camellia sinensis (L.) O. Kuntze) is predominantly grown in acidic soils with severe limitations of P-nutrition. The present study evaluated the effects of an arbuscular mycorrhizal (AM) fungus, Claroideoglomus etunicatum , on root morphology, leaf and root P concentration, phosphatase activity in soils and roots, and the relative expression of root P transporter genes (PT1 and PT4) in Camellia sinensis 'Fuding Dabaicha' seedlings in sands under two levels of P viz., 0.5 μM (P 0.5) and 50 μM (P 50) through Hoagland solutions (pH 4.2) for 24 weeks. Under both P 0.5 and P 50 conditions, AM seedlings displayed a higher growth performance (shoot biomass, root biomass, and plant height), root morphology (total length, taproot length, 2nd- and 3rd-lateral root number, and volume), and root-hair length, but lower root-hair density than non-AM seedlings. Mycorrhizal inoculation significantly increased root P concentrations in P 0.5 and P 50 and leaf P concentrations in P 0.5 over non-mycorrhizal treatment. The AM seedlings recorded considerably higher soil acid, neutral, and total phosphatase activity under P 0.5 treatment, and soil neutral and total phosphatase activity under P 50 treatment, compared with the non-AM seedlings. Root acid phosphatase activity was reduced due to mycorrhization at both of P 0.5 and P 50. AM fungal inoculation up-regulated the relative expression of root CsPT1 , while down-regulated the CsPT4 expression in P 0.5 and P 50 treatments. It was concluded that AM fungal inoculation significantly promoted P acquisition capacity of tea plants, especially in roots through improving root growth and enhancing soil acid phosphatase activity and root CsPT1 expression. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effectiveness of plant growth-promoting rhizobacteria (PGPR; Pseudomonas strain So_08) and arbuscular mycorrhizal fungi (AMF; Rhizoglomus irregulare BEG72 and Funneliformis mosseae BEG234) in mitigating the detrimental effects of cadmium (Cd) and zinc (Zn) stress in tomato plants. Plant biomass, root morphology, leaf relative water content, membrane stability, photosynthetic performance, chlorophyll content, and heavy metals (HMs) accumulation were determined. Furthermore, an ionomic profile was conducted to investigate whether microbial inoculants affected the uptake and allocation of macro- and micronutrients. Metabolomics with pathway analysis of both roots and leaves was performed to unravel the mechanisms underlying the differential responses to HMs stress. The findings revealed that the levels of HMs did not significantly affect plant growth parameters; however, they affected membrane stability, photosynthetic performance, nutrient allocation, and chlorophyll content. Cadmium was mainly accumulated in roots, whilst Zn exhibited accumulation in various plant organs. Our findings demonstrate the beneficial effects of PGPR and AMF in mitigating Cd and Zn stress in tomato plants. The microbial inoculations improved physiological parameters and induced differential accumulation of macro- and micronutrients, modulating nutrient uptake balance. These results provide insights into the mechanisms underlying the plant-microbe interactions and highlight the differential modulation of the biosynthetic pathways of secondary metabolites related to oxidative stress response, membrane lipids stability, and phytohormone crosstalk. [Display omitted] • Microbial biostimulants are proposed to mitigate heavy metal stress in tomato. • A tripartite interaction between tomato, microbes and heavy metals was reported. • Such interaction was found to impact mineral nutrients uptake and allocation. • Photosynthetic performance and the oxidative status were modulated. • Metabolomics unravelled unique signatures to this multifactorial response. [ABSTRACT FROM AUTHOR]

Most arbuscular mycorrhizal fungi exhibit global distributions but have been studied mostly in a specific region of the globe, mainly covering temperate and boreal habitats, where nitrogen is the most common nutrient limiting primary productivity. Yet, it is relatively common to extrapolate our understanding of temperate and boreal systems to other regions of the globe. While the physiology of mycorrhizal associations is unlikely to differ worldwide, there are good chances that environmental settings interact with the way mycorrhizas function across ecoregions. Here, we first argue that mycorrhizal ecologists should develop region-specific hypotheses. We subsequently identify likely differences in how mycorrhizas function in subtropical regions compared with better-studied temperate and boreal areas. We finally use the subtropical region of China to develop five geographically-focused hypotheses, envisaging that they will trigger the interest of the scientific community worldwide in understudied regions into studying mycorrhizas through a new lens. Expanding the range of hypotheses in mycorrhizal ecology to describe understudied regions of the world, has the potential to confer multifaceted benefits to both science and society. We advocate to do so, and present a roadmap on how to develop such hypotheses. [Display omitted] • We tend to overgeneralize our understanding on mycorrhizas. • Encouraging regional studies on mycorrhizas can bring about multifaceted benefits. • The (sub)tropics pose multiple opportunities to further explore mycorrhiza. • We use the case of subtropical China to develop region specific hypotheses. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) symbiosis can strengthen plant defense against abiotic stress, such as drought, through multiple mechanisms; however, the specialized chemical defenses induced by AM symbiosis are largely unknown. In a pot experiment, licorice (Glycyrrhiza uralensis Fisch.) inoculated with and without arbuscular mycorrhizal fungus Rhizophagus irregularis Schenck & Smith were grown under well-watered or water deficit conditions. Transcriptomic and metabolomic analyses were combined to investigate licorice root specialized metabolism induced by AM symbiosis under drought stress. Results showed that mycorrhizal plants had few dead leaves, less biomass reduction, and less differentially expressed genes and metabolite features in response to drought compared with nonmycorrhizal plants. Transcriptomic and metabolomic data revealed that mycorrhizal roots generally accumulated lignin regardless of the water regime; however, the expression of genes involved in lignin biosynthesis was significantly downregulated by drought stress in mycorrhizal plants. By contrast, AM inoculation significantly decreased specialized metabolites accumulation, including phenolics and flavonoids under well-watered conditions, whereas these decreases turned to be nonsignificant under drought stress. Moreover, these specific phenolics and flavonoids showed significant drought-induced accumulation pattern in mycorrhizal roots. These results highlight that accumulation of specific root phenolics and flavonoids may support the drought tolerance of mycorrhizal plants. [Display omitted] • Mycorrhizal symbiosis significantly reduced licorice drought damage. • Mycorrhizal symbiosis enhanced plant drought tolerance. • Mycorrhizal symbiosis increased licorice root lignin accumulation. • Mycorrhizal symbiosis facilitated specific phenolic and flavonoid accumulation under drought. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) participate in fungi-plant symbiotic relationships and mediate the acquisition of soil-borne nutrients by host plants. However, little is known about how AM colonization affects the homeostasis of iron (Fe) and zinc (Zn) in the host plant. Here, we assessed the performance of mycorrhizal growth, oxidative defense, nutrient accumulation, and key gene responses in AM-colonized tobacco (Nicotiana tabacum L.) under different nutrient stress. The total mycorrhizal frequency of AM fungi on tobacco roots reached 86 % and 75 % under low and high phosphorus (P) treatments, respectively. Under Fe/Zn stress, AM alleviated the inhibition of tobacco biomass accumulation, decreased the content of lipid peroxides, and upregulated enzymatic antioxidant capability. In AM-colonized tobacco, Fe/Zn accumulation was increased under deficient conditions and decreased under surplus conditions. Tobacco uptake of P, Fe, and Zn was impaired by excess nutrient concentrations and improved at low concentrations, and this phenomenon was supported by AM colonization. Fe/Zn deficiency upregulated genes related to Fe/Zn uptake, and Fe/Zn excess upregulated genes related to heavy metal efflux, with AM colonization further promoting these upregulations. Notely, we found a possible crosstalk node, Yellow Stripe-Like 7 (NtYSL7), in the AM and Fe/Zn homeostasis regulatory network. NtYSL7 has a plasma membrane-localized oligopeptide transporter domain. NtYSL7 is strongly induced by AM colonization, deficiency of Fe, and surplus Zn, and interacts with many Fe/Zn transporters. AM assists host plants in maintaining Fe/Zn homeostasis by improving nutrient accumulation, redox homeostasis, and transport mechanisms, and NtYSL7 is likely important within the crosstalk network of AM, Fe, and Zn nutrient homeostasis. [Display omitted] • AM helps tobacco uphold Fe and Zn balance via nutrient buildup, defensive oxidation, and transport processes. • AM alleviates the antagonism of tobacco P, Fe and Zn. • Involvement of YSL7 in regulating tobacco Fe and Zn transport mechanisms mediated by AM. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) play a vital role in mediating rhizosphere interactions and plant growth, especially in resource-constrained soils. However, few studies have documented the effects of AMF on plant–plant interaction patterns and resource use efficiency along stress gradients. In this study, a growth environment-controlled experiment was carried out to evaluate the effects of AMF inoculation on maize-grass pea intercropping along three phosphorus (P) and two water gradients. The data indicated that soil water and P availability determined the plant interspecific interaction pattern, and that interaction was strongly mediated by AMF inoculation. Grass pea and maize were mutually facilitated under low P and water conditions and transitioned to a new pattern, i.e., that maize was facilitated but grass pea was neutral role or facilitator with increasing resource availability. The facilitative effect was particularly significant under P- and water-deficient conditions. Moreover, the transition of the plant–plant interaction pattern was mechanically driven by improving rhizospheric phosphatase activities by 5.08–20.02 %, rhizospheric acidification and enhanced microbial activities under resource deficit conditions. Critically, AMF inoculation was observed to significantly improve rhizospheric soil P availability and microbial biomass (p < 0.05); however, it enhanced the complementary utilization of P and water and weakened interspecific competition under high-resource conditions. Therefore, AMF inoculation positively transformed the plant–plant interaction pattern along resource gradients for higher P, nitrogen and water use efficiency. This study validates the context-dependent interspecific interaction and the role of AMF in optimizing resource use in a nutrient-impoverished intercropping system. Illustrating the effect of AMF inoculation on plant growth and plant–plant interaction in maize-grass pea intercropping system. [Display omitted] • Plant diversity increased rhizosphere microbial activity and phosphatase secretion. • AMF inoculation enhanced facilitation intensity with increasing stress conditions. • AMF lowered interspecific competition intensity for higher resource use efficiency. [ABSTRACT FROM AUTHOR]

