Spatial variability of arbuscular mycorrhizal fungal spores in two natural plant communities

Geostatistical techniques were used to assess the spatial patterns of spores of arbuscular mycorrhizal fungi (AMF) in soils from two contrasting plant communities: a salt marsh containing only arbuscular mycorrhizal and non-mycorrhizal plants in a distinct clumped distribution pattern and a maquis with different types of mycorrhiza where most plants were relatively randomly distributed. Also evaluated was the relationship between the spatial distribution of spores and AM plant distribution and soil properties. A nested sampling scheme was applied in both sites with sample cores taken from nested grids. Spores of AMF and soil characteristics (organic matter and moisture) were quantified in each core, and core sample location was related to plant location. Semivariograms for spore density indicated strong spatial autocorrelation and a patchy distribution within both sites for all AM fungal genera found. However, the patch size differed between the two plant communities and AM fungal genera. In the salt marsh, AM fungal spore distribution was correlated with distance to AM plants and projected stand area of AM plants. In maquis, spatial AM fungal spore distribution was correlated with organic matter. These results suggest that spore distribution of AMF varied between the two plant communities according to plant distribution and soil properties.     

崂山茶区茶树根围AM真菌多样性

为调查崂山茶区土壤中丛枝菌根(AM)真菌资源的分布状况, 于2007年9月从青岛崂山茶区12个茶园采集茶树(Camellia sinensis)根围土样, 采用湿筛倾注–蔗糖离心法分离AM真菌, 测定其物种丰度、频度、孢子密度、相对多度、重要值、多样性指数等。共分离到AM真菌3属22种, 无梗囊霉属(Acaulospora)出现的频度最高, 其次是球囊霉属(Glomus)。AM真菌孢子密度以晓望村茶园最高, 高家村茶园最低; 种丰度以常家村茶园最高; 常家村茶园和万来客茶园的Shannon-Wiener指数显著高于其他茶园。光壁无梗囊霉(Acaulospora laevis)是北崂茶厂、万里江茶园、樱山春茶园、万里江有机茶园、常家村茶园和桑园村茶园的优势种; 波状无梗囊霉(Acaulospora undulata)为万里江有机茶园和万来客茶园的优势种; 隐球囊霉(Glomus occultum)为樱山春茶园、晓望村茶园和万来客茶园的优势种。应用典型相关分析(CCA)对环境因子与崂山茶区AM真菌群落组成的关系进行了分析, 各因子的影响大小依次为: 土壤速效磷含量＞土壤有机质含量＞种植年限＞土壤碱解氮含量＞土壤pH值＞土壤速效钾含量。     

青岛胶州湾四种类型湿地AM真菌多样性

对青岛胶州湾4种类型湿地（盐田、滩涂、湖泊和河口）中芦苇Phragmites communis、香蒲Typha orientalis和碱蓬Suaeda glauca 根围土壤中丛枝菌根（arbuscular mycorrhizal,AM）真菌进行孢子分离与鉴定,分析湿地生态系统中植物根围AM真菌群落特征。共分离到AM真菌5属10种,包括斗管囊霉属Funneliformis 2种、无梗囊霉属Acaulospora 3种、近明球囊霉属Claroideoglomus 2种、球囊霉属Glomus 1种、巨孢囊霉属Gigaspora 2种,其中,斗管囊霉属Funneliformis及地斗管囊霉Funneliformis geosporum的分离频度和相对多度最高,分别为湿地中AM真菌优势属和优势种。滩涂和河口湿地中植物AM真菌侵染率显著高于湖泊和盐田湿地植物,AM真菌孢子密度以滩涂湿地最高（572个/20mL）,湖泊湿地最低（220个/20mL）;滩涂湿地的种丰度和Shannon-Wiener指数最高,分别为3.8和1.2。从植物种类来看,AM真菌侵染率总体呈现出香蒲>碱蓬>芦苇,AM真菌孢子密度以香蒲最高,芦苇最低,植物种类对AM真菌种丰度和Shannon-Wiener指数影响不显著（P>0.05）。二因素方差分析和典型RDA相关分析表明,寄主植物种类对AM真菌孢子密度有一定影响,但湿地类型对AM真菌多样性的影响更为显著（P<0.05）,胶州湾湿地土壤因子Ca ²⁺、速效P含量与AM真菌孢子密度、物种丰度和多样性指数显著负相关,而速效K、Na ⁺、pH与其显著正相关。结果表明植物种类主要影响AM真菌孢子密度,AM真菌多样性受植物种类和湿地类型综合影响,滩涂湿地较丰富的AM真菌多样性可能与该湿地较良好的理化性质有关。     

