菌根真菌的生理生态功能

菌根真菌是土壤中重要生物成员之一,不仅具有丰富的遗传多样性和物种多样性,其功能也是丰富多样,主要体现在：1）影响陆生植物起源、进化、演化与分布;2）促进植物的生长发育;3）提高植物的抗逆性;4）修复污染与退化土壤、改善土壤质量与健康状况;5）促进农林牧业的生产;6）保持生态平衡、稳定生态系统及其可持续生产力.随着技术发展和研究的深入,菌根真菌新功能将会不断被发现.     

中国菌根研究60年:过去、现在和将来

菌根(真菌根系)存在于大约90%的植物中,在促进土壤结构、植物养分与生长、元素生物地球化学循环和陆地生态系统结构与功能等方面具有重要作用.过去60年尤其是近30年,中国菌根研究成果举世瞩目,如共鉴定出20种新种与120余种新记录种丛枝菌根真菌、30种新种与800余种新记录种外生菌根真菌以及10种新种与100余种新记录种兰花菌根真菌.同时,在菌根真菌菌种丰富度与遗传结构、菌种生态分布与植物种群,植物养分摄取与生长、植物修复与土地复垦、植物抗病性和与其他土壤微生物相互作用、菌根植物酶学性质及大气CO2和O3浓度升高对丛枝菌根多样性的影响等方面也取得重大进展.本文选介中国菌根主要研究成就,进行研究前景展望,以促进我国菌根研究的深入开展.     

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。     

菌根真菌在生态系统中的作用

 菌根是一种植物营养根与土壤真菌形成的共生体,在自然界中分布广泛。本文着重从以下几个方面介绍相关的研究进展：1) 菌根真菌作为生态系统的重要组成部分,具有不可忽视的生物量,并成为连接绿色植物和食真菌者食物链的重要一环;2) 菌根真菌通过参与凋落物的酶降解过程影响有机物的循环,通过促进生物固氮、加速土壤磷的风化、提高土壤溶液离子的有效性以及直接吸收等过程影响氮、磷、钾、钙、镁等元素的无机循环;3) 菌根真菌与土壤微生物间存在有益的或拮抗的相互作用,并可以直接或间接地影响根际生物区系的组成和数量;菌根真菌通过对宿主植物的有益作用而影响植物的种间竞争,通过菌根网络而形成的种团可以在同种或不同种植物间实现资源的重新分配和共享;由于对种间关系的作用和对食物链的影响,菌根真菌对群落的物种构成和多样性的维持具有重要的作用;菌根真菌是群落演替过程的指示者,也是这一过程的参与者和推动者,并且菌根真菌的存在也有利于提高土壤团聚体的稳定性及促进灰壤的形成;4) 菌根真菌的种类和数量可以指示生态系统中自然的或人类活动引起的变化,并可以在生态系统的保护、恢复或重建过程中发挥重要作用。文章的最后还介绍了最新的研究热点和发展趋势。     

菌根学对生物类学科发展的意义

菌根（mycorrhiza）是真菌与植物之间形成的最广泛的共生体。菌根真菌（rnycorrhizal fungi）具有丰富遗传多样性、形态多样性、物种多样性、生态系统多样性和功能多样性。菌根真菌与植物协同进化,发挥生理生态功能,对促进农林牧业生产、保持生态系统的稳定及其可持续生产力具有重大而不可替代的作用。经过一个多世纪的研究发展,菌根学（mycorrhizology）——菌物学与植物学的杂交学科终于在21世纪诞生了。随着研究的深入,人们发现菌根学不仅与菌物学和植物学关系极为密切,而且还与生态学、土壤学、保护生物学、植物保护学、微生物学、食用菌学、园林园艺学、作物栽培与耕作学、昆虫学等密切相关。作为一门新兴学科,菌根学自身发展的同时,也大大促进了相关学科的进展。本文系统总结了菌根学对其他学科发展所作的贡献,旨在进一步加强菌根学与其他学科的交叉渗透,为菌根学与其他学科协同进化奠定理论基础、促进多学科合作研究,为21世纪生物学的更大发展注入新的活力。     

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。     

甘肃盐碱土植物VA菌根真菌侵染研究

对甘肃盐碱土中植物的VA菌根真菌共生状况进行研究,结果表明：在10科17种植物中,除碱蓬（Suaeda glauca Beg.）外均被菌根真菌侵染,占94.1%;盐碱土中孢子密度较高,表明甘肃盐碱土生态系统中植物对菌根真菌具有较高的依赖性,菌根真菌在盐碱土中产孢能力较强;所调查植物的VA菌根结构类型Arum型占68.75%,Pris型占31.25%;菌根结构类型与宿主植物类型有关,禾本科（Poaceae）和鸢尾科（Iridaceae）植物为P型菌根,百合科（Liliaceae）、胡颓子科（Elaeagnaceae）等其它科植物均为A型菌根;土壤类型影响了宿主植物的菌根侵染率和根际土的孢子密度,相同宿主植物在不同类型土壤中的菌根侵染率和孢子密度具有很大的差异.     