Mycorrhizal fungi considerably improve plant nutrition and help them to cope with changing environments. Particularly, these fungi express proteins to transfer inorganic phosphate (P i) from the soil to colonized roots through symbiotic interfaces. The mechanisms involved in P i transfer from fungal to plant cells are still largely unknown. Here, we discuss the recent progress made on the description of these mechanisms and we propose the most promising hypotheses and alternative mechanisms for this process. Specifically, we present a phylogenetic survey of candidate P i transporters of mycorrhizal fungi that might ensure P i unload into the symbiotic interfaces. Gathering additional knowledge on mycorrhizal P i transport will improve the P i -useefficiency in agroecological systems and will guide towards addressing future research challenges. The acquisition of phosphorus by plants is often mediated by soil microbes colonizing the roots, particularly mycorrhizal fungi. Key molecular mechanisms involved in the transport of phosphorus from the soil to mycorrhizal fungi have been revealed recently. However, the release of phosphorus towards colonized roots is still understudied, even if a recent report highlighted the possible involvement of fungal H+:P i transporters. Based on a survey of fungal transport proteins, others mechanisms possibly ensuring phosphorus efflux in mycorrhizas must coexist besides H+:P i transporters. These include the putative involvement of P i :Na+, low-affinity inorganic phosphate, and organic phosphate transporters. Unravelling the fungal phosphorus transportome will allow a better use of plant–fungus symbioses for the improvement of plant nutrition in cropping systems. [ABSTRACT FROM AUTHOR]

Abstract Nitrous oxide (N 2 O) is a potent greenhouse gas emitted at considerable rates from agricultural soils. A few recent studies have indicated the potential to reduce N 2 O emission rates in agricultural systems through management of soil microbiota, such as mycorrhizal fungi. Our limited understanding of how mycorrhiza influences N 2 O emission rates, however, forestalls such management practices. To address the knowledge gap regarding the mechanism of mycorrhizal modification of N 2 O formation and denitrification, we disentangle the direct effects of arbuscular mycorrhizal fungi (AMF) via hyphal growth on potential denitrification activity from those resulting from indirect AMF-induced changes in soil aggregation. We manipulated AMF status in a factorial experiment through adding or not AMF inoculum in the form of Rhizophagus irregularis and soil aggregation state through either crushing soil aggregates or using agricultural soil with intact soil aggregates. We then grew Zea mays (maize) in compartmentalized mesocosms for 4 months. At harvest, we observed approximately three-fold higher AMF root colonization and hyphal densities in the treatments where we had added Rhizophagus irregularis. Potential N 2 O activity rates and the denitrification ratio were higher in the undisturbed soil and in the mesocosms with a dense AMF hyphal network (direct effect of mycorrhiza). Further, AM-hyphae promoted soil aggregation while also altering potential denitrification activity (indirect effect of mycorrhiza). Overall, we present here a comprehensive case study on how mycorrhiza alters potential denitrification activity and related N 2 O activity from agricultural soils. Highlights • We disentangled direct and indirect effects of AM on denitrification. • AM hyphae (direct) promoted N 2 O activity. • Soil aggregation (indirect) also promoted N 2 O activity. • Mycorrhiza, here, stimulated potential N 2 O activity. [ABSTRACT FROM AUTHOR]

Abstract A wide program of fruit tree planting, notably jujube trees, has been implemented in the framework of the pan-African Great Green Wall (GGW) project to improve food security in arid and semiarid regions. However, the success of such initiatives is highly limited by a low tree growth and high tree mortality rates due to transplant shocks from tree nursery to field. The positive impact of mycorrhiza-based ecological engineering strategies on jujube trees were previously demonstrated in nursery conditions, but field monitoring is necessary to evaluate their sustainability in terms of plant growth and survival. In the current study, local (Tasset) and exotic (Gola) jujube cultivars were tested for their response to mycorrhizal inoculation with the non-native arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis IR 27 and fertilization with rock phosphate. The environmental impacts of both treatments were assessed by characterizing the native AM fungal community in a 13-month-old jujube orchard. Field results demonstrated higher rates of survival and a relative stability of nursery-driven plant benefits of inoculated jujube trees, as well as a potential higher persistence of AM fungal inoculum for the exotic cultivar. The native AM fungal community associated with the local cultivar was the most diverse, but Glomeraceae was predominant in both cultivars. The mycorrhiza-based ecological engineering strategies proposed in this work affected both AM fungal communities, notably Glomeraceae and Gigasporaceae members, but in a higher extent for the local jujube cultivar. Results highlight the strong benefits of mycorrhizal inoculation at the very early stages of tree seedling growth in nursery and their stability in the first year of plantation. Nevertheless, a deeper assessment of mycorrhizal inoculum persistence and spread, and a wider characterization of soil and root microbiome need to be implemented in further field monitoring to better evaluate the environmental impacts. [ABSTRACT FROM AUTHOR]