Effects of climatic and edaphic factors on arbuscular mycorrhizal fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, China

In order to investigate the effects of climatic and edaphic factors on arbuscular mycorrhizal (AM) fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, spore density, mycorrhizal colonization and gene diversity were analyzed by using the methods of microscopy and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) respectively. The results showed that H. rhamnoides could form strong symbiotic relationships with AM fungi. There existed obvious differences in AM fungal colonization among five sampling sites in the Loess Plateau (P < 0.05). Correlation analysis showed that AM fungal colonization and spore density were closely related with climatic and edaphic factors. 42 different species (band types) were found in the DGGE gel. Based on analysing the position and intensity of AM fungal DGGE bands, the gene diversity indices, including species richness, evenness, Simpsom’s and Shannon-Weiner index, showed significant differences among five sampling sites (P < 0.05). All the AM species could be classified into four groups in the biplot of canonical correspondence analysis (CCA), and each group had various responses to climatic and edaphic factors. Monte Carlo random test indicated that soil available phosphorus (F = 2.26, P = 0.025) and spore density (F = 1.76, P = 0.006) were the dominating factors affecting AM fungal communities. In conclusion, AM fungal colonization and community diversity in the rhizosphere of H. rhamnoides showed obvious spatial heterogeneity among the different areas of the Loess Plateau, and climatic and edaphic conditions were important factors affecting the AM fungal communities. Therefore, screening and application of AM fungal strains in the Loess Plateau need to fully consider the local climatic and edaphic conditions.     

比较形态学、聚丙酰胺凝胶电泳与二代测序在AM真菌群落研究中的应用

采集内蒙古荒漠草原沙化梁地羊柴Hedysarum laeve根围土样,采用形态学方法、聚丙酰胺凝胶电泳（denatured gradient gel electrophoresis,DGGE）技术和二代测序（next generation sequencing,NGS）技术分析羊柴根围AM真菌群落组成和多样性。结果表明,应用NGS共鉴定AM真菌3纲4目10科18属,DGGE鉴定2纲2目2科5属,形态学鉴定1纲2目2科3属。AM真菌分类等级越低,NGS、DGGE和形态学鉴定结果差异越大,尤其在属水平上差异显著。与NGS技术相比,形态学和DGGE方法所反映AM真菌种类主要为优势菌种,显著低估了AM真菌物种组成并高估其丰度,分子测序是对形态学分类的补充和完善。     

不同盐碱度土壤中AM菌根真菌群落结构组成及影响因子

为研究黄河三角洲盐渍土壤中植物根围AM菌根真菌多样性及影响多样性的因素,从东营孤东和孤岛油区采集碱蓬和柽柳植物的根围土壤,鉴定了4种土壤试样中丛枝菌根(Arbuscular mycorrhiza,AM)的群落组成。结果表明:球囊霉属(Glomus)是盐碱地中的优势种,同时还有许多未知真菌;考察不同盐碱度情况下菌根真菌群落结构差异,结果表明:碱蓬根围土壤中AM真菌的多样性高于柽柳,孤东根围土壤AM真菌多样性比孤岛高。相关分析表明,铵态氮含量与AM真菌多样性呈现显著负相关。     

Arbuscular mycorrhizal and dark septate endophytic fungi at 5,500 m on a glacier forefront in the Qinghai-Tibet Plateau, China

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi are rarely studied at extremely high elevations. Here, AM and DSE colonization in two dominant plant species (Melandrium apetalum and Poa litwinowiana) were microscopically observed on the forefront of Zhadang Glacier (5,500 m above sea level) in the Qinghai-Tibet Plateau, China. The AM fungal taxa were also identified by molecular methods. Both AM and DSE fungi synchronously colonized these two plant species, but AM dominated in M. apetalum and DSE dominated in P. litwinowiana. A total of five AM fungal spore morphotypes (Acaulospora capsicula, Diversispora sp., Glomus constrictum, G. eburneum and Glomus sp.) were found in the rhizosphere soils. Molecular identification revealed two AM fungal phylotypes: one Claroideoglomus phylotype from roots and one Diversispora phylotype from spores. These results extend the elevation at which both AM and DSE are known to occur.     

