烟草根际土壤真菌多样性的研究

烟草土传病害发生普遍,危害严重。为深入了解烟草根际土壤真菌区系与土传病害间的相互关系,选取黑龙江、山东、广西和云南四省区的代表性烟田,开展了烟草根际土壤真菌多样性的研究。对采自上述四省区12个县市的224份烟草根际土壤样品进行了真菌的分离和培养,共分离获得1,278株真菌,通过形态学特征鉴定出真菌25属86种。其中接合菌门4属6种,子囊菌门1属1种,无性型真菌20属79种。通过分析发现,烟草根际土壤中的优势真菌种群及其菌株数量所占分离真菌总菌株数量的比例分别为：青霉属Penicillium 16.74%,木霉属Trichoderma 14.32%,镰孢菌属Fusarium 13.54%和曲霉属Aspergillus 11.50%。在12个采样地点中,山东诸城的多样性指数（H￠=2.0666）和均匀度指数（J=0.6898）最高,云南玉溪的丰富度指数（R=4.0687）最高。不同采样地点的烟草根际土壤真菌种群的相似性水平也存在差异,其中云南永胜和大理的烟草根际土壤真菌种群的相似性系数最高（Cj=0.9375）,山东沂水和云南玉溪间的相似性最低（Cj=0.5217）。     

宁夏境内腾格里沙漠固沙植物根际土壤真菌多样性研究

从宁夏境内腾格里沙漠不同生境固沙植物根际采集土样108份,共分离得到257株真菌分属于26属,其中青霉属Penicillium、曲霉属Aspergillus、镰刀菌属Fusarium、链格孢属Alternaria、茎点霉属Phoma、毛霉属Mucor、木霉属Trichoderma和丛梗孢属Monilia是固沙植物根际土壤中普遍存在的真菌种群。多样性分析结果表明,沙漠区真菌物种丰富度、Shannon-Wiener多样性指数和Pielou均匀度最高,分别为16、2.5893和0.9339;而草原区物种丰富度、Shannon-Wiener多样性指数和Pielou均匀度最低,分别为14、2.0891和0.7961。Jaccard相似性研究表明,宁夏境内腾格里沙漠地区4个生境固沙植物根际土壤真菌种群相似性为中等不相似。半荒漠区与封育区相似性最高,草原区与沙漠区相似性最低。典范对应分析(CCA)可知,土壤真菌的种类和数量与土壤性状变化密切相关。9个土壤性状中,氮含量和钾含量是根际真菌群落变化的最主要影响因子。     

三七根腐病株根际土壤真菌群落组成与碳源利用特征研究

根腐病是药用植物三七Panax notoginseng的多发性病害,而土壤真菌群落组成与根腐病的发生存在一定的联系。利用末端限制性酶切片段长度多态性分析和Biolog技术研究了云南文山三七种植园健康和发病三七植株根际土壤真菌群落结构和碳源利用特征,结果表明健康和发病植株的根际土壤真菌多样性和代谢活性差异不显著,但是真菌群落组成存在差异。健康和发病植株根际土壤都以小茎点霉Phoma exigua及镰孢菌属Fusarium真菌为主要种群,而健康植株根际土壤中火丝菌属Pyronema和被孢霉属Mortierella等真菌类群的相对丰度显著高于发病植株根际土壤,尖孢镰孢菌F.ox‐ysporum和刺座霉属的Volutella colletotrichoides的相对丰度则显著低于发病植株。     

山东省烟草根际土壤真菌多样性研究

为了有助于研究烟草根际土壤真菌与根茎病害发生程度的相互关系,文中对采自山东省6个地区的122份烟草根际土壤样品进行了真菌的分离和培养,采用形态学方法进行鉴定,并分析了菌群的多样性组成。从山东烟草根际土壤中分离和鉴定出真菌22属79种,其中接合菌门4属6种,子囊菌门1属1种,无性型真菌17属72种。优势真菌种群为青霉属(Penicillium)、木霉属(Trichoderma)、镰孢菌属(Fusarium)和曲霉属(As-pergillus),所占分离真菌总菌数的比例分别为22.39%、13.62%、12.69%和9.88%。6个采样地区间真菌菌群的多样性水平存在差异,其中诸城地区的多样性指数(H′=2.066 6)、均匀度指数(J=0.689 8)和丰富度指数(R=3.730 1)均最高。     

