Search

By the first time an efficient methodology for micropropagation of poplar hybrids by temporary immersion in liquid medium was developed under photomixotrophic conditions. Influence of factors, such as plant regulator/balance in culture medium, number of explants or inoculums per bottle, immersion frequencies in Temporary Immersion Bioreactors (TIBs), reduced sucrose as priming treatment and photoperiod were studied in TIBs with 0.4 MPa CO 2 at a light intensity of 100 μM m −2 s −1 . Protocol was standardized in three poplar clones recommended for their dendroenergetic traits. The highest multiplication rates were obtained by inoculating 20 and 24 nodal segments in TIBs with 200 ml of medium MS + 0.22 μM TDZ. During winter (8 h photoperiod), the highest multiplication rates in TIBs were obtained with 8 h immersion frequencies, while in summer (14 h photoperiod) immersions every 6 h showed the best multiplication rates. The main percent of ex vitro rooted plants was recovered when plantlets were micropropagated in liquid medium supplemented with 1.5% sucrose. A drying pretreatment for 20 min followed by 10 min inoculation with a mycorrhiza solution ( Scleroderma spp.- Pisolithus tinctorius ) allowed us to obtain 97.3% of poplars adapted to ex vitro environmental conditions. DNA patterns amplified with the ISSR primer (CTC)5 showed high genomic similarity without polymorphic bands between samples of the same hybrid, which indicated the non-occurrence of genomic changes in the studied populations. Overall, TIBs technology constitute an advance to the industrial development of clonal propagation of poplars for biomass production, in comparison with the classical micropropagation. [ABSTRACT FROM AUTHOR]

Ilex paraguariensis St. Hil. (Yerba Mate) is an important crop for which a decrease in yields associated to unsustainable agricultural practices is well documented. The aim of this study is to investigate the diversity of bacteria and fungi inhabiting roots of Yerba Mate. This is an important pre-requisite for the use of microorganisms inhabiting roots to modulate plant nutrition and health as an ecologically friendly agricultural alternative for this crop. The diversity of the root-associated microbiome from eleven plantations with different agricultural practices was analyzed by high throughput sequencing of the 16S rRNA gene as a bacterial marker, whereas the fungal communities were targeted by amplifying the ITS region of the ribosomal RNA gene cluster. A comparison of the bacterial and fungal communities between plantation sites and cultivation practices was made to address the major factors contributing to the structure of the root microbiome of this crop. Operational taxonomic units (OTUs) related to well-known plant growth promoting bacteria such as Burkholderia, Bradyrhizobium, Weissella, Enterobacter and Rhizobium were detected. Those might constitute targets for future enrichment efforts of plant growth promoting clades. The analysis of the fungal community composition demonstrated that arbuscular mycorrhizae colonize Yerba Mate roots, and that the frequency of this group is favored in degraded soils. The detection of other groups harboring potential phytopathogens might help to broaden the understanding of the ailments affecting this crop. This study provides the first description of the root-associated microbiome of Yerba Mate and constitutes a stepping-stone towards harnessing the role of microbes in the sustainable cultivation of this crop. [ABSTRACT FROM AUTHOR]

• Feremycorrhiza means 'nearly mycorrhiza'. • Feremycorrhiza has mycorrhiza-like effects on plant growth and nutrition. • Austroboletus occidentalis has ectomycorrhizal traits and lineage. • A. occidentalis has limited saprotrophic capacity similar to ectomycorrhizal fungi. • A. occidentalis genome lacks invertase genes similar to ectomycorrhizal fungi. [ABSTRACT FROM AUTHOR]

Herbivores, microbial mutualists, and soil nutrients can affect plant survival, growth, and reproduction, demographic parameters that are essential to plant restoration. In this study we ask: 1) whether native plants that form early associations with mycorrhizal fungi are more tolerant of mammalian grazers, and 2) how early plant associations with mycorrhizal fungi influence mammalian grazing across gradients in soil nutrients. In eight grassland sites in California (USA), we transplanted seedlings of a native bunchgrass, Stipa pulchra , that were or were not pretreated with mycorrhizal fungi in exclosures designed to exclude different guilds of vertebrate grazers. Pretreated plants had greater establishment eight months after transplantation than untreated plants. Mycorrhizal inoculation resulted in twofold greater biomass and fourfold greater seed production when plants were protected from herbivores; inoculation with mycorrhizae resulted in twofold greater biomass and seed production when plants were accessible by all herbivores. Soil phosphate and potassium concentrations influenced herbivory: vertebrate grazing had less effect on transplant biomass and seed production at sites with high phosphate – low potassium soils, but the effects of grazing were more severe in low phosphate – high potassium soils. Pretreatment with mycorrhizal fungi can result in greater survival, growth, and reproduction of transplanted seedlings of native bunchgrass S. pulchra . Our results also illustrate that soil conditions may influence the extent to which the vertebrate herbivore community limits restoration of S. pulchra : the effects of some small mammalian herbivores (e.g., voles) was little affected by soil conditions, but grazing by larger herbivores had a greater effect on S. pulchra performance at sites with low phosphate – high potassium soils. In helping identify the contribution of soil nutrients, herbivores, and mycorrhizae to establishment and performance, our work has implications for the restoration of a species that is likely a fundamental component of pristine California grassland ecosystems. [ABSTRACT FROM AUTHOR]

Sod culture with white clover is a common practice as part of soil management in citrus orchards. However, it is not clear whether such sod culture affects plant growth, soil properties, and the mycorrhizosphere of citrus. In this study, white clover was planted around trifoliate orange (a popular citrus rootstock) under mycorrhization with or without Rhizoglomus intraradices . After four months, the sod culture substantially stimulated root mycorrhizal colonization and soil hyphal growth. Plant growth performance of trifoliate orange was significantly increased by either mycorrhization under non-sod culture or sod culture under non-mycorrhization, whereas sod culture under mycorrhization significantly decreased the growth performance. Both mycorrhization and sod culture significantly increased the concentrations of easily extractable glomalin-related soil proteins (EE-GRSP), total GRSP (T-GRSP), and soil organic carbon (SOC), the distribution of water-stable aggregates in the size of 2–4, 1–2, and 0.5–1 mm, and the activity of soil peroxidase and phosphatase. The mean weight diameter was notably increased by mycorrhization, irrespective of sod or non-sod culture, but was higher with sod culture under mycorrhization than under non-mycorrhization. Root colonization, soil hyphal length, SOC, EE-GRSP, and T-GRSP were significantly and positively correlated with aggregate stability. These results suggested that sod culture stimulated mycorrhizal development and potentially improved soil properties in an AMF-inoculated citrus orchard. [ABSTRACT FROM AUTHOR]

Soil nutrient acquisition and exchanges through symbiotic plant–fungus interactions in the rhizosphere are key features for the current agricultural and environmental challenges. Improved crop yield and plant mineral nutrition through a fungal symbiont has been widely described. In return, the host plant supplies carbon substrates to its fungal partner. We review here recent progress on molecular players of membrane transport involved in nutritional exchanges between mycorrhizal plants and fungi. We cover the transportome, from the transport proteins involved in sugar fluxes from plants towards fungi, to the uptake from the soil and exchange of nitrogen, phosphate, potassium, sulfate, and water. Together, these advances in the comprehension of the mycorrhizal transportome will help in developing the future engineering of new agro-ecological systems. [ABSTRACT FROM AUTHOR]

