Species Of Vesicular-arbuscular Mycorrhizal Fungi Research Articles

Pigeon Pea and Cowpea-Based Cropping Systems Improve Vesicular Arbuscular Mycorrhizal Fungal Colonisation of Subsequent Maize on the Alfisols in Central Malawi.

Mycorrhizal associations contribute to the sustainability of crop production systems through their roles in nutrient cycling and other benefits in the soil-plant ecosystems. A two-year study was conducted on the Alfisols of Lilongwe and Dowa districts, Central Malawi, to assess the vesicular-arbuscular mycorrhizal (VAM) fungal colonisation levels in pigeon pea, cowpea, and maize grown in sole cropping, legume-cereal, and legume-legume intercropping systems and in the maize grown in short rotation (year 2) as influenced by the previous cropping systems and N fertilizer application. The gridline intersect method was used to assess the VAM fungal colonisation levels. Results showed that all treatments that included legumes whether grown as sole crop, in legume-cereal or in legume-legume cropping systems in the previous year, had significantly higher (P < 0.05) VAM fungal colonisation of the rotational maize crop roots by a range 39% to 50% and 19% to 47% than those in maize supplied and not supplied with N fertilizer, respectively, in a maize-maize short rotation, at the Lilongwe site. A similar trend was reported for the Dowa site. Furthermore, there were positive correlations between VAM fungal colonisation and the plant P content, dry matter yield, and nodule numbers. Further studies may help to assess the diversity of VAM fungal species in Malawi soils and identify more adaptive ones for inoculation studies.

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.

Effects of soil compaction on phosphorus uptake and growth of Trifolium subterraneum colonized by four species of vesicular–arbuscular mycorrhizal fungi

The ability of four species of vesicular–arbuscular mycorrhizal (VAM) fungi to increase phosphorus uptake and growth of clover plants (Trifolium subterraneum L.) at different levels of soil compaction and P application was studied in a pot experiment. Dry matter in the shoots and roots of clover plants decreased with increasing soil compaction. Colonization by Glomus intraradices Schenck &amp; Smith and Glomus sp. City Beach WUM16 increased plant growth and P uptake up to a bulk density of 1·60 Mg m−3, although the response was smaller as soil compaction was increased. Glomus etunicatum Becker &amp; Gerdeman and Glomus mosseae (Nicol. &amp; Gerd.) Gerdemann &amp; Trappe had no effect on the shoot d. wt and P uptake when the bulk density of the soil was 1·40 and 1·60 Mg m−3, respectively. Soil compaction to a bulk density of 1·60 Mg m−3 had no effect on the percentage of root length colonized by G. intraradices and Glomus sp. City Beach, but total root length colonized decreased as soil compaction was increased. Decreased P uptake and growth of clover plants colonized by G. intraradices and Glomus sp. City Beach, with increasing soil compaction up to a bulk density of 1·60 Mg m−3, was mainly attributed to a significant reduction in total root length colonized and in the hyphal biomass. Soil compaction, which increased bulk density from 1·20 to 1·75 Mg m−3, reduced the O2 content of the soil atmosphere from 0·16 to 0·05 m3 m−3. The absence of any observable mycorrhizal growth response to any of the four species of VAM fungi in highly compacted soil (bulk density = 1·75 Mg m−3) was attributed to the significant decrease in the O2 content of the soil atmosphere, change in soil pore size distribution and, presumably, to ethylene production.

Glomus multiforum and G. verruculosum, two new species from Poland

Two new vesicular-arbuscular mycorrhizal fungal species, Glomus multiforum and G. verruculosum (Glomales, Zygomycetes) coming from northwestern Poland are described and illustrated. Glomus multiforum produces spores singly in the soil. The deep yellow to brown spores are globose to subglobose, (170-)215(-230) μm diam or ovoid, 150–220 × 180–310 μm and have a single wall consisting of three layers. Outermost layer 1 is mucilaginous, hyaline, and stains reddish in Melzer's reagent. Layer 2 of young spores is hyaline and ornamented with ingrowths filling the pits of layer 3; it sloughs with spore age. Layer 3 is laminated, colored and ornamented with evenly distributed pits. Glomus verruculosum forms spores singly in the soil. Spores are yellow to orange, (150-)189(-265) μm diam. Their single wall consists of two layers: a hyaline, semiflexible outer layer and a yellow to orange, laminated inner layer ornamented with warts projecting inward from the innermost lamina. None of these layers stain in Melzer's reagent. Both G. multiforum and G. verruculosum formed spores and vesicular-arbuscular mycorrhizae in single-species pot cultures with Plantago lanceolata and Sorghum sudanense.

