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  • Jansa, Jan  (26)
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  • 1
    In: Molecular Ecology, February 2014, Vol.23(3), pp.733-746
    Description: Interactions between arbuscular mycorrhizal fungal () species cocolonizing the same host plant are still little understood in spite of major ecological significance of mycorrhizal symbiosis and widespread occurrence of these fungi in communities rather than alone. Furthermore, shifting the composition of communities has demonstrated consequences for the provision of symbiotic benefits to the host as well as for the qualities of ecosystem services. Therefore, here we addressed the nature and strength of interactions between three different species in all possible two‐species combinations on a gradient of inoculation densities. Fungal communities were established in pots with plants, and their composition was assessed with taxon‐specific real‐time markers. Nature of interactions between the fungi was varying from competition to facilitation and was influenced by both the identity and relative abundance of the coinoculated fungi. Plants coinoculated with and grew bigger and contained more phosphorus than with any of these two fungi separately, although these fungi obviously competed for root colonization. On the other hand, plants coinoculated with and , which facilitated each other's root colonization, grew smaller than with any of these fungi separately. Our results point to as yet little understood complexity of interactions in plant‐associated symbiotic fungal communities, which, depending on their composition, can induce significant changes in plant host growth and/or phosphorus acquisition in either direction.
    Keywords: Barrel Medic ; Claroideoglomus Claroideum ; Functional Complementarity ; Gigaspora Margarita ; Quantitative Real‐Time ; Rhizophagus Irregularis
    ISSN: 0962-1083
    E-ISSN: 1365-294X
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  • 2
    Language: English
    In: Plant and Soil, 2011, Vol.339(1), pp.231-245
    Description: Diversity in phosphorus (P) acquisition strategies was assessed among three species of arbuscular mycorrhizal fungi (AMF) isolated from a single field in Switzerland. Medicago truncatula was used as a test plant. It was grown in a compartmented system with root and root-free zones separated by a fine mesh. Dual radioisotope labeling ( 32 P and 33 P) was employed in the root-free zone as follows: 33 P labeling determined hyphal P uptake from different distances from roots over the entire growth period, whereas 32 P labeling investigated hyphal P uptake close to the roots over the 48 hours immediately prior to harvest. Glomus intraradices , Glomus claroideum and Gigaspora margarita were able to take up and deliver P to the plants from maximal distances of 10, 6 and 1 cm from the roots, respectively. Glomus intraradices most rapidly colonized the available substrate and transported significant amounts of P towards the roots, but provided the same growth benefit as compared to Glomus claroideum , whose mycelium was less efficient in soil exploration and in P uptake and delivery to the roots. These differences are probably related to different carbon requirements by these different Glomus species. Gigaspora margarita provided low P benefits to the plants and formed dense mycelium networks close to the roots where P was probably transiently immobilized. Numerical modeling identified possible mechanisms underlying the observed differences in patterns of mycelium growth. High external hyphal production at the root-fungus interface together with rapid hyphal turnover were pointed out as important factors governing hyphal network development by Gigaspora , whereas nonlinearity in apical branching and hyphal anastomoses were key features for G. intraradices and G. claroideum , respectively.
    Keywords: Arbuscular mycorrhiza ; Extraradical mycelium ; Functional diversity ; Hyphal growth model ; Medicago truncatula ; Phosphorus
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    Language: English
    In: Soil Biology and Biochemistry, July, 2014, Vol.74, p.21(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2014.02.014 Byline: Monika Welc, Emmanuel Frossard, Simon Egli, Else K. Bunemann, Jan Jansa Abstract: The abundance, distribution and functions of soil fungi in alpine ecosystems remain poorly understood. We aimed at linking the fungal community structure with soil enzymatic activities in the rhizospheres of several plants associating with mycorrhizal fungi (arbuscular, ecto- and ericoid) and growing along a soil developmental gradient on the forefield of an alpine glacier. Fungal communities in roots and in rhizosphere soils were assessed using a site-tailored set of quantitative PCR assays with fluorescent hydrolysis probes. Enzymatic activities of mycorrhizal roots and rhizosphere soils were assessed using fluorogenic substrates. In this study we addressed: i) whether and how the structure of fungal communities and enzymatic activities in rhizosphere soils change along the soil developmental gradient, ii) whether the type of mycorrhiza shows a clear relationship to the pattern of enzymatic activities in the rhizosphere, and iii) how the structure of fungal communities and enzymatic activities in rhizosphere soils is related to plant species abundances along the soil chronosequence. The results suggest that plant identity affected the structure of both ecto- and arbuscular mycorrhizal fungal communities in rhizosphere soil and roots, whereas the community of non-mycorrhizal fungi was rather dictated by the soil developmental stage. Both plant identity and associated mycorrhizal fungi affected the enzymatic activity in the rhizosphere soil. Species-specific elevations of rhizosphere enzyme activities were detected for Salix helvetica (chitinase and [alpha]-glucosidase), Rhododendron ferrugineum ([alpha]-glucosidase and sulfatase), and Agrostis gigantea (phosphatase and xylosidase). These results indicate different functional roles played by different types of mycorrhizal symbiosis in a young alpine ecosystem. Author Affiliation: (a) Swiss Federal Institute of Technology (ETH) Zurich, Institute of Agricultural Sciences, FMG C 18, Eschikon 33, 8315 Lindau, ZH, Switzerland (b) Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zurcherstrasse 111, 8903 Birmensdorf, ZH, Switzerland (c) Institute of Microbiology, Academy of Sciences of the Czech Republic, VideAska 1083, 14220, Praha 4, KrA, Czech Republic Article History: Received 20 August 2013; Revised 17 February 2014; Accepted 20 February 2014