Although phosphorus (P) is known to reduce zinc (Zn) uptake by roots and root-to-shoot translocation, how this interaction is affected by changes in root morphology and arbuscular mycorrhizae (AM) are poorly understood. The current study determined the effects of P application rate (0, 25, 50, 100, 200, and 400 kg P ha −1 ) on Zn uptake by roots and root-to-shoot translocation in a high-yielding winter wheat system on calcareous soil. Root dry weight (RDW), root length density (RLD), and root surface area (RSA) significantly increased as P application increased from 0 to 50 kg ha −1 but were unaffected by rates >50 kg ha −1 . Zn accumulation (mg m −2 or μg m −2 ) by roots at flowering increased with application of 25 and 50 kg P ha −1 but slightly decreased with application of 100–400 kg P ha −1 . Zn accumulation in roots and in shoots at flowering and grain yield at maturity were positively correlated with RDW, RLD, and RSA. Root Zn accumulation was increasing with increased AM colonization from low AM (<10%) to 30% AM colonization. Whereas, continuously increasing AM colonization induced root Zn accumulation decrease, which may be mainly due to the decrease of root dry weight affected by P deficiency. P application rate did not significantly affect the ratio of Zn concentrations in roots vs. shoots or the ratio of Zn accumulation in roots vs. total Zn accumulation in the plant, indicating that Zn translocation from roots to shoots is not the primary factor limiting Zn concentrations in grain. These results indicate 1) that P application affects the Zn accumulation of wheat by affecting Zn uptake by roots and 2) that the changes in Zn uptake by roots and Zn accumulation following P application reflect changes in root morphology and AM colonization of roots. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) improve the uptake of immobile mineral nutrients such as phosphate, thereby enhancing the growth of most plants. However, plants belonging to the Brassicaceae family such as rapeseed ( Brassica napus L.) do not associate with AMF. In Argentina, one of the crops frequently used in rotation with rapeseed is soybean ( Glycine max L.). The aim of this study was to evaluate the impact of the non-mycorrhizal rapeseed (inoculated with the phosphorus solubilizing bacteria Bacillus sp. LRCP-4 or Arthrobacter sp. LRCP-11) as the preceding crop, on soybean plants growth, nodulation and AMF colonization. Green house experiments were done using soil samples from rapeseed cultivated fields to growth soybean plants. Results indicated that the soybean interaction with the microsymbiont Bradyrhizobium japonicum E109 was not affected and that the growth of plants in soil previously planted with rapeseed inoculated with Bacillus sp. LRCP-4 was increased (31% and 29% for shoot and root fresh weight respectively). However, it was evident from this study that inclusion of rapeseed in the soybean-based system decrease by a 30% the AMF soybean root colonization. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Demand for organic blueberries has risen in response to consumers’ interest in healthy eating and greater awareness of the environment. Although organic production systems share many challenges with conventional systems, they have specific limitations and questions. Synchronisation of plant nutrient demand with the release of mineral nutrients from organic nutrient sources presents a particular challenge for the organic grower. In this paper we address belowground challenges in blueberry production from an organic perspective, such as soil properties and amendments as well as the choice of mulching material and organic fertilisers. We also address potential toxicity problems for blueberries associated with high concentrations of aluminium and manganese as well as salt stress. Symbiosis with ericoid mycorrhizal fungi is of potential interest in organic blueberry production as the fungi may improve plant access to nutrients from organic sources. The effects of management factors and limitations associated with the commercial utilisation of the symbiosis are also discussed. [ABSTRACT FROM AUTHOR]

The main challenge for plants growing in nutrient poor, contaminated soil is biomass reduction, nutrient deficiency and presence of heavy metals. Our aim is to overcome these challenges using different microbial combinations in mining-impacted soil and focus on their physiological and biochemical impacts on a model plant system, which has multiple applications. In the current study, sorghum BTx623 seedlings grown in mining-impacted soil in greenhouse were subjected to plant growth promoting bacteria (PGPB or B) alone, PGPB with arbuscular mycorrhizal fungi (My), My alone and control group with no treatment. Root biomass and uptake of most of the elements showed significant increase in all treatment groups in comparison with control. Mycorrhiza group showed the best effect followed by My + B and B groups for uptake of majority of the elements by roots. On the contrary, biomass of both shoot and root was more influenced by B treatment than My + B and My treatments. Metabolomics identified compounds whose levels changed in roots of treatment groups significantly in comparison to control. Upregulation of stearic acid, sorbitol, sebacic acid and ferulic acid correlated positively with biomass and uptake of almost all elements. Two biochemical pathways, fatty acid biosynthesis and galactose metabolism, were regulated in all treatment groups. Three common pathways were upregulated only in My and My + B groups. Our results suggest that PGPB enhanced metabolic activities which resulted in increase in element uptake and sorghum root biomass whether accompanied with mycorrhiza or used solely. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizas (AM) are adapted to soils with higher pH, less organic matter and more available nitrogen than ectomycorrhizas (EM). We hypothesise that also climatic factors have a direct role in the relative success of the two types. We tested their colonisation rates after soil freezing. Soil was taken from forest and meadow sites to comprise propagules of both types of mycorrhizal fungi. The soil was sieved (6 mm) and mixed. Soil batches were exposed to +5 °C (control), −12, −25, −48 or −130 °C, time at target temperature was 6 h. Silver birch ( Betula pendula ), grey alder ( Alnus incana ) and white clover ( Trifolium repens ) were sown to these soils and grown in favourable conditions for 11 weeks. EM colonisation in birch and alder was similar in all treatments. Arbuscule formation in alder and clover was not affected, but vesicles, AM fungal hyphae and spores in roots were reduced with decreasing temperature. Soil soluble phosphorus (P) was increased by freezing as were also the foliar concentrations in birch. By contrast, clover had less foliar P in the lowest temperature treatments which may be due to less efficient functioning of AM. To conclude, the development and function of AM were impaired to some extent by very low temperatures, while EM were not affected. The low-temperature tolerance of EM may be another explanation to their predominance in cold climates. [ABSTRACT FROM AUTHOR]

