Ability Of Arbuscular Mycorrhizal Fungi Research Articles

Preliminary Insights into Sustainable Control of Solanum lycopersicum Early Blight: Harnessing Arbuscular Mycorrhizal Fungi and Reducing Fungicide Dose

Tomato (Solanum lycopersicum L.) production is constantly threatened by several fungal pathogens, such as Alternaria solani, the causal agent of early blight disease. In this study, a greenhouse experiment was set up to evaluate the biocontrol ability of arbuscular mycorrhizal fungi (AMF) against A. solani in the presence of reduced doses of fungicides (i.e., captan and copper oxychloride). Disease severity, plant growth traits, chlorophyll and phosphorus content, phenolic compounds, and antioxidant activity were assessed. The effects of fungicide dose on AMF were investigated by root colonization, spore density, and mycorrhizal dependence evaluation. AMF-inoculated and fungicide-treated plants reduced disease severity compared to fungicide-treated and non-mycorrhizal plants, in most cases, regardless of the fungicide dose. AMF improved plant growth, especially when combined with copper oxychloride. However, plant fresh weight decreased in plants treated with the lowest dose of captan (25 g 100 L−1). Overall, AMF colonization decreased in plants with high fungicide doses, while the leaf color parameters did not show differences between treatments. The results suggest reducing the fungicide dose using AMF is possible, particularly for copper oxychloride. Further studies will be required to confirm these data. This integrated approach could offer a sustainable alternative to decrease the use of chemical control.

Synergy between Arbuscular Mycorrhizal Fungi and Rhizosphere Bacterial Communities Increases the Utilization of Insoluble Phosphorus and Potassium in the Soil by Maize.

Arbuscular mycorrhizal (AM) fungi can enhance plant uptake of phosphorus (P) and potassium (K), but it is not yet clear whether rhizosphere bacteria can enhance the ability of AM fungi to acquire insoluble P and K from the soil. Here, pot experiments confirmed that AM fungus-promoted insoluble P and K uptake by plants requires rhizosphere bacteria. The changes of rhizosphere bacterial communities associated with AM fungi were explored by 16S rRNA amplicon sequencing and metagenomic sequencing. Five core bacteria genera identified were involved in P and K cycles. Synthetic community (SynCom) inoculation revealed that SynCom increased soil available P and K and its coinoculation with AM fungi increased P and K concentration in the plants. This study revealed that AM fungi interact with rhizosphere bacteria and promote insoluble P and K acquisition, which provided a foundation for the application of AM fungal-bacterial biofertilizers and was beneficial for the sustainable development of agriculture.

Arbuscular Mycorrhizal Fungi and Compost-Based Biostimulants Enhance Fitness, Physiological Responses, Yield, and Quality Traits of Drought-Stressed Tomato Plants.

Climate change-driven water resource constraints cause tomatoes to suffer from drought. The use of biostimulants has emerged as an important approach to enhancing resilience to drought. However, the roles of biostimulants in the physicochemical characteristics of tomatoes in response to drought are poorly understood. In this study, we evaluated the ability of arbuscular mycorrhizal fungi (AMF) and compost (versus NPK application) to improve the agro-physiology, yield, and fruit quality of tomato plants and their tolerance to drought by comparing them with conventional chemical fertilizers (NPK). Under drought conditions, plant growth traits associated with yield and fruit bioactive compounds (carotenoids: 73%; lycopene: 53%; polyphenols: 310%; and flavonoids: 158%) were increased in the AMF-tomato treatment. Compost significantly enhanced sugars (ca. 60%) and protein contents (ca. 20%). Moreover, AMF protected the photosynthetic apparatus from drought-induced oxidative stress, improved photosynthetic efficiency, leaf water potential, and osmolytes, and reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation by increasing peroxidase (POX) (140%) and polyphenol oxidase (PPO) (340%) activities compared to their controls. Our findings revealed that NPK is an important nutrient-based fertilizer for plant growth and development. However, its efficiency as a fertilizer is quite low. In addition, we highlighted different mechanisms mediated by AMF and compost, inducing drought tolerance in tomato plants.

