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Arbuscular Mycorrhizal (arbuscular + mycorrhizal)
Terms modified by Arbuscular Mycorrhizal Selected AbstractsInteractions between arbuscular mycorrhizal fungi and bacteria and their potential for stimulating plant growthENVIRONMENTAL MICROBIOLOGY, Issue 1 2006Veronica Artursson Summary Arbuscular mycorrhizal (AM) fungi and bacteria can interact synergistically to stimulate plant growth through a range of mechanisms that include improved nutrient acquisition and inhibition of fungal plant pathogens. These interactions may be of crucial importance within sustainable, low-input agricultural cropping systems that rely on biological processes rather than agrochemicals to maintain soil fertility and plant health. Although there are many studies concerning interactions between AM fungi and bacteria, the underlying mechanisms behind these associations are in general not very well understood, and their functional properties still require further experimental confirmation. Future mycorrhizal research should therefore strive towards an improved understanding of the functional mechanisms behind such microbial interactions, so that optimized combinations of microorganisms can be applied as effective inoculants within sustainable crop production systems. In this context, the present article seeks to review and discuss the current knowledge concerning interactions between AM fungi and plant growth-promoting rhizobacteria, the physical interactions between AM fungi and bacteria, enhancement of phosphorus and nitrogen bioavailability through such interactions, and finally the associations between AM fungi and their bacterial endosymbionts. Overall, this review summarizes what is known to date within the present field, and attempts to identify promising lines of future research. [source] Genetic processes in arbuscular mycorrhizal fungiFEMS MICROBIOLOGY LETTERS, Issue 2 2005Teresa E. Pawlowska Abstract Arbuscular mycorrhizal (AM) fungi (Glomeromycota) colonize roots of the majority of land plants and facilitate their mineral nutrient uptake. Consequently, AM fungi play an important role in terrestrial ecosystems and are becoming a component of sustainable land management practices. The absence of sexual reproductive structures in modern Glomeromycota combined with their long evolutionary history suggest that these fungi may represent an ancient asexual lineage of great potential interest to evolutionary biology. However, many aspects of basic AM fungal biology, including genome structure, within-individual genetic variation, and reproductive mode are poorly understood. These knowledge gaps hinder research on the mechanisms of AM fungal interactions with individual plants and plant communities, and utilization of AM fungi in agricultural practices. I present here the current state of research on the reproduction in AM fungi and indicate what new findings can be expected in the future. [source] Co-existing grass species have distinctive arbuscular mycorrhizal communitiesMOLECULAR ECOLOGY, Issue 11 2003P. Vandenkoornhuyse Abstract Arbuscular mycorrhizal (AM) fungi are biotrophic symbionts colonizing the majority of land plants, and are of major importance in plant nutrient supply. Their diversity is suggested to be an important determinant of plant community structure, but the influence of host-plant and environmental factors on AM fungal community in plant roots is poorly documented. Using the terminal restriction fragment length polymorphism (T-RFLP) strategy, the diversity of AM fungi was assessed in 89 roots of three grass species (Agrostis capillaris, Festuca rubra, Poa pratensis) that co-occurred in the same plots of a field experiment. The impact of different soil amendments (nitrogen, lime, nitrogen and lime) and insecticide application on AM fungal community was also studied. The level of diversity found in AM fungal communities using the T-RFLP strategy was consistent with previous studies based on clone libraries. Our results clearly confirm that an AM fungal host-plant preference exists, even between different grass species. AM communities colonizing A. capillaris were statistically different from the others (P < 0.05). Although grass species evenness changed in amended soils, AM fungal community composition in roots of a given grass species remained stable. Conversely, in plots where insecticide was applied, we found higher AM fungal diversity and, in F. rubra roots, a statistically different AM fungal community. [source] Microarray analysis and functional tests suggest the involvement of expansins in the early stages of symbiosis of the arbuscular mycorrhizal fungus Glomus intraradices on tomato (Solanum lycopersicum)MOLECULAR PLANT PATHOLOGY, Issue 1 2010VLADIMIR DERMATSEV SUMMARY Arbuscular mycorrhizal (AM) symbiosis occurs between fungi of the phylum Glomeromycota and most terrestrial