Vesicular-arbuscular Mycorrhizal Fungi Research Articles

Mineralization of nitrogen from crop residues and N recovery by maize inoculated with vesicular-arbuscular mycorrhizal fungi

Legume crop residues serve as a source of nitrogen (N) for succeeding crops in low-input production systems, and characterizing the release of this N supports efforts to develop sound economic and environmental management practices. Nitrogen mineralization of 15N-labelled field crop residues was monitored in a Greenville sandy loam during a 140-day laboratory incubation at 25°C. Residue type strongly influenced the rate of N mineralization; decomposition rate constants were 0.283, 0.083, 0.00047 and 0.0014 day-1 for alfalfa (Medicago sativa L.) stover (above-ground plant parts), alfalfa roots, maize (Zea mays L.) stover (above-ground plant parts excluding cob and kernels) and maize roots, respectively. At the end of the incubation, 50% of alfalfa stover and 25% of alfalfa root residues N were mineralized, whereas these proportions were 8% for maize stover and 12% for root residues. Mineralization of 15N from alfalfa stover residues was also monitored in a greenhouse experiment to determine N availability during the growth of maize inoculated or not with vesicular-arbuscular mycorrhizal (VAM) fungi, and to evaluate the effects of the presence of plants on the decomposition of the residues. Stover and root dry matter yields were greatest for maize inoculated with VAM fungi and grown in residue-amended soil. At the final harvest, maize grown in residue-amended soils had accumulated 44% more dry matter and 40% more N than maize grown in unamended soils. Enhanced VAM colonization of roots inoculated with a mixture of three Glomus spp. increased the residue N accumulation in maize roots at 5 weeks after silking and at the final harvest. Alfalfa stover decomposed rapidly both in the presence and absence of maize plants, but the amount of 15N mineralized at the end of the experiment was influenced by the presence of living roots; 23% of the 15N in alfalfa stover residues was mineralized in soil without plants compared to about 38% when maize plants were present. These results suggest that N mineralization is enhanced by the presence of living roots.

Effect of Citrus Juice Pomace Extracts on in vitro Hyphal Growth of Vesicular-Arbuscular Mycorrhizal Fungi and their in vivo Infections of Citrus Roots.

The effect of citrus juice pomace extracts on in vitro hyphal growth of vesicular-arbuscular mycorrhizal (VAM) fungi and the mycorrhizal formation on trifoliate orange (Poncirus trifoliata Raf.) seedlings and Citrus iyo Tanaka trees was investigated. One hundred μl [equivalent to 6.5 g dry weight (DW) of satsuma mandarin (Citrus unshiu Marc.) and 4.3 gDW of Citrus hassaku Tanaka] of the 25% MeOH eluates of citrus juice pomace extracts significantly increased in vitro hyphal growth of Gigaspora ramisporophora Spain, but a 100% MeOH eluates inhibited it. In a plot where the solution consisting of 25% MeOH eluates of satsuma mandarin juice pomace extracts (equivalent to 10 gDW) and liquid fertilizers was applied to the soil inoculated with the spores of Gigaspora ramisporophora, the percentage of VAM infection in trifoliate orange roots was six times higher than that in the control (water only) after one week. When the above mixed solution was administered to a Citrus iyo orchard via a sprinkler irrigation system, VAM development was markedly stimulated as compared to the untreated plots (liquid fertilizer only) and the control (solid fertilizer only). These results show that 25% MeOH eluates of citrus juice pomace extracts contain stimulatory substances for VAM fungi. Furthermore, the application of the 25% MeOH eluates to the soil is very effective in stimulating VAM development.

Distribution of Vesicular-Arbuscular Mycorrhizal Hyphae in the Rhizospheres of Trifoliate Orange and Bahia Grass Seedlings under an Intercropping System.