辽宁碱蓬根际土壤真菌多样性的季节变化及其耐盐性

采用稀释平板法和形态学鉴定法进行了辽宁碱蓬(Suaeda liaotungensis)根际土壤真菌的分离鉴定及季节、盐度对真菌多样性的影响分析。结果表明:春、夏、秋、冬四季辽宁碱蓬根际土壤中的真菌菌落数分别为6410、4180、5730和3340,种类分别为6属13种、9属16种、11属31种、6属12种,共分离鉴定出13属42种真菌;其根际土壤真菌的多样性指数、丰富度指数和均匀度指数,从大到小的次序均为秋夏春冬,3种指数均在秋季达到峰值;多样性指数和丰富度指数差异较大,均匀度指数波动较小,春季和冬季的均匀度指数相近。辽宁碱蓬根际土壤真菌种类明显多于无植被土壤,是无植被土壤的7倍,多样性指数和均匀度指数分别是无植被土壤的4—8倍和1—1.2倍;其根际土壤真菌优势种群包括青霉属(Penicillium)、葡萄穗霉属(Stachybotrys)、枝孢属(Cladosporium)、木霉属(Trichoderma)、曲霉属(Aspergillus)和镰孢属(Fusarium);4个季节的优势菌不尽相同,但均有一个共同的优势菌属青霉属。以Na Cl浓度梯度法制造盐胁迫生境,检测辽宁碱蓬根际土壤真菌对盐胁迫的响应,结果表明:60%左右的菌种能耐受5%以下盐度、15%左右的菌种能耐10%—20%盐度;筛选出了6株高度耐盐菌:细交链孢霉、草酸青霉、产黄青霉、烟曲霉、细极链格孢和赭曲霉,其中最高耐盐菌种赭曲霉可耐20%盐度。创新之处在于以盐度和季节为变量检测辽宁碱蓬根际土壤真菌的种群构成,为其深入研究奠定了理论基础。     

单叶蔓荆根际土壤真菌多样性

对江西鄱阳湖区5个不同地区单叶蔓荆(Vitex trifolia)的根际土壤真菌种类和多样性进行了研究。从100份单叶蔓荆植物根际土壤样品中分离获得128株真菌,隶属于无性型菌和接合菌,共15个属,其中青霉属(Penicillium)为单叶蔓荆根际土壤真菌的优势属,占总菌株数的14.06%,其次为单端孢属(Trichothecium),占总菌株数的11.72%,葡萄孢属(Botrytis)、卷头霉属(Helicocephalum)、茎点霉属(Phoma)、根霉属(Rhizopus)占总菌株数的7.81%,可见单叶蔓荆根际真菌具有较丰富的多样性。研究还发现不同地区单叶蔓荆根际土壤真菌的种群组成和结构存在一定的差异,各属真菌在不同地区的单叶蔓荆根际土壤中所占的优势度也不同。     

辽宁地区药用植物根际土壤真菌多样性的研究

作者于2007和2008年的5-10月间在辽宁省的丹东、凤城、清原、桓仁等药材产区采集土壤样品200余份,通过采用稀释平板法和土壤颗粒平板法进行土壤真菌的分离和培养,共分离和鉴定出27属54种真菌,其中接合菌2属3种、子囊菌1属1种、无性型真菌24属50种。分离到的部分真菌种类是重要的药用植物病原菌,如Cylindrocarpon destructans、Fusarium oxysporum和F.solani。研究发现,Penicillium paxilli、P.expansum、Trichoderma atroviride及T.viride的分离频率最高,是辽宁省4个调查地区药用植物根际土壤真菌的优势菌群。     