plants. However, little is known about the molecular symbiotic signalling between AM fungi (AMFs) and non-leguminous plant species. We sought to further elucidate the molecular events occurring in tomato, a non-leguminous host plant, during the early, pre-symbiotic stage of AM symbiosis, i.e. immediately before and after contact between the AMF (Glomus intraradices) and the host. We adopted a semi-synchronized AMF root infection protocol, followed by genomic-scale, microarray-based, gene expression profiling at several defined time points during pre-symbiotic AM stages. The microarray results suggested differences in the number of differentially expressed genes and in the differential regulation of several functional groups of genes at the different time points examined. The microarray results were validated and one of the genes induced during contact between AMF and tomato, the expansin-like EXLB1, was functionally analysed. Expansins, encoded by a large multigene family, facilitate plant cell expansion. However, no biological or biochemical function has yet been established for plant-originated expansin-like proteins. EXLB1 transcripts were localized early during the association to cells that may perceive the fungal signal, and later during the association in close proximity to sites of AMF hypha,root colonization. Moreover, in transgenic roots, we demonstrated that a reduction in the steady-state level of EXLB1 transcript was correlated with a reduced rate of infection, reduced arbuscule expansion and reduced AMF spore formation. [source] Functional complementarity in the arbuscular mycorrhizal symbiosisNEW PHYTOLOGIST, Issue 2 2000ROGER T. KOIDE The causes and consequences of biodiversity are central themes in ecology. Perhaps one reason for much of the current interest in biodiversity is the belief that the loss of species (by extinction) or their gain (by invasion) will significantly influence ecosystem function. Arbuscular mycorrhizal (AM) fungi are components of most terrestrial ecosystems and, while many research programs have shown that variability among species or isolates of AM fungi does occur (Giovannetti & Gianinazzi-Pearson, 1994), the basis for this variability and its consequences to the function of communities and ecosystems remains largely unexplored. Smith et al. (pp. 357,366 in this issue) now show clearly that ecologically significant functional diversity exists among AM fungal species in the regions of the soil from which they absorb phosphate, and their results suggest that such diversity may have significant ecological consequences. [source] Rice root colonisation by mycorrhizal and endophytic fungi in aerobic soilANNALS OF APPLIED BIOLOGY, Issue 2 2009M. Vallino Abstract Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts that form intimate associations with the majority of plants growing in aerobic soil; fungal endophytes live internally, either intercellularly or intracellularly, and asymptomatically within plant tissues. Their presence is correlated with an increased response to biotic and abiotic stress. The populations of AM and of endophytic fungi were studied in the roots of different rice varieties grown in aerobic condition, in experimental fields in Vercelli, North Italy. All the rice varieties resulted colonised by AM fungi with a percentage of arbuscularisation ranging between 4% and 28%. Preliminary molecular analyses on some rice varieties showed that the AM population was composed of fungi identified as Glomus intraradices, on the basis of 18S ribosomal gene. All the varieties analysed but one resulted in colonisation by endophytic fungi. About 300 fungal isolates were obtained, belonging mainly to the genera Neotyphodium, Stagonospora and Penicillium. [source] Combined bromodeoxyuridine immunocapture and terminal-restriction fragment length polymorphism analysis highlights differences in the active soil bacterial metagenome due to Glomus mosseae inoculation or plant speciesENVIRONMENTAL MICROBIOLOGY, Issue 12 2005Veronica Artursson Summary High numbers of bacteria are associated with arbuscular mycorrhizal (AM) fungi, but their functions and in situ activities are largely unknown and most have never been characterized. The aim of the present study was to study the impact of Glomus mosseae inoculation and plant type on the active bacterial communities in soil by using a molecular approach, bromodeoxyuridine (BrdU) immunocapture in combination with terminal-restriction fragment length polymorphism (T-RFLP). This approach combined with sequence information from clone libraries, enabled the identification of actively growing populations, within the total bacterial community. Distinct differences in active bacterial community compositions were found according to G. mosseae inoculation, treatment with an antifungal compound (Benomyl) and plant type. The putative identities of the dominant bacterial species