Highlights • The common garden study shows that R S in the AM stands is significantly greater than that in the ECM stands. • The AM and ECM stands display different influences on R S through biotic, substrate and environmental factors. • The drivers of the R S and their degree of influence differ between the AM and ECM stands. • Shifts in AM or ECM tree abundance in forest management are of significance in ecosystem carbon cycling. Abstract Tree species associated with different mycorrhizal fungi play a crucial role in the carbon (C) cycling of forest ecosystems, while their effects on soil respiration (R S) and the underlying mechanisms remain uncertain. In this study, we used a common garden experiment that included five monocultures (two arbuscular mycorrhizal – (AM) and three ectomycorrhizal-associated (ECM) temperate tree species) to explore the effects of mycorrhizal associations on the R S and the driving factors. Our specific objectives were to (1) compare the R S between the AM and ECM stands, and (2) explore the driving factors of the R S. We found that the R S in the AM stands was significantly greater (34.3%) than that in the ECM stands. The R S was significantly and positively correlated with microbial biomass C (C mic), fine roots biomass (B root), or soil water content (W 5), but negatively with forest floor mass (F mass) or soil dissolved organic C content (C dis). The best-fitted models of R S explained 46.3%, 38.3%, and 45.4% of the variations in the R S for the AM stands, the ECM stands, and the combined dataset, respectively. However, the factors contributing to the R S varied with mycorrhizal groups. The R S of the AM stands was mainly influenced by C mic , B root , root C/N ratio, F mass , and C dis , whereas the R S of the ECM stands was mainly affected by litter C/N ratio, C dis , soil dissolved nitrogen content, soil temperature and W 5. These findings highlight the significance of shifts in AM or ECM tree abundance due to forest management and global change in forest C cycling. [ABSTRACT FROM AUTHOR]

Abstract Intensive organic matter removal (OMR) associated with timber harvest has the potential to impart long-term alterations to soil biota and associated properties and processes; however, there is a lack of data to say if this trend persists at depth. This study investigated how OMR influences long-term stability of soil fungi to a depth of 1 m using a replicated experimental pine forest in the Gulf Coastal Plain, USA. Treatments included unharvested control stands as well as low- and high-OMR stands. Intensive OMR led to significant differences in community structure and the abundance of functional guilds in surficial soil. Saprophytic taxa increased while ectomycorrhizal (ECM) taxa decreased with intensive-OMR, which correlated strongly with increased surface temperature and reduced soil nitrogen. Ericoid mycorrhizae (ERM) also increased in intensive-OMR stands, which may indicate that following disturbance, ERM could outcompete ECM for colonization of subsequent seedlings. Overall, no differences were observed below 30 cm, except for alpha diversity, which was a function of high inter-replicate variability. Our results illustrate a distinct long-term structural and functional response of soil fungi to intensive-OMR in the upper portions of the soil profile, which could lead to altered stand productivity and ecosystem services. Highlights • Fungal community structure at 0–10 cm and 10–30 cm was altered by timber harvest. • Saprophytes increased and ectomycorrhizae decreased in intensively harvested stands. • Fungal communities at depth possessed high inter-replicate variability. [ABSTRACT FROM AUTHOR]

The presence of living roots can markedly change soil properties, microbial activities, and biogeochemical cycling in the rhizosphere compared to bulk soil. Such rhizosphere effect has been increasingly recognized to play a crucial role in carbon (C) and nitrogen (N) cycling in terrestrial ecosystems. Here, we investigated the rhizosphere effects of 12 tree species associated with two contrasting mycorrhizal types (arbuscular mycorrhizal, AM vs. ectomycorrhizal, ECM) and co-occurring in a temperate secondary forest in Northeast China. The adhering soil method was adopted to sample paired rhizosphere and bulk soils of field-grown trees in the peak growing season. Generally, we found positive rhizosphere effects on soil properties (ammonium and nitrate content, total C and N content, and C:N ratio), microbial abundances (bacteria, fungi, and actinomycetes), enzyme activities (C- and N-degradation enzymes), and C mineralization rate (C min), but minor rhizosphere effects on soil pH, phosphorus content and phosphatase activity, net N mineralization rate (N min), and specific C min and N min (per unit soil C or N). Because of large intraspecific and particularly interspecific variations, less than half of the rhizosphere effects were statistically significant (P < 0.05), and none of the rhizosphere effects differed significantly between the two mycorrhizal types (AM vs. ECM). Moreover, most soil variables varied greatly within and across species, and thus did not differ significantly between the two mycorrhizal types (AM vs. ECM). However, soil pH, nitrate content, microbial abundance, and C-degradation enzyme activity were notably lower under ECM species than under AM species. Collectively, these results show that rhizosphere effects varied greatly among the six species within both mycorrhizal groups, and such variations within mycorrhizal group were even larger than those between mycorrhizal group. Future work should include a larger number of tree species to increase statistical power, and combine phylogenic history and functional traits of plant species with the type and traits of mycorrhizal fungi to better understand how plant-microbe interactions influence biogeochemical cycling in the rhizosphere. Highlights • We quantified rhizosphere effects of 12 co-existing temperate tree species. • Six arbuscular mycorrhizal (AM) and six ectomycorrhizal (ECM) species were included. • Rhizosphere effects on soil properties, microbial abundances and activities were either positive or neutral. • Rhizosphere effects showed larger variations within mycorrhizal group than between mycorrhizal group. • Rhizosphere effects may be controlled by phylogeny and traits of plants and mycorrhizal fungi. [ABSTRACT FROM AUTHOR]

Research on mycorrhizal interactions has traditionally developed into separate disciplines addressing different organizational levels. This separation has led to an incomplete understanding of mycorrhizal functioning. Integration of mycorrhiza research at different scales is needed to understand the mechanisms underlying the context dependency of mycorrhizal associations, and to use mycorrhizae for solving environmental issues. Here, we provide a road map for the integration of mycorrhiza research into a unique framework that spans genes to ecosystems. Using two key topics, we identify parallels in mycorrhiza research at different organizational levels. Based on two current projects, we show how scientific integration creates synergies, and discuss future directions. Only by overcoming disciplinary boundaries, we will achieve a more comprehensive understanding of the functioning of mycorrhizal associations. Highlights Mycorrhiza research has traditionally developed into distinct disciplines at different organizational levels from the cellular to ecosystem level. This separation leads to a limited understanding of mycorrhiza functioning and its role within ecosystems. Here, we show how the different disciplines in mycorrhiza research commonly address the same general questions and how these questions are nested in the next organizational level. By integrating different disciplines, these disciplines are able to complement each other and foster the development of a comprehensive understanding of mycorrhizal associations. We introduce two ongoing projects as examples where the integration of disciplines in mycorrhiza research is already common practice. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity limits growth and symbiotic interactions of plants. Calcium plays essential roles in abiotic stresses and legume- Rhizobium symbiosis, but the sites and mechanism of Ca 2+ mobilization during mycorrhizae have not been analyzed. In this study, the changes of cytoplasmic Ca 2+ and calreticulin (CRT) in Medicago truncatula mycorrhizal (MR) and non-mycorrizal (NM) roots under short Al stress [50 μM AlCl 3 pH 4.3 for 3 h] were analyzed. Free Ca 2+ ions were detected cytochemically by their reaction with potassium pyroantimonate and anti-CRT antibody was used to locate this protein in Medicago roots by immunocytochemical methods. In MR and NM roots, Al induced accumulation of CRT and free Ca 2+ . Similar calcium and CRT distribution in the MR were found at the surface of fungal structures (arbuscules and intercellular hyphae), cell wall and in plasmodesmata, and in plant and fungal intracellular compartments. Additionally, degenerated arbuscules were associated with intense Ca 2+ and CRT accumulation. In NM roots, Ca 2+ and CRT epitopes were observed in the stele, near wall of cortex and endodermis. The present study provides new insight into Ca 2+ storage and mobilization in mycorrhizae symbiosis. The colocalization of CRT and Ca 2+ suggests that CRT is essential for calcium mobilization for normal mycorrhiza development and response to Al stress. [ABSTRACT FROM AUTHOR]