攀枝花市麻疯树根际土壤内生菌根菌分布特征

【目的】研究天然麻疯树根际土壤中内生菌根菌孢子果密度,揭示麻疯树根际土壤中内生菌根菌的分布特征,为麻疯树育苗繁殖和栽植推广提供科学依据。【方法】采用随机采样的方法对攀枝花市仁和区天然麻疯树根际土壤中内生菌根菌孢子果数量进行调查,确定了20个采样点,采集了20个土根混合样,利用解剖镜测定其孢子果密度,再根据1999年林业行标测定样品中的水分含量,养分含量等。【结果】天然麻疯树根际土壤采样从海拔1025m开始,直到1500m。土壤样品中均含有AM菌根菌孢子果,且数量丰富的,含量最高的土壤样品中AM菌根菌孢子果密度为236个/g干土,最小的密度为9个/g干土,平均密度为80个/g干土。土样含水量在4.01%-13.39%之间,平均值为6.79%,与AM菌根菌孢子果含量正相关。有机质平均含量为3.80g/kg,与AM菌根菌孢子果含量正相关。【结论】天然麻疯树根际土壤中均能检测出AM菌根菌孢子果,且含量高,但分布不均。它的密度随着海拔高度的升高逐渐降低,随土壤含水量的增加而增加,随土壤有机质含量的增加而增加。     

The effect of sunlight on allergen release from spores of the fungus Alternaria

Airborne fungal spores are known carriers of allergen. Correlations between spore counts and allergen concentrations are poor. It is known that germination increases allergen release, implicating spore viability as a determinant of allergen release. During aerial dispersal, spores can be exposed to prolonged periods of ultraviolet (UV) light which can reduce viability of spores. We examined the relation between spore viability and allergen release in two experiments: firstly spores from culture were treated with a UV wavelength of 254?nm (not present in sunlight reaching the earth's surface) or autoclaved, and secondly, spores were exposed to simulated sunlight over three days. In both studies viability was measured (by germination on agar and by metabolic activity with nitro-blue tetrazolium vital stain) and allergen release by the Halogen immunoassay. The UV light reduced the proportion of spores able to germinate but did not affect metabolic activity or allergen release. Autoclaving reduced the proportion of spores releasing allergen by half (p<0.0001). Three days' exposure to simulated sunlight correlated negatively with spore germination and metabolic activity (p<0.0001), but did not affect allergen release (p=0.799). In conclusion, simulated sunlight reduced the metabolic activity and germinability of spores however the proportion releasing allergen remained unaffected. These findings suggest that spore counts may reflect allergen concentrations in the air if spores are dead or dormant. The contribution of viable spores to concentrations of airborne allergen, as well as the role of germination in allergen delivery to the respiratory tract, remains to be resolved.     

A new approach for enhanced multiplication of arbuscular mycorrhizal fungi and isolation of ITS regions from Glomus deserticola and Laccaria fraterna

Rootlets induced from the petiole base of L. purpureus, using IAA and kinetin was used for enhanced multiplication of arbuscular mycorrhizal (AM) fungus, G. deserticula. Using conserved short arbitrary oligonucleotides, as specific primers, we amplified the ITS-region, a molecular marker for fungal identification, from the genomic DNA extracted from cultured spores of G. deserticola, and genomic DNA extracted from the mycelium of L. fraterna. The capacity of fungal colonization and subsequent spore formation of G. deserticola, compared with the natural root system was evaluated. This technology would provide a simple way to multiply AM fungi and to produce spores without microbial contamination useful for further molecular characterization.     

