Spore Diversity Of Arbuscular Mycorrhizal Fungi Research Articles

Soil Arbuscular Mycorrhizal Fungal Communities Differentially Affect Growth and Nutrient Uptake by Grapevine Rootstocks.

Arbuscular mycorrhizal fungi (AMF) deliver potentially significant services in sustainable agricultural ecosystems, yet we still lack evidence showing how AMF abundance and/or community composition can benefit crops. In this study, we manipulated AMF communities in grapevine rootstock and measured plant growth and physiological responses. Glasshouse experiments were set up to determine the interaction between rootstock variety and different AMF communities, using AMF communities originating under their own (i.e., "home") soil and other rootstocks' (i.e., "away") soil. The results revealed that specific AMF communities had differential effects on grapevine rootstock growth and nutrient uptake. It was demonstrated that a rootstock generally performed better in the presence of its own AMF community. This study also showed that AMF spore diversity and the relative abundance of certain species is an important factor as, when present in equal abundance, competition between species was indicated to occur, resulting in a reduction in the positive growth outcomes. Moreover, there was a significant difference between the communities with some AMF communities increasing plant growth and nutrient uptake compared with others. The outcomes also demonstrated that some AMF communities indirectly influenced the chlorophyll content in grapevine leaves through the increase of specific nutrients such as K, Mn, and Zn. The findings also indicated that some AMF species may deliver particular benefits to grapevine plants. This work has provided an improved understanding of community level AMF-grapevine interaction and delivered an increased knowledge of the ecosystem services they provide which will benefit the wine growers and the viticulture industry.

The Role of Arbuscular Mycorrhizal Fungi Density and Diversity on The Growth and Biomass of Corn and Sorghum Forage in Trapping Culture

This study aimed to determine the effectiveness of arbuscular mycorrhizal fungi (AMF) in the absorption of nutrients in trapping culture and its effects on the growth and biomass production of corn ( Zea mays L.) and sorghum ( Sorghum sp.). Soil samples with rhizosphere were collected from three different places: Bambusa sp., Cichorium intybus L., and Pinus merkusii . The density and genus of AMF spores were evaluated. AMF effectiveness was tested using six levels of rhizosphere and two species (corn and sorghum) of plants with a 2×6 factorial experiment with eight replications of each treatment. Six types of rhizospheres were: (i) bamboo rhizosphere ( Bambusa sp.) (T1), (ii) control for T1 (C1), (iii) chicory rhizosphere ( C. intybus L.) (T2), (iv) control for T2 (C2), (v) Pine rhizosphere ( P. merkusii ) (T3), and (vi) control for T3 (C3). The control treatment was derived from sterilized planting media. The results showed that the root rhizosphere of Bambusa sp. had more density and diversity of AMF spores than the root rhizosphere of C. intybus L. and P. merkusii . At the end of the trapping culture, the host plants sorghum and corn increased the density of spores in the carrier medium or propagules of the three rhizosphere types. The difference in the amount of initial AMF had a significant (p<0.05) effect on plant height, the number of leaves, and the biomass production of trapping plants. It can be concluded that more density and colonization of arbuscular mycorrhizal spores show higher growth and biomass of trapping plants.

Arbuscular Mycorrhizal Association with Rattan Species of the Belum-Temengor Forest Complex, Perak, Malaysia