The long cultivation of field pea led to an enormous diversity which, however, seems to hold just little resistance against the ascochyta blight disease complex. The potential of below ground microbial symbiosis to prime the immune system of Pisum for an upcoming pathogen attack has hitherto received little attention. This study investigates the effect of beneficial microbes on the leaf proteome and metabolome as well as phenotype characteristics of plants in various symbiont interactions (mycorrhiza, rhizobia, co-inoculation, non-symbiotic) after infestation by Didymella pinodes . In healthy plants, mycorrhiza and rhizobia induced changes in RNA metabolism and protein synthesis. Furthermore, metal handling and ROS dampening was affected in all mycorrhiza treatments. The co-inoculation caused the synthesis of stress related proteins with concomitant adjustment of proteins involved in lipid biosynthesis. The plant's disease infection response included hormonal adjustment, ROS scavenging as well as synthesis of proteins related to secondary metabolism. The regulation of the TCA, amino acid and secondary metabolism including the pisatin pathway, was most pronounced in rhizobia associated plants which had the lowest infection rate and the slowest disease progression. Biological significance A most comprehensive study of the Pisum sativum proteome and metabolome infection response to Didymella pinodes is provided. Several distinct patterns of microbial symbioses on the plant metabolism are presented for the first time. Upon D. pinodes infection, rhizobial symbiosis revealed induced systemic resistance e.g. by an enhanced level of proteins involved in pisatin biosynthesis. [ABSTRACT FROM AUTHOR]

This study evaluates the responses of Lavandula dentata under drought conditions to the inoculation with single autochthonous arbuscular mycorrhizal (AM) fungus (five fungal strains) or with their mixture and the effects of these inocula with a native Bacillus thuringiensis (endophytic bacteria). These microorganisms were drought tolerant and in general, increased plant growth and nutrition. Particularly, the AM fungal mixture and B. thuringiensis maximized plant biomass and compensated drought stress as values of antioxidant activities [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase APX)] shown. The AMF-bacteria interactions highly reduced the plant oxidative damage of lipids [malondialdehyde (MDA)] and increased the mycorrhizal development (mainly arbuscular formation representative of symbiotic functionality). These microbial interactions explain the highest potential of dually inoculated plants to tolerate drought stress. B. thuringiensis “in vitro” under osmotic stress does not reduce its PGPB (plant growth promoting bacteria) abilities as indole acetic acid (IAA) and ACC deaminase production and phosphate solubilization indicating its capacity to improve plant growth under stress conditions. Each one of the autochthonous fungal strains maintained their particular interaction with B. thuringiensis reflecting the diversity, intrinsic abilities and inherent compatibility of these microorganisms. In general, autochthonous AM fungal species and particularly their mixture with B. thuringiensis demonstrated their potential for protecting plants against drought and helping plants to thrive in semiarid ecosystems. [ABSTRACT FROM AUTHOR]

Trifoliate orange seedlings were grown in perspex pots of a split-root system, where one half of the split roots was inoculated with or without arbuscular mycorrhizal fungi (AMF, Acaulospora scrobiculata or Funneliformis mosseae ). Five months after inoculation, the growth performance, leaf, stem and root biomass and photosynthetic rate were generally significantly higher in AM than in non-AM seedlings. Greater root morphological traits were observed in the AM root side than in the non-AM side for the same plant and in AM than in non-AM plants. AM seedlings had significantly higher leaf sucrose and glucose contents and total (leaf + root) glucose and fructose contents as compared to non-AM ones. In the split roots, the AM side displayed substantially higher sucrose, glucose and fructose contents than the non-AM side for the same plant, and in AM than in non-AM plants. These results showed greater C movement into the non-AM side from an AM-colonized plant than from a non-AM-colonized plant. These results conclude that the presence of AM in one side of the split roots benefited C acquisition and root development to another half non-AM side, suggesting functional equilibrium and resource allocation of AM within a root system. [ABSTRACT FROM AUTHOR]

Concurrent interactions and the availability of resources (e.g., light) affect the cost/benefit balance during mutualistic and antagonistic interactions, as well as plant resource allocation patterns. Mycorrhizal interactions and herbivory concur in most plants, where mycorrhizae can enhance the uptake of soil nutrients by plants as well as consuming a large fraction of the plant's carbon, and defoliation usually reduces light interception and photosynthesis, thereby causing direct losses to the hosts of mycorrhizal fungi. Both types of interactions affect the carbon budget of their host plants and thus we predict that the relative costs of herbivory and mycorrhizal colonization will increase when photosynthesis is reduced, for instance in light limited environments. We conducted a greenhouse experiment using Datura stramonium to investigate the effects of defoliation and mycorrhizal inoculation on the resource allocation patterns in two different light environments. Defoliated plants overcompensated in terms of leaf mass in both light environments, but total seed mass per fruit was negatively affected by defoliation in both light environments. Mycorrhizal inoculation had a positive effect on vegetative growth and the leaf nitrogen content, but defoliation negates the benefit of mycorrhizal interactions in terms of the leaf nitrogen content. In general, D . stramonium compensated for the relative costs of concurrent mycorrhizal interactions and defoliation; plants that lacked both interactions exhibited the same performance as plants with both types of interactions. [ABSTRACT FROM AUTHOR]

Basal stem rot is one of the major diseases of oil palm ( Elaies guineensis Jacq.) caused by pathogenic Ganoderma species. Trichoderma and mycorrhizae were proposed to be able to reduce the disease severity. However, their roles in improving oil palm defence system by possibly inducing defence-related genes in the host are not well characterized. To better understand that, transcript profiles of eleven putative defence-related cDNAs in the roots of oil palm inoculated with Trichoderma harzianum T32 and mycorrhizae at different time points were studied. Transcripts encoding putative Bowman-Birk protease inhibitor (EgBBI2) and defensin (EgDFS) increased more than 2 fold in mycorrhizae-treated roots at 6 weeks post inoculation (wpi) compared to those in controls. Transcripts encoding putative dehydrin (EgDHN), glycine-rich RNA binding protein (EgGRRBP), isoflavone reductase (EgIFR), type 2 ribosome inactivating protein (EgT2RIP), and EgDFS increased in the oil palm roots treated with T. harzianum at 6 and/or 12 wpi compared to those in the controls. Some of these genes were also expressed in oil palm roots treated with Ganoderma boninense . This study provides an insight of some defence-related genes induced by Trichoderma and mycorrhizae, and their roles as potential agents to boost the plant defence system. [ABSTRACT FROM AUTHOR]