that were activated as a result of G. mosseae inoculation were found to be mostly uncultured bacteria and Paenibacillus species. These populations may represent novel bacterial groups that are able to influence the AM relationship and its subsequent effect on plant growth. [source] Mycoparasitism of arbuscular mycorrhizal fungi: a pathway for the entry of saprotrophic fungi into rootsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2010Nathalie De Jaeger Abstract Within the rhizosphere, arbuscular mycorrhizal (AM) fungi interact with a cohort of microorganisms, among which is the biological control agent, Trichoderma spp. This fungus parasitizes a wide range of phytopathogenic fungi, a phenomenon also reported in the extraradical mycelium (ERM) of AM fungi. Here, we question whether the mycoparasitism of the ERM could be extended to the intraradical mycelium (IRM), thus representing a pathway for the entry of Trichoderma harzianum within the root. Microcosm experiments allowing interactions between Glomus sp. MUCL 41833 placed in a clade that contains the recently described species Glomus irregulare and T. harzianum were set up under in vitro autotrophic culture conditions using potato as a host. A microscope camera-imaging system, coupled with succinate dehydrogenase staining, was used to assess the mycoparasitism in the ERM and IRM. Trichoderma harzianum colonized the ERM of the AM fungus and spread into the IRM, before exiting into the root cells. Intrahyphal growth of T. harzianum caused protoplasm degradation, decreasing the ERM and IRM viability. ERM of the AM fungus represented a pathway for the entry of T. harzianum into the roots of potato. It further sets off the debate on the susceptibility of the AM fungi of being infected by microorganisms from the rhizosphere. [source] Influence of arbuscular mycorrhizal mycelial exudates on soil bacterial growth and community structureFEMS MICROBIOLOGY ECOLOGY, Issue 2 2007Jonas F. Toljander Abstract Plant root systems colonized by arbuscular mycorrhizal (AM) fungi have previously been shown to influence soil bacterial populations; however, the direct influence of the AM extraradical mycelium itself on bacterial growth and community composition is not well understood. In this study, we investigated the effects of exudates produced by AM extraradical mycelia on the growth and development of an extracted soil bacterial community in vitro. The chemical composition of the mycelial exudates was analysed using proton nuclear magnetic resonance spectrometry. Following the addition of exudates to a bacterial community extracted from soil, bacterial growth and vitality were determined using a bacterial vitality stain and fluorescence microscopy. Changes in community composition were also analysed at various times over the course of 3 days by terminal restriction fragment length polymorphism analysis, in combination with cloning and sequencing of 16S rRNA genes. Mycelial exudates increased bacterial growth and vitality and changed bacterial community composition. Several Gammaproteobacteria, including a taxon within the Enterobacteriaceae, increased in frequency of occurrence in response to AM mycelial exudates. This study is the first attempt to identify carbohydrates from the extraradical mycelium of an AM fungus, and demonstrates the direct effects of mycelial exudates on a soil bacterial community. [source] Soil animals influence microbial abundance, but not plant,microbial competition for soil organic nitrogenFUNCTIONAL ECOLOGY, Issue 5 2004L. COLE Summary 1In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2- 13C- 15N) between a grassland plant, Agrostis capillaris, and the soil microbial biomass, to determine how soil fauna and their diversity influence plant,microbial competition for organic N. 2We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the microbial biomass, due to the effect of animal grazing on the microbial biomass, and hence its ability to sequester N. 3Certain individual species of Collembola influenced the microbial community of the soil. Folsomia quadrioculata reduced microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on microbial 15N. 5Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6Our data suggest that, while single species and variations in diversity of microarthropods influence microbial abundance in soil, there is no effect on microbial or plant uptake of N. Overall, these data provide little support for the notion that microbial-feeding soil animals are regulators of microbial,plant competition for N. [source] Manipulation of flooding and arbuscular mycorrhiza formation influences growth and nutrition of two semiaquatic grass speciesFUNCTIONAL ECOLOGY, Issue 6 2000S. P. Miller Abstract 1Two semiaquatic grasses, Panicum hemitomon Schultes and Leersia hexandra Schwartz, were grown for 12 weeks in sterilized soil in experimental mesocosms, with and without the addition of arbuscular mycorrhizal (AM) fungal inoculum (as nonsterilized soil), under the following rooting-zone flood regimes: waterlogged (W), free-draining (D), beginning W and ending D (W,D), and beginning D and ending W (D,W). The purpose of the experiment was to determine whether these controlled water regimes affected both colonization of wetland grasses by AM fungi and the effects of the colonization on various plant parameters. 