Rattan Calamus spp. is a high commercial value palm from the subfamily Calamoideae the primary source for cane in the well-developed rattan industry. Most studies on rattan have focused on its biodiversity, distribution, quality, strength, physical, mechanical, and morphological properties and genetics. Still, only a few have investigated the association of rattan with arbuscular mycorrhizal (AM) fungi. These mycorrhizal fungi are well known to play essential functions as promoting plant growth, maintaining plant community biodiversity and nutrient cycles in soil. This study aims to identify the established AM fungi community and their ecological interactions with Calamus spp. in the Belum-Temengor Forest Complex, Perak, Malaysia. Calamus spp. roots and their rhizospheric soil samples were collected from six sampling sites in the Belum-Temengor Forest Complex, one of the oldest rainforests in the world. The degree of mycorrhizal colonisation in Calamus spp. was evaluated using the grid lines method. At the same time, the AM fungi spore diversity in the rhizospheric soils were isolated using the wet sieving method and identified taxonomically analysed into different genera. Calamus insignis showed the highest degree of mycorrhizal colonisation amongst all the Calamus spp. present on the sampling sites. The AM fungi spores isolated from the rhizospheric soil from Belum-Temengor Forest Complex belonged to the genera Acaulospora, Entrophospora, Gigaspora, Glomus, and Scutellospora. Glomus was the most frequently found genus in all the sampling sites. This study is the first record of the AM fungal diversity found in the Belum-Temengor Forest Complex.

Phosphorus Fractions and Arbuscular Mycorrhizal Fungi Communities in a Tropical Coarse-Textured Soil under Natural Forest and Para Rubber Ecosystems

Soil phosphorus (P) plays an essential role in rubber tree plantations that are rapidly and extensively being established in Southeast Asia. However, available information is quite limited on soil P fractions and arbuscular mycorrhizal fungi (AMF) in the tropical region. Herein, we investigated P fractions and AMF community under natural forest and rubber plantations at different ages of 5 years, 11 years, and 22 years in tropical coarse-textured soils from Thailand. The studied loamy sand soils were acidic (pH=5.0-5.7) with low available P concentrations (1.73-6.48 mg/kg). Data on the P fractions data revealed that the labile P (water-extractable Pi and NaHCO3-extractable Pi) and moderately labile P (NaOH0.1-extractable Po and HCl-extractable Pi) pools in rubber-growing soils were higher than those in the natural forest soil. Elevated values of these properties were substantial with increasing stand ages. The rubber monocropping systems declined in the density and diversity of AMF spores compared to the natural forest site. Glomus badium, Rhizophagus fasciculatus, Acaulospora Laevis, and Ambispora appendiculata were the most dominant and tolerant AMF species across the rubber stands (&gt;50% of the total species). The P fractions and AMF were correlated with soil labile-P forms. Soil labile and moderately P fractions were the important factors affecting the difference in AMF community. This study highlighted that long-term rubber plantations in tropical ecosystems promoted labile P fraction but demoted AMF density and diversity.

Diversity of Arbuscular Mycorrhizal Fungi Species Associated with Soybean (&amp;lt;i&amp;gt;Glycine max&amp;lt;/i&amp;gt; L. Merill) in Benin

Arbuscular Mycorrhizal Fungi (AMFs) could be used to sustainably improve crop yields. The present study evaluated the diversity of AMF species associated with soybean (Glycine max L. Merill) in main soybean-producing areas in Benin. Composite soil samples from 13 production areas at a rate of 04 villages per production areas were collected. A spore trapping device was set up to reveal the diversity of spores. The physical and chemical properties of the soils, the frequency and intensity of mycorrhization of roots, and the diversity of AMF spores were determined in the soil samples following trapping. As result, eight morphotypes belonging to four genera: Glomus, Acaulospora Gigaspora and Disversispora and three families: Diversisporales, Glomérales and Paraglomérales were observed. An important variability of spore densities was observed from one production areas to another with a higher abundance in the production areas of Copargo estimated at 3584 spores/100g soil. The biological diversity indexes as Shannon (0.0311), Simpson (0.0204) and Hill (0.0235), varied significantly (p < 0.05) from one production areas to another. There was significant correlation between the parameters studied, particularly between the physico-chemical parameters of the soils and between the physico-chemical parameters and the biological diversity indexes. For the mycorrhization parameters, the mycorhization frequencies did not vary from one production areas to another, unlike the intensities, which significantly varied from one production areas to another (2.31% to 24.62%). Finally, this study revealed that the physico-chemical parameters of the soils had an influence on the other parameters studied. Moreover, there were an abundance and a significant diversification of AMFs associated with soybean in the different production areas, which are influenced by certain physico-chemical soil parameters.