Global taxonomic and phylogenetic assembly of AM fungi.

Arbuscular mycorrhizal (AM) fungi are a ubiquitous group of plant symbionts, yet processes underlying their global assembly - in particular the roles of dispersal limitation and historical drivers - remain poorly understood. Because earlier studies have reported niche conservatism in AM fungi, we hypothesized that variation in taxonomic community composition (i.e.,unweighted by taxon relatedness) should resemble variation in phylogenetic community composition (i.e., weighted by taxon relatedness) which reflects ancestral adaptations to historical habitat gradients. Because of the presumed strong dispersal ability of AM fungi, we also anticipated that the large-scale structure of AM fungal communities would track environmental conditions without regional discontinuity. We used recently published AM fungal sequence data (small-subunit ribosomal RNA gene) from soil samples collected worldwide to reconstruct global patterns in taxonomic and phylogenetic community variation. The taxonomic structure of AM fungal communities was primarily driven by habitat conditions, with limited regional differentiation, and there were two well-supported clusters of communities - occurring in cold and warm conditions. Phylogenetic structure was driven by the same factors, though all relationships were markedly weaker. This suggests that niche conservatism with respect to habitat associations is weakly expressed in AM fungal communities. We conclude that the composition of AM fungal communities tracks major climatic and edaphic gradients, with the effects of dispersal limitation and historic factors considerably less apparent than those of climate and soil.

Effects of Funneliformis mosseae on the utilization of organic phosphorus in Camellia oleifera Abel.

Arbuscular mycorrhizal (AM) fungi play an important role in the acquisition of phosphorus(P) by plants. The external hyphae of AM fungi function as an extension of plant roots and may downregulate related functions in the roots. It is not clear whether the ability of AM fungi to mineralize organicP affects root phosphatase activities. A pot experiment was conducted to investigate the effect of Funneliformis mosseae on soil organicP mineralization under phytate application and to explore root phosphatase activities, Puptake, and growth in Camellia oleifera Abel. The plants and their growth substrates were harvested 4 and 8months after planting. The results showed that organicP application had no effect on the total dry mass of nonmycorrhizal plants, but differences in dry mass under P application were observed in mycorrhizal plants in both harvests. Inoculation with F.mosseae increased soil acid phosphatase, phytase, and alkaline phosphatase activities and reduced the soil organicP content. Mycorrhizal plants had higher root activity, shoot and root P contents and root acid phosphatase and phytase activities than nonmycorrhizal plants irrespective of organicP application. In conclusion, AM fungi enhanced the mineralization of soil organicP and positively affect root phosphatase activities.

Aboveground resource allocation in response to root herbivory as affected by the arbuscular mycorrhizal symbiosis

Arbuscular mycorrhizal (AM) fungi associate with the majority of terrestrial plants, influencing their growth, nutrient uptake and defence chemistry. Consequently, AM fungi can significantly impact plant-herbivore interactions, yet surprisingly few studies have investigated how AM fungi affect plant responses to root herbivores. This study aimed to investigate how AM fungi affect plant tolerance mechanisms to belowground herbivory. We examined how AM fungi affect plant (Saccharum spp. hybrid) growth, nutrient dynamics and secondary chemistry (phenolics) in response to attack from a root-feeding insect (Dermolepida albohirtum). Root herbivory reduced root mass by almost 27%. In response, plants augmented investment in aboveground biomass by 25%, as well as increasing carbon concentrations. The AM fungi increased aboveground biomass, phosphorus and carbon. Meanwhile, root herbivory increased foliar phenolics by 31% in mycorrhizal plants, and increased arbuscular colonisation of roots by 75% overall. AM fungi also decreased herbivore performance, potentially via increasing root silicon concentrations. Our results suggest that AM fungi may be able to augment plant tolerance to root herbivory via resource allocation aboveground and, at the same time, enhance plant root resistance by increasing root silicon. The ability of AM fungi to facilitate resource allocation aboveground in this way may be a more widespread strategy for plants to cope with belowground herbivory.

