Impact of a soil sampling strategy on the spatial distribution and diversity of arbuscular mycorrhizal communities at a small scale in two winter cover crop rotational systems

It is vital to evaluate how soil sampling affects the spatial distribution and diversity of arbuscular mycorrhizal fungi (AMF) in agricultural ecosystems. Here, the impact of soil sampling on the spatial distribution and diversity of AMF in agricultural ecosystems was evaluated using field experiments. A molecular approach was taken to assess the spatial distribution of the AMF community from 1 m2 plots from fields cropped with soybeans [Glycine max (L.) Merr.], in rotation with wheat (Triticum aestivum L.) and winter fallow. Phylogenetic analysis revealed 18 AMF phylotypes, including five Glomus, three Gigaspora, two each from Racocetra, Acaulospora, and Funneliformis and one each from Claroideoglomus, Rhizophagus, Diversispora, and Paraglomus at different sampling points in this study. Our results showed that the molecular diversity and composition of AMF communities in soil cropped with wheat, or left fallow did not change at scales of < 1 m2. Canonical correspondence analysis (CCA) demonstrated that AMF communities by soil sampling point within each rotation were not significantly different. Thus, random soil sampling did not show any difference in AMF communities in soil under winter cover crop rotational systems, no matter where soil samples were collected from at a small scale (< 1 m2) in agricultural fields. Our results suggest that agricultural management can affect the diversity and composition of AMF communities more than soil sampling strategies.     

Genetic structure of arbuscular mycorrhizal populations in fallow and cultivated soils

The impact of fallowing on the genetic structure of arbuscular mycorrhizal fungi (AMF) was studied by hierarchical sampling of spores from four plots in a fallow and a cultivated field. A nested multiplex PCR approach was used to assign the spores to genotypes. Variable introns of the two protein-coding genes GmFOX2 and GmTOR2 were used as co-dominant genetic markers together with the large subunit (LSU) rDNA. The gene diversity and genetic structure of Glomus mosseae, Glomus geosporum and Glomus caledonium were compared within and between the fields. Spores of G. caledonium and G. geosporum were more abundant in the cultivated field, whereas G. mosseae was more frequent in the fallow field. The number of genotypes was not different between the two fields. Analysis of gene diversity of G. caledonium in the fallow field indicated that a larger part of the heterogeneity could be attributed to variation between plots rather than subplots, suggesting that the lack of soil cultivation resulted in more heterogeneous population genetic structures. Analyses of haplotype networks of the fungi suggested a subdivision of G. mosseae haplotypes between the two fields, whereas no such division was seen in G. geosporum and G. caledonium. The results show that agricultural practices differently affect both the abundance and the population structure of different AMF species.     

我国北方农田土壤中AM真菌的多样性

AM真菌是农业生态系中一类重要的土壤微生物,它在农田土壤中的发生和分布受多种环境因素的影响。为深入了解我国北方农田土壤中AM真菌的多样性规律,于2000年在河北、山东的农田土壤中采集有代表性的土样127个。通过进一步扩繁、纯化,从中分离出AM真菌5属22种,鉴定了20个种,包括一个国内新记录种沾屑球囊霉(Glomus spurcum)。分析AM真菌的多样性特点及其影响因素发现,农田土壤中以球囊霉属(Glomus)的频度最高,其次为无梗囊霉属(Acaulospora);优势种类为幼套球囊霉(Glomus etunicatum)和摩西球囊霉(Glomus mosseae).土壤速效磷含量、pH状况主要对孢子密度产生影响,对种群分布影响不大。宿主植物类型对AM真菌的侵染状况和多样性影响较大;比较玉米(Zea mays)、甘薯(Ipomoea batatas)根区AM真菌的种群组成后发现两者有所不同,但优势种一致.     

Specificity and localised distribution of mycorrhizal fungi in the soil may contribute to co-existence of orchid species

Co-occurring orchid species tend to occupy different areas and associate with different mycorrhizal fungi, suggesting that orchid mycorrhizal (OrM) fungi may be unevenly distributed within the soil and, therefore, impact the aboveground spatial distribution of orchids. To test this hypothesis, we investigated spatial variations in the community of potential OrM associates within the roots of three co-habitating orchid species (Anacamptis morio, Gymnadenia conopsea, and Orchis mascula) and the surrounding soil in an orchid-rich calcareous grassland in Southern Belgium using 454 amplicon pyrosequencing. Putative OrM fungi were broadly distributed in the soil, although variations in community composition were strongly related to the proximal host plant. The diversity and frequency of sequences corresponding to OrM fungi in the soil declined with increasing distance from orchid plants, suggesting that the clustered distribution of orchid species may to some extent be explained by the localised distribution of species-specific mycorrhizal associates.     