    Keywords: Alpine Ecosystems ; Enzymes ; Plants (Organisms) ; Hydrolysis
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, December 2014, Vol.79, pp.117-124
    Description: Crop production in subsistence agriculture in tropical Africa is still sustained mainly by short-to medium-term fallows to recuperate natural fertility of the soils. Microbes play a pivotal role both in the process of soil fertility restoration and in nutrient acquisition by the crops. Here we ask the question how the duration of fallow affects the composition of indigenous arbuscular mycorrhizal fungal (AMF) communities and their contribution to maize nutrition and growth, in acidic, low P soils of southern Cameroon. This question has been addressed in a bioassay where soils collected from continuously cropped fields, short-term fallows dominated by and long-term fallows (secondary forests) have been sterilized and back- and cross inoculated with living soils from the different land-use systems. Particular microbes larger than the pore size of the filter paper (mainly the fungi including the AMF) contained in the cropped and short-fallowed soils caused greater growth and P uptake stimulations to the maize as compared to the forest soil. By using molecular profiling, we demonstrated a shift in the composition of AMF communities along a gradient of fallow duration, changing from dominance by in the forest fallow soil, to dominance by under cropland. Our results contradict the hypothesis that deterioration of quality of root symbiotic communities would be responsible for a rapid yield decline following deforestation, and indicate a positive feedback of cropping on mycorrhizal functioning under conditions of shifting agriculture in tropical Africa.
    Keywords: Arbuscular Mycorrhiza ; Bioassay ; Chromolaena Odorata ; Fallow ; Maize ; Phosphorus ; Quantitative Real-Time Pcr ; Southern Cameroon ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    Language: English
    In: Soil Biology and Biochemistry, June, 2012, Vol.49, p.184(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2012.01.032 Byline: Monika Welc (a), Else K. Bunemann (a), Andreas Flie[sz]bach (b), Emmanuel Frossard (a), Jan Jansa (a)(c) Abstract: Microbial communities are important components of terrestrial ecosystems. The importance of their diversity and functions for natural systems is well recognized. However, a better understanding of successional changes of microbial communities over long time scales is still required. In this work, the size and composition of microbial communities in soils of a deglaciation chronosequence at the Damma glacier forefield were studied by fatty acid profiling. Soil fatty acid concentrations clearly increased with soil age. The abundances of arbuscular mycorrhizal fungi (AMF), bacteria and other soil fungi, however, were more affected by abiotic soil parameters like carbon content and pH than by soil age. Analysis of ratios of the different microbial groups (AMF, fungi, bacteria) along the soil chronosequence indicated that: i) the ratios of AMF to bacteria and AMF to fungi decreased with soil age; and ii) the ratio of fungi to bacteria remained unchanged along the soil chronosequence. These two pieces of evidence suggest that the evolution of this ecosystem proceeds at an uneven pace over time and that the role of AMF is less important in older, more organic and acidified soils than in mineral soils. In contrast to other studies, no successional replacement of bacteria with fungi in more acidified and organic soil was observed. Author Affiliation: (a) ETH Zurich, Institute of Agricultural Sciences, FMG C 18, Eschikon 33, 8315 Lindau (ZH), Switzerland (b) Research Institute of Organic Agriculture (FiBL), Department of Soil Sciences, Ackerstrasse, 5070 Frick, Switzerland (c) Institute of Microbiology, Academy of Sciences of the Czech Republic, VideAska 1083, Praha 4 - KrA, Czech Republic Article History: Received 10 October 2011; Revised 21 January 2012; Accepted 30 January 2012
    Keywords: Soil Microbiology -- Analysis ; Soil Carbon -- Analysis ; Organic Farming -- Analysis ; Ecosystems -- Analysis ; Bacteria -- Analysis ; Fatty Acids -- Analysis ; Terrestrial Ecosystems -- Analysis ; Fungi -- Analysis
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: PLoS ONE, 2011, Vol.6(12), p.e27825
    Description: Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions. ; First, under controlled glasshouse conditions, we screened growth responses of nine weed species and three crops to a widespread AMF, . None of the weeds screened showed a significant positive mycorrhizal growth response and four weed species were significantly reduced by the AMF (growth responses between −22 and −35%). In a subsequent experiment, we selected three of the negatively responding weed species – , and – and analyzed their responses to a combination of three AMF (, and ). Finally, we tested whether the presence of a crop (maize) enhanced the suppressive effect of AMF on weeds. We found that the growth of the three selected weed species was also reduced by a combination of AMF and that the presence of maize amplified the negative effect of AMF on the growth of . ; Our results show that AMF can negatively influence the growth of some weed species indicating that AMF have the potential to act as determinants of weed community structure. Furthermore, mycorrhizal weed growth reductions can be amplified in the presence of a crop. Previous studies have shown that AMF provide a number of beneficial ecosystem services. Taken together with our current results, the maintenance and promotion of AMF activity may thereby contribute to sustainable management of agroecosystems. However, in order to further the practical and ecological relevance of our findings, additional experiments should be performed under field conditions.