EFFECT OF MYCORRHIZA INOCULATION OF PEPPER SEEDLINGS (Capsicum annuum L.) ON THE GROWTH AND PROTECTION AGAINST Fusarium oxysporum INFECTION

A study was conducted to investigate the ability of arbuscular mycorrhizal fungi (AMF) in enhancing the growth and control of a root rot caused by different isolates of Fusarium oxysporum in sweet pepper seedlings. The plants were grown in plastic pots filled with sterilized horticultural soils. There were four treatments applied as follows: Fo (seedlings infected with fungus), M (seedlings inoculated with mycorrhizal fungi), Fo + M (seedlings inoculated with mycorrhiza and infected with fungus) and control. A randomized experiment was used and the growth, disease index, and photosynthetic activity of the plants were measured after 4 weeks. The investigations showed that the mycorrhizal inoculation had a protective effect on the F. oxysporum-infected pepper seedlings. The plants were characterized by a higher growth rate and a lower disease index than those growing only in the presence of the pathogenic fungus. The roots inoculated with mycorrhizal fungi were better developed than those infected only with F. oxysporum. The mycorrhiza contributed to an increase in the photosynthetic activity of the pepper seedlings.

Mycorrhizal symbiosis affects ABA metabolism during berry ripening in Vitis vinifera L. cv. Tempranillo grown under climate change scenarios

Arbuscular mycorrhizal symbiosis is a promising tool for improving the quality of grapes under changing environments. Therefore, the aim of this research was to determine if the ability of arbuscular mycorrhizal fungi (AMF) to enhance phenolic content (specifically, anthocyanins) in a climate change framework could be mediated by alterations in berry ABA metabolism during ripening. The study was carried out on fruit-bearing cuttings of cv. Tempranillo (CL-1048 and CL-1089) inoculated (+M) or not (−M) with AMF. Two experimental designs were implemented. In the first experiment +M and -M plants were subjected to two temperatures (24/14 °C or 28/18 °C (day/night)) from fruit set to berry maturity. In the second experiment, +M and -M plants were subjected to two temperatures (24/14 °C or 28/18 °C (day/night)) combined with two irrigation regimes (late water deficit (LD) and full irrigation (FI)). At 28/18 °C AMF contributed to an increase in berry anthocyanins and modulated ABA metabolism, leading to higher ABA-GE and 7′OH-ABA and lower phaseic acid (PA) in berries compared to –M plants. Under the most stressful scenario (LD and 28/18 °C), at harvest +M plants exhibited higher berry anthocyanins and 7´OH-ABA and lower PA and dihydrophaseic acid (DPA) levels than –M plants. These findings highlight the involvement of ABA metabolism into the ability of AMF to improve some traits involved in the quality of grapes under global warming scenarios.

Potential Role of Arbuscular Mycorrhizal Fungi and Pseudomonas fluorescens on Growth, Physiological Parameters, and Yield of Capsicum frutescens L.

ABSTRACTLimited land resources affect production of Hot Pepper (Capsicum frutescens L.). Strategies to increase production of hot pepper include use of chemical fertilizers, pesticides, and insecticides, but these can negatively impact the soil. Methods must be derived to improve nutrient uptake while reducing synthetic chemical inputs. Soil microbes including, arbuscular mycorrhizal (AM) fungi, represent a link between plants and soil mineral nutrients. The investigation was carried out to determine the ability of AM fungi [Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe] applied alone and in combination with the bacterium Pseudomonas fluorescens to affect growth, biochemical attributes and yield of hot pepper. All treatments enhanced C. frutescens growth, physiological parameters, and yield over the untreated control. Inoculation with G. mosseae (G) + A. laevis (A) + P. fluorescens (P), followed by G + A inoculation produced the best growth response, AM colonization, phosphorus uptake, and biochemical responses due to a positive interaction among rhizospheric microorganisms. Soil amended with G. mosseae + A. laevis + P. fluorescens at transplanting increased production of high-quality hot pepper and reduced fertilizer required.