In the last decades, an increasing number of forest decline events and widespread tree mortality have been reported worldwide as a consequence of different global change drivers. Such a general decrease in tree health and cover has a large potential to impact mycorrhizal communities, but this issue remains largely unexplored. We used a Bayesian framework to analyze the impact of Quercus suber decline on spatial patterns of seedling-mycorrhiza interactions in mixed Mediterranean forests in Southern Spain, and evaluate the relative importance of this symbiosis as a driver of oak seedling establishment. Our models showed that the spatial variability found in the patterns of oak seedling colonization by both arbuscular mycorrhizas and ectomycorrhizas was partially linked to the process of Q. suber decline. Moreover, seedling survival and growth was influenced by the intensity of mycorrhizal colonization, but in quite unexpected ways. Arbuscular mycorrhizas had a larger effect on seedling performance than ectomycorrhizas, and the effects of both groups were negative or neutral but never positive. We conclude that because the spatial distribution of the seedling-mycorrhiza association responded to the identity and health status of individual trees, and mycorrhizal infection did in turn affect seedling performance, tree decline might affect forest dynamics through changes in plant–soil biota feedbacks. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) form symbioses with most plants, potentially improving their growth and nutrient assimilation activities. Cysteine (Cys) and methionine (Met) are nitrogen (N)- and sulphur (S)-containing amino acids. Compared with phosphate and N, limited attention has been paid to the role of AMF in low molecular weight organic S acquisition. To explore the uptake and relative contributions of organic and inorganic N and S to plants, and the role of AMF in S uptake, a pot study was conducted based on 14C, 35S, 13C, and 15N quad labelling (6-h labelling test after adding the labelled solution to the soil–plant system) using a mutant tomato genotype with highly decreased AMF symbiosis capacity. Tomato roots can uptake limited amounts of added Met and Cys (<1.77%) within 6 h, as indicated by the 14C and 13C labelling results, and most of them were utilised by soil microorganisms. After uptake for 6 h, 10.0–14.8% of N and 1.4–6.1% of S derived from added Cys and Met were utilised by plants, mainly in inorganic N and S forms derived from Cys and Met decomposition. Met and Cys could be important S sources (Met: 3.0–9.8%, Cys: 8.8–22.0%) for plants, however have negligible roles in N nutrition (∼1%), as most N uptake by plants was derived from soil inorganic N. The tomato uptake of inorganic S derived from Cys decomposition was much higher than that derived from Met, as higher ratios of S-Cys were released as SO 4 2− from microorganisms during the 6-h testing periods. Even with the artificial addition of AMF, most of the added Met and Cys were utilised by Gram-negative bacteria, as indicated by 13C-PLFA biomarkers. AMF reduced host plant uptake of organic N and S, but stimulated plant N uptake from Met and Cys, which was mainly inorganic N following mineralisation. AMF not only utilise organic carbon from host plants but also capture soil organic matter to satisfy their energy demands. In the spaces where both root and AMF occur, AMF colonisation decreased tomato 35S uptake from Cys, Met, and SO 4 2− by 24.6%, 20.6%, and 11.0% within the 6-h uptake period, respectively, when compared with that in the mutant genotype with reduced colonisation capacity; in contrast, AMF colonisation increased 35S-Cys uptake by 118.7% from areas that roots could not reach. Overall, AMF enhanced host plant N uptake but reduced organic N uptake under competition with plant roots for S in the rhizosphere, but stimulated plant S uptake by extraradical mycelia, based on this short-term pulse-chase test. • Limited Met and Cys was absorbed by tomato under competition with microorganisms. • Inorganic S uptake by tomato from Cys decomposition higher than that from Met. • Met and Cys could be key S sources for plants, with negligible roles in N nutrition. • AMF reduce plant organic N/S uptake but stimulate plant N uptake from Met and Cys. • AMF colonisation increased 35S-Cys uptake from areas roots could not reach. [ABSTRACT FROM AUTHOR]

The arbuscular mycorrhizal (AM) fungus promotes plant growth and can alter the production of primary and secondary metabolites. The aim of this work was to determine the influence of AM fungi colonization on the content of phenolic compounds, flavonoids and soluble carbohydrates in olive ( Olea europaea L.) tree roots. The results revealed that mycorrhizal plants had a higher content of flavonoids and total phenols. Analysis of sugar contents showed enhanced levels of sucrose and fructose in mycorrhizal roots, while glucose amounts stayed constant. The DPPH radical-scavenging activity of the mycorrhizal root methanolic extracts was higher than that of the non- mycorrhizal root methanolic extracts. These results indicated that olive tree roots contain significant amounts of phenolic compounds, important factors for antioxidant capacity, which can be substantially modified by colonization of olive trees with AM fungi. [ABSTRACT FROM AUTHOR]

Agriculture often leads to altered composition and reduced diversity of arbuscular mycorrhizal fungal (AMF) communities compared to natural grassland systems. However, the ecology of taxa that are lost in this transition has thus far not been well characterized. In this study we found that reduced or lost AMF taxa in farmlands were significantly stronger correlated with soil N:P ratio than a randomly sampled community; this indicates that taxa that prevail at high N:P ratio in grasslands are the ones most sensitive to agriculture. As a high N:P environment is also commonly argued to impose the highest AMF benefit to plants, the observation that those taxa are lost could indicate that agricultural fields are left with communities of reduced symbiotic quality. [ABSTRACT FROM AUTHOR]

Mycorrhizas play a pivotal role in phosphorus (P) acquisition of plant roots, by enhancing the soil volume that can be explored. Non-mycorrhizal plant species typically occur either in relatively fertile soil or on soil with a very low P availability, where there is insufficient P in the soil solution for mycorrhizal hyphae to be effective. Soils with a very low P availability are either old and severely weathered or relatively young with high concentrations of oxides and hydroxides of aluminium and iron that sorb P. In such soils, cluster roots and other specialised roots that release P-mobilising carboxylates are more effective than mycorrhizas. Cluster roots are ephemeral structures that release carboxylates in an exudative burst. The carboxylates mobilise sparingly-available sources of soil P. The relative investment of biomass in cluster roots and the amount of carboxylates that are released during the exudative burst differ between species on severely weathered soils with a low total P concentration and species on young soils with high total P concentrations but low P availability. Taking a modelling approach, we explore how the optimal cluster-root strategy depends on soil characteristics, thus offering insights for plant breeders interested in developing crop plants with optimal cluster-root strategies. [ABSTRACT FROM AUTHOR]

Roots and flowers are formed at the extreme ends of plants and they differ in almost every aspect of their development and function; even so, they exhibit surprising molecular commonalities. For example, the calcium and calmodulin-dependent protein kinase (CCaMK) plays a central role in root symbioses with fungi and bacteria, but is also highly expressed in developing anthers. Moreover, independent evidence from transcriptomics, phylogenomics, and genetics reveals common developmental elements in root symbioses and reproductive development. We discuss the significance of these overlaps, and we argue that an integrated comparative view of the two phenomena will stimulate research and provide new insight, not only into shared components, but also into the specific aspects of anther development and root symbioses. [ABSTRACT FROM AUTHOR]

Arundo donax has become one of the most promising species for cellulose paste, biomass, and second-generation biofuel production. Because this species is not able to produce viable seeds, micropropagation is the best method for large scale production. Several studies have demonstrated that arbuscular mycorrhizal fungi (AMF) can improve the acclimatization of micropropagated plantlets, enhancing their growth and survival. In this study, we evaluated the effect of AMF during the acclimatization period of A. donax plantlets and its posterior establishment to the field. Plantlets were inoculated with mycorrhiza-based biofertilizer (AEGIS SYM ® ) that contained Rhizophagus intraradices and Funneliformis mosseae . The inoculum was applied at the time of transplantation of plantlets to 28-cm 3 cell trays filled with commercial nutrient-rich agricultural substrate. The results showed that during acclimatization, mycorrhized plantlets (AM) present higher number of leaves and height increments as compared to non-mycorrhized plantlets (control). Moreover, at the end of the hardening process, AM plantlets presented higher height, number of leaves, biomass, shoot:root ratio and chlorophyll a and b content than control plantlets. After open field establishment, AM plantlets presented greater size, number of stems and survival rate. These results demonstrate that inoculating micropropagated A. donax with AMF enhances its growth and development as well as produces better quality plantlets, which can be very useful for the large-scale production of this energetic crop. [ABSTRACT FROM AUTHOR]