Intercropped Silviculture Systems,a Key to Achieving Soil Fungal Community Management in Eucalyptus Plantations

Fungi are ubiquitous and important contributors to soil nutrient cycling, playing a vital role in C, N and P turnover, with many fungi having direct beneficial relationships with plants. However, the factors that modulate the soil fungal community are poorly understood. We studied the degree to which the composition of tree species affected the soil fungal community structure and diversity by pyrosequencing the 28S rRNA gene in soil DNA. We were also interested in whether intercropping (mixed plantation of two plant species) could be used to select fungal species. More than 50,000 high quality sequences were analyzed from three treatments: monoculture of Eucalyptus; monoculture of Acacia mangium; and a mixed plantation with both species sampled 2 and 3 years after planting. We found that the plant type had a major effect on the soil fungal community structure, with 75% of the sequences from the Eucalyptus soil belonging to Basidiomycota and 19% to Ascomycota, and the Acacia soil having a sequence distribution of 28% and 62%, respectively. The intercropping of Acacia mangium in a Eucalyptus plantation significantly increased the number of fungal genera and the diversity indices and introduced or increased the frequency of several genera that were not found in the monoculture cultivation samples. Our results suggest that management of soil fungi is possible by manipulating the composition of the plant community, and intercropped systems can be a means to achieve that.     

Insights into fungal communities colonizing the acarosphere in a forest soil habitat

Knowledge on the diversity and ecology of microfungi associated with soil-dwelling mites is rather limited. To get insights into associations between the two highly diverse groups, we studied composition and potential function of mite-associated fungal communities occurring in soil. Two different mite species living in temperate region pine forest soil were screened for associated fungi. The fungal community was assessed by restriction fragment length polymorphism (RFLP) analyses in a predatory (Leptogamasus obesus) and a predominantly saprobic (Oppiella subpectinata) mite species as well as in the organic soil layer. Key fungi were identified by sequencing, and community composition was exemplarily compared between the RFLP and a 454 metabarcoding approach. Composition of the fungal communities differed between mite species and between mites and organic soil layer. The mites were predominantly associated with Zygomycota, less frequently with Ascomycota, and rarely with Basidiomycota. The bulk soil was colonized by roughly equal proportions of the three phyla. Fungal taxa being known to exhibit chitinolytic activity were predominantly restricted to mites. Compositional and functional differences between the communities suggest that mites represent a particular microhabitat for fungi, the “acarosphere.” This mobile habitat may contribute to nutrient cycling by combining fungal and animal decomposition activities and serve as vector for soil-inhabiting fungi.     

Afforested fields benefit nutrient‐demanding fungi

Impaired ecosystems are converted back to natural ecosystems or some other target stage by means of restoration and management. Due to their agricultural legacy, afforested fields might be valuable compensatory habitats for rare fungal species that require nutrient‐rich forest soils. Using a large‐scale field experiment in Finland, we studied community composition of macrofungi (agarics and boletes) on former fields, which had been afforested as monocultures 20 years ago using native spruce Picea abies, pine Pinus sylvestris, and birch Betula pendula. We studied the effect of soil quality, tree species, and site on community composition and structure. Many nutrient‐demanding as well as rare fungal species were recorded, particularly from pine and spruce plots. Pine plots supported more nutrient‐demanding fungi than birch plots. There was no relationship between soil pH, bulk density, P, N, or Ca, and species richness of nutrient‐demanding fungi. Fungal community composition was more similar within sites than among sites for all tree species. Among sites, spruce plots had the smallest fungal species turnover, and birch plots largest. Within sites, however, fungal species turnover from plot to plot was similar among tree species. Our results indicate that tree species has a relatively mild influence on species composition of fungi after 20 years of succession. Interestingly, the results show that afforested fields can be valuable complementary habitats for rare, red‐listed, and nutrient‐demanding fungal species. Field afforestation is a potential conservation tool that could be used to complement the poor representation of rare habitat types in highly fragmented protected area networks.     