Arbuscular mycorrhizal fungi altered the hypericin, pseudohypericin, and hyperforin content in flowers of Hypericum perforatum grown under contrasting P availability in a highly organic substrate.

St. John's Wort (Hypericum perforatum) is a perennial herb able to produce water-soluble active ingredients (a.i.), mostly in flowers, with a wide range of medicinal and biotechnological uses. However, information about the ability of arbuscular mycorrhizal fungi (AMF) to affect its biomass accumulation, flower production, and concentration of a.i. under contrasting nutrient availability is still scarce. In the present experiment, we evaluated the role of AMF on growth, flower production, and concentration of bioactive secondary metabolites (hypericin, pseudohypericin, and hyperforin) of H. perforatum under contrasting P availability. AMF stimulated the production of aboveground biomass under low P conditions and increased the production of root biomass. AMF almost halved the number of flowers per plant by means of a reduction of the number of flower-bearing stems per plant under high P availability and through a lower number of flowers per stem in the low-P treatment. Flower hyperforin concentration was 17.5% lower in mycorrhizal than in non-mycorrhizal plants. On the contrary, pseudohypericin and hypericin concentrations increased by 166.8 and 279.2%, respectively, with AMF under low P availability, whereas no effect of AMF was found under high P availability. These results have implications for modulating the secondary metabolite production of H. perforatum. However, further studies are needed to evaluate the competition for photosynthates between AMF and flowers at different nutrient availabilities for both plant and AM fungus.

Mycorrhiza consortia suppress the fusarium root rot (Fusarium solani f. sp. Phaseoli) in common bean (Phaseolus vulgaris L.)

The ability of Arbuscular Mycorrhizal Fungi (AMF) to alleviate the lethal effects incited by root pathogens in a range of plant hosts has been demonstrated. Accumulated evidence also shows that multiple rather than single AMF species exhibit greater potential against pathogens and could mimic natural systems. Nevertheless, it is well established that the effectiveness of a consortium of beneficial organisms is function of interaction among the partners and the involved host. In the present study, four AMF formulations made up of three strains each (1:1:1 w/w) from propagated units of selected AMF strains, Glomus intraradices, Glomus hoi, Gigaspora margarita, and Scutellospora gigantea were evaluated in enhancing common bean (Phaseolus vulgaris L.) growth and biocontrol vis-à-vis Fusariumsolani under greenhouse conditions. The results revealed that all the mycorrhizal preparations significantly reduced the levels of disease severity and incidence in infected bean plants. The biocontrol efficiency of AMF was a function of genera diversity. Though, either neutral or significantly increased growth parameters were recorded upon mycorrhizal colonization. The rhyzospheric competence (root colonization and spore density) of the mycorrhizal formulations was negatively affected upon Fusarium solani inoculation. Moreover, the total soluble phenols and flavonoids contents as well as the specific activity of Phenylalanine Ammonia Lyase (PAL) were boosted after mycorrhizal colonization, indicating the strengthening of plant immune system against the pathogen. Further studies should confirm our formulations after open field assays as alternatives to agrochemicals.

Radioactivity and the environment: technical approaches to understand the role of arbuscular mycorrhizal plants in radionuclide bioaccumulation.