• Conspecific negative distance-dependent (CNDD) mortality creates species diversity. • Species replacement under adults is also important to create species diversity. • We found a close relationship between CNDD and species replacement. • The type of mycorrhizal fungi strongly affected strength of both CNDD and species replacement. • To achieve species diversity, type of mycorrhizal fungi in individual trees should be considered. Maintaining and recovering species diversity is one of the main management goals of forest managers. It is thus important to understand the mechanisms that drive species diversity. The mechanism is strongly related to the harsh biological environment surrounding the tree, especially its interaction with natural enemies, and a well-known mechanism is the Janzen-Connell hypothesis. The hypothesis is best understood by evaluating not only conspecific negative distance-dependent (CNDD) seedling mortality but also replacement of conspecific seedlings by heterospecifics. However, it remains unclear how antagonistic pathogens and mutualistic mycorrhizae affect the strength of replacement. A reciprocal seed-sowing experiment was conducted for five tree species with different mycorrhizal types in forest understorey (FU) and gaps (Gap) in a temperate forest. We investigated seedling mass, mortality, mortality agents, and root infection with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi. In both FU and Gap sites, two AM species were attacked by pathogens causing damping-off and leaf diseases more severely beneath conspecific than heterospecific adults, and more severely among conspecifics than heterospecifics of focal adults, resulting in strong CNDD and replacement, whereas seedling mortality in two EM species due to damping-off pathogens and leaf diseases did not differ among treatments, resulting in weak CNDD and replacement. One AM species showed an intermediate trend between two AM species and two EM species. Thus, CNDD and replacement caused by pathogens were positively correlated in FU but not Gap sites. These traits reveal that replacement closely correlated with CNDD play an important role in maintaining species diversity, especially when gaps are absent. This study also suggest that replacement plays an important role in regulating the spatial distribution of individual trees and subsequent relative abundance of tree species, as well as CNDD effects. Forest managers need to consider differences in the strength of CNDD and replacement between mycorrhizal fungi types when attempting to achieve successful seedling establishment after harvesting without compromising species diversity. [ABSTRACT FROM AUTHOR]

• Arbuscular mycorrhizal symbiosis lowers walnut rootstock dependency on Pi supply. • Symbiosis improves sapling development and quality under low Pi fertilization. • Arbuscular mycorrhizal benefits are rootstock-dependent. • Symbiotic growth gains are observed after acclimatization and post-acclimatization. The English walnut (Juglans regia L.) is the main species cultivated for the production of edible nuts. In vitro micropropagation of walnut explants, necessary for mass propagation of high-quality walnut rootstocks, needs an ex vitro acclimatization phase followed by a post -acclimatization growth in greenhouse when plantlets become photoautotrophic. However, poor survival and slow growth rates are common difficulties encountered in nurseries when establishing micropropagated walnut saplings. Walnut exhibits dependency on symbiotic soil-borne arbuscular mycorrhizal fungi for better soil nutrient acquisition and development due to a coarse root architecture that limits soil inorganic phosphate (Pi) uptake. In the context of rootstock production, the objective of this study was to investigate for the first time the effect of the arbuscular mycorrhizal fungus Rhizophagus irregularis on the growth, quality, and Pi nutrition of seven in vitro grown walnut rootstocks of economic interest (RG2, RG6, R17, RX1, VLACH, VX211, and WIP3). For this purpose, inoculation was performed before both acclimatization and post -acclimatization of rootstocks under two contrasting Pi fertilization regimes. Two months after inoculation, we analysed mycorrhizal growth, phosphate and quality responses in the four conditions tested by measuring plant height, root length, root surface, branch number, collar, biomass dry weight, Pi content, and quality (Dickson's index). The results indicated that Pi fertilization impacted root colonization parameters only in a few cases. Irrespective of root colonization parameters and developmental stages, mycorrhizal growth depression after inoculation with R. irregularis was generally observed with increasing Pi availability in the substrate. Principal component analysis showed that mycorrhizal dependency, growth and quality responses were positively correlated to each other under the lowest Pi fertilization regime tested, both at the acclimatization and post -acclimatization stages. We also found that mycorrhizal benefits in terms of growth, quality and Pi nutrition, were rootstock-dependent, indicating that walnut dependency for Pi nutrition varies between cultivars. [ABSTRACT FROM AUTHOR]

The study aimed at investigating Arbuscular Mycorrhiza (AM) mediated metabolic changes in two genotypes of mungbean (Vigna radiata) differing in their salt tolerance in presence of salt stress (100 mM NaCl). Colonisation by Claroideoglomus etunicatum resulted in higher growth, photosynthetic efficiency, total protein content, and lower levels of stress markers, indicating alleviation of stress in mungbean plants. AM differentially upregulated the components of Tricarboxylic acid (TCA) cycle in salt tolerant (ST) and salt sensitive (SS) genotypes that could be correlated to AM-mediated moderation in nutrient uptake. Under salt stress, while maximum increase in the activity of α-ketoglutarate dehydrogenase (65%) was observed in mycorrhizal (M)-ST; the increase in isocitrate dehydrogenase (79%) and fumarase (133%) activities was maximum in M-SS plants over their non-mycorrhizal (NM) counterparts. Apart from TCA, AM also affected gamma-aminobutyric acid (GABA) and glyoxylate pathways. Activities of enzymes implicated in GABA shunt increased in both the genotypes under stress resulting in increase in GABA concentration (46%). Notably, glyoxylate pathway was induced by AM in SS only, wherein M-SS exhibited significantly higher isocitrate lyase (49%) and malate synthase (104%) activities, reflected in higher malic acid concentration (84%), than NM under stress. The results suggest that AM moderates the central carbon metabolism and strategizes towards boosting the formation of stress-alleviating metabolites such as GABA and malic acid, especially in SS, bypassing the steps catalysed by salt-sensitive enzymes in TCA cycle. The study, therefore, advances the understanding on mechanisms by which AM ameliorates salt stress. [Display omitted] • Report on differential effects of AMF in salt tolerant (ST) and salt sensitive (SS) mungbean genotypes. • AMF enhances TCA cycle enzyme activities on account of moderation in nutrient uptake. • AMF induces glyoxylate cycle and GABA shunt in SS genotype, while only GABA shunt is induced in ST. • Higher Na ion accumulation by SS shunts isocitrate towards glyoxylate cycle, evading the salt-sensitive steps of TCA. [ABSTRACT FROM AUTHOR]