    Keywords: Research Article ; Agriculture ; Biology ; Plant Biology ; Biotechnology ; Ecology
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: Soil Biology and Biochemistry, July 2014, Vol.74, pp.21-30
    Description: The abundance, distribution and functions of soil fungi in alpine ecosystems remain poorly understood. We aimed at linking the fungal community structure with soil enzymatic activities in the rhizospheres of several plants associating with mycorrhizal fungi (arbuscular, ecto- and ericoid) and growing along a soil developmental gradient on the forefield of an alpine glacier. Fungal communities in roots and in rhizosphere soils were assessed using a site-tailored set of quantitative PCR assays with fluorescent hydrolysis probes. Enzymatic activities of mycorrhizal roots and rhizosphere soils were assessed using fluorogenic substrates. In this study we addressed: i) whether and how the structure of fungal communities and enzymatic activities in rhizosphere soils change along the soil developmental gradient, ii) whether the type of mycorrhiza shows a clear relationship to the pattern of enzymatic activities in the rhizosphere, and iii) how the structure of fungal communities and enzymatic activities in rhizosphere soils is related to plant species abundances along the soil chronosequence. The results suggest that plant identity affected the structure of both ecto- and arbuscular mycorrhizal fungal communities in rhizosphere soil and roots, whereas the community of non-mycorrhizal fungi was rather dictated by the soil developmental stage. Both plant identity and associated mycorrhizal fungi affected the enzymatic activity in the rhizosphere soil. Species-specific elevations of rhizosphere enzyme activities were detected for (chitinase and α-glucosidase), (α-glucosidase and sulfatase), and (phosphatase and xylosidase). These results indicate different functional roles played by different types of mycorrhizal symbiosis in a young alpine ecosystem.
    Keywords: Fungal Community ; Structure and Functions ; Mycorrhiza ; Rhizosphere ; Enzymes ; Salix Helvetica ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 8
    Language: English
    In: Soil Biology and Biochemistry, June 2012, Vol.49, pp.184-192
    Description: Microbial communities are important components of terrestrial ecosystems. The importance of their diversity and functions for natural systems is well recognized. However, a better understanding of successional changes of microbial communities over long time scales is still required. In this work, the size and composition of microbial communities in soils of a deglaciation chronosequence at the Damma glacier forefield were studied by fatty acid profiling. Soil fatty acid concentrations clearly increased with soil age. The abundances of arbuscular mycorrhizal fungi (AMF), bacteria and other soil fungi, however, were more affected by abiotic soil parameters like carbon content and pH than by soil age. Analysis of ratios of the different microbial groups (AMF, fungi, bacteria) along the soil chronosequence indicated that: i) the ratios of AMF to bacteria and AMF to fungi decreased with soil age; and ii) the ratio of fungi to bacteria remained unchanged along the soil chronosequence. These two pieces of evidence suggest that the evolution of this ecosystem proceeds at an uneven pace over time and that the role of AMF is less important in older, more organic and acidified soils than in mineral soils. In contrast to other studies, no successional replacement of bacteria with fungi in more acidified and organic soil was observed. ► Microbial succession at a glacier forefield was investigated by fatty acid profiling. ► Concentrations of fatty acids in soil increase with soil age. ► Soil C and pH affect abundances of both soil bacteria and fungi. ► Ratios of AMF to bacteria or to soil fungi decrease with soil age. ► Ratio of soil fungi to bacteria remains constant along the soil chronosequence.