Phytoaccumulation of radionuclides is of significant interest with regards to monitoring radionuclide build-up in food chains, developing methods for environmental bioremediation and for ecological management. There are many gaps in our understanding of the characteristics and mechanisms of plant radionuclide accumulation, including the importance of symbiotically-associated arbuscular mycorrhizal (AM) fungi. We first briefly review the evidence that demonstrates the ability of AM fungi to enhance the translocation of 238U into plant root tissues, and how fungal association may prevent further mobilization into shoot tissues. We then focus on approaches that should further advance our knowledge of AM fungi–plant radionuclide accumulation. Current research has mostly used artificial cultivation methods and we consider how more ecologically-relevant analysis might be performed. The use of synchrotron-based X-ray fluorescence imaging and absorption spectroscopy techniques to understand the mechanisms of radionuclide transfer from soil to plant via AM fungi is evaluated. Without such further knowledge, the behavior and mobilization of radionuclides cannot be accurately modeled and the potential risks cannot be accurately predicted.

Contribution of Arbuscular Mycorrhizal Fungi (AM Fungi) and Rhizobium Inoculation on Crop Growth and Chemical Properties of Rhizospheric Soils in High Plants

Soil microorganisms commonly named biofertilizers can be used to decrease input of fertilizers, pesticides and other chemicals in Agriculture. Among soil microorganisms, arbuscular mycorrhizal (AM) fungi and Rhizobium spp. can promote plant growth and control plant fungal diseases. However these microorganisms are not yet used in commercial biocontrol products. Integration of Arbuscular Mycorrhizal Fungi with Rhizobium sp. thus appears to be a promising approach for sustainable agriculture especially in legume crops where the net influence of this combination is supposed to be very high compare to other types of crop families. Arbuscular Mycorrhizal fungi and root-nodule bacterium Rhizobium are two root symbionts. Arbuscular mycorrhizal fungi increases soil nutrients and water absorption, while root-nodule bacteria fix atmospheric nitrogen and produce antibiotics and phytoalexins. These microbes modify the quality and abundance of rhizosphere microflora and alter overall microbial activity of the rhizosphere. They induce changes in the host root exudation pattern. A procedure for successful development of these microorganisms is required by selection and screening of efficient isolates. Knowledge of culture systems that are adapted to their establishment and multiplication is needed. Arbuscular mycorrhizal fungi provide specific niches for bacteria. Arbuscular mycorrhizal bacteria improve nutrient acquisition in plants and subsequently, growth of the particular crops is advantaged indeed. Arbuscular mycorrhizal bacteria may contribute to ability of arbuscular mycorrhizal fungi to inhibit pathogens acquire mineral nutrients and modify plant root growth. Combined use of these microorganisms is more beneficial than their use alone. Together, they Influence plant root morphology changes and chemical properties of Rhizospheric soils of high plants with the significant extent. These symbionts also interact with other beneficial microorganisms synergistically and can be exploited for sustainable agriculture. The sound influence of these symbionts on root morphology and growth of the whole

The role of the arbuscular mycorrhiza-associated rhizobacteria in the biocontrol of soilborne phytopathogens: a review

The mutualistic symbiosis of most land plants with arbuscular mycorrhizal (AM) fungi has been shown to favor mineral and water nutrition and to increase resistance to abiotic and biotic stresses. This review reports the main mechanisms involved in the control of the disease symptoms and of the intraradical proliferation of soilborne phytopathogens by root colonization with AM fungi, with a special emphasis on the role of the rhizobacteria shown to be specifically associated with the AM extraradical network and the mycorrhizosphere (the soil zone with particular characteristics under the influence of the root/AM association). The mycorrhizosphere would constitute an environment conducive to microorganisms antagonistic to pathogen proliferation. Moreover, attempts to identify rhizobacteria from AM structures and/or the mycorrhizosphere often lead to the isolation of organisms showing strong properties of antagonism on various soilborne pathogens. The ability of AM fungi to control soilborne diseases would be strongly related to their capacity to specifically stimulate the establishment of rhizobacteria unfavorable to pathogen development within the mycorrhizosphere before root infection. Current knowledge concerning the mechanisms involved in AM/rhizobacteria interactions are also described in this review.