Arbuscular mycorrhizal and dark septate fungi are not common in roots of epiphytic pteridophytes of a transitional forest area in South Brazil

Arbuscular mycorrhizal fungi (AMF) and dark septate fungi (DSF) are symbionts that are associated with the roots of plants, including epiphytic lycophytes and ferns. Paris-type mycorrhiza and glomoid structures are the most common forms of colonization in these plants. This work aimed to evaluate the occurrence of these symbionts in the roots of epiphytic lycophytes and ferns as well as the diversity of AMF spores recovered from substrate associated with the roots of eleven species. Roots of Asplenium gastonis, Campyloneurum aglaolepis, C. nitidum, Niphidium crassifolium, Pecluma pectinatiformis, Phlegmariurus mandiocanus, Pleopeltis hirsutissima, P. pleopeltifolia andSelaginella microphyllahad hyphae and vesicles typical of AMF colonization, but not arbuscules.Campyloneurum nitidum, Pecluma pectinatiformis, Phlegmariurus mandiocanus, Pleopeltis pleopeltifolia and Selaginella microphyllahad melanized hyphae and microsclerotia typical of DSF. All species colonized by DSF were also colonized by AMF. Seventeen spore morphotypes of AMF were identified, of which six were acaulosporoid and eleven glomoid. Glomus aff. formosanum andAcaulospora aff. lacunosa were the most abundant and frequent species. Epiphytic lycophytes and ferns host concurrently AMF and DSF but colonization is scanty in their roots. For the first time, acaulosporoid spores and intraradical vesicles are reported for this group of plants.

Bracken fern does not diminish arbuscular mycorrhizal fungus inoculum potential in tropical deforested areas.

Tropical montane forests are threatened by uncontrolled fire events because of agricultural expansion. Consequently, deforested areas frequently are dominated by the bracken fern, Pteridium spp., for long periods, and forest regeneration is limited. Despite considerable research on bracken-dominated ecosystems, little is known about the relationship between bracken mycorrhizal fungi and tree seedlings. Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with terrestrial plants, providing nutrients and protection against pathogens and promoting seedling growth and establishment. Therefore, AMF inoculum have high potential for forest restoration programs. Here, we compare the species diversity of AMF spores, root colonization, and seedling growth of Clusia trochiformis 1year after the addition of different liquefied root inocula: forest conspecific, forest heterospecific, and from Pteridium rhizomes. Thirteen morphospecies of arbuscular mycorrhizal fungi were identified on the roots of C. trochiformis, and Glomus spp. were the most abundant in all treatments. No differences were observed in spore species richness and diversity among treatments, but spore density was the highest subsequent to the Pteridium inoculum. There was no significant difference in mycorrhizal root colonization and seedling growth of C. trochiformis among inoculated treatments. We found a positive relation between root colonization and total biomass. This study shows that the AMF communities in bracken areas and forests present similar characteristics and that the bracken fern does not limit AMF inoculum potential, favouring seedling growth of Clusia.

Inga edulis Mart. intercropped with pasture improves soil quality without compromising forage yields

This study evaluated the effect of Inga edulis trees on soil quality attributes and forage yield and moisture in a pasture field in the county of Carrancas, Minas Gerais, Brazil. Soil samples were collected under the canopy and beyond the canopy projection of five I. edulis trees, at four distances from the tree trunks to beyond the canopy projection, along the radius line. A randomized block design was used, in which five trees represented five blocks and the four distances from the trees corresponded to the treatments. The forage yield and moisture, soil moisture and chemical attributes, density and diversity of arbuscular mycorrhizal fungi (AMF) spores and the presence of nodule-forming nitrogen-fixing bacteria in legumes were evaluated. The statistical analysis was performed using ANOVA and the Scott-Knott test (p = 0.05). No statistical differences between forage yield and moisture were found in the soil under or beyond the canopy projection. The soil quality was elevated, indicated by the improved soil pH, base saturation, sum of bases and effective cation exchange capacity in the samples collected closer to I. edulis. No changes in the density and diversity of AMF spores or in the nodulation and development of inoculated seedlings were observed in soil collected at different distances from the trees. Consequently, I. edulis trees can be intercropped with pasture to increase the soil quality without affecting forage yields.