An experiment was conducted under green house conditions to observe the distribution of vesicular-arbuscular mycorrhizal (VAM) hyphae between plants. Special acrylic root boxes with three compartments were constructed. The two outer compartments, into which the trifoliate orange (Poncirus trifoliata Raf.) seedlings and Bahia grass (Paspalum notatum Flugge.) were transplanted, were separated from the center compartment by a barrier made of a nylon screen of 37μm mesh. The inoculation with a VAM fungus, Gigaspora margarita Becker and Hall, was done in the center compartment. The density of hyphae, percentage of infection, and the number of spores were higher in the Bahia grass compartment than those in the compartment with trifoliate orange. A petri dish experiment showed that although the Bahia grass and trifoliate orange root exudates stimulated the hyphal growth of G. margarita, the length of hyphae in the Bahia grass treatment was longer than that of the trifoliate orange. In this experiment it was possible to observe in detail the distribution of hyphae in the rhizosphere of two plants under intercropping system conditions. These hyphae would be related to the interconnection between plants to promote a network system ; the formation and development of this network system is influenced by some root exudates.

Traits associated with improved P-uptake efficiency in CIMMYT's semidwarf spring bread wheat grown on an acid Andisol in Mexico.

Phosphorus deficiency is a major yield limiting constraint in wheat cultivation on acid soils. The plant factors that influence P uptake efficiency (PUPE) are mainly associated with root characteristics. This study was conducted to analyze the genotypic differences and relationships between PUPE, root length density (RLD), colonization by vesicular arbuscular and arbuscular mycorrhizal (V)AM fungi and root excretion of phosphatases in a P-deficient Andisol in the Central Mexican Highlands. Forty-two semidwarf spring-bread-wheat (Triticum aestivumL.) genotypes from CIMMYT were grown without (−P) and with P fertilization (+P), and subsequently in subsets of 30 and 22 genotypes in replicated field trials over 2 and 3 years, respectively. Acid phosphatase activity at the root surface (APASE) was analyzed in accompanying greenhouse experiments in nutrient solution. In this environment, PUPE contributed more than P utilization efficiency, in one experiment almost completely, to the variation of grain yield among genotypes. Late-flowering genotypes were higher yielding, because the postanthesis period of wheat was extended due to the cold weather at the end of the crop cycles, and postanthesis P uptake accounted for 40–45% of total P uptake. PUPE was positively correlated with the numbers of days to anthesis (at −P r=0.57 and at +P r=0.73). The RLD in the upper soil layer (0–20 cm) of the wheat germplasm tested ranged from 0.5 to 2.4 cm cm-3 at –P and 0.7 to 7.7 at +P. RLD was the most important root trait for improved P absorption, and it was positively genetically correlated with PUPE (at –P r=0.42 and at +P r=0.63) and the number of spikes m-2 (at –P r=0.58 and at +P r=0.36). RLD in the upper soil layer was more important with P fertilizer application. Without P fertilization, root proliferation in the deeper soil profile secured access to residual, native P in the deeper soil layer. (V)AM-colonisation and APASE were to a lesser degree correlated with PUPE. Among genoptypes, the level of (V)AM-colonisation ranged from 14 to 32% of the RLD in the upper soil layer, and APASE from 0.5 to 1.1 nmol s-1 plant-1 10-2.

Influence of Inoculation with Vesicular-Arbuscular Mycorrhizae on Posttransplant Growth of Prairie Forb Seedlings

The objectives of this study were to compare the growth of prairie forb seedlings inoculated with vesicular-arbuscular mycorrhizal (VAM) fungi to noninoculated seedlings transplanted to a highway right-of-way and to evaluate the effect of different VAM fungal species or combinations on posttransplant seedling growth. Four species of prairie forbs: pale-purple coneflower (Echinacea pallida Nutt.), prairie blazingstar (Liatris pycnostachya Michx.), prairie phlox (Phlox pilosa L.), and gray-headed coneflower [Ratibida pinnata (Venten.) Barnh.], were grown in greenhouse mix and inoculated with Gigaspora margarita Becker and Hall, or Glomus interadicies Schenk and Smith, or with a native Indiana prairie soil inoculum, or with a mix of all three. They were transplanted to a highway site in June, 1994. Only gray-headed coneflower exhibited a positive growth response to VAM inoculation. Inoculation of gray-headed coneflower with G. margarita produced the largest growth response by the end of the experiment.