Association between legumes and rhizobia results in the formation of root nodules, where symbiotic nitrogen fixation occurs. The early stages of this association involve a complex of signalling events between the host and microsymbiont. Several genes dealing with early signal transduction have been cloned, and one of them encodes the leucine-rich repeat (LRR) receptor kinase (SymRK; also termed NORK). The Symbiosis Receptor Kinase gene is required by legumes to establish a root endosymbiosis with Rhizobium bacteria as well as mycorrhizal fungi. Using degenerate primer and BAC sequencing, we cloned duplicated SymRK homeologues in soybean called GmSymRKα and GmSymRKβ . These duplicated genes have high similarity of nucleotide (96%) and amino acid sequence (95%). Sequence analysis predicted a malectin-like domain within the extracellular domain of both genes. Several putative cis -acting elements were found in promoter regions of GmSymRKα and GmSymRKβ , suggesting a participation in lateral root development, cell division and peribacteroid membrane formation. The mutant of SymRK genes is not available in soybean; therefore, to know the functions of these genes, RNA interference (RNAi) of these duplicated genes was performed. For this purpose, RNAi construct of each gene was generated and introduced into the soybean genome by Agrobacterium rhizogenes -mediated hairy root transformation. RNAi of GmSymRKβ gene resulted in an increased reduction of nodulation and mycorrhizal infection than RNAi of GmSymRKα , suggesting it has the major activity of the duplicated gene pair. The results from the important crop legume soybean confirm the joint phenotypic action of GmSymRK genes in both mycorrhizal and rhizobial infection seen in model legumes. [ABSTRACT FROM AUTHOR]

Scots pine ( Pinus sylvestris L.) is adapted to various soil types with diverse water availabilities. However, Scots pine seedlings are vulnerable to abiotic stress during the early growth, when they may be exposed to both dry and wet conditions. Here, we focused on the above and below ground coping strategies of Scots pine seedlings under controlled wet, optimal and dry soil conditions by investigating morphological traits including seedling biomass, number of root tips, proportion of mycorrhizal root tips and brown needles. In addition, we studied metabolic and physiological responses including gene expression involved in biosynthesis and catabolism of polyamines (PA), PSII efficiency and the expression of the catalase ( CAT ) late-embryogenesis abundant protein ( LEA ), pyruvate decarboxylase ( PDC ), glutamate-cysteine ligase ( GCL ) and glutathione synthetase ( GS ) genes. We found that seedlings invested in shoots by maintaining stable shoot water content and high PSII efficiency under drought stress. Free and soluble conjugated putrescine (Put) accumulated in needles under drought stress, suggesting the role of Put in protection of photosynthesizing tissues. However, the expression of the PA biosynthesis genes, arginine decarboxylase ( ADC ), spermidine synthase ( SPDS ) and thermospermine synthase ( ACL5 ) was not affected under drought stress whereas catabolizing genes diamino oxidase ( DAO ) and polyamine oxidase ( PAO ) were down-regulated in shoots. The morphology of the roots was affected by peat water content. Furthermore, both drought stress and water excess restricted the seedling ability to sustain a symbiotic relationship. The consistent pattern of endogenous PAs seems to be advantageous to the Scots pine seedlings also under stress conditions. [ABSTRACT FROM AUTHOR]

Meeting increasing global demand for food, fibre, and bioenergy requires efficient use of finite resources, and presents a key sustainability challenge to the agricultural industry, scientists and policy-makers. Increased interest in low-input agriculture in recent years has seen the growing development and use of commercial biological inoculants (bacteria and/or fungi) to increase the mobilisation of key nutrients, especially phosphorus (P), and enhance their availability to crop plants. Here, we review the terminology, composition and function of bio-inoculants and the many factors which impact on their efficacy for increasing P availability in different soil and plant environments. We conclude that the beneficial attributes of commercial bio-inoculants for integrated production systems are not clearly defined. Evidence to support their effectiveness is currently confounded by inadequate quality standards and insufficient knowledge of the underlying mechanisms, which have led to contradicting reports on field performance. There is, however, scope to engineer specific inoculant formulae for more sustainable P management in different system-soil-plant combinations, provided future research is properly structured to help understand the complexity and dynamism of microbial functioning and interactions in soils. [ABSTRACT FROM AUTHOR]

Onion ( Allium cepa L.) is a crop with great economic importance over the world. The vigor of seedlings plays a crucial role in the posterior growth and quality of bulbs. Application of humic substances (HS), inoculation of arbuscular mycorrhizal fungi (AMF) in the soil and enhancement of atmospheric CO 2 are three factors that can influence plant growth and development. Therefore, our main objective was to assess the effect of each of the abovementioned factors, separately or interacting, on the metabolism and growth of onion seedlings before bulb formation and under greenhouse conditions. Results showed that these three factors appear as valid horticultural techniques for improving growth and quality of onion seedlings cultivated in greenhouse even when mycorrhizal colonization of roots does not achieve high rates. Beneficial effects of HS were additive to those of mycorrhizal inoculation or elevated CO 2 (ECO 2 ) on shoot and root biomass production. The triple interaction between exogenous HS application, mycorrhizal inoculation and ECO 2 induced the highest accumulation of soluble sugars, proteins and proline in leaves, suggesting that such interaction was the most effective for increasing the quality of onion shoots as source organs for posterior growth and quality of bulbs and also for enhancing the tolerance of onion seedlings to environmental stresses. [ABSTRACT FROM AUTHOR]

Next-generation sequencing technologies are providing us with new opportunities to characterize plant–fungal communities in more depth and with better replication than ever before. The application of network concepts and numerical tools to analyze those extensive data sets is also rapidly increasing. Here we show, however, that network-based tools will further advance our understanding of the ecology of plant–fungal symbioses if (1) researchers characterize both the interaction patterns among species, and investigate the likely biotic and abiotic drivers of such interactions (e.g. species' abundance, functional traits, environmental conditions) and (2) researchers make sure that the assumptions made by their network-based numerical tools are met by their data sets. [ABSTRACT FROM AUTHOR]

Phalaenopsis ( Phalaenopsis amabilis ‘KC1410’) grow slowly and experience photoinhibition during the daytime. Thus, this study used orchid mycorrhizal (OM) fungus to promote orchid growth hypothetically via increasing the photoacclimation capacity of Phalaenopsis in response to high light (HL). By combining chlorophyll fluorometer and spectral reflectance techniques, the influences of OM colonization on the growth potentials and the photosynthetic performance of HL-grown Phalaenopsis were investigated. OM symbiosis significantly promoted the growth of HL-grown orchids, such as leaf span, fresh weight, and dry weight. Consistent with these observations, OM symbiosis obtained higher value of normalized difference vegetation index (NDVI) and enhanced CO 2 uptake rate. This could be attributed to an increase in photosynthetic performance in OM plants. Notably, maximum quantum efficiency of PSII photochemistry (Fv/Fm) was not altered by OM symbiosis, however, the light-adapted fluorescence measurements of PSII operating efficiency (ФPSII) and electron transport rate (ETR) were increased. Nevertheless, OM orchids had higher photochemical quenching (qP) and lower non-photochemical quenching (NPQ). This indicates a relative higher photosynthetic performance and radiation-use efficiency (RUE) in OM plants. The photochemical reflectance index (PRI) as a photoprotection indicator was also enhanced. Based on these results, we proposed that OM symbiosis increases both the photosynthetic performance and the RUE in the HL-acclimated Phalaenopsis , resulting in an advantage to the OM plants to survive the HL stress. [ABSTRACT FROM AUTHOR]