CHARACTERIZATION OF RHIZOBIA AND ARBUSCULAR MYCORRHIZAL FUNGI IN AREAS IMPACTED BY GRAVEL MINING IN BRAZIL

ABSTRACT On-shore oil exploration is one of the main economic activities in the semiarid region (Caatinga biome) of the state of Rio Grande do Norte (RN), Brazil. Gravel mining is an activity associated with oil exploration that causes environmental impacts. Gravel is a base-material for constructions, such as roads and pumpjack bases. The areas of gravel mining and other decommissioned areas where the gravel has been deposited must be revegetated with species native to the biome at end of the activity in the site. An efficient strategy for revegetation of degraded areas has been the planting of leguminous species that can associate with rhizobia and arbuscular mycorrhizal fungi (AMF). Nevertheless, the impact of mining activities on the autochthonous populations of these microorganisms is unknown. The objective of the present work is to characterize the density of rhizobia and AMF spores in four areas impacted by the oil exploration in RN when compared to non-impacted adjacent areas. Gravel samples were collected in dry and rainy seasons in two mining areas: one in a pumpjack base, and one in a waste disposal area. Surface soil (topsoil) samples were collected in adjacent areas with native Caatinga vegetation. Assays were carried out to evaluate the most probable number (MPN) of rhizobia and to identify the type and density of arbuscular mycorrhizal fungi (AMF), using rhizobia trap plants Mimosa tenuiflora (Mart.) Benth. and Mimosa caesalpiniifolia Benth. The MPN of rhizobia was low in all areas, but higher in the rainy season. The highest amount and diversity of AMF spores were found in the dry season. Among the symbiotic microorganisms studied, the AMF presented lower densities in the evaluated areas when compared to those in the adjcent native vegetation areas, denoting the impact of this activity.

Intercropping Acacia mangium stimulates AMF colonization and soil phosphatase activity in Eucalyptus grandis

Arbuscular mycorrhizal fungi (AMF) are very important to plant nutrition, mostly in terms of acquisition of P and micronutrients. While Acacia mangium is closely associated with AMF throughout the whole cycle, Eucalyptus grandis presents this symbiosis primarily at the seedling stage. The aim of this study was to evaluate the dynamics of AMF in these two tree species in both pure and mixed plantations during the first 20 months after planting. We evaluated the abundance, richness and diversity of AMF spores, the rate of AMF mycorrhizal root colonization, enzymatic activity and soil and litter C, N and P. There was an increase in AMF root colonization of E. grandis when intercropped with A. mangium as well as an increase in the activity of acid and alkaline phosphatase in the presence of leguminous trees. AMF colonization and phosphatase activities were both involved in improvements in P cycling and P nutrition in soil. In addition, P cycling was favored in the intercropped plantation, which showed negative correlation with litter C/N and C/P ratios and positive correlation with soil acid phosphatase activity and soil N and P concentrations. Intercropping A. mangium and E. grandis maximized AMF root colonization of E. grandis and phosphatase activity in the soil, both of which accelerate P cycling and forest performance.