Glomus multiforum and G. verruculosum, Two New Species from Poland

Two new vesicular-arbuscular mycorrhizal fungal species, Glomus multiforum and G. verruculosum (Glomales, Zygomycetes) coming from northwestern Poland are described and illustrated. Glomus multiforum produces spores singly in the soil. The deep yellow to brown spores are globose to subglobose, (170-)215(-230) μm diam or ovoid, 150–220 × 180–310 μm and have a single wall consisting of three layers. Outermost layer 1 is mucilaginous, hyaline, and stains reddish in Melzer's reagent. Layer 2 of young spores is hyaline and ornamented with ingrowths filling the pits of layer 3; it sloughs with spore age. Layer 3 is laminated, colored and ornamented with evenly distributed pits. Glomus verruculosum forms spores singly in the soil. Spores are yellow to orange, (150-)189(-265) μm diam. Their single wall consists of two layers: a hyaline, semiflexible outer layer and a yellow to orange, laminated inner layer ornamented with warts projecting inward from the innermost lamina. None of these layers stain in Melzer's reagent. Both G. multiforum and G. verruculosum formed spores and vesicular-arbuscular mycorrhizae in single-species pot cultures with Plantago lanceolata and Sorghum sudanense.

Influence of edaphic and climatic factors on dynamics of root colonization and spore density of vesicular-arbuscular mycorrhizal fungi in Acacia farnesiana Willd. and A. planifrons W.et.A.

A study was conducted to assess the dynamics of vesicular-arbuscular mycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planifrons in moderately fertile alkaline soils. The intensity of root colonization by VAM fungi and the distribution of VAM fungal structures varied with host species over a period of time. The occurrence of vesicles with varied morphology in the mycorrhizal roots indicates infection by different VAM fungal species. This was further confirmed from the presence of spores belonging to different VAM fungal species in the rhizosphere soils. Root colonization and spore number ranged from 56% – 72% and 5 – 14 g – 1soil in A. farnesiana and from 60% – 73% and 5 – 15 g – 1 soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albida, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were isolated from the rhizosphere of A. farnesiana whereas A. scrobiculata,G. pustulatum, G. fasciculatum,G. geosporum and G. microcarpum were isolated from that of A. planifrons. The response of VAM status to fluctuating edaphic factors varied with host species. In A. farnesiana though soil nitrogen (N) was positively correlated with root colonization, soil moisture, potassium and air temperature were negatively correlated to both root colonization and spore number. Per cent root colonization and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were negatively correlated with the density of VAM fungal spores, the same edaphic factors along with soil moisture negatively influenced root colonization.

Correction of dual phosphorus and zinc deficiencies of linseed ( Linum usitatissimum L.) with cultures of vesicular-arbuscular mycorrhizal fungi

A glasshouse experiment demonstrated that cultures of vesicular-arbuscular mycorrhizal fungi (VAMF) can correct dual phosphorus and zinc deficiencies of linseed ( Linum usitatissimum L.) that are typical of long-fallow disorder. Linseed was grown in pots of steamed vertisolic soil from a field site with a history of long-fallow disorder. The soil was inoculated with cultured sppores of several VAMF species in factorial combinations with or without P and Zn fertilizers. Linseed plants without VAMF in steamed soil grew very poorly unless supplied with both P and Zn fertilizers. Inoculation of soil with cultured spores of local VAMF isolates of Glomus mosseae, or a mixture of isolates of G. mosseae and G. etunicatum, markedly improved P and Zn uptake and dry matter accumulation of linseed. Inoculation with spores of an isolate of G. macrocarpum resulted in slower VA-mycorrhizal colonization and poorer shoot growth and seed yield. Non-mycorrhizal plants responded poorly to either P or Zn alone but showed a marked synergistic response to the combination of both elements. My study demonstrates that VAMF are responsible for substantially improving uptake of both P and Zn and increasing growth and seed yield of linseed (99% mycorrhizal dependency). Long-fallowing, which markedly reduces VAMF populations in the soil, can result in dual P and Zn deficiencies in crops that are highly mycorrhizal-dependent. Farming practices that maintain VAMF populations will result in more efficient use of both P and Zn from soil.