2Water regime, addition of inoculum, and their interaction were highly significant effects on total and proportion of root length colonized by AM fungi. Trends were very similar for the two grass species. Colonization was less and plants smaller in the W and W,D than in the D and D,W treatments. The viability of mycorrhiza at the end of the experiment, as measured by vital staining techniques, was not affected by changes in water level. 3Colonized plants in all water level treatments showed an improvement in phosphorus (P) nutrition over noncolonized plants. Colonized grasses of both species gained consistently more P per plant and had greater tissue P concentrations, with the greatest P concentration in the most heavily colonized plants (from the D and D,W treatments). 4The effect of flooding on the mycorrhizal association depended largely on the extent to which the association was already established when the flooding occurred. Flooding reduced the initiation of colonization either directly or indirectly, but once the fungi were established in the roots they were able to maintain and expand with the growing root system. [source] Patterns of rhizosphere carbon flux in sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) saplingsGLOBAL CHANGE BIOLOGY, Issue 6 2005Richard P. Phillips Abstract Despite its importance in the terrestrial C cycle rhizosphere carbon flux (RCF) has rarely been measured for intact root,soil systems. We measured RCF for 8-year-old saplings of sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) collected from the Hubbard Brook Experimental Forest (HBEF), NH and transplanted into pots with native soil horizons intact. Five saplings of each species were pulse labeled with 13CO2 at ambient CO2 concentrations for 4,6 h, and the 13C label was chased through rhizosphere and bulk soil pools in organic and mineral horizons for 7 days. We hypothesized yellow birch roots would supply more labile C to the rhizosphere than sugar maple roots based on the presumed greater C requirements of ectomycorrhizal roots. We observed appearance of the label in rhizosphere soil of both species within the first 24 h, and a striking difference between species in the timing of 13C release to soil. In sugar maple, peak concentration of the label appeared 1 day after labeling and declined over time whereas in birch the label increased in concentration over the 7-day chase period. The sum of root and rhizomicrobial respiration in the pots was 19% and 26% of total soil respiration in sugar maple and yellow birch, respectively. Our estimate of the total amount of RCF released by roots was 6.9,7.1% of assimilated C in sugar maple and 11.2,13.0% of assimilated C in yellow birch. These fluxes extrapolate to 55,57 and 90,104 g C m,2 yr,1 from sugar maple and yellow birch roots, respectively. These results suggest RCF from both arbuscular mycorrhizal and ectomycorrhizal roots represents a substantial flux of C to soil in northern hardwood forests with important implications for soil microbial activity, nutrient availability and C storage. [source] Improvement of Cupressus atlantica Gaussen growth by inoculation with native arbuscular mycorrhizal fungiJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007L. Ouahmane Abstract Aims: The study aimed to determine whether inoculation with native arbuscular mycorrhizal (AM) fungi could improve survival and growth of seedlings in degraded soils of Morocco. Methods and Results: Soil samples were collected from the rhizosphere of Cupressus atlantica trees in the N'Fis valley (Haut Atlas, Morocco). AM spores were extracted from the soil, identified and this mixture of native AM fungi was propagated on maize for 12 weeks on a sterilized soil to enrich the fungal inoculum. Then C. atlantica seedlings were inoculated with and without (control) mycorrhizal maize roots, cultured in glasshouse conditions and further, transplanted into the field. The experiment was a randomized block design with one factor and three replication blocks. The results showed that a high AM fungal diversity was associated with C. atlantica; native AM fungi inoculation was very effective on the growth of C. atlantica seedlings in glasshouse conditions and this plant growth stimulation was maintained for 1 year after outplanting. Conclusions: Inoculation of C. atlantica with AM fungi increased growth and survival in greenhouse and field. Significance and Impact of the Study: The data indicate