浙江镜湖湿地3种菌根植物根部真菌群落多样性及对金属元素富集能力的研究

城市湿地（urban wetland）植物多样性水平高,并具有积极的净化和美化环境的作用。本研究以浙江绍兴镜湖城市湿地公园为研究样地,通过ICP-AES检测了人工园区和次生林土壤中几种金属元素（Al、Cr、Cu、K和Zn）的含量,比较不同类型的菌根植物——黑麦草（Lolium perenne L.）（AM）、六月霜（Monochasma sauatieri Franch）（AM）和乌饭树（Vaccinium bracteatum Thunb）（ERM）对金属元素的富集作用。通过高通量测序分析各宿主植物根部真菌群落的组成和结构,比较其对宿主植物金属富集能力的影响。结果表明：（1）人工园区土壤中5种金属元素的含量均显著高于次生林下的土壤;（2）乌饭树对Al的富集能力较强,黑麦草和六月霜富集Cr能力都较强;（3）3种植物根部真菌主要来自Ascomycota,而乌饭树根部Basidiomycota也是优势真菌,AM真菌在黑麦草和六月霜根部真菌群落结构中较少,而公认的ERM真菌Helotiales和Sebacinales在乌饭树根部真菌群落中的比例较高,且与所测金属元素无显著相关性。绍兴镜湖城市湿地公园次生林土壤环境保持良好。     

Springtail community (Hexapoda,Collembola) in arable chernozems of Kursk oblast

The composition of springtail communities (the ratio of taxa, species richness, morphoecological spectrum, and spatial organization) in typical deep chernozems of Kursk oblast has been studied in crop fields, forest strips, and an old fallow. Approximately 40 springtail species have been recorded, with the Onychiuridae being dominant with respect to species diversity and contribution to the total abundance. Springtails are distributed over the soil profile to a depth of no less than 50 cm. The pattern of their vertical distribution in areas with tree and shrub vegetation differs from that in arable land. The response of springtails to weakly expressed sheet erosion of chernozem proved to be insufficient for using them as bioindicators of the initial stages of soil erosion.     

Discrimination of microbial diversity by fatty acid profiles of phospholipids and lipopolysaccharides in differently cultivated soils

The effects of long-term management practices on the diversity of the microbial community were examined by analyzing the composition of fatty acids (FAs) in phospholipids (PL) and lipopolysaccharides (LPS). According to the Principal Component Analysis (PCA) of total fatty acids the soils were divided in two groups: a) Black fallow soil (1) and soils cropped with potatoes (3, 4), and b) green fallow soil (2), soils cropped with wheat (5, 6), crop rotation (7) and grassland (8). The PCA for saturated FAs and for hydroxy FAs of both PL and LPS shows that the green fallow soil (2) can be distinguished from the other soils. For monounsaturated FAs the grassland soil (8) and for polyunsaturated FAs the wheat with vetch soil (6) clearly differed from the other soils. Fatty acids with biomarker quality such as 15:0 for bacteria and 18:26 for fungi were used for determining the ratio between bacteria and fungi: the black fallow soil (1) and the soil managed with crop rotation (7) contained significantly higher proportions of bacteria than the other soils. The largest proportion of the indicator fatty acid il5:0 for Gram-positive bacteria was measured in the black fallow soil (1), while the-hydroxy FAs indicative of Gram-negative bacteria most frequently occurred in manured potato cropped soil (4). Both indicator fatty acids 18:26 for fungi and cy19:0 for anaerobic bacteria had their highest concentrations in the manured potato cropped soil (4).     