The functional similarity between root and gut microbiota, both contributing to the nutrition and protection of the host, is often overlooked. A central mechanism for efficient protection against pathogens is defense priming, the preconditioning of immunity induced by microbial colonization after germination or birth. Microbiota have been recruited several times in evolution as developmental signals for immunity maturation. Because there is no evidence that microbial signals are more relevant than endogenous ones, we propose a neutral scenario for the evolution of this dependency: any hypothetic endogenous signal can be lost because microbial colonization, reliably occurring at germination or birth, can substitute for it, and without either positive selection or the acquisition of new functions. Dependency of development on symbiotic signals can thus evolve by contingent irreversibility. [ABSTRACT FROM AUTHOR]

Host-plants may rarely leave their ancestral niche and in which case they tend to be surrounded by phylogenetically distant neighbours. Phylogenetically isolated host-plants might share few mutualists with their neighbours and might suffer from a decrease in mutualist support. In addition host plants leaving their ancestral niche might face a deterioration of their abiotic and biotic environment and might hence need to invest more into mutualist partners. We tested whether phylogenetic isolation of hosts from neighbours decreases or increases abundance and activity of their mutualists and whether mutualist activity may help to compensate deterioration of the environment. We study oak-hosts and their ectomycorrhizal fungi mutualists established in the litter layer formed by the phylogenetically closely or distantly related neighbourhood. We find that oaks surrounded by phylogenetically distant neighbours show increased abundance and enzymatic activity of ectomycorrhizal fungi in the litter. Moreover, oaks surrounded by phylogenetically distant neighbours also show delayed budburst but ectomycorrhizal fungi activity partly compensates this negative effect of phylogenetic isolation. This suggests decreased nutrient availability in a phylogenetically distant litter partly compensated by increased litter-degradation by ectomycorrhizal fungi activity. Most observed effects of phylogenetic isolation cannot be explained by a change in baseline soil fertility (as reflected by nutritional status of fresh oak litter, or soil microbial biomass and activity) nor by simple reduction of percentages of oak neighbours, nor by the presence of gymnosperms. Our results show that colonizing new niche represented by the presence of distantly related neighbours may delay plant phenology but may be supported by mycorrhizal mutualists. Studies on other host-plant species are required to generalize our findings. [ABSTRACT FROM AUTHOR]

The restoration of degraded areas in mined land has not always achieved the desired success. Biological tools such as the use of arbuscular mycorrhizal fungi (AMF) are needed to increase and accelerate the restoration effectiveness of natural processes and ecosystem services in restored degraded areas. AMF can increase water and nutrient uptake by the host plants, therefore decreasing plant stress and improving habitat development in mined areas under restoration. We conducted a global meta-analysis from 193 independent outcomes to understand the overall effect of employing AMF as a restoration tool and to evaluate sources of variation on the effects of AMF inoculation on plant development in areas degraded by mining. Our results emphasize the great potential of the use of AMF to stimulate plant growth in the restoration of mined areas with stronger effects if associated with the utilization of organic matter and other soil microorganisms. Although AMF studies are concentrated in temperate regions, AMF inoculum promoted greater plant development on mined substrates regardless of the region and fungi type or origin. Inoculation also improved plant growth in materials of difficult restoration, such as overburden and tailings, but the AMF effects depended upon the exploited mineral type. Further investment in long-term field studies on the effects of AMF inoculation on plant survival, reproduction, fitness, and related ecological processes is essential to further consolidate the use of AMF on the restoration of mined areas. • Arbuscular mycorrhiza fungi is an efficient tool for restoration of mined areas. • Mycorrhiza fungi effects depended on the exploited mineral type. • Arbuscular mycorrhiza fungi improve plant growth on substrates from tailings. • Symbiotic microorganism addition enhances mycorrhizal effect on plant growth. [ABSTRACT FROM AUTHOR]

Abstract: Truffles have hypogeous fruit bodies that are dependent on mycophagous animals for spore dispersal. In our study we assessed the effect of passage through the gut of Sus scrofa on the morphology and viability of Tuber aestivum asci and ascospores. Light and Atomic Force Microscopy showed that passage through the gut freed spores from the asci, eroded the walls of free spores and modified their structure but spores were still viable. We believe this was the reason for the observed improvement in forming mycorrhizas with oak. These results confirm the role of wild boars in long distance dispersal of Tuber and support the theory that pigs play a significant role in truffle survival and territorial expansion during climatic changes. [Copyright &y& Elsevier]

Highlights: [•] At 30mgkg−1 Cd accumulation in the shoots was 1.7-fold higher in the wild genotype. [•] ECM inoculation influenced biometric traits of Pinus pinaster exposed to Cd. [•] Ectomycorrhizal fungi induced differential responses in each genotype regarding Cd uptake. [•] The combination of Pinus pinaster genotype-ECM species could be important in the restoration of lands contaminated with Cd. [Copyright &y& Elsevier]

Abstract: Both biotic and abiotic stresses are major constrains to agricultural production. Under stress conditions, plant growth is affected by a number of factors such as hormonal and nutritional imbalance, ion toxicity, physiological disorders, susceptibility to diseases, etc. Plant growth under stress conditions may be enhanced by the application of microbial inoculation including plant growth promoting rhizobacteria (PGPR) and mycorrhizal fungi. These microbes can promote plant growth by regulating nutritional and hormonal balance, producing plant growth regulators, solubilizing nutrients and inducing resistance against plant pathogens. In addition to their interactions with plants, these microbes also show synergistic as well as antagonistic interactions with other microbes in the soil environment. These interactions may be vital for sustainable agriculture because they mainly depend on biological processes rather than on agrochemicals to maintain plant growth and development as well as proper soil health under stress conditions. A number of research articles can be deciphered from the literature, which shows the role of rhizobacteria and mycorrhizae alone and/or in combination in enhancing plant growth under stress conditions. However, in contrast, a few review papers are available which discuss the synergistic interactions between rhizobacteria and mycorrhizae for enhancing plant growth under normal (non-stress) or stressful environments. Biological interactions between PGPR and mycorrhizal fungi are believed to cause a cumulative effect on all rhizosphere components, and these interactions are also affected by environmental factors such as soil type, nutrition, moisture and temperature. The present review comprehensively discusses recent developments on the effectiveness of PGPR and mycorrhizal fungi for enhancing plant growth under stressful environments. The key mechanisms involved in plant stress tolerance and the effectiveness of microbial inoculation for enhancing plant growth under stress conditions have been discussed at length in this review. Growth promotion by single and dual inoculation of PGPR and mycorrhizal fungi under stress conditions have also been discussed and reviewed comprehensively. [Copyright &y& Elsevier]