Effect of vesicular-arbuscular mycorrhizal fungi on verticillium wilt of cotton

The development of vesicular-arbuscular mycorrhizal fungi (VAMF): Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe, Glomus versiforme (Karsten) Berch, Sclerocystis sinuosa Gerdemann and Bakhi and Verticillium dahliae and the effects of the VAMF on the verticillium wilt of cotton (Gossypium hirsutum L. and Gossypium barbadense L.) were studied with paper pots, black plastic tubes and clay pots under natural growth conditions. All of the tested VAMF were able to infect all the cotton varieties used in the present experiment and typical vesicles and arbuscules were formed in the cortical cells of the cotton roots after inoculation. The cap cells, meristem, differentiating and elongating zones of the root tip were found to be colonized by the VAMF. In the case of most V. dahliae infection, the colonization occurred mostly from the root tip up to 2 cm. VAMF and V. dahliae mutually reduced their percentage of infection when inoculated simultaneously. VAMF inoculation reduced the numbers of germinable microsclerotia in the soil of the mycorrhizosphere, while the quantity of VAM fungal spores in the soil was not influenced by infection of with V. dahliae. The % of arbuscule colonization in roots was negatively correlated with the disease grades, while the numbers of vesicles in roots were not. These results suggest that certain vital competition and antagonistic reactions exist between VAMF and V. dahliae. VAMF reduced the incidence and disease indices of verticillium wilt of cotton during the whole growth phase. It is evident that cotton seedling growth was promoted, flowering was advanced, the numbers of flowers and bolls were increased, and this resulted in an increase in the yield of seed cotton. Among the VAMF species, Glomus versiforme was the most effective, and Sclerocystis sinuosa was inferior. So far as the author is aware, such an effect of VAMF on the increase of cotton wilt tolerance/resistance is reported here far the first time.

Effect of fungicides on vesicular-arbuscular mycorrhizal infection and nodulation in groundnut ( Arachis hypogea L.)

The effects of field application rates of six fungicides (Bavistin, Dithane, Emisan, Fytolan, Thiram and Ziram), applied both as seed dress and soil drench, on the formation and function of vesicular-arbuscular mycorrhizal (VAM) and rhizobial nodular systems in groundnut ( Arachis hypogea L.) were investigated. Fytolan treatment produced a remarkable range of positive responses in VAM infection and spore production, rhizobial nodulation and growth and yield of the host plant. The other fungicides restricted mycorrhizal infection to different levels. The rhizosphere spore count was increased in the early growth stages of the host by fungicides, but declined in the later stages. Their effect on sporulation varied depending on VAM fungal species. Root nodulation, growth and yield of the host plant were not significantly affected by the application of fungicides, excepting the interference of Emisan in the early growth stages. The inhibitory effects of Emisan on the VAM and Rhizobium colonisation resulted in a significant decrease in the growth and yield of the host plant.

Fitting plants to soil through mycorrhizal fungi: plant nutrition in host-endophyte combinations evaluated by the diagnosis and recommendation integrated system

Vesicular-arbuscular mycorrhizal (VAM) fungi improve plant growth in marginal soils. This study was conducted to determine the effects of three species of VAM fungi on plant nutrition in two cultivars of corn (Zea mays L.) and one of sunflower (Helianthus annus L.). Plants were grown in pot cultures under controlled (greenhouse) conditions in a soil high in K, Mg, and P, and low in Ca and N, and were supplied with amounts of VAM-fungal inocula in which equal numbers of infective propagules had previously been determined. Analysis of variance showed highly significant main effects and interactions due to both factors (plant and fungus) for N, P, Ca, and Mg. For K, only plant effects were significant (P<0.043). The uptake of nutrients was selectively enhanced or inhibited by one or the other VAM fungus relative to non-VAM control plants. In sunflower, N concentration was markedly enhanced (73%) by the mixed inoculum of the three fungi, even though individual effects were not significant. Evaluation of leaf nutrient analyses by the Diagnosis and Recommendation Integrated System (DRIS) revealed the utility of this system to rank nutritional effects by VAM fungi in an order of relative nutrient deficiency. The DRIS therefore is seen as a useful tool in evaluating and selecting VAM fungi for the alleviation of specific nutrient disorders.