The production of the redox-active signaling molecule, NO, has long been associated with interactions between microbes and their host plants. Emerging evidence now suggests that specific NO signatures and cognate patterns of PHYTOGLOBIN1 (PHYTOGB1) expression, a key regulator of cellular NO homeostasis, may help determine either symbiosis or pathogenicity. [ABSTRACT FROM AUTHOR]

Tempranillo grapevine is widely cultivated in Spain and other countries over the world (Portugal, USA, France, Australia, and Argentina, among others) for its wine, but leaves are scarcely used for human or animal nutrition. Since high temperatures affect quality of fruits and leaves in grapevine and the association of Tempranillo with arbuscular mycorrhizal fungi (AMF) enhances the antioxidant properties of berries and leaves, we assessed the effect of elevated air temperature and mycorrhization, separately or combined, on the nutritional properties of Tempranillo leaves at the time of fruit harvest. Experimental assay included three clones (CL-260, CL-1048, and CL-1089) and two temperature regimes (24/14 °C or 28/18 °C day/night) during fruit ripening. Within each clone and temperature regime there were plants not inoculated or inoculated with AMF. The nutritional value of leaves increased under warming climate: elevated temperatures induced the accumulation of minerals, especially in CL-1089; antioxidant capacity and soluble sugars also increased in CL-1089; CL-260 showed enhanced amounts of pigments, and chlorophylls and soluble proteins increased in CL-1048. Results suggested the possibility of collecting leaves together with fruit harvest with different applications of every clone: those from CL-1089 would be adequate for an energetic diet and leaves from CL-260 and CL-1048 would be suitable for culinary processes. Mycorrhization improved the nutritional value of leaves by enhancing flavonols in all clones, hydroxycinnamic acids in CL-1089 and carotenoids in CL-260. [ABSTRACT FROM AUTHOR]

In the light of the global increase in forest pests and diseases, accompanied by withdrawal of chemical pesticides and fungicides, we review recent advances in how forest tree resistance to pests and diseases might be influenced by manipulation of characteristics of the trees’ community of associated plants and other organisms. These include associational resistance (AR), effected by manipulation of tree species composition or richness, genotypic diversity, or by tree density/frequency of resistant species or genotypes, use of hybrids, and strategic use of bacterial and fungal symbionts to engender systemic induced resistance, or defense priming. Due to the rotation times in forest production systems, none of the community-based actions that attempt to disrupt a tree-pest or tree-pathogen interaction, can be used in a rapidly mobilised targeted response to currently known pests or pathogens or to unknown ones that are yet to emerge. The only exception is the possible use of non-pathogenic or mutualistic organisms to induce systemic resistance or prime tree defence systems against attack. Due to the range of permutations of participating species and assemblages and the idiosyncratic nature of their ecological interactions and processes, it is not currently possible to formulate predictive rules to protect forests using only these community-based methods. It is however possible to use them as part of a long-term prophylactic strategy by structuring future forests to increase their general resistance, and reduce the probability of impacts of pests and diseases, e.g. via diversification of tree species and genotypes. [ABSTRACT FROM AUTHOR]

Plant roots contribute substantially to the formation of stable soil organic matter (SOM), and there is evidence that species differ in their contribution to SOM stabilization. However, it remains unclear what specific root traits contribute to the three SOM stabilization mechanisms: recalcitrance against decomposition, occlusion in soil aggregates and interaction with soil minerals and metals. This is likely because research is highly fragmented and hampered by disciplinary barriers. By reviewing both plant functional ecology and soil science literature, we identified 18 different traits: architectural, morphological, physiological, symbiotic and chemical root characteristics, influencing the three SOM stabilization mechanisms. We found that traits increasing root recalcitrance promote short term stabilization by slowing decomposition, but that traits reducing recalcitrance contribute to long term stabilization by reaction of microbial products with mineral surfaces. Root length density, mycorrhizal association and rhizodeposition contribute to microaggregation. These and other traits, such as hemicellulose, soluble compounds, and high root branching index, favor macroaggregation. For stabilization by minerals and metals, those root traits promoting higher microbial activity: root nitrogen, hemicellulose and soluble compound concentrations are fundamental, while polyphenols, and litter Al and Mn also contribute to complexification and stabilization. Root depth distribution is the most important trait to control root C storage and stabilization in the subsoil; once roots have reached deeper soil layers, other traits, such as rhizodeposition and root chemistry, influence interaction with minerals and metals. Both mycorrhizal presence and root suberin promote SOC stabilization by means of all three mechanisms, indicating that these are important targets for continued work. Surprisingly, morphological traits commonly measured, namely specific root length and root diameter, poorly relate to stabilization mechanisms. Alternative traits such as chemical composition of the different root orders, root apex characteristics, quantity and quality of rhizodeposits as well as mycorrhizal fungal traits, should be further investigated. For future research, this review highlights the need to evaluate root decomposition and root-C stabilization concomitantly over the long-term, considering simultaneously root litter quality, estimated by root traits, the microbial products and properties of the soil matrix. The information accrued in this review can be used to evaluate the potential of plant species and cultivars to promote SOM stabilization, based on their root traits. [ABSTRACT FROM AUTHOR]

Climate change is leading to the intensification of drought effects worldwide, which considerably reduce crop production. A better understanding of the drought-tolerance mechanisms would lead into a more productive agriculture. The arbuscular mycorrhizal (AM) symbiosis has been shown to improve plant tolerance to drought. Salicylic acid (SA) is a phenolic compound involved in many aspects of plant growth and development. Apart from its role in biotic interactions, it is also involved in the regulation of important plant physiological processes, including plant water relations under stressful conditions. However, despite the importance of SA in plant physiology and in AM colonization, little is known about its effect on regulation of root water transport. Thus, the aim of this work was to study the combined effect of AM symbiosis and SA on root hydraulic properties under drought stress, with special focus on how these factors can alter radial root water transport pathways through aquaporin regulation. Also, the crosstalk between SA and other phytohormones was taken into account. Results showed that the AM symbiosis modifies root hydraulic responses to drought episodes. Under these conditions, AM plants showed increased Lpr and Lo. Exogenous SA application decreased Lpr and Lo under drought. SA modulation of water conductivity could be due to a fine-regulation of root aquaporins (as ZmPIP2;4 or ZmTIP1;1 ). Furthermore, SA application differently modulated the percentage of water flowing by the apoplastic pathway, decreasing its contribution to total root water flow in AM plants and increasing it in non-AM plants. An intricate relationship between Lpr, aquaporins and endogenous levels of SA, ABA and jasmonic acid was observed. Future studies should explore more in detail the crosstalk mechanism between these hormones in the regulation of water transport in AM roots, in order to better understand the mechanism through which the AM symbiosis copes with drought stress. [ABSTRACT FROM AUTHOR]

Mycorrhization of nursery plants with arbuscular mycorrhizal fungi (AMF) has become a usual practice in olive nurseries. Mycorrhizal associations increase plant tolerance to biotic and abiotic stresses after transplanting by improving root system structure and development. Nutrient fertilization is also desirable because roots are confined in a limited amount of soil in the nursery containers. Since the olive tree is a species with low phosphorus requirements, and AMF can affect root system development and nutrient uptake, it is of interest to study the possible interaction between both factors. Three different experiments with potted plants growing in a shade house, and one experiment under field conditions, were preformed using young olive plants to explore these questions. Inoculation with Glomus intraradices did not affect the phosphorus level in the plants but reduced shoot growth in plants growing in phosphorus-rich soil. When the substrate was a soil poor in phosphorus, shoot growth of AMF-inoculated plants was similar to the control but root development was greater. Mycorrhization also increased flower number and quality in ‘Arbequina’. Shoot growth also was reduced when a sterilized substrate was used, suggesting that the use of natural soil is preferred. Since no mycorrhization effect was observed when inoculation was performed at the moment of transplanting to the field, inoculation during the nursery-growing period is recommended to improve plant quality for orchard establishment. [ABSTRACT FROM AUTHOR]