丛枝菌根共生的信号转导及其相关基因

大多数植物根系能够与某些真菌形成相互依存、互惠互利的菌根共生关系.植物在提供给丛枝菌根真菌赖以生存的碳源的同时,也通过真菌从土壤中吸取矿质营养.丛枝菌根能够促进植物生长,提高植物抗逆性和抵御外界不良环境,对提高农林业生产效率、增强生态系统稳定性及维护生物多样性具有重要的意义.菌根的形成是一系列信号分子交换传递和共生相关基因表达调控的结果.在信号转导途径中,共生受体样蛋白激酶、离子通道和钙/钙调依赖性蛋白激酶基因的表达对菌根的形成是不可或缺的.就丛枝菌根共生的信号转导机制以及信号途径中3个必需基因的结构、功能及研究现状进行了综述.     

春兰和蕙兰菌根真菌rDNA ITS序列及共生专一性分析

春兰(Cymbidium goeringii)和蕙兰(Cymbidium faberi)是我国较为广泛分布的地生类型兰属植物,具有悠久的栽培历史和很高的经济价值.菌根真菌与兰科植物专一性关系一直是兰科茵根研究中的热点.该文对35株分离自浙江天目山野生春兰和蕙兰的菌根真菌进行了rDNA ITS序列分析,并在此基础上初步探讨了菌根真菌与春兰、蕙兰之间的专一性关系.结果表明,分离获得的菌根真菌与其共生兰属植物在种的层面具显著专一性,即物种是影响或决定浙江天目山地区春兰、蕙兰与共生菌根真菌专一性的重要因素;研究同时发现,自蕙兰同一条根分离获得的菌根真菌菌株间亦表现丰富的多样性差异.     

丛枝菌根真菌多样性对植物群落构建和稀有种维持的研究进展

丛枝菌根(AM)是植物与微生物联系中最为古老的共生体,全球范围内约80%的陆生植物与AM真菌共生形成丛枝菌根。这一共生关系在气候稳定和土壤磷贫瘠的热带、亚热带森林中更为普遍。以往的研究表明AM真菌通过提高植物对磷的吸收促进植物生长和定植,即产生植物-土壤正反馈。植物-土壤正反馈可降低由土壤病原菌引起的植物-土壤负反馈,进而降低植物-土壤负反馈维持植物多样性的能力,这与热带、亚热带森林中极高的植物多样性以及占比惊人的稀有种相悖。随着对热带、亚热带森林中AM真菌多样性研究的不断深入,越来越多的研究发现AM真菌多样性在不同的生境条件下以及不同的宿主植物间存在较大差异,这些差异可引起植物适合度的不同,进而影响植物群落构建。该文整合了AM真菌在宿主植物群落构建、宿主植物共存及稀有种维持等方面的研究进展,以期为验证“稀有种优势”假说提出新的研究思路,进而更有效地保护稀有植物。     

Methods of studying soil microbial diversity

Soil microorganisms, such as bacteria and fungi, play central roles in soil fertility and promoting plant health. This review examines and compares the various methods used to study microbial diversity in soil.     

Recombination in Glomus intraradices, a supposed ancient asexual arbuscular mycorrhizal fungus

Background  

Arbuscular mycorrhizal fungi (AMF) are important symbionts of most plant species, promoting plant diversity and productivity. This symbiosis is thought to have contributed to the early colonisation of land by plants. Morphological stasis over 400 million years and the lack of an observed sexual stage in any member of the phylum Glomeromycota led to the controversial suggestion of AMF being ancients asexuals. Evidence for recombination in AMF is contradictory.     