Growth and symbiotic effectiveness of an arbuscular mycorrhizal fungus in organic matter in competition with soil bacteria

Arbuscular mycorrhizal (AM) fungi can enhance the rate of decomposition of organic material, and can acquire nitrogen (N) from organic sources, although they are not saprotrophs. These fungi may instead indirectly influence decomposition through interactions with other soil microorganisms. We investigated the impact of both AM hyphae and a bacterial filtrate on N capture by a host plant from sterilized organic material (Lolium perenne shoots dual labelled with (15) N and (13) C), using compartmented microcosms. The addition of a bacterial filtrate considerably suppressed AM hyphal growth in the patch and reduced the root phosphorus content, demonstrating that bacterial populations can reduce symbiotic effectiveness. In contrast, AM hyphae had only a limited impact on bacterial community structure. Uptake of (15) N greatly exceeded that of (13) C, demonstrating that fungi acquired N in an inorganic form. We also examined the ability of AM fungi in gnotobiotic hairy root culture to acquire N directly from organic materials of varying complexities (glutamic acid, urea, bacterial lysate and L. perenne shoots). AM colonization did not enhance root N capture from these materials, although the bacterial lysate reduced both total AM colonization and arbuscule frequency. Collectively, these data demonstrate antagonistic interactions between AM fungi and bacteria that reflect resource competition for decomposition products.

English

The production of quality native plants materials is essential to large- scale reclamation efforts being undertaken at mine sites throughout the United States. Some studies have shown that nursery inoculation with arbuscular mycorrhizal (AM) fungi improved survival, growth, and drought tolerance of installed tree and shrub seedlings. The production of AM-colonized plant material, however, has proven problematic due to a lack of integration between the biotechnical firms that produce inoculum and cultural procedures at commercial nurseries. The objective of our research has been to integrate mycorrhizal inoculum successfully into a nursery program, thereby, producing plant materials with improved outplanting performance. Multiple studies were conducted to investigate the efficacy of various inoculum products, the influence of growth media types, and the influence of standard fertilization techniques on the ability of AM fungi to colonize plant materials under nursery conditions. Our research has resulted in a growth media which promotes colonization of plant materials by AM inoculum in a nursery environment. Plants produced by this tecnhique have significantly higher colonization rates than controls. This study reviews the results of greenhouse trials to increase AM-colonization rates in plant materials and outplanting field trials established in Oregon, Montana, and Utah to compare traditionally grown seedlings with those grown in the AM-promoting growth media formulation.

Arbuscular mycorrhizal fungal spore-associated bacteria affect mycorrhizal colonization, plant growth and potato pathogens

Arbuscular mycorrhizal (AM) fungi and their bacterial associates are essential living components of the soil microbiota. From a total of 385 bacteria previously isolated from spores of AM fungi (AMB), 10 were selected based on ability to inhibit growth of plant pathogens. Effects of these isolates on AM fungal colonization, plant growth in potato ( Solanum tuberosum L.) and inhibition of pathogens was investigated. AM fungal root colonization of potato was 7-fold higher in the presence of the Pseudomonas FWC70 isolate in a greenhouse and was 6–9-fold higher in the presence of the three isolates Pseudomonas FWC70, Stenotrophomonas FWC94 and Arthrobacter FWC110 in an outdoor pot experiment. Several growth traits of potato were stimulated by the Pseudomonas isolates FWC16, FWC30 and FWC70 and by the Stenotrophomonas isolate FWC14. All three Pseudomonas isolates showed inhibition against Erwinia carotovora, Phytophthora infestans and Verticillium dahliae but Stenotrophomonas isolates were variable. Protease(s), siderophores and indole acetic acid were produced by all isolates. Chitinase(s) were produced by all Stenotrophomonas and phosphate-solubilizing activity by all Pseudomonas isolates, the Stenotrophomonas FWC14 isolate and the Arthrobacter FWC110 isolate. We conclude that some AMB are multifunctional and production of extracellular enzymes and bioactive compounds are likely mechanisms for their multifunctional activities. Our results show that some AMB are likely to contribute to the often described ability of AM fungi to inhibit pathogens, acquire mineral nutrients and modify plant root growth.