In many tropical regions, such as New Caledonia, soil erosion from anthropogenic activities and subsequent ecological restoration are major issues that require detailed soil and vegetation data for the production of management plans. To determine if some plant species are more useful for stabilizing soil aggregates and thus reducing erodibility, we examined three species endemic to New Caledonia, and measured how root traits and associated mycorrhizas and fungi influenced Ferralsol aggregate stability (MWD). The three species are hosts to different types of mycorrhizas and were: (i) the sedge Costularia arundinacea (Sol. Ex Vahl) Kük. , an AMF (arbuscular mycorrhizal fungi) host, (ii) the shrub Tristaniopsis glauca Brongn. & Gris and (iii) the tree Arillastrum gummiferum (Pancher ex Brongn. & Gris) Baill. , both of the latter are ectomycorrhizal fungi (ECM) hosts. Fungal abundance, aggregate stability, soil organic carbon (SOC), iron (Fe) and aluminium (Al) sesquioxides were measured in the soil beneath 20 individuals for each species, as well as in 20 control samples of bare soil. Root functional traits including root mass density (RMD), root length density (RLD) and percentage of fine roots were measured on all individuals. Results showed that plant species can significantly influence soil aggregate stability. MWD was greater in soil beneath Costularia characterized by high RMD, RLD, percentage of fine roots and fungal abundance, while MWD in the rhizosphere of Tristaniopsis and Arillastrum was similar to that of bare soil. Fe and Al were very high in all soil samples and are suspected of masking the influence of roots, fungi and SOC on MWD at the scale of isolated ECM-hosts. Therefore, MWD alone would not be a relevant predictor of restoration on such soil and further investigations should be carried out to identify a set of predictors useful for indicating the restoration of degraded soils on ultramafic substrates. [ABSTRACT FROM AUTHOR]

A global data analysis shows that rice grain arsenic (As) concentrations increase with increasing soil As concentrations until about 60 mg As kg −1 soil and then decreases. Of the total grain As, 54% is composed of inorganic As. Therefore, when considering the WHO-permissible grain inorganic As concentration, i.e. 0.2 mg As kg −1 , the permissible grain total As concentrations is 0.37 mg total As kg −1 grain. Soil total As concentration when grain total As concentration reaches permissible level is 5.5 mg As kg −1 soil. Therefore, the suitable soil As concentrations for screening rice cultivars in rice agroecosystems for As resistance is 5–60 mg As kg −1 soil. Rice has traits to reduce uptake and translocation of As to grains. Cultivars with higher root porosity, radial oxygen loss, or formation of iron plaques bind more As to iron plaques, reducing As uptake (i.e. As avoidance). Once taken up, glutathione/glutaredoxin-mediated As reduction, and phytochelatin-dependent complexation and sequestration in vacuoles result in less translocation of As to the grain. Moreover, generation of reactive oxygen species and the production of antioxidant enzymes further reduce As toxicity (i.e. As resistance). These resistance mechanisms in rice agroecosystems are further enhanced when adequate concentrations of silicon and sulfur are present in soils and tissues, and when plants are associated with arbuscular mycorrhizal fungi, particularly under aerobic or intermittent-aerobic soil condition. Therefore, As concentrations in rice ecosystems decrease in the order of: roots > leaves > grains, and in grains: hull > bran polish > brown rice > raw rice> polished rice > cooked rice. Within the grain, As speciation is affected by the location in the grain, forms of As species, the grain-filling stage, geographic origin, ecosystem management and cultivars used. Indica type accumulates more As in their grains than japonica type. Rice grain production, within safe limits of As, requires the consideration of soil As dynamics including soil management, cultivar responses including uptake and translocation, and post-harvest processing techniques. [ABSTRACT FROM AUTHOR]

Tree roots and mycorrhizal fungi form an important resource for soil microinvertebrates; however, there is little knowledge on the role of root feeders and microbial grazers on belowground carbon flux of forest trees. Using oak ( Quercus robur ) microcuttings (Clone DF159) inoculated with an ectomycorrhizal symbiont partner ( Piloderma croceum ), the present study investigated the impact of multitrophic interactions in the rhizosphere on the carbon flow to the soil food web in a pulse-chase labelling experiment. Changes in plant biomass, microbial communities (soil phospholipid fatty acids - PLFAs) and Collembola lipid pattern (total lipid fatty acids - TLFAs) as well as the 13 C incorporation into fatty acids were assessed at 2, 5 and 20 days post labelling of oak microcuttings. Microcosms were inoculated with Pratylenchus penetrans (root-feeding nematode), Protaphorura armata (fungal-feeding Collembola) or their combination. The interaction of P. penetrans and P. armata synergistically reduced oak biomass. Both soil animals independently impacted growth of microorganisms in the rhizosphere, P. penetrans inhibited whilst P. armata promoted bacterial biomass. Irrespective of treatment and time, Gram-positive bacteria derived most of the recent photoassimilated oak carbon, with amounts ranging between 80 and 92% of the total 13 C allocated in microbial PLFAs. Presence of either P. armata or P. penetrans enhanced the incorporation of plant carbon in bacteria, whereas collective effects of these two functional groups was scarce. Predominantly the impact of the root-feeding nematode on belowground carbon flow diminished with time. In sum, root feeders and detritivores played independent roles in carbon allocation patterns and community structure of microorganisms in the rhizosphere of oaks. [ABSTRACT FROM AUTHOR]

Drought stress affects the growth and mortality of forage sorghum cultivated in arid and semi-arid environments. Arbuscular mycorrhizal (AM) fungi can promote plant growth, protect host plants from various stresses, and mediate plant–plant interactions. In this study, a greenhouse experiment was conducted to investigate: (1) the function of an AM fungus ( Funneliformis mosseae ) in the alleviation of drought-induced growth retardation and mortality of forage sorghum plants, and (2) whether common mycorrhizal networks (CMNs) are more beneficial to plants that join CMNs earlier than to those that join later. AM formation largely promoted sorghum growth, and the biomass and the specific leaf area (SLA) of mycorrhizal plants were larger than those of non-mycorrhizal plants, regardless of whether they were grown under well-watered or drought stress conditions. Progressive drought stress suppressed plant growth and even induced plant mortality, while AM alleviated plant growth retardation and prolonged plant lifespan. Intriguingly, plants connected to the CMN and that formed an AM symbiosis earlier than other plants benefited more under intensive drought stress, with longer lifespans, more arbuscules and larger ratios of intact arbuscules. These findings may help to elucidate the seemingly random death of individual plants induced by drought stress in agricultural practices. The plants that formed AM earlier than other plants were not significantly superior in terms of biomass accumulation, SLA and AM colonization under well-watered conditions. Our results confirmed that the formation of an AM association could alleviate growth retardation and prolong the lifespan of plants under drought stress, demonstrating the prospect of utilizing AM fungi to increase the forage yield of sorghum plants cultivated under semi-arid and arid environments. [ABSTRACT FROM AUTHOR]