Growth Stimulants for Vesicular-Arbuscular Mycorrhizal Fungi in Satsuma Mandarin Pomace.

The isolation and identification of growth stimulants for vesicular-arbuscular mycorrhizal (VAM) fungi in the 25% methanol (MeOH) extracts of satsuma mandarin (Citrus unshiu Marc.) pomace extracts were carried out. Three compounds were isolated from the eluates by using a high pressure liquid chromatograph (HPLC). When the effect of the three compounds was tested on the in vitro hyphal growth of a VAM fungus, Gigaspora margarita, two compounds had a stimulatory effect. The two stimulants were identified as hesperidin (hesperetin-7-β-rutinoside) and narirutin (naringenin-7-β-rutinoside). Narirutin at 1 to 30 ppm and hesperidin at 1 to 10 ppm significantly stimulated the hyphal growth of G. margarita.

The mycorrhizal colonization of six wetland plant species at sites differing in land use history

Five wetland prairie sites and six native plant species in western Oregon were examined to determine patterns of vesicular-arbuscular mycorrhizal fungal (VAMF) colonization. The sites differed in type and intensity of past land use. VAMF colonization was tested in situ on seedlings from both field-sown seeds and from transplants. Colonization was measured as the percentage of root length with arbuscles or vesicles. All species (Deschampsia cespitosa, Downingia elegans, Eriophyllum lanatum, Hordeum brachyantherum, Microseris laciniata, and Plagiobothrys figuratus) became colonized by VAMF during the study. This is the first report of mycorrhizal colonization of these important native species. All sites supported mycorrhizal colonization of some of the experimental species. Average VAMF colonization ranged from 58% to 92% but was unrelated to subjective rankings of land use intensity. These results suggest that VAMF inoculum at all sites was sufficient to support revegetation by at least some species of native plants.

Strategies for Mycorrhizal Inoculation of Six Annual Bedding Plant Species

We inoculated six common annual bedding plant species with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith using two fertilizer P concentrations (3 or 15 μg·mL-1) and three inoculation timings (inoculation at sowing, at transplanting, or at both times). The plant species used were: Salvia splendens F. Sellow ex Roem. & Schult. cv. Firecracker Rose; Impatiens walleriana Hook. f. cv. Sun and Shade Royal Red; Tagetes patula L. cv. Girls Golden; Petunia ×hybrida Hort. Vilm.-Andr. cv. Freedom Blue; Coleus ×hybridus Voss. cv. Jazz Salmon; and Viola ×wittrockiana Gams. cv. Majestic Giant White. In general, Coleus, Petunia, and Viola were colonized more than were Impatiens, Tagetes, and Salvia. Inoculation at sowing required less inoculum than either of the other methods. Moreover, it was generally as effective in promoting colonization as double inoculation, and was often more effective than inoculation at transplanting. Mycorrhizal colonization was significantly reduced by the higher P concentration. The use of Myconate®, a water-soluble form of the flavonoid formononetin, significantly stimulated colonization in Salvia.

Effect of a vesicular-arbuscular mycorrhizal fungus ( Glomus epigaeus ) on herbicide uptake by roots

Vesicular-arbuscular mycorrhizal (VAM) fungi increase root uptake of P and other minerals, but their role in the uptake of herbicides has received far less attention. These experiments were conducted to determine the effect of the VAM fungus, Glomus epigaeus (Daniels and Trappe), on the absorption of atrazine and trifluralin by roots of corn and soybean. Atrazine uptake by excised corn-root segments was consistently increased by the VAM fungus, but VAM enhancement of atrazine uptake by soybeans was less than that observed for corn. Roots from corn grown for 8 weeks in the greenhouse prior to the experiment took up 25 pmol mm–3 root, whereas non-mycorrhizal roots took up only 11 pmol mm–3 root. Soybean and corn root uptake of trifluralin was also enhanced by VAM infection. Addition of P did not increase herbicide uptake by non-VAM plants. The direct role of VAM hyphae on atrazine uptake was demonstrated using a two-chamber system, where only the fungal hyphae had access to 14C-atrazine-treated soil. Hyphal systems of the fungus were able to remove and transfer 14C-atrazine residues from soil to corn plants, demonstrating direct uptake of the herbicide by the fungal hyphae.