不同品种牡丹对丛枝菌根真菌群落结构的影响

对山东菏泽赵楼牡丹园栽培的不同品种牡丹(Paeonia suffruticosa)根围丛枝菌根(ar-buscular mycorrhiza,AM)真菌孢子密度、种属构成、种丰度、分布频度、物种多样性指数及其物种组成相似性等进行了研究.结果表明:不同品种牡丹根围AM真菌的种属构成、种丰度和分布频度等均不相同,其中,从‘凤丹'和‘赵粉'根围中各分离到10种AM真菌,从‘乌龙捧盛'和‘洛阳红'根围中分离到9种,从‘胡红'根围中分离到8种;‘凤丹'根围AM真菌孢子密度最高,为59个·50 g-1土,‘胡红'最低,为47个·(50 g)-1土;‘赵粉'的物种多样性指数最高(1.89),‘胡红'最低(1.71).‘凤丹'和‘胡红'的菌根侵染率最高,为63.6%,‘乌龙捧盛'最低,为52.7%.不同牡丹品种之间AM真菌种类组成的相似性系数在0.71～0.95,其中‘乌龙捧盛'和‘凤丹'的相似性系数最高(0.95),而‘胡红'与‘洛阳红'的相似性系数最低(0.71).牡丹基因型能改变AM真菌群落结构特征.     

西双版纳热带雨林中丛枝菌根真菌的初步研究*

对西双版纳热带雨林中30个科的42种植物根系的丛枝菌根真菌定居情况进行了调查,并从这些植物的根际土壤中分离鉴定了分属于无梗囊霉属(Acaulospora)、球囊霉属(Glomus)和硬囊霉属(Sclerocystis)的25种丛枝菌根真菌。对热带雨林土壤中丛枝菌根真菌的孢子密度（spore density）、物种丰富度（species richness）以及已鉴定种的出现频率进行统计分析发现：热带雨林土壤中丛枝菌根真菌的孢子密度在每100g土壤116~1560个之间,平均478个;物种丰富度在2~7之间,平均为4.5;无梗囊霉属和球囊霉属真菌是热带雨林土壤中丛枝菌根真菌的优势类群。     

Availability and function of arbuscular mycorrhizal and ectomycorrhizal fungi during revegetation of dewatered reservoirs left after dam removal

Revegetation following dam removal projects may depend on recovery of arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungal communities, which perform valuable ecosystem functions. This study assessed the availability and function of AM and EM fungi for plants colonizing dewatered reservoirs following a dam removal project on the Elwha River, Olympic Peninsula, Washington, United States. Availability was assessed via AM fungal spore density in soils and EM root tip colonization of Salix sitchensis (Sitka willow) in an observational field study. The effect of mycorrhizal fungi from 4 sources (reservoir soils, commercial inoculum, and 2 mature plant community soils) on growth and nutrient status of S. sitchensis was quantified in a greenhouse study. AM fungal spores and EM root tips were present in all field samples. In the greenhouse, plants receiving reservoir soil inoculum had only incipient mantle formation, while plants receiving inoculum from mature plant communities had fully formed EM root tips. EM formation corresponded with alleviation of phosphorus stress in plants (lower shoot nitrogen:phosphorus). Thus, revegetating plants have access to AM and EM fungi following dam removal, and EM formation may be especially important for plant P uptake in reservoir soils. However, availability of mycorrhizal fungi declines with distance from established plant communities. Furthermore, EM fungal communities in recently dewatered reservoirs may not be as effective at forming beneficial mycorrhizae as those from mature plant communities. Whole soil inoculum from mature plant communities may be important for the success of revegetating plants and recovery of mycorrhizal fungal communities.     

荒漠植物根际AM真菌的空间分布和定殖

 通过分析以色列荒漠地区Zygophyllum dumosum, Hammada scoparia, Artemisia herba-alba 和 Atriplex halimus 等4种灌木根际AM真菌的空间分布和定殖程度,研究了AM真菌分布和定殖与植物种类和土壤因子间的相关性。样品分别从0～10 cm,10～20 cm,20～30 cm,30～40 cm和40～50 cm等5个土层中采取,土样过2 mm筛。收集的根样切成1 cm根段,经染色后,根据感染长度确定AM真菌不同结构的定殖率;用湿筛倾析法和蔗     