Commiphora leptophloeos (Mart.) J.B. Gillett is a Brazilian medicinal species commonly used by Brazilians for its pharmacological properties, which are related to the presence of primary and secondary plant metabolism compounds. The inoculation with arbuscular mycorrhizal fungi (AMF) in various medicinal plants increases the growth of plants and the production of therapeutically important metabolites. However, missing studies about the effects of mycorrhizal fungi on the growth and production of biomolecules in C. leptophloeos . The objective of this paper is to determine the growth and the concentration of primary and secondary metabolites and the total foliar antioxidant activity in C. leptophloeos seedlings in terms of inoculation with arbuscular mycorrhizal fungi. C. leptophloeos plantlets were transplanted into sacs containing 1.2 kg of soil and 10% vermicompost, which received soil-inoculum in the root region. After 140 days in a greenhouse, growth variables, primary and secondary metabolite concentration, and total foliar antioxidant activity were determined. AMF reduce the concentration of soluble carbohydrates, and increase the concentration of total foliar phenols and tannins in C. leptophloeos inoculated with G. albida and C. etunicatum . A. longula was fewer effective in relation to the other tested mycorrhizal fungi. The inoculation with G. albida or C. etunicatum favors the production of C. leptophloeos seedlings with increase of total foliar phenols and tannins, which are compounds with pharmacological importance. [ABSTRACT FROM AUTHOR]

Ascochyta blight causes severe losses in field pea production and the search for resistance traits towards the causal agent Didymella pinodes is of particular importance for farmers. Various microsymbionts have been reported to shape the plants' immune response. However, regardless their contribution to resistance, they are hardly included in experimental designs. We delineate the effect of symbionts (rhizobia, mycorrhiza) on the leaf proteome and metabolome of two field pea cultivars with varying resistance levels against D. pinodes and, furthermore, show cultivar specific symbiont colonisation efficiency. The pathogen infection showed a stronger influence on the interaction with the microsymbionts in the susceptible cultivar, which was reflected in decreased nodule weight and root mycorrhiza colonisation. Vice versa, symbionts induced variation of the host's infection response which, however, was overruled by genotypic resistance associated traits of the tolerant cultivar such as maintenance of photosynthesis and provision of sugars and carbon back bones to fuel secondary metabolism. Moreover, resistance appears to be linked to sulphur metabolism, a functional glutathione-ascorbate hub and fine adjustment of jasmonate and ethylene synthesis to suppress induced cell death. We conclude that these metabolic traits are essential for sustainment of cell vitality and thus, a more efficient infection response. Significance The infection response of two Pisum sativum cultivars with varying resistance levels towards Didymella pinodes was analysed most comprehensively at proteomic and metabolomic levels. Enhanced tolerance was linked to newly discovered cultivar specific metabolic traits such as hormone synthesis and presumably suppression of cell death. [ABSTRACT FROM AUTHOR]

In recent years, the use of woody plants in phytoremediation has gained popularity due to their high biomass production and their association with mycorrhizal fungi, which can improve their survival and development rates under stress conditions. In this study, mycorrhized and non-mycorrhized white birch plants ( Betula pubescens Ehr.) were grown in control and a metal-polluted industrial soil. After 60 days of culture, plant growth and metal accumulation, the content of photosynthetic pigments and oxidative-stress markers, as well as the enzymatic activities and gene expressions of antioxidant enzymes were measured. According to our results, mycorrhized birch plants grown in control soil showed an increased activity and gene expression of catalase and ascorbate peroxidase, along with hydrogen peroxide overproduction, which could support the importance of the reactive oxygen species as signaling molecules in the regulation of plant-fungus interactions. Additionally, in polluted soil mycorrhized plants had higher biomass but lower metal accumulation, probably because the symbiotic fungus acted as a barrier to the entrance of metals into the host plants. This behavior led to mitigation in the oxidative challenge, reduced hydrogen peroxide content and diminished activities of the antioxidant enzymes in comparison to non-mycorrhized plants. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) are nutrients that frequently limit plant performance and crop yield. Currently, awareness of the importance of plant-microbe interactions in plant nutrient acquisition and growth promotion persist, particularly under stressful conditions, such as those resulting from P scarcity. The aim of the present study was to evaluate the effects of P starvation on the influence of arbuscular mycorrhiza (AM) symbiosis on N 2 -fixing capacities, plant growth, nutrient uptake and photosynthetic performance of soybean plants at flowering and grain filling stages. To this end, soybean ( Glycine max ) plants were nodulated with Bradyrhizobium elkanii and inoculated or not with the AM fungus Glomus macrocarpum . The +AM and −AM plants were grown under low P conditions (50 μM), and a control treatment with −AM plants under sufficient P concentration (500 μM) was also performed (−AM + P). Plants were grown until the beginning of the flowering and another set till the grain filling stage. The results showed that mycorrhization improved soybean plant performance under P scarcity compared with non-AM associated plants under the same conditions. AM positively influenced growth and plant nodulation at both flowering and grain-filling stages, without significant changes in plant P content. AM symbiosis increased nitrogenase activity, P content in nodules and leaf N content, the maximum carboxylation rate of Rubisco and reduced the metabolic limitation of photosynthesis under P starvation, which indicated the AM stimulus to symbiotic N 2 fixation (SNF) and photosynthesis. Under these conditions, mycorrhizal symbiosis could not completely meet soybean P demand compared with well-nourished soybean plants, which produced higher plant and nodules biomass. In conclusion, AM association in nodulated soybean plants is likely an important strategy for maintaining SNF functioning, conferring increased plant growth and better N status under P scarcity conditions and significantly attenuating the negative effects of low Pi in nodulated-soybean plants. [ABSTRACT FROM AUTHOR]

Root feeding larvae of Phyllophaga vetula causes severe damage in maize agroecosystems and their conventional management with chemical pesticides adversely affects the environment. Plant beneficial rhizosphere microorganisms such as mycorrhzial and entomopathogenic fungi (EPF) offer an alternative sustainable pest management strategy, but their successful integration in agroecosystems requires profound knowledge about their ecology. Here we explored interactions between a commercial isolate of the EPF Beauveria bassiana and indigenous maize mycorrhizas and their single and combined effects against root herbivory from the insect larvae P. vetula. Maize plants were grown in a greenhouse for seven weeks in pots with P limited soil with all possible combinations of the three main factors including native arbuscular mycorrhizal fungi (AMF) (without and with), EPF (without and with) and P. vetula (without and with). Root herbivory by P. vetula reduced plant growth and nutrition, and in addition reduced AMF root colonization. In contrast, AMF improved plant growth and P nutrition, but also reduced the population density of B. bassiana . Inoculation with B. bassiana increased root dry weight and counteracted a decrease in shoot N content from P. vetula root herbivory, despite that only 5% of P. vetula larvae were infected with B. bassiana . Dual inoculation with AMF and B. bassiana increased plant growth and N shoot content allowing the plants to compensate for the damage caused by P. vetula herbivory. In conclusion our results show that combination of native AMF populations and the EPF B. bassiana induce tolerance in maize from root herbivory by P. vetula in terms of plant growth performance and nutrition. [ABSTRACT FROM AUTHOR]