The influence of vesicular-arbuscular mycorrhizal fungi alone or in combination with Meloidogyne incognita on Hyoscyamus niger L.

Three vesicular-arbuscular mycorrhizal (VAM) fungi; Glomus aggregatum, Glomus fasciculatum and Glomus mosseae were evaluated for protecting against the reproduction and infection potential of Meloidogyne incognita on black henbane, Hyoscyamus niger. Different VAM fungi enhanced the growth and biomass of the plant. The results also indicated that treatments of plants with VAM fungi increased fresh and dry root and shoot weight and decreased M. incognita populations in both soil and roots in pot experiments. A significant reduction in M. incognita reproduction potential (Rf=4.4) was observed when G. aggregatum was used. Treatment with G. aggregatum alone yielded the highest mycorrhizal infection (88%) followed by G. aggregatum + M. incognita (75%), G. mosseae (69%), G. fasciculatum (57%), G. Mosseae + M. Incognita (53%) and G. fasciculatum + M. incognita (45%). A similar trend was also observed in the multiplication of VAM spores in soil.

Spore-in-spore syndrome in vesicular-arbuscular mycorrhizal fungi and its seasonality in a tropical grassland

Spore-in-spore syndrome in vesicular-arbuscular mycorrhizal fungi and its seasonality in a tropical grassland

The mycorrhizal status of the dominant vegetation along a peatland gradient in southern boreal Alberta, Canada

We investigated the mycorrhizal status of the dominant vascular plant species occurring in ten peatlands along a bog—fen—marsh gradient in southern boreal Alberta in 1997. All members of the Ericaceae were ericoid mycorrhizal, and members of the Salicaceae and Pinaceae were ectomycorrhizal. Also, some members of the Salicaceae and Betulaceae were simultancously ecto- and vesicular-arbuscular mycorrhizal (VAM). Fruiting bodies of the known ectomycorrhizal fungal generaCortinarius, Lactarius, andRussula were collected in late fall. Furthermore, the cosmopolitan ectomycorrhizal taxonCenococcum geophilum was associated with trees and shrubs in all fens and bogs. VA-mycorrhizal fungi were not found in any of the dominant herbaceous plant species in these peatlands; however, vesicles suggesting the presence of VAM fungi were found inCalamagrostis canadensis in the riverine marsh andRubus chamaemorus in the bog. NeitherCarex species in fens and marshes, norTypha latifolia in the lacustrine marsh were mycorrhizal; however, microsclerotia, sclerotial plaques, septate, aseptate, and clamped hyphae were observed to grow on and within cortical cells of their roots. Many of these hyphae were dematiaceous and may belong to theMycelium radicis atrovirens complex (MRA), partially consisting of the endophytic fungal generaPhialocephala andLeptodontidium. Hyphac resemblingRhizoctonia were also observed, although definitive identifications were not attempted. The ecological significance of MRA genera remains largely unknown. Thus, the dominant vegetation in southern boreal bogs and fens is mycorrhizal, possibly enabling these plant species to proliferate in these nutrient-poor ecosystems by accessing otherwise unavailable nutrient pools. In contrast, marsh vegetation is generally non-mycorrhizal, possibly due to higher surface-water nutrient concentrations and fluctuating water levels.