青枯病易感和钝感桑树品种根际土壤真菌群落结构比较

为研究青枯病易感和钝感桑树品种植株根际土壤真菌群落组成,该研究以ITS1F和ITS2R为引物,基于高通量测序技术对桑树青枯病易感品种(台湾长果桑,SM)和桑树青枯病钝感品种(桂桑12号,IM)植株根际土壤真菌群落结构进行分析。结果表明：(1)两个品种间指示真菌丰富度的ACE、Chao1指数及表征多样性的Shannon指数无显著差异,门分类水平,被孢霉门(Mortierellomycota)和球囊菌门(Glomeromycota)是青枯病钝感桑树品种植株根际土壤中特有的优势真菌门;而属分类水平,Apiotrichum、地丝菌属(Geotrichum)、足放线病菌属(Scedosporium)和腐质霉属(Humicola)等是青枯病易感桑树品种植株根际土壤中富集的特有优势真菌属。(2)青枯病易感桑树品种植株根际土壤中,缺失了被孢霉门、球囊菌门真菌,以及被孢霉属(Mortierella)、镰刀菌属(Fusarium)、曲霉菌属(Aspergillus)和毛壳菌属(Chaetomium)等具有生防功能的优势真菌门属,可能是其易感青枯病的重要原因。(3)根据真菌群落对同类环境资源的利用途径进行功...     

除虫菊内生真菌类群与分布的初步研究

为了解除虫菊内生真菌的种类和分布情况,采用常规分离方法,从除虫菊(Pyrethrum cinerariifolium Trev.)根、茎、叶、花中分离获得内生真菌共计128株,经形态观察,鉴定出12个属:镰孢霉属(Fusarium),毛壳菌属(Chaetomium),茎点霉属(Phoma),链格孢属(Alternaria),内多隔孢属(Endophragmiella),拟盘多毛孢属(Pestalotiopsis),腐殖霉属(Humicola),黑孢霉属(Nigrospora),韦氏孢属(Wiesneriomyces),色串孢属(Torula),阜孢霉属(Papularia),丝核菌属(Rhizoctonia),其中镰孢菌属、链格孢属、腐殖霉属为优势种群。除虫菊不同部位内生真菌的数量、分布、种群及其组成存在差异。     

羊肚菌烂柄病发生对土壤真菌群落结构的影响

为了解羊肚菌(Morel)烂柄病的发生对土壤真菌群落结构的影响,采用Illumina MiSeq高通量测序技术,对健康羊肚菌根际土、烂柄病发病子实体根际土及相同环境下未栽培羊肚菌土壤的真菌群落结构进行研究。结果表明,测序样品共获得344 163条序列,归为7个真菌门。各样品真菌多样性分析结果表明,未栽培土壤真菌群落多样性较高,栽培羊肚菌根际土壤真菌多样性显著降低,烂柄病发生后土壤真菌多样性增加。群落结构分析表明,烂柄病根际优势真菌类群为拟青霉属(Paecilomyces)、木霉属(Trichoderma)、葡萄穗霉属(Stachybotrys)、枝顶孢属(Acremonium)、Paratritirachium、Zopfiella、被孢霉属(Mortierella)和柄孢壳属(Podospora)。烂柄病的发生改变了土壤真菌群落结构,促进了根际真菌的繁殖。为了解羊肚菌烂柄病的发生、传播机理及防治提供了参考。     

Rhizosphere disturbance influences fungal colonization and community development on dead fine roots

Little is known about the community dynamics of fungi on decomposing fine roots, despite the importance of fine roots as a source of carbon to detrital systems in forests. We examined fungal communities on dead roots in a sugar-maple dominated northern hardwood forest to test the hypothesis that community development is sensitive to rhizosphere disruption. We generated cohorts of dead fine roots in root windows and disturbed the rhizosphere microbial community in half of the windows by moving roots into sieved bulk soil. We sampled root fragments repeatedly over time and cultured fungi from these fragments to explore temporal patterns of fungal species composition. Disturbing the root rhizosphere prior to initiating decomposition changed the dominant fungal taxa, the distribution of dominant species within the community, and the temporal development in the culturable fungal community. Dominance in control roots shifted from Neonectria in early decay to Umbelopsis in later decay. Disturbance roots were more evenly dominated over time by Trichoderma, Neonectria, another species of Umbelopsis, and Pochonia. Our results suggest that species interactions are important in the ecology of fine root decay fungi, with the rhizosphere community of the living root influencing development of the decay community.     