Arbuscular mycorrhizal status of spring ephemerals in the desert ecosystem of Junggar Basin, China

A survey was made of the arbuscular mycorrhizal (AM) status of 73 spring ephemeral plant species that grow in the desert ecosystem of Junggar Basin, northwest China. The proportion of AM colonization ranged from 7 to 73% with a mean value of 30%. A total of 65 plant species studied were AM with coils/arbuscules or vesicles and the remaining eight species were possibly AM with no coils/arbuscules or vesicles but with fungal mycelia in the root cortex. AM fungal spores were isolated from rhizosphere samples of all 73 plant species and identified. The mean spore density was 22 per 20 ml of air-dried soil, ranging from 0 to 120. Colonization and spore density of perennials were slightly higher than of annuals and varied among different plant families. A total of 603 AM fungal spore (or sporocarp) specimens were isolated belonging to six genera, Acaulospora, Archaeopora, Entrophospora, Glomus, Paraglomus, and Scutellospora; Glomus was the dominant genus. We conclude that spring ephemerals may be highly dependent on AM associations for survival in the very infertile and arid soils of this desert ecosystem.Electronic supplementary material Supplementary material is available for this article at     

Rapid differentiation and enumeration of the total, viable vegetative cell and spore content of thermophilic bacilli in milk powders with reference to Anoxybacillus flavithermus

AIMS: The development of a rapid method for the selective detection and enumeration of the total and viable vegetative cell and spore content of thermophilic bacilli in milk powder by PCR. METHODS AND RESULTS: Quantitative PCR and microscopy indicate the presence of up to 2.9 log units more cells in milk powder than accounted for by plate counting due to the majority of cells being killed during milk processing. Two approaches for viable and dead cell differentiation of thermophilic bacilli by quantitative PCR were evaluated, these being the nucleic binding dye ethidium monoazide (EMA) and DNase I digestion. The former agent exposed to a viable culture of Anoxybacillus flavithermus caused considerable cell inactivation. In contrast, DNase I treatment had no effect on cell viability and was utilized to develop DNA extraction methods for the differential enumeration of total, viable vegetative cells and spores in milk powder. Moreover, the methods were further applied and evaluated to 41 factory powder samples taken throughout eight process runs to assess changes in numbers of vegetative cells and spores with time. DNase I treatment reduced vegetative cell numbers enumerated with PCR by up to 2.6 log units. The quantification of spores in the factory milk powders investigated indicates on average the presence of 1.2 log units more spores than determined by plate counting. CONCLUSIONS: The method presented in this study provides the ability to selectively enumerate the total and viable cell and spore content of reconstituted milk. SIGNIFICANCE AND IMPACT OF THE STUDY: The current study provides a tool to monitor the extent of thermophilic contamination during milk powder manufacturing 60-90 min after sampling.     

青藏高原高寒草地AM真菌分布及其对近自然恢复的生态作用

超载过牧以及全球气候变化等导致大部分青藏高原高寒草地呈现持续退化态势。青藏高原高寒草地退化致使地上植物群落逐渐发生更替,地下土壤微生物群落多样性和丰富度发生改变。本文旨在探析青藏高原高寒草地丛枝菌根（arbuscular mycorrhizal,AM）真菌的分布特征、对近自然恢复的生理生态效应及其作用机制。青藏高原高寒草地中已报道4目14属61种AM真菌,约占已知AM真菌物种的20%。高寒草地禾本科植物根围AM真菌物种丰度最高,而莎草科植物根围AM真菌孢子密度最高。3种高寒草地植被类型中,高寒草原AM真菌丰度最高（33种）,山地灌丛草原次之（32种）,高寒草甸最低（22种）。高寒草原以光壁无梗囊霉Acaulospora laevis和闪亮和平囊霉Pacispora scintillans为优势种,山地灌丛草原以摩西斗管囊霉Funneliformis mosseae为优势种,高寒草甸以光壁无梗囊霉A. laevis、近明球囊霉Claroideoglomus claroideum和闪亮和平囊霉P. scintillans为优势种。高寒草地土著AM真菌与植物构建的菌根网络可以通过调节营养元素吸收、分配,促进植物建植和生长;但是毒杂草入侵可以改变土著AM真菌物种多样性和菌根网络,限制本地植被的实际生态位扩张。退化高寒草地中,AM真菌群落具有高的环境适应性和恢复力,其不仅调控地上植物群落建植和多样性,同时AM真菌建植也增加了代谢产物-球囊霉素相关土壤蛋白产生,进而协同改善地下土壤微生态系统,为退化高寒草地早期植被恢复塑造土壤生境。因此,AM真菌在退化高寒草地近自然恢复中具有较大的应用潜力。     