Highlights: [•] Spartina argentinensis may be useful in phytorremediation. [•] Diesel contamination resulted in negative effects on the growth of S. argentinensis. [•] Mycorrhizal roots of S. argentinensis were reduced by the presence of diesel fuel. [•] But diesel fuel did not affect the nutritional status of S. argentinensis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mycorrhizae species increased citrus dry matter weight. [•] Different growth media have significant effect on plant growth. [•] Mycorrhizal species have different effect on seedling growth. [•] Mycorrhizae inoculated plant increased plant P and Zn concentrations. [Copyright &y& Elsevier]

Abstract: Truffles are generally known to form a mycorrhizal relationship with plants. Kalaharituber pfeilii (Hennings) Trappe & Kagan-Zur is a species of desert truffle that is found in the southern part of Africa. The life cycle of this truffle has not been fully investigated as there are many unconfirmed plant species that have been suggested as potential hosts. Many mycorrhizal associations often involve other role players such as associated bacteria that may influence the establishment of the mycorrhizal formation and function. As part of an effort to understand the life cycle of K. pfeilii, laboratory experiments were conducted to investigate the role of ascocarp associated bacteria. Bacterial isolates obtained from the truffle ascocarps were subjected to microbiological and biochemical tests to determine their potentials as mycorrhizal helper bacteria. Tests conducted included stimulation of mycelial growth in vitro, indole acetic acid (IAA) production and phosphate solubilising. A total of 17 bacterial strains belonging to the Proteobacteria, Firmicutes and Actinobacteria were isolated from the truffle ascocarps and identified with sequence homology and phylogenetic methods. Three of these isolates showed potential to be helper bacteria in at least one of the media tested through the stimulation of mycelial growth. Furthermore, four isolates produced IAA and one was able to solubilise CaHPO3 in vitro. One isolate, identified as a relative of Paenibacillus sp. stimulated mycelial growth on all the media tested. Other bacterial isolates that showed potential stimulation of mycelial growth were identified molecularly as a Bacillus sp. and two strains of Rhizobium sp. This study has contributed to the existing knowledge on the biotic interactions with K. pfeilii which may be useful in further symbiont and re-synthesis investigations. [Copyright &y& Elsevier]

Abstract: The bacterial blight of pomegranate (Punica grantum L.) caused by Xanthomonas axonopodis pv punicae (Xap) is an important disease in India affecting severely the crop and bringing down domestic and export production drastically. The actinomycetes isolated from Glomus mosseae spores and characterized molecularly were tested on pomegranate seedling growth. All the actinomycetes strains improved shoot and root growth increasing biomass by 68–277% in 3 months period which may be attributed to production of varying levels of growth hormones. Streptomyces canus produced the highest amount of IAA (10.1 μg ml−1) and GA3 (12.0 μg ml−1). The strains were also tested for antibacterial activity against Xap by agar diffusion method. Streptomyces fradiae recorded the highest zone of inhibition (2.41 cm dia) followed by Streptomyces avermitilis (2.31 cm), Streptomyces cinnamonensis (2.22 cm), S. canus (2.0 cm) and Non-Streptomyces actinomycetes (NSA) Leifsonia poae (1.83 cm). Detached leaf assay revealed that S. fradiae, S. avermitilis, S. cinnamonensis and S. canus effectively reduced the infection caused by Xap in pomegranate leaves under in vitro conditions. In whole plant bioassay also the Xap infection was significantly reduced by actinomycetes treatment. The findings from this study clearly indicated the possibilities of using mycorrhizae associated actinomycetes as bioinoculant for growth promotion and for control of bacterial blight in pomegranate cultivation. [Copyright &y& Elsevier]

Highlights: [•] We detected two pathways through which glyphosate can affect grassland mycorrhiza. [•] Application on the soil, even at low doses, reduced directly spore viability. [•] Arbuscules were more affected indirectly, when glyphosate was applied to plant tissue. [•] Mycorrhizal root colonization was similarly reduced by both pathways. [•] Glyphosate application affects AMF functionality regardless of the pathway involved. [ABSTRACT FROM AUTHOR]

Abstract: Multiproxy evidence indicates that warmer-than-present summers became established in Eastern Beringia as early as 14,000–13,000 years ago, but the dispersal of spruces, pines, cedars and hemlocks across the Pacific Northwest (PNW) region of southern Alaska did not begin until at least 1500 years afterwards, and took many thousands of years to be completed. There are many potential reasons for this slow spread of PNW conifers towards their modern range limits. The absence of mycorrhizae in the soils of southern Alaska may have slowed conifer establishment. The availability of soil moisture was another limiting factor. With the exception of Pinus contorta, the other PNW conifers become established most readily from seeds that fall on moist, shaded substrates, thus they are not good pioneering species. Competition with alder and birch played an important role, especially along Prince William Sound and the Kenai Peninsula. Alder or alder and birch dominated these regions until the mid- to late Holocene. The other key element for most PNW conifer species is the precipitation regime. The hemlocks, cedars and Sitka spruce are not drought-hardy. So although the PNW temperature regime may have been warm enough in early postglacial times to support the growth of PNW conifers, it was probably too dry for them to successfully become established in new regions. The conflation of these environmental factors limits our present understanding of the problem, but the recent trend of multi-proxy analysis in Quaternary paleoecology will certainly sharpen our reconstructions. Such proxies as conifer needle stomata and insect fossil remains hold significant promise. [Copyright &y& Elsevier]

Highlights: [•] We propose a novel four-phase model of mycorrhiza-induced resistance (MIR). [•] Phase I: root exudation of mycorrhiza-recruiting chemicals. [•] Phase II: the plant immune system responding to infection by abuscular mycorrhizal fungi (AMF). [•] Phase III: immune suppression by AMF and recruitment of mycorrhizosphere bacteria. [•] Phase IV: establishment of the mycorrhizosphere and induction of systemic resistance by mycorrhizosphere bacteria. [Copyright &y& Elsevier]