that use of native species of AM fungi may accelerate reforestation of degraded soils. Further studies have to be performed to determine the persistence of these mycorrhizae for a longer period of plantation and to measure the effects of this microbial inoculation on soil biofunctioning. [source] Localized and Systemic Increase of Phenols in Tomato Roots Induced by Glomus versiforme Inhibits Ralstonia solanacearumJOURNAL OF PHYTOPATHOLOGY, Issue 10 2004H. H. Zhu Abstract Ralstonia solanacearum is an important plant pathogen in tropical and subtropical countries. Here, we describe the inhibition of R. solanacearum as a result of increased phenols induced locally or systemically by an arbuscular mycorrhizal (AM) fungus. In pot cultures, R. solanacearum populations in the rhizosphere, on root surfaces and in the xylem were decreased by 26.7, 79.3 and 81.7%, respectively, following inoculation of tomato plants (Lycopersicon esculentum Mill.) with Glomus versiforme Berch. Colonization of the plants by both R. solanacearum and G. versiforme increased the contents of soluble phenols and cell-wall bound phenols in root tissue, but with different patterns. Whereas R. solanacearum preferably promoted the cell-wall bound phenol content, G. versiforme preferably enhanced the soluble phenol content. Split root experiments revealed that R. Solanacearum was inhibited by G. versiforme, and that G. versiforme also increased the phenol content systemically, but to a lesser extent than locally. [source] Technique for visual demonstration of germinating arbuscular mycorrhizal spores and their multiplication in potsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2007Jitendra Panwar Abstract We describe a simple technique for the germination of arbuscular mycorrhizal (AM),fungal spores and their multiplication in pots. Glomus fasciculatum, G. mosseae, and Gigaspora margarita were used. A single wheat seedling was tied to a glass slide, previously covered with filter paper with the help of thread. One single surface-sterilized AM-fungal spore was placed on the middle portion of the root of the wheat seedling using a sterilized syringe. The slide was placed vertically in a 100,mL glass beaker filled with 25,mL of root exudates,water (1:4, v/v) solution, which was collected by growing twenty wheat seedlings in a 150,mL beaker filled with 100,mL sterilized distilled water for 7 d. The slide was observed daily using a compound microscope to follow the time course of germination. In this technique, the spore is directly in contact with the host root, and a visualization of spore germination, hyphal development, and appressorium formation is possible without disrupting fungal growth or the establishment of the symbiosis. The method allows to document the germination events and to assess hyphal-elongation rates by photographing the same spore on consecutive days. The inoculated seedling was used to initiate single-spore multiplication in a sterilized (autoclave on 3 alternate days at 120°C for 120,min at 1.05,kg,cm,2 pressure) potted sandy soil (150,mL volume) into which the slide with the inoculated seedling was inserted carefully through a previously made slit. The wheat seedlings in all pots (4 treatments and 15 replications) became colonized by mycorrhiza, confirming that the establishment of the AM-fungal symbiosis is highly reproducible. Our technique permits the relatively undisturbed growth of the symbiotic partners, the visualization of germinating AM-fungal spores, and their multiplication in pots. This simple and low-cost method facilitates the production of pure lines of AM fungi from single spores, allowing for the study of intraspecific variation and potentiality for cytological, biochemical, physiological, and taxonomical studies. [source] Establishment of Retama sphaerocarpa L. seedlings on a degraded semiarid soil as influenced by mycorrhizal inoculation and sewage-sludge amendmentJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2004María del Mar Alguacil Abstract A field experiment was carried out to evaluate the effectiveness of mycorrhizal inoculation with three arbuscular mycorrhizal (AM) fungi (Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge), and Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe) and the addition of composted sewage sludge (SS) with respect to the establishment of Retama sphaerocarpa L. seedlings, in a semiarid Mediterranean area. Associated changes in soil chemical (nutrient content and labile carbon fractions), biochemical (enzyme activities), and physical (aggregate stability) parameters were observed. Six months after planting, both the addition of composted SS and the mycorrhizal-inoculation treatments had increased total N content, available-P content, and aggregate stability of the soil. Values of water-soluble C and water-soluble carbohydrates were increased only in the mycorrhizal-inoculation treatments. Rhizosphere soil from the mycorrhizal-inoculation treatments had significantly higher enzyme activities (dehydrogenase, protease-BAA, acid phosphatase, and ,-glucosidase) than the control soil. In the short-term, mycorrhizal inoculation with AM fungi was the most effective treatment for enhancement of shoot biomass, particularly with G. mosseae (about 146% higher with respect to control plants). The addition of the composted SS alone was sufficient to restore soil structural stability but was not effective with respect to improving the performance of R. sphaerocarpa plants. Besiedlung eines degradierten semiariden Bodens mit Retama sphaerocarpa L.