Glomalean mycorrhizal fungi from tropical Australia

A comparison of different methods for isolation of vesicular-arbuscular mycorrhizal (VAM) fungi into open-pot cultures was undertaken as part of a study of the diversity of these fungi. Four different isolation techniques using spores separated from soil, soil trap cultures, root samples, or transplanted seedlings grown in intact soil cores were used to obtain as many fungi as possible from each site. Isolation methods were compared using paired samples from the same locations within natural (savanna, rocky hill, wetland, rainforest) and disturbed (minesite) habitats in a seasonally dry tropical region in the Northern Territory of Australia. There were large differences in (i) the efficiency (rate of increase in mycorrhizal colonisation), (ii) the proportion of successful cultures, (iii) fungal diversity (number of fungal species in each culture) and (iv) specificity (identity of species isolated) between these four procedures. However, the less-efficient procedures generally resulted in a higher proportion of cultures of one fungus, which could be used without further isolation steps. Most species of Scutellospora, Acaulospora and Gigaspora were obtained primarily from field-collected spores, but only 50% of these culture attempts were successful. Spores from these initial cultures produced mycorrhizas much more rapidly and successfully when used to start second-generation cultures. Several species of fungi, rarely recovered as living spores from field soils, were dominant in many trap cultures started from soil or roots. Most of these fungi were Glomus species, that were first distinguished by colonisation patterns in roots and eventually identified after sporulation in second- or third-generation trap cultures. These experiments demonstrated that glomalean fungi in the habitats sampled belonged to two functional categories, based on whether or not spores were important propagules. The "non-sporulating" fungi were dominant in many trap cultures, which suggests that these fungi had higher total inoculum levels in soils than other fungi. Pot-culturing methods provided additional information on fungal diversity which complemented spore occurrence data obtained using the same soil samples and provided valuable new information about the biology of these fungi.

Effects of phosphorus and nitrogen on growth of pasture plants and VAM fungi in SE Australian soils with contrasting fertiliser histories (conventional and biodynamic)

The soil biological community has been reported to differ between conventional and alternative (organic and biodynamic) farming systems. However, few studies have investigated whether this results in substantial differences in the biological pathways controlling major ecosystem processes, such as plant nutrient uptake. This paper describes a glasshouse experiment conducted using a red-brown earth (Natrixeralf) soil sampled from three conventional and three biodynamic irrigated dairy pastures located in the Goulburn River Valley, Victoria, Australia. The biodynamic soils had not had organic or inorganic fertilisers applied for, on average, 17 years, while the conventional soils had received regular inputs of fertilisers containing soluble phosphorus (P) and nitrogen (N). The experiment examined whether the contrasting fertiliser histories had resulted in different pathways of plant nutrient uptake through assessing the response of white clover ( Trifolium repens L.), perennial rye grass ( Lolium perenne L.) and the indigenous vesicular-arbuscular mycorrhizal (VAM) fungi to addition of four levels of soluble P and N. The response to added P and N did not differ between the conventional and biodynamic soils, although, plants in the biodynamic soils had a slower growth rate and a higher level of colonisation by VAM fungi due to lower initial soil P and N concentrations. Overall, there was no indication that the biodynamic and conventional soils had developed substantially different processes to enhance plant nutrient uptake or that the indigenous VAM fungi differed in their tolerance to applications of soluble nutrients.

High coffee population density to improve fertility of an oxisol

The objective of this work was to evaluate the effect of coffee (Coffea arabica L.) population densities on the chemical and microbiological properties of an Oxisol. The work was carried out on soil samples of 0-20 cm depth originated from an experimental site which had been used for coffee tree spacing studies during 15 years, in Paraná State, Brazil. Eight coffee tree populations were evaluated: 7143, 3571, 2381, 1786, 1429, 1190, 1020, and 893 trees/ha. Increasing plant population increased soil pH, exchangeable Ca, Mg, K, extractable P, organic carbon, moisture content and coffee root colonization by vesicular arbuscular mycorrhizal fungi, and decreased exchangeable Al and microbial biomass. Such results were attributed to better erosion control, improved plant residue management and nutrient cycling, and decreased leaching losses. Increasing coffee tree population per unit of area has shown to be an important reclamation recuperation strategy for improving fertility of the acid soils in Paraná, Brazil.

Influences of double aerial CO2 concentration on plant root surface area and viability and infection intensity of vesicular-arbuscular mycorrhizal fungi

Using recently developed methods for root research, an investigation initiated concerning effects of doubled atmospheric CO2 concentration on root surface area and infection of vesicular-arbuscular mycorrhizal (VAM) fungi in seedlings of maize, wheat and soybean. Results showed that doubled CO2 concentration significantly extended root system surface area and promoted VAM fungal infection intensity and viability. However, interspecific variation existed in these responses. It is suggested that plant community succession would be changed due to altered characteristics of roots among species in the future climate.