Arbuscular mycorrhizal fungal communities in an iron mining area and its surroundings: Inoculum potential, density, and diversity of spores related to soil properties

ABSTRACT Arbuscular mycorrhizal fungi (AMF) interact symbiotically with most plant species, facilitating revegetation of areas under rehabilitation. The aim of this study was to evaluate the inoculum potential, density, and diversity of AMF spores in five environments, as well as the relation of species with soil properties. Soil samples were collected in five environments in a mining area and its surroundings in the Quadrilátero Ferrífero, Minas Gerais (Brazil): tailings piles in rehabilitation with grass, canga, Cerrado, native forest, and eucalyptus plantation; these samples were subjected to chemical and physical analyses. Spores were directly extracted from field samples and from trap cultures (TCs) established in two locations in the Southeast and South regions of Brazil for taxonomic identification of the species. Species richness, the Shannon diversity index (H’), and equitability were determined. Principal component analysis (PCA) was used to identify soil properties that most influenced AMF occurrence. Spore density showed no significant difference among the environments. A total of 59 AMF species were found. This is the first report of the occurrence of Acaulospora nivalis and Acaulospora alpina in Brazil. Higher H’ and species richness in the field were found in tailings piles and lower in canga. Canga showed higher inoculum potential. The development of TCs in two locations allowed a wider diversity of AMF species to be captured. Environments of the Quadrilátero Ferrífero are hotspots of AMF diversity, and the soil pH and exchangeable S and P contents are the properties that best explain the distribution of AMF species.

Impacto do controle de plantas espontâneas sobre propágulos de fmas e micorrização de cafeeiro

A manutenção de uma comunidade diversificada e ativa de fungos micorrízicos arbusculares (FMAs) em ecossistemas agrícolas é importante para a sustentabilidade de culturas como a do cafeeiro. Este trabalho teve como objetivo avaliar o efeito de técnicasde controle de plantas espontâneas, aplicadas na entrelinha do cafeeiro, sobre a ocorrência de propágulos de FMAs e, consequentemente, namicorrização desta cultura. Esta avaliação foi realizada em uma lavoura de café da Fazenda Experimental da Empresa de Pesquisa Agropecuária de Minas Gerais (Epamig), em São Sebastião do Paraíso (MG). As técnicas de controle de plantas espontâneas foram: 1) roçadora, 2) grade, 3) enxada rotativa, 4) herbicida de pré-emergência, 5) herbicida de pós-emergência, 6) capina manual e 7) controle sem capina. As variáveis analisadas foram: intensidade e porcentagem de colonização, comprimento de micélio ativo e total no solo, densidade e diversidade de esporos. Entre as técnicas de controle de plantas espontâneas nas entrelinhas de cafeeiro, a aplicação de roçadora, de grade e de capina manual foram as que mais favoreceram a manutenção dos propágulos de FMAs e a micorrização das plantas, contrariamente ao uso de herbicidas de pré-emergência.

Diversity of Arbuscular Mycorrhizal Fungi of Durum Wheat (Triticum durum Desf.) Fields of the East of Algeria

In Algeria, in the semi-arid and arid areas cereal production is limited because of many constraints like lack of mineral elements (phosphorus and nitrogen), low organic matter and an insufficient water reserve due to the low rainfall. Most researches on durum wheat (Triticum durum Desf.) are undertaken to increase its productivity. In recent years several methods have been used including using microorganisms. Arbuscular Mycorrhizal fungi (AMF) appear to have important roles in plants in various soil conditions. In Algeria and particularly in the eastern regions, the diversity of AMF spores in the soil is so far little studied. In this context this study focuses on the study of the diversity and the abundance of AMF spores in Triticum durum Desf. fields in arid, semi-arid and coastal regions. Soil samples were collected and characterized and the spores isolated by the wet sieving methods were observed, counted and identified. The results of the physic-chemical characterization of all soil samples reveal a clay loam, loam clay and loam sandy soils with an alkaline pH (7.54-8.27), a total nitrogen content from 0.023 to 0.082% and phosphorus content ranging from 1.63% to 7.74%. We noted the presence of several morphotypes that were classified as follow: Glomeraceae, Acaulosporaceae and Scutellosporaceae with a predominance of Glomeraceae in different sites depending on climate and soil type. The presence of these families demonstrates a biodiversity of the eastern wheat fields of Algeria.