Fitting plants to soil through mycorrhizal fungi: Mycorrhiza effects on plant growth and soil organic matter

Vesicular-arbuscular mycorrhizal (VAM) fungi affect diverse aspects of plant form and function. Since mycorrhiza-mediated changes in host-plant responses to root colonization by different VAM fungi vary widely, it is important to assess each endophyte for each specific effect it can elicit from its host as part of the screening process for effectiveness. Three species of VAM fungi and a mixture of species were compared with non-VAM controls for their effects on soil organic matter contents and on nutrition and morphology in two varieties (native and hybrid) of corn (Zea mays L.) and one of sunflower (Helianthus annuus L.) in P-sufficient and N-deficient soil in pot cultures. Differences in soil organic matter due to the fungal applications were highly significant with all host plants. Native corn responded more to VAM colonization than the hybrid did; differences in treatments were significant in leaf area, plant biomass, and root: shoot ratio in the former, but not in the latter. Responses in the sunflower were similar to those in the native corn. Significant VAM treatment-related differences in shoot N and P contents were not reflected in shoot biomass, which was invariant. Correlations between plant or soil parameters and the intensity of VAM colonization were found only in soil organic matter with the native corn, in specific leaf area in the hybrid corn, and in plant biomass in the sunflower. The presence of the different endophytes and not the intensity of colonization apparently elicited different host responses.

Factors affecting appressorium development in the vesicular–arbuscular mycorrhizal fungus Glomus mosseae (Nicol. &amp; Gerd.) Gerd. &amp; Trappe

SUMMARYInvestigations on the luck of appressorium formation in the roots of the non‐host plant Lupinus albus L. showed that root exudates do not inhibit mycelial growth of the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. &amp; Gerd.) Gerd. &amp; Trappe, but that they hinder hyphal attachment and fungal recognition of roots. Exudates do not stimulate hyphal proliferation in the rhizosphere. G. mosseae hyphae were able to recognize and attach to excised root of both lupin and host plants, forming swellings resembling apressoria. No growth of G. mosseae hyphae was observed around simulated roots consisting of nylon, silk, polyamide and glass threads, whereas appressoria were formed on heterologous hyphae of VAM fungal species. The hypothesis that a purely thigmotropic stimulate could trigger hyphal attachment and the further differentiation of appressoria was excluded.

Plant and Soil Controls on Mycorrhizal Fungal Communities

A field experiment was conducted to examine the relative importance of soil factors and plant species on communities of vesicular—arbuscular mycorrhizal (VAM) fungi. Populations of VAM fungal spores were studies in 4—yr—old monocultures of five successional grass species grown in gradient of soil mixtures ranging from pure subsurface sand to pure sandy loam topsoil. A total of 19 species of VAM fungi were found across all treatments. Of the 12 most abundant VAM fungal species, 6 species had a significant dependence on both soil mixture and host species, while 2 were dependent only on soil and 2 only on host. To our knowledge, these are the first results indicating that even closely related hosts (five grasses) may cause divergence in VAM fungal communities on initially identical soils. Cluster analysis of the similarity of fungal communities by host plant species showed that fungal communities in the two late successional grasses to be most similar to one another and least similar to the fungal communities in the early successional grass species. Cluster analysis of the similarity of fungal communities by soil mixture showed the fungal communities in the sandy end of the soil gradient diverged predictably from the fungal communities in the black soil end of the gradient. These results support the hypothesis that soil factors and plant species may be of equal importance in regulating the species composition of VAM fungal communities.

Mycorrhizae: Possible Explanation for Yield Decline with Continuous Corn and Soybean

AbstractEarlier studies showed that mycorrhizal fungi selectively proliferate in soils cropped in monoculture to corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. This study evaluated whether the dominant mycorrhizal fungi, based on spore numbers present in soil, affected growth and nutrient uptake of the following crop. Plots at two locations in Minnesota with a continuous corn or continuous soybean history were planted to both corn and soybean. The relationship between spore numbers of proliferating species of mycorrhizal fungi and crop yield and nutrient concentrations were assessed using simple correlation analysis. Spore populations of mycorrhizal fungi which proliferated in corn were generally negatively correlated with the yield and tissue mineral concentrations of corn, but were positively correlated with the yield and tissue mineral concentrations of soybean. Spore populations of soybean proliferators exhibited the reciprocal relationship, although less clearly. We suggest that, compared to other fungi, proliferating VAM fungal species may be less beneficial (or perhaps detrimental) to the crop in which they proliferate. We propose a mechanism to explain how vesicular‐arbuscular mycorrhizal (VAM) fungi could cause yield depressions associated with monoculture, and outline research needed to test this hypothesis.

Multiple mycorrhizal associations of individual calcicole host plants in the alpine grass-heath zone

Mycorrhizal colonization of the fibrous roots of alpine grasses and perennial herbs in microhabitats on rendzina soil were examined. Various host plants were associated simultaneously with more than one species of vesicular-arbuscular mycorrhizal fungi. All dominant graminoids had a high degree of endomycorrhizal infection. Septate endophytes (Phialophora sp., Rhizoctonia sp.) often occurred together with Acaulospora sp., Glomus tenue, G. tortuosum and Scutelispora calospora on individual hosts.