-Setzlingen, beeinflusst durch Mykorrhiza-Inokulation und Klärschlammzugabe Ein Feldversuch wurde durchgeführt, um den Effekt einer Inokulation mit drei arbuskulären Mykorrhizapilzen (AM) (Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge) und Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe) einerseits und der Zugabe von kompostiertem Klärschlamm (SS) andererseits auf die Besiedlung von Retama sphaerocarpa L.-Setzlingen in einem mediterranen semiariden Gebiet zu untersuchen. Es wurden chemischer Nährstoffgehalt, labile C-Fraktion, biochemische Enzymaktivitäten und physikalische Bodenparameter (Aggregatstabilität) untersucht. Sechs Monate nach der Pflanzung erbrachten beide Behandlungen , die Zugabe von kompostiertem Klärschlamm und die Mykorrhiza-Inokulation , Steigerungen des Gesamtstickstoff-Gehaltes, des verfügbaren Phosphor-Gehaltes sowie der Aggregatstabilität des Bodens. Wasserlöslicher Kohlenstoff und wasserlösliche Kohlenhydrate waren nur nach Mykorrhiza-Inokulation erhöht. Boden aus der Rhizosphäre, der mit Mykorrhizapilzen inokuliert wurde, zeigte signifikant höhere Enzymaktivitäten (Dehydrogenase, Protease-BAA, saure Phosphatase und ,-Glucosidase) als der Kontrollboden. In der kurzen Periode war die Inokulation mit AM-Pilzen die effektivste Behandlung bei der Bildung von Sprossbiomasse, speziell bei G. mosseae (eine um über 146,% höhere Biomasse im Vergleich zu den Kontrollpflanzen). Die Zugabe von kompostiertem Klärschlamm allein war ausreichend, die Stabilität der Bodenstruktur wiederherzustellen, aber sie war nicht effektiv hinsichtlich der Entwicklung der R. sphaerocarpa -Pflanzen. [source] Comparative effect of biofertilizers on fodder production and quality in guinea grass (Panicum maximum Jacq.)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2008Seema Mishra Abstract BACKGROUND:Panicum maximum Jacq. is one of the most important fodder grasses of the tropics. For good production and growth it requires high amounts of N fertilizer. Chemical fertilizers have a deleterious effect on soil fertility and are not economical for resource-poor farmers. Utilization of plant growth-promoting bacteria and fungi proved to be beneficial for improving crop production as well as the soil fertility. In the present paper the effect of inoculation of N fixer (Azospirillum brasilense) and P solubilizers (arbuscular mycorrhizal (AM) fungi consortia and inoculum of Glomus intraradiaces) was studied in single as well as mixed inoculation on forage yield and quality in guinea grass (Panicum maximum Jacq.) at different cuttings under the cut-and-carry system. RESULTS: Overall five cuttings were obtained during the year. Dual inoculation, i.e., Azospirillum with indigenous AM consortia, significantly improved fodder growth, production and quality in terms of crude protein (CP) content, while neutral detergent fiber (NDF) and acid detergent fiber (ADF) content decreased after this treatment. The density of soil microbes (number of Azospirillum colony-forming units, number of AM spores) was enhanced in mixed inoculation. Chemical fertilizer improved fodder production and CP content significantly over control but also enhanced NDF and ADF content and suppressed the Azospirillum colony-forming units, AM spores and AM root infection. CONCLUSION: It could be concluded from the present study that inoculated N fixer and P solubilizer have a synergistic effect which enhanced overall fodder production, quality and also beneficial microflora in the rhizosphere soil, which also demonstrated the sustainability of biofertilizers. Copyright © 2008 Society of Chemical Industry [source] Mycorrhization of coriander (Coriandrum sativum L) to enhance the concentration and quality of essential oilJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2002Rupam Kapoor Abstract The effect of association of two vesicular arbuscular mycorrhizal (VAM) fungi, Glomus macrocarpum and G fasciculatum, on the concentration and composition of essential oil in coriander (Coriandrum sativum) was studied. VAM inoculation increased the essential oil concentration in fruits by as much as 43%. Although significant variation in effectiveness of the two fungal species was observed, the quality of essential oil was significantly