Plant identity strongly structures the root-associated fungal community in a diverse subtropical forest

Revealing the relationship between plants and root-associated fungi is very important in understanding diversity maintenance and community assembly in ecosystems. However, the community assembly of root-associated fungi of focal plant species along a subtropical plant species diversity gradient is less documented. Here, we examined root-associated fungal communities associated with five ectomycorrhizal (EM) plant species (Betula luminifera, Castanea henryi, Castanopsis fargesii, C. sclerophylla, and Quercus serrate) in a Chinese subtropical woody plant species diversity (1, 2, 4, 8, 16 and 24 species) experiment, using paired-end Illumina MiSeq sequencing of the ITS2 region. In total, we detected 1933 root-associated fungal operational taxonomic units (OTUs) at a 97% sequence similarity level. Plant identity had a significant effect on total and saprotrophic fungal OTU richness, but plant species diversity level had a significant effect on saprotrophic and pathogenic fungal OTU richness. The community composition of total, saprotrophic and EM fungi was structured by plant identity and plant species diversity level. However, the community composition of pathogenic fungi was only shaped by plant identity. This study highlights that plant identity has a stronger effect on the root-associated fungal community than plant species diversity level in a diverse subtropical forest ecosystem.     

Patterns and regulation of mycorrhizal plant and fungal diversity

The diversity of mycorrhizal fungi does not follow patterns of plant diversity, and the type of mycorrhiza may regulate plant species diversity. For instance, coniferous forests of northern latitudes may have more than 1000 species of ectomycorrhizal (EM) fungi where only a few ectomycorrhizal plant species dominate, but there are fewer than 25 species of arbuscular mycorrhizal (AM) fungi in tropical deciduous forest in Mexico with 1000 plant species. AM and EM fungi are distributed according to biome, with AM fungi predominant in arid and semiarid biomes, and EM fungi predominant in mesic biomes. In addition, AM fungi tend to be more abundant in soils of low organic matter, perhaps explaining their predominance in moist tropical forest, and EM fungi generally occur in soils with higher surface organic matter.EM fungi are relatively selective of host plant species, while AM tend to be generalists. Similar morphotypes of AM fungi collected from different sites confer different physiological benefits to the same plant species. While the EM fungi have taxonomic diversity, the AM fungi must have physiological diversity for individual species to be so widespread, as supported by existing studies. The environmental adaptations of mycorrhizal fungi are often thought to be determined by their host plant, but we suggest that the physiology and genetics of the fungi themselves, along with their responses to the plant and the environment, regulates their diversity. We observed that one AM plant species,Artemisia tridentata, was associated with different fungal species across its range, indicating that the fungi can respond to the environment directly and must not do so indirectly via the host. Different species of fungi were also active during different times of the growing season on the same host, again suggesting a direct response to the environment.These patterns suggest that even within a single functional group of microorganisms, mycorrhizal fungi, considerable diversity exists. A number of researchers have expressed the concept of functional redundancy within functional groups of microorganisms, implying that the loss of a few species would not be detectable in ecosystem functioning. However, there may be high functional diversity of AM fungi within and across habitats, and high species diversity as well for EM fungi. If one species of mycorrhizal fungus becomes extinct in a habitat, field experimental data on AM fungi suggest there may be significant shifts in how plants acquire resources and grown in that habitat.     

菌物在森林生态系统中的功能和作用研究进展

 综述了菌物在森林生态系统中的功能和作用方面的研究进展,表明菌物是森林生态系统中不可忽视的重要组成部分,对森林生态系统的建立、演替、稳定、物质循环和能量流动等都具有重要的影响。菌物与植物的共生是植物起源和森林形成的基础,而且是森林健康发展的关键;菌物在森林中的分解作用和对土壤母岩的风化作用是生物地球化学循环的重要环节,且菌体本身是森林中的主要碳、氮汇成员;菌物多样性是森林物种多样性和生态稳定的决定因素之一,其多样性的丧失可以直接影响森林的生态系统乃至加剧地球的大气温室效应。菌物在我国森林保护和可持续发展以及生态环境建设上具有重要的位置。     

Host plant species effects on arbuscular mycorrhizal fungal communities in tallgrass prairie

Symbiotic associations between plants and arbuscular mycorrhizal (AM) fungi are ubiquitous in many herbaceous plant communities and can have large effects on these communities and ecosystem processes. The extent of species-specificity between these plant and fungal symbionts in nature is poorly known, yet reciprocal effects of the composition of plant and soil microbe communities is an important assumption of recent theoretical models of plant community structure. In grassland ecosystems, host plant species may have an important role in determining development and sporulation of AM fungi and patterns of fungal species composition and diversity. In this study, the effects of five different host plant species [Poa pratensis L., Sporobolus heterolepis (A. Gray) A. Gray, Panicum virgatum L., Baptisia bracteata Muhl. ex Ell., Solidago missouriensis Nutt.] on spore communities of AM fungi in tallgrass prairie were examined. Spore abundances and species composition of fungal communities of soil samples collected from patches within tallgrass prairie were significantly influenced by the host plant species that dominated the patch. The AM fungal spore community associated with B. bracteata showed the highest species diversity and the fungi associated with Pa. virgatum showed the lowest diversity. Results from sorghum trap cultures using soil collected from under different host plant species showed differential sporulations of AM fungal species. In addition, a greenhouse study was conducted in which different host plant species were grown in similar tallgrass prairie soil. After 4 months of growth, AM fungal species composition was significantly different beneath each host species. These results strongly suggest that AM fungi show some degree of host-specificity and are not randomly distributed in tallgrass prairie. The demonstration that host plant species composition influences AM fungal species composition provides support for current feedback models predicting strong regulatory effects of soil communities on plant community structure. Differential responses of AM fungi to host plant species may also play an important role in the regulation of species composition and diversity in AM fungal communities. Received: 29 January 1999 / Accepted: 20 October 1999     