黄土高原半干旱区轮作休耕模式对土壤真菌的影响

通过田间试验,研究休耕（CK）、残膜覆盖、伏天深耕、施有机肥、秸秆还田和绿肥还田对土壤微生物量碳氮、酶活性及真菌群落的影响。结果表明,除过氧化氢酶外,不同处理对土壤微生物量碳氮、脲酶、碱性磷酸酶、脱氢酶、pH及有机质均有显著影响。从门水平上看,土壤真菌群落主要由子囊菌门、担子菌门和被孢霉门构成。其中伏天深耕、玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理的子囊菌相对丰度分别为43.23%和69.38%,显著高于CK （33.71%）;从纲水平上看,座囊菌纲、粪壳菌纲、伞菌纲和被孢霉纲为优势菌纲,其中玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理以座囊菌纲为主（60.69%）,其余处理以粪壳菌纲为主（4.11%-24.79%）;真菌多样性指数施牛羊粪+深翻耕+连续3年种植豌豆（拌根瘤菌粉8.5 g/kg种子）并在盛花期翻压还田、玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年、玉米秸秆粉碎还田+施牛羊粪+深翻耕+连续3年种植箭筈豌豆并在盛花期翻压还田处理显著低于CK和其他处理,丰富度指数玉米秸秆粉碎还田+施牛羊粪+深翻耕+连续3年种植毛苕子并在盛花期翻压还田处理显著高于CK和其他处理;真菌营养类型玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理以腐生营养型为主（62.9%）,其他处理以病理营养型和腐生营养型为主。冗余分析和Monte Carlo置换检验结果显示,土壤微生物量碳、微生物量氮、pH和有机质含量对土壤真菌群落结构影响显著（P<0.05）。与休耕（CK）、残膜覆盖、伏天深耕相比,施有机肥、秸秆还田、绿肥还田结合深耕均降低了土壤中病理营养型真菌的相对丰度,利于保持农田土壤生态系统健康。     

Effect of Soils from Six Management Systems on Root-knot Nematodes and Plant Growth in Greenhouse Assays

The effects of soil management systems on root-knot nematode (Meloidogyne incognita) eggs and gall incidence on tomato (Lycopersicon esculentum) and cucumber (Cucumis sativus) following tomato were evaluated. Soil was collected from a replicated field experiment in which six management systems were being assessed for vegetable production. Soil management systems were conventional production, organic production, bahiagrass (Paspalum notatum) pasture, bahiagrass: Stylosanthes (Stylosanthes guianensis) pasture, bare ground fallow, and weed fallow. Soil was collected from field plots and used in greenhouse experiments. Identification of egg-parasitic fungi and the incidence of root-knot nematode galling were assessed both on tomato and cucumber planted in the same pots following the removal of tomato plants. Organic, bare ground fallow and conventional production treatments reduced galling both on tomato and on cucumber following tomato. Although no treatment consistently enhanced egg-parasitic fungi, management system did affect egg viability and the types of fungi isolated from parasitized eggs.     

Dynamics of vesicular-arbuscular mycorrhizae during old field succession

Summary 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.     

森林母土异地迁播后的土壤真菌和细菌变化

【背景】森林土壤中携带了大量种子和微生物,已经被广泛用于各种退化生态系统的植被恢复。但是,关于土壤迁播到退化生态系统后的真菌和细菌群落变化研究较少。【目的】研究土壤迁播后真菌和细菌的组成和多样性,比对其与森林母土和受体土壤之间的物种组成与群落差异。【方法】通过Illumina HiSeq高通量测序,获取迁播15个月的土壤、森林母土及受体土壤中真菌和细菌特征值,比对其多样性和丰富度。【结果】3类样地真菌优势菌门为担子菌门和子囊菌门,细菌优势菌门为酸杆菌门、变形菌门、放线菌门和绿弯菌门,土壤迁播后显著改变了真菌和细菌优势菌门的相对丰度。主成分分析表明3类样地真菌和细菌群落组成存在显著差异。聚类分析表明迁播土壤与受体土壤聚类距离更近,物种组成更相似,真菌和细菌优势属与受体土壤无显著差异。迁播土壤的真菌和细菌丰富度和多样性与森林母土差异显著(P0.05)。【结论】森林土壤迁播15月后,其细菌和真菌物种组成逐步趋同于受体土壤。该结果为进一步研究石漠化微生物生态系统、改善和提升土壤迁播技术提供支撑。     

Slow arbuscular mycorrhizal colonisation of field-grown cotton caused by environmental conditions in the soil