海藻抽出物がＶＡ菌根菌の菌糸生長ならびにカラタチ樹の菌根形成に及ぼす影響

海藻抽出物がVAM菌の菌糸生長やカラタチ実生苗のVAM形成に及ぼす影響を, Gigaspora ramisporophora SpainというVAM菌を用いて調査を行った.海藻抽出物として, コンブおよびワカメから75%MeOHを用いて抽出したもの(粗抽出物)とともに, これらの粗抽出物からODSカラム使用のフラッシュクロマトグラフィーによって得られた0, 10, 25, 50および100%MeOH溶出物を本実験に供試した.この結果, コンブおよびワカメの粗抽出物処理区におけるVAM菌の菌糸生長は対照(水)区と比較して差異がみられなかったが, コンブの25%MeOH溶出物(0.1および0.3gDW相当量)と50%MeOH溶出物(0.3gDW相当量), ならびにワカメの10%MeOH溶出物(0.3gDW相当量)と25%MeOH溶出物(0.1および0.3gDW相当量)処理区では有意な生長促進効果が認められた.特に, コンブ, ワカメともに, 25%MeOH溶出物(0.3gDW相当量)処理区での促進効果は顕著であった.一方, 土壌へのコンブおよびワカメの粗抽出物ならびに25%MeOH溶出物の処理によって, カラタチ実生苗の菌根感染率は対照区と比べて良好となる傾向が認められた.特にコンブ, ワカメともに, 25%MeOH溶出物(1.0gDW相当量)処理区におけるVAM形成は顕著であった.これらの結果から, コンブおよびワカメ抽出物, 特に25%MeOH溶出物にはVAM菌生長促進物質が存在しており, これがカラタチ根における菌根形成を良好にさせたものと考えられる.

Ecological Aspects of Vesicular-Arbuscular Mycorrhizal Fungi in Satsuma Mandarin Grown in Plastic Green Houses and Fields.

Ecological Aspects of Vesicular-Arbuscular Mycorrhizal Fungi in Satsuma Mandarin Grown in Plastic Green Houses and Fields.

Inoculation with phosphate-solubilizing microorganisms and a vesicular-arbuscular mycorrhizal fungus improves dry matter yield and nutrient uptake by wheat grown in a sandy soil

The effect of inoculating wheat (Triticum aestivum L.) with the PO43–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils.

Inhibition of hyphal growth of a vesicular-arbuscular mycorrhizal fungus in soil containing sodium chloride limits the spread of infection from spores

The hyphal growth of some vesicular-arbuscular (VA) mycorrhizal fungi is inhibited by increasing concentrations of NaCl in soil, and this may influence the formation of mycorrhizas. Our objective was to examine the effect of NaCl on the distance that hyphae of a VA mycorrhizal fungus, Gigaspora decipiens Hall and Abbott can grow through soil and infect roots of a known host plant, Trifolium resupinatum. L. cv. Kyambro. An experimental procedure was developed to enable the effect of NaCl on the pre-symbiotic growth of hyphae of a VA mycorrhizal fungus to be studied separately from other phases of the life-cycle. Roots 1 cm from the spores were infected after 15 d in soils moistened with 0 or 75 m m NaCl, indicating that the initial hyphal growth was not inhibited in soil moistened with 75 m m NaCl. With time, hyphal growth became increasingly inhibited by NaCl, as roots 2.5 cm from the spores were not infected after 26 d in soil moistened with 75 m m NaCl, but were infected in soil without NaCl added. In soil moistened with 150 m m NaCl, roots 1 cm from the spores were infected after 26 d, but roots 2 cm from the spores were not infected after 36 d. Increasing concentrations of NaCl inhibited either the hyphal growth or the infectivity of G. decipiens hyphae after they had grown through soil. The latter may be unlikely, because the infectivity of G. decipiens hyphae placed directly onto the roots was not affected by NaCl. Increasing concentrations of NaCl also inhibited the spread of infection after the initial infection had occurred, and this is probably due to NaCl in the soil inhibiting hyphal growth as well as possibly affecting the supply of carbohydrates from the plant to the fungus.