Diversity of arbuscular mycorrhizal fungi in undisturbed forest, slash-and-burn field, and monoculture forest of Indo-Burma megadiverse region

Conversion of pristine forests to agricultural lands is one of the leading causes of biodiversity loss worldwide. To assess the impact of such forest disturbance on microbial diversity, we investigated the diversity of arbuscular mycorrhizal fungi (AMF) in the rich forests of Karbi Anglong hills of Assam, a biodiversity hotspot part of Indo-Burma region. AMF spore diversity was assessed in distinct study sites with different intensities of disturbances that encompassed a pristine undisturbed forest (UF), slash-and-burn field (SBF), and monoculture forest (MF). A total of 35 arbuscular mycorrhizal (AM) fungal species belonging to 9 genera were isolated. Species forming glomoid spores were dominant in all the three sites followed by acaulosporoid spores. Highest spore density was found in UF and lowest in MF. Multivariate analyses revealed similarity in UF and SBF. It was found that in MF, AMF diversity was significantly modified and reduced, resulting in an ecological degraded ecosystem. Our results show that natural UF and SBF contained similar and a high AM fungal diversity. The AM fungal diversity is not significantly affected by the slash-and-burn agricultural land use practices practised by the ethnic hilly tribes and, therefore, could be a component of a tropical forest “conservation-agriculture matrix.” Also because of the high generic and species diversity found, this region can be considered as AMF hotspot and a priority place for conservation.

Fungos micorrízicos arbusculares em um latossolo vermelho sob manejos e usos no cerrado

As modificações nas comunidades de fungos micorrízicos arbusculares (FMAs) induzidas por mudança de uso do solo e por diferentes usos agrícolas ainda são insuficientemente estudadas, particularmente no Cerrado. O presente estudo teve como objetivo avaliar como a interferência antrópica pelo manejo e mudança de uso do solo atua sobre a densidade de esporos e diversidade dos FMAs em um Latossolo Vermelho distroférrico de Cerrado. O estudo avaliou cinco áreas: Mata Ciliar (MC), Borda da Mata (BM), Pastagem (Past), Plantio Direto (PD) e Área Desmatada (AD). Foram retirados 20 pontos amostrais, em delineamento inteiramente casualizado, para avaliação da densidade de esporos e diversidade de FMAs. Cada ponto amostral representava uma área de 250 m² dentro de cada área. A área com o sistema de PD e a AD apresentaram menor densidade de esporos recuperados e baixa colonização micorrízica em relação às demais áreas devido à baixa quantidade de plantas vegetando nelas. As famílias de FMAs que apresentaram maior ocorrência nas áreas estudadas foram Acaulosporaceae, Glomeraceae e Gigasporaceae, sendo as duas primeiras dominantes nos ambientes menos antropizados de MC e BM. As espécies de FMAs de maior ocorrência foram Acaulospora scrobiculata, Glomus macrocarpum e Acaulospora tuberculata; as duas primeiras apareceram em todas as áreas, e a terceira apenas não ocorreu na área de PD. Essas espécies mostraram grande capacidade de adaptação aos ambientes alterados. As espécies Acaulospora rehmii, Acaulospora sp.3, Glomus etunicatum, Glomus tortuosum, Glomus sp.1, Gigaspora sp.2 e Scutellospora heterogama apresentaram baixa ocorrência, sendo recuperadas somente em uma das áreas estudadas. A área com maior densidade e ocorrência de espécies foi a Past, com 414 esporos (indivíduos) e 11 espécies. As áreas extremas quanto à diversidade de Shannon (H') foram a Past e a BM, com maior e menor índices, respectivamente. A análise de componentes principais indicou a formação de três grupos, sendo o primeiro formado pela MC e BM; o segundo, por AD e PD; e o terceiro, somente por Past. Conclui-se que a mudança no uso do solo promove alterações na comunidade de FMAs, podendo a densidade e diversidade de esporos ser ampliadas, no caso da pastagem, ou reduzidas, no caso de desmatamento.