 Slow arbuscular mycorrhizal colonisation is characteristic of a growth disorder of cotton occurring in crops in northern New South Wales, Australia. To determine whether or not slow colonisation is caused by poor survival of mycorrhizal fungi between crops, we examined colonisation of cotton in field crops and in a series of pot bioassays. Cotton roots were sampled at sites with or without severe symptoms of the growth disorder in each of three fields in 1991 and two fields in 1993. The bioassays were at intervals over the winter fallow prior to the crops in both years. In each bioassay, soil was collected from the field sites and sown with cotton in pots in a controlled environment cabinet. Colonisation was assessed at 14, 28 and 42 days after sowing. In the bioassay series, colonisation at 14 days, which was representative of primary infections of roots and hence propagule density in soil, tended to decline over the winter fallow. In contrast, colonisation at 42 days, which included secondary spread of infection, first declined and then returned to its original level or higher. In the field, plants affected by the growth disorder were colonised slowly, while healthy plants were colonised rapidly. In the bioassays, however, colonisation in the soil from sites with the growth disorder equalled or surpassed that in soil from sites with healthier cotton. Thus, the slow colonisation and growth of field-grown cotton did not result from a lack of mycorrhizal inoculum and was most likely caused by soil factors. Accepted: 21 August 1998     

六种海桑属红树植物根际真菌特征及其影响因子

真菌多样性是植物根际生态系统的重要构成与植物健康稳定的重要指标。海桑属是红树林的先锋物种,采用真菌ITS1区高通量测序方法,分析了六种海桑属红树根际真菌的组成和多样性,结合土壤理化性质探讨影响不同植物根际真菌群落组成差异的因素。结果显示,根际真菌隶属于7门、96科、155属,子囊菌门作为优势菌门在海桑属不同红树中相对丰度无显著差异,都超过27%,但次优势的担子菌门丰度含量有差异;属水平上,优势菌属的丰度含量不同,曲霉属在卵叶海桑的丰度最高(29.57%),在海南海桑最低(3.47%)。六种红树植物根际存在特有的代表类群,如无瓣海桑的马拉色菌(9.31%)和毛腐菌属(10.05%),海南海桑中的Talaromyces(19.61%)和Acremonium(13.58%)。比较多样性指数Simpson和Shannon,发现拟海桑是六种植物中丰度最高的,卵叶海桑最低。RDA分析发现子囊菌门与全磷含量呈显著负相关,担子菌门与速效钾呈明显正相关。六种海桑属红树植物根际核心物种分析表明,优势真菌类群曲霉属和一些低丰度的真菌类群,通过降解有机质参与碳循环,对根际土壤生态系统的稳定起重要作用。六种海桑...     

免耕覆盖及有机肥施用对土壤真菌群落组成及多样性的影响

为揭示土壤真菌群落对免耕、覆盖及有机肥施用的响应机制,在宁夏南部山区冬小麦农田连续3年采用免耕覆盖+施有机肥(NF)、免耕覆盖+不施有机肥(NC)、传统耕作不覆盖+施有机肥(TF)和传统耕作不覆盖+不施有机肥(TC)4个处理,依托Illumina MiSeq 高通量测序平台,研究了土壤真菌群落组成、多样性及其与土壤环境因子间的关系。结果表明: 4个处理共获得3490个可操作分类单元(OTUs),其中含有一些未知真菌。在已知的真菌群落中,子囊菌门和担子菌门为优势菌门,其相对丰度占总丰度的82.1%～94.2%,且TF处理下子囊菌门座囊菌纲的相对丰度最高,NF处理下担子菌门银耳菌纲的相对丰度最高。4个处理真菌群落多样性指数(Shannon和Simpson指数)依次为NC>TC>NF>TF。多元分析结果表明,微生物生物量碳是影响担子菌门和接合菌门相对丰度的主要因素,而土壤全磷、速效钾和速效磷含量高低是驱动子囊菌门真菌相对丰度变化的关键因素。在宁夏南部山区推广以免耕覆盖并施用有机肥的保护性耕作措施有利于提高土壤真菌群落多样性。     

Nitrogen deposition and temperature structure fungal communities associated with alpine moss-sedge heath in the UK

Moss-sedge heath, an important habitat of oceanic alpine regions, is under threat from elevated nitrogen (N) deposition and rising temperatures increasing decomposition rates and fragmentation of the extensive, thick moss mats of Racomitrium lanuginosum which characterise this habitat. Here, we examine the potential effects of N deposition and temperature on fungal communities associated with R. lanuginosum mats. Fungal community composition in both green moss shoots and underlying soil were significantly influenced by mat temperatures and green moss shoot N contents. Total OTU, Ascomycota, Basidiomycota and saprotrophic fungal richness in shoots were all positively related to temperature, while in soil, the richness of all groups, except Basidiomycota, was positively related to moss tissue N. The observed community changes suggest that increased N loading and increasing temperatures are ameliorating growing conditions for fungi associated with moss-sedge heath. Further study is required to determine if the observed changes in fungal communities contribute to accelerated decomposition of moss mats and degradation of the habitat.     