Effects of Arbuscular Mycorrhizal Fungi on The Exotic Invasive Vine Pale Swallow-Wort (Vincetoxicum rossicum)

Abstract The ability of arbuscular mycorrhizal fungi (AMF) to influence the performance of nonnative invasive plants in their introduced range has received increasing attention. The dependence of the invasive nonnative vine pale swallow-wort on AMF was studied in three greenhouse experiments. The aims of the present work were to (1) determine AMF colonization levels of field-collected pale swallow-wort plants and several co-occurring native and nonnative plant species, (2) evaluate the growth response of pale swallow-wort to different components of the soil microbial community from an infested site, and (3) determine the growth response of pale swallow-wort when grown with a nonlocal AMF species. AMF root colonization was greater in pale swallow-wort (85, 98, and 50% arbuscules, hyphae, and vesicles, respectively) than in leek (72, 80, and 25%), a species that has been frequently used as a predictor of AMF density in soil. Root colonization of pale swallow-wort in the field was also greater than root colo...

Arbuscular Mycorrhizal Fungi Enhance Tolerance of Rosa multiflora cv. Burr to Bicarbonate in Irrigation Water

ABSTRACT High bicarbonate (HCO3 −) of irrigation water can be detrimental to plant growth in sustainable horticultural production systems. The ability of arbuscular mycorrhizal fungi (AMF), ZAC-19, (composed of Glomus albidum, Glomus claroideum, and Glomus diaphanum) to enhance tolerance to HCO3 − was tested on Rosa multiflora cv. Burr. Arbuscular mycorrhizal colonized and non-inoculated (non-AMF) plants were treated with 0, 2.5, 5, and 10 mM HCO3 −. Increasing HCO3 − concentration and associated high pH and electrical conductivity (EC)—reduced plant growth, nutrient uptake, and acid phosphatase activity, while increasing alkaline phosphatase activity (ALP). Inoculation with AMF enhanced plant tolerance to HCO3 −, as indicated by greater growth (leaf, stem, and total plant dry weight, leaf area and leaf area ratio), leaf elemental concentration [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), zinc (Zn), aluminum (Al), boron (B)], leaf chlorophyll concentration, higher mycorrhizal inoculation effect, lower root Fe reductase activity, and generally lower soluble ALP activity. While AMF colonization was reduced by increasing HCO3 − concentration, colonization still occurred at high HCO3 − concentration. At 2.5 mM HCO3 −, AMF plant growth was comparable to plants at 0 mM HCO3 −, further indicating the beneficial effect of AMF for alleviation of HCO3 − plant stress.

Adaptability study of differentGlomus mosseaestrains to soil heavy metal content

required. Using plants in remediation of soils is regarded as an environmental friendly cleanup method (Gdspdr et al., 2004) and used w dely due to its va ious types (phytostabil zation, phytoextraction, rhizofiltration etc.) according to the aim of remediation (Simon et al., 2005). As the availability of heavy metals to plants and their toxicity depend on the reaction of the microbial activities in the rhizosphere (SchtltzendUbel et al., 2002), the efficiency of phytoremediation can be enhanced using by adequate selected, metal-tolerant inoculums of root symbionts such as arbuscular mycorrhizal fungi (AMF). AMF form obligatory mutualistic associations with a wide range of plant species. Many studies indicated the ability of AMF in improving of the nutrient supply of plants and protecting their hosts against heavy metal toxicity (Marschner et al., 1994; Leyval et al., 1997). However, to date little is known about what kind of factors may play the important roles in developing of tolerance and adaptation to heavy metals. The aim of this study was to compare the adaptability to the high soil Cd content of the five Glomus mosseae strains isolated from different soil types. The changing of infectivity and effectiveness of the strains were investigated in a pot experiment in soils treated with Cd at three levels (0, 50, 100 mg kg"1) harvested after 11 and 20 weeks.