Arbuscular mycorrhizas in a valley-type savanna in southwest China

The arbuscular mycorrhizal (AM) status of 67 plant species in a savanna community in the hot, dry valley of Jinsha River, southwest China was surveyed. It was found that about 95% of the plant species formed AM and 5% possibly formed AM. The composition of AM fungi (AMF) in the rhizosphere soils was also investigated. The AMF spore density ranged from 5 to 6,400 per 100 g soil, with an average of 1,530, and these spores/sporocarps were identified as belonging to six genera. Fungi belonging to the genera Glomus and Acaulospora were the dominant AMF. High densities of AMF spores in the rhizosphere soils, and the intensive colonization of the plant roots, indicated that plants grown in this valley-type savanna may be highly dependent on AM.     

Arbuscular mycorrhizal fungi associated with the Meliaceae on Hainan island, China

Species richness, spore density, frequency of occurrence, and relative abundance of AM fungi were determined in rhizosphere soil samples from nine tropical rainforest sites on Hainan island, south China, and the arbuscular mycorrhizal (AM) status of members of the Meliaceae was examined. All 28 plant taxa investigated (25 species including two varieties of 1 species and three varieties of another) were colonized by AM fungi. The mean proportion of root length colonized was 56% (range 10–95%). Vesicles were observed in 27 and hyphal coils in 26 of the 28 plant taxa. Mycorrhizas were of the Paris-type or intermediate-type, with no Arum-type mycorrhizas observed. Species richness of AM fungi varied from 3 to 15 and spore density from 46 to 1,499 per 100 g rhizosphere soil. Of 33 AM fungal taxa in five genera isolated and identified, 18 belonged to Glomus, 9 to Acaulospora, 1 to Entrophospora, 2 to Gigaspora, and 3 to Scutellospora. Acaulospora and Glomus were the dominant genera identified. Glomus claroideum was the taxon most commonly isolated, with a frequency of occurrence of 56.5% and relative abundance of 10.4%. A positive correlation was found between percentage of root length colonization and species richness. However, there was no correlation between spore density and percentage of root length colonized by AM fungi.     

Colonization Characteristics and Diversity of Arbuscular Mycorrhizal Fungi in the Rhizosphere of <i>Iris lactea</i> in Songnen Saline-alkaline Grassland

To understand arbuscular mycorrhizal (AM) fungi resources and develop AM fungal species in ornamental plants with saline-alkaline tolerances, Iris lactea, which grows in the Songnen saline-alkaline grassland with a high ornamental value, was selected as the experimental material, and the colonization characteristics of its roots and the AM fungal diversity in its rhizosphere were explored. The results of the observations and calculations of mycorrhizae from ten different samples showed that AM fungi colonized the roots of I. lactea and formed Arum-type mycorrhizal structures. There was a significant correlation between soil spore density and pH value, while the colonization rate showed a fluctuating trend with increasing pH values. The observed colonization intensities were of Levels II (1%–10%) or III (11%–50%), and the vesicle abundances were of grades A₂ or A₃ among different sites. AM fungi produced a large number of mycelia and vesicles in the roots of I. lactea after colonization. Thirty-seven species belonging to 15 genera of AM fungi were isolated from the rhizosphere of I. lactea and identified by morphological identification. Funneliformis and Glomus were the dominant genera, accounting for 21.79% and 20.85% of the total number, respectively. F. mosseae and Rhizophagus intraradices were isolated in all samples with importance values of 58.62 and 51.19, respectively. These results are expected to provide a theoretical basis for the analysis of the salt tolerance mechanism of I. lactea and for the discovery, exploration and further screening of AM fungal resources with salinity tolerances in saline-alkaline soils.