Local vs. landscape controls on diversity: a test using surface-dwelling soil macroinvertebrates of differing mobility

Aim A better understanding of the processes driving local species richness and of the scales at which they operate is crucial for conserving biodiversity in cultivated landscapes. Local species richness may be controlled by ecological processes acting at larger spatial scales. Very little is known about the effect of landscape variables on soil biota. The aim of our study was to partly fill this gap by relating the local variation of surface‐dwelling macroarthropod species richness to factors operating at the habitat scale (i.e. land use and habitat characteristics) and the landscape scale (i.e. composition of the surrounding matrix). Location An agricultural landscape with a low‐input farming system in Central Hesse, Germany. Methods We focused on five taxa significantly differing in mobility and ecological requirements: ants, ground beetles, rove beetles, woodlice, and millipedes. Animals were caught with pitfall traps in fields of different land use (arable land, grassland, fallow land) and different habitat conditions (insolation, soil humidity). Composition of the surrounding landscape was analysed within a radius of 250 m around the fields. Results Factors from both scales together explained a large amount of the local variation in species richness, but the explanatory strength of the factors differed significantly among taxa. Land use particularly affected ground beetles and woodlice, whereas ants and rove beetles were more strongly affected by habitat characteristics, namely by insolation and soil characteristics. Local species richness of diplopods depended almost entirely on the surrounding landscape. In general, the composition of the neighbouring landscape had a lower impact on the species richness of most soil macroarthropod taxa than did land use and habitat characteristics. Main conclusions We conclude that agri‐environment schemes for the conservation of biodiversity in cultivated landscapes have to secure management for both habitat quality and heterogeneous landscape mosaics.     

Analysis of fungal diversity in the wheat rhizosphere by sequencing of cloned PCR-amplified genes encoding 18S rRNA and temperature gradient gel electrophoresis.

Like bacteria, fungi play an important role in the soil ecosystem. As only a small fraction of the fungi present in soil can be cultured, conventional microbiological techniques yield only limited information on the composition and dynamics of fungal communities in soil. DNA-based methods do not depend on the culturability of microorganisms, and therefore they offer an attractive alternative for the study of complex fungal community structures. For this purpose, we designed various PCR primers that allow the specific amplification of fungal 18S-ribosomal-DNA (rDNA) sequences, even in the presence of nonfungal 18S rDNA. DNA was extracted from the wheat rhizosphere, and 18S rDNA gene banks were constructed in Escherichia coli by cloning PCR products generated with primer pairs EF4-EF3 (1. 4 kb) and EF4-fung5 (0.5 kb). Fragments of 0.5 kb from the cloned inserts were sequenced and compared to known rDNA sequences. Sequences from all major fungal taxa were amplified by using both primer pairs. As predicted by computer analysis, primer pair EF4-EF3 appeared slightly biased to amplify Basidiomycota and Zygomycota, whereas EF4-fung5 amplified mainly Ascomycota. The 61 clones that were sequenced matched the sequences of 24 different species in the Ribosomal Database Project (RDP) database. Similarity values ranged from 0.676 to 1. Temperature gradient gel electrophoresis (TGGE) analysis of the fungal community in the wheat rhizosphere of a microcosm experiment was carried out after amplification of total DNA with both primer pairs. This resulted in reproducible, distinctive fingerprints, confirming the difference in amplification specificity. Clear banding patterns were obtained with soil and rhizosphere samples by using both primer sets in combination. By comparing the electrophoretic mobility of community fingerprint bands to that of the bands obtained with separate clones, some could be tentatively identified. While 18S-rDNA sequences do not always provide the taxonomic resolution to identify fungal species and strains, they do provide information on the diversity and dynamics of groups of related species in environmental samples with sufficient resolution to produce discrete bands which can be separated by TGGE. This combination of 18S-rDNA PCR amplification and TGGE community analysis should allow study of the diversity, composition, and dynamics of the fungal community in bulk soil and in the rhizosphere.