Long‐term effects of soil nutrient deficiency on arbuscular mycorrhizal communities

Summary1. Arbuscular mycorrhizal fungi (AMF) have been proposed as a mechanism to reduce nutrient inputs in agriculture, thereby reducing costs and increasing environmental sustainability. However, before this can be achieved, we need to gain a better understanding of the importance of the prolonged selective pressures acting on indigenous AMF communities.2. Much research concentrates on short‐term ecological soil × plant × AMF interactions. However, we have little understanding of how long‐term manipulations of abiotic conditions can be strong selection agents for AMF communities. Here, we ask how the long‐term management of soil fertility and fertilizer use can influence the AM symbiosis. More specifically, we investigated whether 70 years of consistently imposed nutrient limitations affected the structure and symbiotic functioning of indigenous AMF communities.3. Using the long‐term Static Nutrient Deficiency Experiment carried out since 1937 in Thyrow, Germany, with and without nitrogen (N) and phosphorus (P) additions, we addressed the following questions: (i) Do different soil fertilizer treatments affect the overall abundance and diversity of indigenous AMF in an agricultural field; and (ii) Does the depletion of a nutrient select for an enhanced AMF ability to supply the deficient nutrient?4. We assessed AMF spore diversity in the field and established a common garden experiment where soil nutrient treatments were calibrated against those in the long‐term field experiment. For each soil nutrient treatment, we compared the growth responses of barley plants to the indigenous AMF communities isolated from the different soil fertilization treatments in the field.5. We found that the long‐term use of specific soil fertilization treatments altered the effects of the AMF symbiosis on plant and fungal growth. Consistent with the optimal foraging theory, AMF from N‐ or P‐deficient soils grew larger but reduced plant growth more in those conditions relative to AMF isolated from non‐deficient soils. This could result from both community‐level changes and/or adaptations within species.6. Thus, we propose that the ongoing agronomic management of abiotic selective pressures such as soil fertility needs to be considered as a strong determinant of AMF symbiotic functioning.

Forest fragment size and nutrient availability: complex responses of mycorrhizal fungi in native–exotic hosts

In the past few decades, it has been widely accepted that forest loss due to human actions alter the interactions between organisms. We studied the relationship between forest fragment size and arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) colonization, and the AMF spore communities in the rhizosphere of two congeneric Euphorbia species (native and exotic/invasive). We hypothesized that these fungal variables will differ with fragment size and species status, and predicted that (a) AMF and DSE colonization together with AMF spore abundance and diversity would be positively related to forest fragment size; (b) these relationships will differ between the exotic and the native species; and (c) there will be a negative relationship between forest fragment size and the availability of soil nutrients (NH4+, NO3−, and phosphorus). This study was performed in the eight randomly selected forest fragments (0.86–1000 ha), immersed in an agricultural matrix from the Chaquean region in central Argentina. AMF root colonization in the native and exotic species was similar, and was positively related with forest fragment size. Likewise, AMF spore diversity and spore abundance were higher in the larger fragments. While DSE root colonization in the native host was positively related with forest fragment size, DSE colonization in the exotic host showed no relationship. Soil nutrients contents were negatively related with forest fragment size. In addition, NH4+ and NO3− were negatively correlated with AMF spores abundance and root colonization and with DSE colonization in the native species. The results observed in this study show how habitat fragmentation might affect the interaction between key soil components, such as rhizospheric plant-fungal symbiosis and nutrient availability. These environmental changes may have important consequences on plant community composition and nutrient dynamics in this fragmented landscape.