enhanced on mycorrhization. GC characterisation of essential oil showed increased concentration of geraniol and linalool in plants inoculated with G macrocarpum and G fasciculatum respectively. © 2002 Society of Chemical Industry [source] Integration of arbuscular mycorrhiza inoculation in hydroseeding technology: effects on plant growth and inter-species competitionLAND DEGRADATION AND DEVELOPMENT, Issue 6 2007V. Estaún Abstract Hydroseeding is a technique increasingly used to establish vegetation on large degraded areas, such as large-scale road construction sites and quarries. Native grasses and legume species are used on rehabilitation and restoration projects as a first step in the recovery of such places, prior to the establishment of native forbs and shrubs that occurs at a slower pace. The effect of mycorrhizal inoculation on the development of nine species of grasses and legumes that can be potentially used in restoration processes in the Mediterranean area was studied, in microcosm experiments under greenhouse conditions. The effect of adding arbuscular mycorrhizal (AM) inoculum to a hydroseeding mixture was also investigated in greenhouse and in field conditions. In the hydroseeding experiments the mycorrhizal inoculum was added to the seed slurry in a jet agitated hydroseeding machine and sprayed to the soil surface with a pressurised spray in a one-step application. The study shows that Glomus intraradices Schenk & Smith BEG72 is able to establish the symbiosis when applied at sowing while Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe BEG116 is not. It also confirms that legumes are more highly mycotrophic than grasses. The results of the hydroseeding experiments demonstrate the establishment of the symbiosis using this technology, both in the greenhouse and in the field. Mycorrhizal inoculation improved above ground plant growth and increased the legumes/grasses ratio. Copyright © 2007 John Wiley & Sons, Ltd. [source] Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forestMOLECULAR ECOLOGY, Issue 12 2002R. Husband Abstract We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests. [source] Arbuscular mycorrhizal fungi can transfer substantial amounts of nitrogen to their host plant from organic materialNEW PHYTOLOGIST, Issue 1 2009Joanne Leigh Summary ,,Nitrogen (N) capture by arbuscular mycorrhizal (AM) fungi from organic material is a recently discovered phenomenon. This study investigated the ability of two Glomus species to transfer N from organic material to host plants and examined whether the ability to capture N is related to fungal hyphal growth. ,,Experimental microcosms had two compartments; these contained either a single plant of Plantago lanceolata inoculated with Glomus hoi or Glomus intraradices, or a patch of dried shoot material labelled with 15N and 13carbon (C). In one treatment, hyphae, but not roots, were allowed access to the patch; in the other treatment, access by both hyphae and roots was prevented. ,,When allowed, fungi proliferated in the patch and captured N but not C, although G. intraradices transferred more N than G. hoi to the plant. Plants colonized with G. intraradices had a higher concentration of N than controls. ,,Up to one-third of the patch N was captured by the AM fungi and transferred to the plant, while c. 20% of plant N may have been patch derived. These findings indicate that uptake from organic N could be important in AM symbiosis for both plant and fungal partners and that some AM fungi may acquire inorganic N from organic sources. [source] Arbuscular mycorrhizal fungi respond to the substrate pH of their extraradical mycelium by altered growth and root colonizationNEW PHYTOLOGIST, Issue 1 2002Ingrid M. Van Aarle Summary ,,To test the response of arbuscular mycorrhizal (AM) fungi to a difference in soil pH, the extraradical mycelium of Scutellospora calospora or Glomus intraradices, in association with Plantago lanceolata, was exposed to two different pH treatments, while the root substrate pH was left unchanged. ,,Seedlings of P. lanceolata, colonized by one or other of the fungal symbionts, and nonmycorrhizal controls, were grown in mesh bags placed in pots containing pH-buffered sand (pH around 5 or 6). The systems were harvested at approximately 2-wk intervals between 20 and 80 d. ,,Both fungi formed more extraradical mycelium at the higher pH. Glomus intraradices formed almost no detectable extraradical mycelium at lower pH. The extraradical mycelium of S. calospora had higher acid phosphatase activity than that of G. intraradices. Total AM root colonization decreased for both fungi at the higher pH, and high pH also reduced arbuscule and vesicle formation in G. intraradices. ,,In conclusion, soil pH influences AM root colonization as well as the growth and phosphatase activities of extraradical mycelium, although the two fungi responded differently. [source] An