Food webs obscure the strength of plant diversity effects on primary productivity

Plant diversity experiments generally find that increased diversity causes increased productivity; however, primary productivity is typically measured in the presence of a diverse food web, including pathogens, mutualists and herbivores. If food web impacts on productivity vary with plant diversity, as predicted by both theoretical and empirical studies, estimates of the effect of plant diversity on productivity may be biased. We experimentally removed arthropods, foliar fungi and soil fungi from the longest‐running plant diversity experiment. We found that fungi and arthropods removed a constant, large proportion of biomass leading to a greater reduction of total biomass in high diversity plots. As a result, the effect of diversity on measured plant productivity was much higher in the absence of fungi and arthropods. Thus, diversity increases productivity more than reported in previous studies that did not control for the effects of heterotrophic consumption.     

濒危药用植物掌裂兰根部内生真菌和根际土真菌多样性分析

【背景】植物内生真菌对宿主植物促生长、抗旱和增强抗病能力等方面有着重大的研究和利用价值,尤其对兰科植物的生长起到重要的作用。【目的】通过对掌裂兰根部内生真菌和根际土真菌多样性进行系统分析,掌握掌裂兰根部内生真菌与根际土真菌群落结构,为进一步探究掌裂兰植物与真菌共生规律提供参考。【方法】采用Illumina MiSeq高通量测序技术分析掌裂兰根部内生真菌和根际土真菌多样性。【结果】掌裂兰根部内生真菌隶属于7门89属,优势菌属为瘤菌根菌属(Epulorhiza)(16.93%)、头梗霉属(Cephaliophora)(10.41%)、酵母属(Saccharomyces)(5.73%)、角担菌属(Ceratobasidium)(5.32%)和镰刀菌属(Fusarium)(5.12%),其中Epulorhiza和Ceratobasidium为兰科植物菌根真菌;根际土真菌隶属于11门269属,优势菌属为镰刀菌属(Fusarium)(8.09%)、丛赤壳属(Neonectria)(6.79%)、Plectosphaerella (3.39%)和被孢霉属(Mortierella)(3.01%)。通过...     

Diversity and Antimicrobial and Plant-Growth-Promoting Activities of Endophytic Fungi in Dendrobium loddigesii Rolfe

Endophytic fungi are ubiquitously distributed in orchids and have a great impact on the host plant. The diversity of endophytic fungi in the medicinal orchid Dendrobium loddigesii Rolfe was investigated and their bioactivities in microbe and plant growth were explored here. Endophytic fungi were identified by using morphological and molecular biological methods. Antimicrobial activity was determined by a standard disk assay. Activity in promoting plant growth was confirmed by root inoculation of endophytic fungi in seedling tray and pot experiments. Overall, 48 isolates were isolated from D. loddigesii and identified to belong to 18 genera, with Fusarium and Acremonium being the most dominant populations. A total of 17 isolates belonging to 9 genera were screened for their antimicrobial activity, and Fusarium spp., 8 of the 17 isolates, was also the dominant population. In the seedling tray experiment, two isolates, one of Fusarium named DL26 and the other of Pyrenochaeta named DL351, were shown to enhance plant growth in alder bark–humus medium, and the latter displayed weak activity against Bacillus subtilis (As 1.308) and Aspergillus fumigatus (As 3.2910). In the pot experiment, after inoculation of DL26 and DL351, five out of seven media were fit for plant-endophyte symbionts. Medium #1 of red brick fragments and sphagna was optimal in accelerating plant growth. In conclusion, a great diversity of endophytic fungi in D. loddigesii was first confirmed in a considerable proportion of antimicrobial isolates. Furthermore, two endophytes exhibited the ability to enhance plant growth although their activities were influenced by the growth media.