Our recent studies have demonstrated that forest litter used in a bare-root forest nursery promoted survival and growth of two-year-old Scots pine seedlings and positively shaped the development of their ectomycorrhizal (ECM) fungal communities. To determine whether the beneficial effects of litter treatment can be extended to the next growing seasons, litter-treated seedlings were outplanted to four sites with different environmental conditions: forest clear-cut (S1), area formerly polluted by emissions from nitrogen fertilizer plant (S2), abandoned agricultural land (S3) and coastal sand dunes (S4). Seedlings grown in mineral nursery soil without litter amendment served as controls. Height and survival of seedlings were measured over three consecutive years after outplanting. At the end of the third growing season, the mycorrhizal status of seedlings was assessed using DNA-based identification techniques. Litter treatment during the nursery phase significantly improved the height of seedlings at the end of the first growing season at all tested sites. In the second and third growing seasons after outplanting, the heights of litter treated seedlings remained greater compared to control seedlings at three of the four sites; however, at the abandoned agricultural site (S3), significantly lower growth of litter-treated seedlings was observed. After the third growing season, the differences in seedling heights at the forest clear-cut (S1) and the site formerly polluted by nitrogen (S2) were not statistically significant. Survival of all outplanted seedlings varied by season and study site, but litter treated seedlings showed a clear tendency towards enhanced survival. Three years after outplanting, the survival rates of litter-treated seedlings ranged from approximately 81% at S4 to 96% at S2; for control seedlings, survival rates ranged from 63% at S4 to 81% at S3. At sites S1, S2 and S4, the survival of litter-treated seedling was significantly higher. There was a substantial transformation in ECM community composition with low persistence of suilloid mycorrhizas for both litter-treated and control seedlings three years after outplanting. Two-way analysis of similarities (ANOSIM) indicated that differences in ECM fungal community composition across seedlings from different sites likely were due to site specificity rather than previous litter treatment. Our results indicated that nursery soil amended with pine forest litter creates favourable conditions for the production of pine seedlings with better root quality and high abundance of suilloid mycorrhizas, thus allowing for potential reductions in mortality after outplanting on unfavourable sites. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi inoculation is considered a potential biotechnological tool for an eco-friendly remediation of hazardous contaminants. However, the mechanisms explaining how AM fungi attenuate the phytotoxicity of metal(oid)s, in particular arsenic (As), are still not fully understood. The influence of As on plant growth and the antioxidant system was studied in Leucaena leucocephala plants inoculated with different isolates of AM fungi and exposed to increasing concentrations of As (0, 35, and 75 mg dm-3) in a Typic Quartzipsamment soil. The study was conducted under greenhouse conditions using isolates of AM fungi selected from uncontaminated soils (Acaulospora morrowiae, Rhizophagus clarus, Gigaspora albida; and a mixed inoculum derived from combining these isolates, named AMF Mix) as well as a mix of three isolates from an As-contaminated soil (A. morrowiae, R. clarus, and Paraglomus occultum). After 21 weeks, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were determined in the shoots in addition to measuring plant height and mineral contents. In general, AM fungi have shown multiple beneficial effects on L. leucocephala growth. Although the activity of most of the stress-related enzymes increased in plants associated with AM fungi, the percentage increase caused by adding As to the soil was even greater for non-mycorrhizal plants when compared to AM-fungi inoculated ones, which highlights the phytoprotective effect provided by the AM symbiosis. The highest P/As ratio observed in AM-fungi plants, compared to non-mycorrhizal ones, can be considered a good indicator that the AM fungi alter the pattern of As(V) uptake from As-contaminated soil. Our results underline the role of AM fungi in increasing the tolerance of L. leucocephala to As stress and emphasize the potential of the symbiosis L. leucocephala-R. clarus for As-phytostabilization at moderately As-contaminated soils. [ABSTRACT FROM AUTHOR]

It is well known that the over exploitation of soil resources decreases the density and diversity of arbuscular mycorrhizal (AM) fungal propagules. It has been postulated that agricultural practices could promote the occurrence and functioning of remaining and resilient AM fungal ecotypes in order to benefit from AM associations. Using C. ochroleuca , a highly mycotrophic plant species, the aims of this study were to determine in controlled conditions, the impact of this legume species on: (i) the mycorrhizal soil infectivity (MSI), (ii) the Rock Phosphate (RP) solubilising activity and (iii) the soil microbial functions. The expected benefits of C. ochroleuca cultivation have been evaluated by comparing its biological influences with those recorded with a non-mycorrhizal plant species, Brassica oleracea in order to attest of the importance of the AM potential in RP weathering and soil functioning. The results show that: C. ochroleuca was effective in improving the mycorrhizal soil potential, (ii) functional abilities of soil microflora were influenced by the cultured plant species and the mycorrhizal soil potential and (iii) the efficiency of rock phosphate amendment on plant growth depended on the level of mycorrhizal soil potential and was linkedto the extent of the mycorrhizal network.The C. ochroleuca impact was significantly reinforced with KRP amendment (i.e. +29.3% for the Catabolic Eveness, +45.7% for the hyphal length). According to these results, it could be concluded that agricultural strategies based on the management of local biodiversity (i.e. the use of native legume species) could be considered as a sustainable practice to optimally manage AM fungi and to ensure their functionalities in order to maintain a sustainable production of food crops in the tropics. [ABSTRACT FROM AUTHOR]

The rapid global conversion of biodiverse landscapes to intensively managed arable fields may decrease microbial diversity and threaten the long-term fertility of native soils. Previous laboratory and experimental studies provide conflicting results: some have recorded declines in overall microbial diversity and certain beneficial microorganisms under intensified cultivation while others report no change (or even increased) diversity. However, few studies have been carried out in actual agricultural fields. We analysed the soil metagenomic communities of 36 current and former grasslands in Oxfordshire, England using Illumina sequencing of the bacterial 16S and fungal ITS1 regions to examine how agricultural intensification alters native microbial communities and whether arable reversion can reverse these processes. We demonstrate that land-use change did not affect bacterial diversity or specific beneficial taxa (nitrogen-fixing bacteria and mycorrhizas). However, fungal diversity declined and certain microbiota known to be plant pathogens (e.g. Olpidium ) were significantly more abundant on agriculturally improved fields. On sites where arable reversion took place, microbial communities were similar to those from unimproved grasslands although overall vegetation diversity and fungal richness were lower. The conservation of species-rich grasslands and their associated microbial diversity could therefore be a key resource for sustainable agriculture in the future. [ABSTRACT FROM AUTHOR]

Little is known about how the adverse physical and chemical environment in sodic soils affects plant-mycorrhizal relationships. We investigated mycorrhizal colonisation and plant nutrient uptake of cotton plants under highly stressed (Exchangeable Na percentage (ESP) 21) and less stressed (ESP 7) conditions with two rates of applied P. The relative hyphal contribution to P uptake was quantified using dual isotope labelling techniques ( 32 P and 33 P). Root colonisation and P uptake of mycorrhizal cotton plants reduced by 16% and 20%, respectively, in highly sodic soil as compared to plants in low sodic soil, however, the relative proportion of P delivered via hyphal pathways ( 32 P from root-free hyphal compartment) was similar. Under high P conditions, the relative increase in the proportion of 33 P (root + hyphae compartment) taken up by inoculated plants was greater in the low sodic soil relative to the high sodic soil. Mycorrhization improved early seedling vigour, and nutrient uptake. Reduced colonisation and hyphal exploration of the soil, possibly due to the physical and chemical constraints imposed by highly-sodic soil, rather than poorer mycorrhizal function, may be responsible for limited early P uptake of cotton in highly-sodic soil. [ABSTRACT FROM AUTHOR]