overview of methods for the detection and observation of arbuscular mycorrhizal fungi in roots,PHYSIOLOGIA PLANTARUM, Issue 4 2005Horst Vierheilig One of the most cited papers in arbuscular mycorrhizal (AM) research was published by Phillips and Hayman in 1970 describing an easy standard method to stain AM fungi (AMF) in roots. Since then, a number of other methods (destructive,non-destructive; vital,non-vital) on how to visualize AMF in roots have been published. Our review provides an overview on present techniques used to visualize AMF in roots and gives recommendations on their use. We hope that the present review will help the readers to choose an appropriate method to visualize AMF in roots for their specific experimental set-up. [source] Effect of arbuscular mycorrhizal (AM) colonization on terpene emission and content of Artemisia annua L.PLANT BIOLOGY, Issue 1 2008F. Rapparini Abstract Plant roots interact with a wide variety of rhizospheric microorganisms, including bacteria and the symbiontic arbuscular mycorrhizal (AM) fungi. The mycorrhizal symbiosis represents a series of complex feedbacks between plant and fungus regulated by their physiology and nutrition. Despite the widespread distribution and ecological significance of AM symbiosis, little is known about the potential of AM fungi to affect plant VOC metabolism. The purpose of this study was to investigate whether colonization of plant roots by AM fungi and associated soil microorganisms affects VOC emission and content of Artemisia annua L. plants (Asteraceae). Two inoculum types were evaluated: one consisted of only an arbuscular mycorrhizal (AM) fungus species (Glomus spp.), and the other was a mixture of different Glomus species and associated soil bacteria. Inoculated plants were compared with non-inoculated plants and with plants supplemented with extra phosphorus (P) to obtain plants of the same size as mycorrhizal plants, thus excluding potentially-confounding mycorrhizal effects on shoot growth. VOC emissions of Artemisia annua plants were analyzed by leaf cuvette sampling followed by off-line measurements with pre-concentration and gas chromatography mass spectrometry (GC-MS). Measurements of CO2 and H2O exchanges were conducted simultaneously. Several volatile monoterpenes were identified and characterized from leaf emissions of Artemisia annua L. by GC-MS analysis. The main components identified belong to different monoterpene structures: ,-pinene, ,-pinene, camphor, 1,8-cineole, limonene, and artemisia ketone. A good correlation between monoterpene leaf concentration and leaf emission was found. Leaf extracts included also several sesquiterpenes. Total terpene content and emission was not affected by AM inoculation with or without bacteria, while emission of limonene and artemisia ketone was stimulated by this treatment. No differences were found among treatments for single monoterpene content, while accumulation of specific sesquiterpenes in leaves was altered in mycorrhizal plants compared to control plants. Growth conditions seemed to have mainly contributed to the outcome of the symbiosis and influenced the magnitude of the plant response. These results highlight the importance of considering the below-ground interaction between plant and soil for estimating VOC emission rates and their ecological role at multitrophic levels. [source] Morphological and Molecular Evidence of Arbuscular Mycorrhizal Fungal Associations in Costa Rican Epiphytic Bromeliads,BIOTROPICA, Issue 2 2005Annette R. Rowe ABSTRACT Arbuscular mycorrhizal fungi influence the growth, morphology, and fitness of a variety of plant species, but little is known of the arbuscular mycorrhizal (AM) fungal associations of plant species in forest canopies. Plant species' associations with AM fungi are most often elucidated by examining the roots for fungal structures; however, morphological data may provide a limited resolution on a plant's mycorrhizal status. We combined a traditional staining technique with a molecular marker (the 18S ribosomal gene) to determine whether or not a variety of epiphytic bromeliads form arbuscular mycorrhizal fungal associations. Using these methods we show that the epiphytic bromeliad Vriesea werkleana forms arbuscular mycorrhizal fungal associations with members of the genus Glomus. AM fungal sequences of this plant species formed three distinct clades nested within a larger Glomus clade; two of the clades did not group with any previously sequenced lineage of Glomus. Novel clades may represent novel species. Although Vriesea werkleana is associated with multiple AM fungal species, each individual plant is colonized by a single lineage. The combination of morphological and molecular methods provides a practical approach to the characterization of the mycorrhizal status of epiphytic bromeliads, and perhaps other tropical epiphytes. [source] | |||||||||||||||||||||||||