    Keywords: Fatty Acid Methyl Esters (Fame) ; Glacier Forefield ; Soil Chronosequence ; Microbial Community ; Mycorrhizal Fungi ; Community Size ; Environmental Determinants ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 9
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(7), p.e101487
    Description: Zinc (Zn) deficiency is a major problem for many people living on wheat-based diets. Here, we explored whether addition of green manure of red clover and sunflower to a calcareous soil or inoculating a non-indigenous arbuscular mycorrhizal fungal (AMF) strain may increase grain Zn concentration in bread wheat. For this purpose we performed a multifactorial pot experiment, in which the effects of two green manures (red clover, sunflower), ZnSO4 application, soil γ-irradiation (elimination of naturally occurring AMF), and AMF inoculation were tested. Both green manures were labeled with 65Zn radiotracer to record the Zn recoveries in the aboveground plant biomass. Application of ZnSO4 fertilizer increased grain Zn concentration from 20 to 39 mg Zn kg-1 and sole addition of green manure of sunflower to soil raised grain Zn concentration to 31 mg Zn kg-1. Adding the two together to soil increased grain Zn concentration even further to 54 mg Zn kg-1. Mixing green manure of sunflower to soil mobilized additional 48 µg Zn (kg soil)-1 for transfer to the aboveground plant biomass, compared to the total of 132 µg Zn (kg soil)-1 taken up from plain soil when neither green manure nor ZnSO4 were applied. Green manure amendments to soil also raised the DTPA-extractable Zn in soil. Inoculating a non-indigenous AMF did not increase plant Zn uptake. The study thus showed that organic matter amendments to soil can contribute to a better utilization of naturally stocked soil micronutrients, and thereby reduce any need for major external inputs.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 10
    Language: English
    In: Geoderma, June, 2013, Vol.200-201, p.120(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geoderma.2013.01.019 Byline: Lalajaona Randriamanantsoa, Christian Morel, Lilia Rabeharisoa, Jean-Marie Douzet, Jan Jansa, Emmanuel Frossard Keywords: Ferralsol; Andosol; Phosphate ion sorption; Low P availability; Isotopic technique Abstract: The isotopic exchange kinetic (IEK) method allows assessing the rate of orthophosphate ions (Pi) exchange between the solid phase and the solution of the soil with time. However, two challenges have to be tackled when using this technique in soils with a very low water extractable Pi concentration (C.sub.P) and with a high sorbing capacity for Pi. The first is that current colorimetric methods do not allow quantifying Pi concentrations lower than 10[mu]gP L.sup.-1. While the second challenge is that a significant fractionation between P isotopes may occur in the soil solution system in the presence of soils with high Pi sorption capacity. We assessed here: i) whether concentrating the blue phosphomolybdate complex (BPMC) in hexanol prior to its measurement would allow to lower the detection and quantification limits of Pi, ii) whether a significant isotopic fractionation between.sup.32Pi and.sup.33Pi could occur during IEK experiments conducted in the presence of high Pi sorbing substrates (e.g., pure goethite or Malagasy soils) and iii) whether the IEK method when used in conjunction with the hexanol concentration of the BPMC to measure C.sub.P would detect changes in Pi isotopic exchangeability in a ferralsol cropped with upland rice following the input of manure or water soluble fertilizer. The detection and quantification limits of the BPMC concentrated by hexanol were 0.3 and 0.8[mu]gPL.sup.-1, respectively, using a cell of 10cm length for the colorimetric measurement. The IEK conducted on Pi amended goethite and on Malagasy soils with.sup.32Pi and.sup.33Pi did not show any systematic isotopic fractionation between both isotopes, suggesting that in these soils.sup.31Pi and.sup.32Pi or.sup.33Pi have a similar behavior during isotopic exchange. The analysis of the soils sampled in the field experiment showed a significant increase in the amount of Pi isotopically exchangeable after 1min only after the application of water soluble P. This increase was paralleled by increases in rice yield and P export by grains demonstrating an increased P availability in this treatment. In conclusion, the IEK method can be used in low P and high Pi sorbing soils as the hexanol concentration method allows measuring very low C.sub.P and as the different P isotopes have a similar behavior in the soil/solution system. The IEK experiments conducted in the presence of goethite, however, point out to the necessity of taking into account the dispersion of particles for a proper interpretation of the isotopic data. Article History: Received 20 August 2012; Revised 26 January 2013; Accepted 30 January 2013
    Keywords: Fertilizers -- Analysis ; Fertilizers -- Methods ; Iron Oxides -- Analysis ; Iron Oxides -- Methods ; Soils -- Analysis ; Soils -- Methods ; Phosphates -- Analysis ; Phosphates -- Methods
    ISSN: 0016-7061
    Source: Cengage Learning, Inc.
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