• Application of silicon and mycorrhizal inoculum mitigate drought stress in licorice. • Amino acid profile of Glycyrrhiza glabra root were changed by applied treatments. • Irrigation at 100% of field capacity with applying silicon, showed maximum proline. • Histidine and lysine were highest by 80% irrigation, silicon and fungi inoculation. • Silicon at 300 ppm and mycorrhizal inoculation enhance tolerance to drought stress. Abiotic stresses usually trigger plant responses that entail several changes in the metabolism of amino acids. The Glycyrrhiza glabra rhizomes activate integrative biochemical networks in response to water deficit conditions, mycorrhiza inoculation, and silicon application. In the present study, irrigation was performed to make the soil reach 5 different levels of 20, 40, 60, 80, and 100% of field capacity (control). Silicon application was used at 300 ppm concentration solute in irrigation water for half of treatments. The Claroiedoglomus etunicatum is used as mycorrhizal inoculum. After 2 months, the amino acid profile of treated plants (from acidic root extracts) was analyzed by Liquid Chromatography–tandem mass spectrometry (LC-MS/MS). Results were indicated that amino acids changed as a result of water deficiency, silicon nutrition, and mycorrhiza inoculation. As proline accumulation can be one of the indicator responses to drought stress, in this study, 100% irrigation with applying silicon, without mycorrhiza inoculation showed increased levels in proline (83.09 mg.g−1 dry biomass), while minimum proline (18.27 mg.g−1 dry biomass) was observed by 40% irrigation with mycorrhiza inoculation, without applying silicon. Maximum values of histidine (23.19 mg.g−1 dry biomass) and lysine (36.29 mg.g−1 dry biomass) were observed by application of 80% field capacity water irrigation with silicon solution and fungi inoculation. Minimum histidine and valine were in the treatment of 100% field capacity irrigation without silicon and inoculation (3.15 and 6.64 mg.g−1 dry biomass, respectively). As minimum amino acids were almost observed in treatments that were not achieved silicon and mycorrhiza, so results of this study showed that silicon at 300 ppm and licorice root inoculation by C. etunicatum effectively can change amino acid profile and protein quality under drought stress. Comprehensive results were achieved with a detailed understanding of how drought stress can trigger plant responses via relevant mechanisms, therefore enabling the use of mineral nutrition, such as silicon, and biofertilizers, including mycorrhiza, in crop enhancements. [ABSTRACT FROM AUTHOR]

• Arbuscular mycorrhizal fungi (AMF) increased litter decomposition by stimulating saprotrophs in nutrient poor soils. • AMF inoculation amplified hotspot areas of enzyme activities in the rhizosphere by 13%-400%. • The importance of AMF to plant growth was greater in nutrient poor soils than in nutrient rich soils. Plants acquire and recycle nutrients from soil organic matter, and these dynamics depend on a highly diverse array of microorganisms in the rhizosphere. Although functions of many microbial groups have been identified, how different groups interact to affect biogeochemical processes is still poorly understood. We investigated the interactive effects of saprotrophs and arbuscular mycorrhizal fungi (AMF) on Medicago sativa litter decomposition and spatial distribution of enzyme activity in the rhizosphere in nutrient poor and rich soils, using compartmented microcosms designed for zymography. In nutrient poor soils, co-inoculation of saprotrophic bacteria (Alcaligenes faecalis) or fungi (Phanerochaete chrysosporium) with AMF (Rhizophagus irregularis) resulted in faster litter decomposition and greater hotspot areas of enzymes in the rhizosphere compared to mono-inoculations. These positive effects were stronger in the interaction of AMF with saprotrophic bacteria than that with saprotrophic fungi. The synergy of saprotrophic bacteria with AMF for litter decomposition and enzymatic hotspot formation was weaker in nutrient rich soils than that in nutrient poor soils. In contrast, in nutrient rich soils, co-inoculation of saprotrophic fungi with AMF reduced litter decomposition. A partial least squares path modeling (PLS-PM) analysis indicated that faster litter decomposition and larger enzymatic hotspots increased overall plant growth. These findings suggest the existence of important synergistic relationships between these two microbial guilds for plant growth in nutrient poor soils. Specifically, AMF accelerated litter mineralization by increasing saprotrophic biomass and enzyme activities (i.e., nitrate reductase, urease and cellulase). At the same time, saprotrophs increased AMF colonization rate, which increased the hotspot areas of enzyme activities. These hotspots, in turn, broadened the nutrient mobilization zone around the roots - in the rhizosphere. Consequently, the synergistic interactions between saprotrophs and AMF for litter decomposition and the formation of enzymatic hotspots may be an important mechanism for promoting plant fitness under low soil nutrient availability. [ABSTRACT FROM AUTHOR]

Denitrification by microorganisms in soil regulates ecosystem nitrogen availability and cycling. Although arbuscular mycorrhiza fungi (AMF) are best known as the key connectors between plant and microorganisms in below-ground soil, however, less knowledge is available about the interactive effects of AMF and vegetation community traits on soil denitrifiers. In this study, we manipulated experimental pots with or without AMF inoculation (AMF+ and AMF− treatments) under three plant richness levels and 27 different plant community compositions. Our results provided evidence that inoculation of AMF significantly increased the abundances of nirS -, nirK - and nosZ -type denitrifiers as revealed by quantitative PCR (qPCR), which inferred a positive role of AMF in N-cycling microorganisms. Plant community traits, including richness, community composition, biomass and species, were less important in influencing the abundances of soil denitrifiers, and no significant interactive effect was detected between AMF inoculation and plant richness or plant community compositions, indicating a weak direct relationship between plants and soil denitrifiers. Our study provided comprehensive insights into the roles of AMF-plant associate bio-system in driving the variation of soil denitrifiers. • AMF inoculation increased abundances of nirK , nirS and nosZ genes. • Plant traits were less important in influencing the abundances of soil denitrifiers. • The effect of AMF on denitrifiers' abundances was related with plant compositions. [ABSTRACT FROM AUTHOR]

Tools for accurate measurements of microbial biomass/abundance are imperative in soil ecology. This perspective was prompted by a lack of consistency in how the neutral lipid fatty acid (NLFA) and phospholipid fatty acid (PLFA) 16:1ω5 are used to estimate arbuscular mycorrhizal (AM) fungal abundance, which we argue can lead to erroneous conclusions within studies and complicate among-study comparisons. We show that more than half of all studies published to date use PLFA 16:1ω5 to quantify AM fungal biomass without proper controls. This is problematic because AM fungi cannot be separated from the bacterial contribution to this fatty acid signature. We provide a set of recommendations for future research and specifically urge researchers to extract and analyze NLFA 16:1ω5 for more accurate and sensitive assessments of AM fungal biomass as this can be done without doubling effort. • Large number of studies have used PLFA 16:1ω5 as AM fungal indicator. • The use of PLFA 16:1ω5 without proper non-mycorrhizal controls is problematic as it can also reflect bacterial biomass. • We urge researchers to use NLFA 16:1ω5 to estimate AM fungal biomass as this can be done without doubling effort. [ABSTRACT FROM AUTHOR]

Highlights: [•] Chromium contents were determined in 167 samples of edible mushrooms belonging to 22 species. [•] The highest levels were found in L. utriforme, C. comatus and A. campestris and the lowest in T. portentosum. [•] The highest concentrations of chromium were observed in terrestrial saprophytic species in relation to mycorrhizal species. [•] All mushroom species were bioexclusors of chromium (BCF<1) in relation to the chromium concentration in the underlying soils. [Copyright &y& Elsevier]

Highlights: [•] Ectomycorrhiza fungus Melanogaster variegatus increases root length of Alnus incana. [•] Mycorrhized Alnus incana (White Alder) increases soil aggregate stability (SAS). [•] Effects of mycorrhized roots on SAS correspond to an increase in dry unit weight. [•] SAS is correlated with dry unit weight as is known for the friction angle Φ’. [•] SAS may be used to add biological effects to Φ’ in slope stability calculation. [Copyright &y& Elsevier]