Seasonal variation and distribution at different soil depths of arbuscular mycorrhizal fungi spores in a tropical sclerophyllous shrubland

Limited information is available for the diversity of arbuscular mycorrhizal fungi (AMF) in most tropical soils. To assess the biodiversity of AMF in a sclerophyllous shrubland ecosystem, an exhaustive collection of spores from soil collected in the Venezuelan Guayana was undertaken. Spores were collected from the first 15 cm of soil, four times throughout the year, and at four different depths during dry and wet seasons. A total of 50 AMF morphotypes were collected in the field, and 2 more were isolated from pot cultures. There was a reduction in spore density with soil depth, although richness of spores remained the same up to a depth of 45 cm. Spore density and richness based on soil cores were higher in the dry season than in the rainy season. Only 24% of the AMF morphotypes present could be identified to species level, since most of them did not fit published descriptions available. It is important to perform an exhaustive sampling of spores in the different seasons throughout the year and at different soil depths to obtain an accurate view of AMF spore diversity associated with a particular ecosystem.

Biodiversity and distribution of arbuscular mycorrhizal fungi in Araucaria angustifolia forest

Araucaria angustifolia (Bert.) O. Ktze. is an endangered Brazilian coniferous tree that has been almost exterminated in the native areas because of uncontrolled wood exploitation. This tree has been shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) and, therefore, AMF may be essential for forest sustainability and biological diversity. Root colonization, density and diversity of AMF spores were assessed in two Araucaria forest stands at the State Park of Alto Ribeira (PETAR), at two sampling dates: May and October. A comparison was made between a mature native stand composed of Araucaria trees mixed into a variety of tropical trees and shrubs, without any sign of anthropogenic interference (FN) and an Araucaria stand planted in 1987 (R), which has been used as a pasture. Assessments included percent root colonization, AMF spore numbers and species richness, Simpson's dominance index (Is), and Shannon's diversity index (H). Mycorrhizal root colonization did not differ between ecosystems in May. In October, however, the native stand (FN) presented a higher colonization than the planted forest (R), and the root colonization was more intense than in May. When considering both sampling periods and forests, 27 species of AM fungi, with higher numbers of spores in FN than in R were found. Canonical discriminant analysis (CDA) indicated Shannon's diversity index as the ecological attribute that contributed the most to distinguish between forest ecosystems, with higher value of H in FN in relation to R. CDA showed to be a useful tool for the study of ecological attributes.

Impact of agricultural management on arbuscular mycorrhizal fungal communities in Kenyan ferralsol

Arbuscular mycorrhizal fungi (AMF) represent a functionally important component of soil microbial community, being of particular significance for plant mineral nutrition in tropical agroecosystems. The effects of crop rotation of maize ( Zea mays L.) with crotalaria ( Crotalaria grahamiana Wight & Arn.) versus continuous maize and phosphorus (P) fertilization on AMF spore community composition and diversity were studied in a long term field experiment in western Kenya. The spores were isolated from the soil, identified according to their morphologies, and enumerated. Trap pots using soil from the maize–crotalaria rotation were sown with four different plant species, sunflower ( Helianthus annuus (L.) Merill.), leek ( Allium porrum L.), maize, and crotalaria. The spores isolated from the traps were identified according to their morphology and by sequencing of their large ribosomal subunits (LSU). Ten AMF species were isolated from the field soil and 16 species from the traps. Altogether, 18 species were recorded in the field site. The spore communities in the field soil were dominated by Scutellospora and Acaulospora species. The species diversity of AMF spores in the soil was affected neither by crop rotation nor by P fertilization. However, the composition (relative species abundances) of AMF spore communities was significantly affected by crop rotation. The abundance of Acaulospora scrobiculata and Scutellospora verrucosa spores was significantly higher in soil under maize–crotalaria rotation than under continuous maize. Both the composition and diversity of spore communities, as well as spore densities in the traps were strongly affected by species identity of the host plant, whereas the P fertilization history of the soil only affected diversity of the spore communities. Functional consequences of changing composition of AMF communities through agricultural management practices are discussed.