Dynamics of vesicular-arbuscular mycorrhizae during old field succession.

The species composition of vesicular-arbuscular mycorrhizal (VAM) fungal communities changed during secondary succession of abandoned fields based on a field to forest chronosequence. Twenty-five VAM fungal species were identified. Seven species were clearly early successional and five species were clearly late successional. The total number of VAM fungal species did not increase with successional time, but diversity as measured by the Shannon-Wiener index tended to increase, primarily because the community became more even as a single species, Glomus aggregatum, became less dominant in the older sites. Diversity of the VAM fungal community was positively correlated with soil C and N. The density of VAM fungi, as measured by infectivity and total spore count, first increased with time since abandonment and then decreased in the late successional forest sites. Within 12 abandoned fields, VAM fungal density increased with increasing soil pH, H2O soluble soil C, and root biomass, but was inversely related to extractable soil P and percent cover of non-host plant species. The lower abundance of VAM fungi in the forest sites compared with the field sites agrees with the findings of other workers and corresponds with a shift in the dominant vegetation from herbaceous VAM hosts to woody ectomycorrhizal hosts.

The mycorrhizal status of Arbutus unedo in relation to compatible and incompatible fungi

Ectendomycorrhizae of Arbutus unedo L. were synthesized in the laboratory and were observed over the first 80 days of development. After 40 days some roots showed many hyphae running around enlarged tips, on the 60th day short roots had assumed a clavate form, and on the 80th day mycorrhizae could be observed with the naked eye. The laboratory-synthesized ectendomycorrhizae had a cruciform structure and were smooth, shiny, and pale orange-brown. They presented a loose sheath and a Hartig net. The first layer of cortical root cells was invaded by the fungus. Running hyphae and vesicles of Glomus microcarpum invaded A. unedo roots, but no root invasion was observed in the presence of five other vesicular–arbuscular mycorrhizal fungal species. The ericoid mycorrhizal fungus Hymenoscyphus ericae caused a darkening of cortical cells and root tips and the death of many seedlings. The correspondence between specific plant species and particular kinds of mycorrhizae and the possibility of intracellular colonization by nonspecific fungi are also discussed.

Effects of species of VA-mycorrhizal fungi on growth and mineral uptake of sorghum at different temperatures

Sorghum [Sorghum bicolor (L.) Moench] plants were grown in growth chambers at 20, 25 and 30°C in a low P Typic Argiudoll (3.65 µg P g−1 soil, pH 8.3) inoculated with Glomus fasciculatum, Glomus intraradices, and Glomus macrocarpum to determine effects of vesicular-arbuscular mycorrhizal fungi (VAMF) species on plant growth and mineral nutrient uptake. Sorghum root colonization by VAMF and plant responses to Glomus species were temperature dependent. G. macrocarpum colonized sorghum roots best and enhanced plant growth and mineral uptake considerably more than the other VAMF species, especially at 30°C. G. fasciculatum enhanced shoot growth at 20 and 25°C, and mineral uptake only at 20°C. G. intraradices depressed shoot growth and mineral uptake at 30°C. G. macrocarpum enhanced shoot P, K, and Zn at all temperatures, and Fe at 25 and 30°C above that which could be accounted for by increased biomass. Sorghum plant growth responses to colonization by VAMF species may need to be evaluated at different temperatures to optimize beneficial effects.

Variation in propagule numbers of vesicular-arbuscular mycorrhizal fungi in a semi-arid soil

Measured by the MPN method, low densities of propagules of vesicular-arbuscular mycorrhizal fungi were found in a soil from a semi-arid site in South Australia. The only spores that germinated within 7 days were found more than 10 cm down the soil profile. The proportion of germinated spores of Scutellospora calospora was greater than the measured density of propagules, suggesting that the MPN method underestimates the number of propagules. Spores are unlikely to be important for the initiation of vesicular-arbuscular mycorrhizas at the site, since pre-germinated seedlings transplanted to moistened soil became mycorrhizal within 6 days. The only spores found below 30 cm in the profile did not survive when exposed to the wet/dry cycles which occur at the soil surface over summer. The results suggest that different species of vesicular-arbuscular mycorrhizal fungi have different survival strategies for existence at the study site.

Selection of A Vesicular-Arbuscular Mycorrhizal Fungus for Practical Inoculation ofUniola Paniculata

(1988). Selection of A Vesicular-Arbuscular Mycorrhizal Fungus for Practical Inoculation of Uniola Paniculata. Mycologia: Vol. 80, No. 4, pp. 565-568.