Community Structure of Rhizomicrobiomes in Four Medicinal Herbs and Its Implication on Growth Management

Medicinal plants are the basic materials of traditional Chinese medicine. Soil characteristics and microbial contribution play important roles in the growth and product quality of medicinal plants, but the link between them in the rhizosphere of medicinal plants has been overlooked. Accordingly, Mentha haplocalyx, Perilla frutescens, Glycyrrhiza uralensis, and Astragalus membranaceus, four plants used in traditional Chinese medicines, were investigated in this study in order to elucidate bacterial and arbuscular mycorrhizal fungal (AMF) diversity in the rhizosphere and its possible association with soil quality. DGGE-based 16S rRNA and 18S rRNA gene sequencing results indicated that the diversity of both bacteria and AMF in Glycyrrhiza uralensis and Astragalus membranaceus was significantly higher than those in Mentha haplocalyx and Perilla frutescens, suggesting that medicinal plants have different preferences even under the same conditions. In addition, enzymatic activities and nutrition were enhanced in the rhizospheric soil of Mentha haplocalyx and Perilla frutescens, and the correlation among AMF diversity, soil enzymatic activities and nutrition was confirmed using RDA analysis. These results suggest the potential to grow medicinal plants with a reasonable rotation or intercrop in order to maintain long-term continuous soil development.     

Bioactivity of endophytic Trichoderma fungal species from the plant family Cupressaceae

Trichoderma fungal species are universal soil residents that are also isolated from decaying wood, vegetables, infected mushroom and immunocompromised patients. Trichoderma species usually biosynthesize a plethora of secondary metabolites. In an attempt to explore endophytic fungi from healthy foliar tissues of the plant family Cuppressaceae, we explored Cupressus arizonica, C. sempervirens var. cereiformis, C. sempervirens var. fastigiata, C. sempervirens var. horizontalis, Juniperus excelsa, Juniperus sp. and Thuja orientalis plants and recovered several endophytic Trichoderma fungal strains from Trichoderma atroviride and Trichoderma koningii species. We found that the host plant species and biogeographical location of sampling affected the biodiversity and bioactivity of endophytic Trichoderma species. Furthermore, the bioactivity of Trichoderma isolates and the methanol extracts of their intra- and extra-cellular metabolites were assessed against a panel of pathogenic fungi and bacteria. Fungal growth inhibition, conidial cytotoxicity, minimum inhibitory concentration and minimum bactericidal concentration were evaluated and analyzed by statistical methods. Our data showed that both intra- and extracellular secondary metabolites from all endophytic isolates had significant cytotoxic and antifungal effects against the model target fungus Pyricularia oryzae and the cypress fungal phytopathogens Diplodia seriata, Phaeobotryon cupressi and Spencermartinsia viticola. Further research indicated their significant antimicrobial bioactivity against the model phytopathogenic bacteria Pseudomonas syringae, Erwinia amylovora and Bacillus sp., as well. Altogether, the above findings show for the first time the presence of T. atroviride and T. koningii as endophytic fungi in Cupressaceae plants and more importantly, the Trichoderma isolates demonstrate significant bioactivity that could be used in future for agrochemical/drug discovery and pathogen biocontrol.     

Plant pathogens but not antagonists change in soil fungal communities across a land abandonment gradient in a Mediterranean landscape

We assessed whether the presence and abundance of plant pathogens and antagonists change in soil fungal communities along a land abandonment gradient. The study was carried out in the Cilento area (Southern Italy) at a site with three different habitats found along a land abandonment gradient: agricultural land, Mediterranean shrubland and woodland. For all microbiological substrates the colony forming units were about 3.1 × 10⁶ g⁻¹ soil for agricultural land and about 1.1 × 10⁶ g⁻¹ soil for Mediterranean shrubland and woodland. We found the following genera in all habitats: Cladosporium, Mortierella, Penicillium and Trichoderma. In agricultural land, the significantly most abundant fungus genera were Aspergillus, Fusarium, Cylindrocarpon and Nectria; in Mediterranean shrubland, Rhizopus and Trichoderma; and in woodland, Bionectria, Mortierella, Cladosporium, Diplodia, Paecilomyces, Penicillium and Trichoderma. We found a total of 8, 8 and 9 species of fungal antagonist, and 16, 6 and 6 species of fungal plant pathogens in agricultural land, Mediterranean shrubland and woodland respectively. Fungal plant pathogens decreased significantly over a land abandonment gradient, while we no found significant differences among fungal antagonists in the three habitats. We conclude that a decrease in the number of fungal pathogen species occurs when formerly cultivated areas are abandoned. On the other hand, fungal antagonists seem not to be affected by this process.     

Caffeine fostering of mycoparasitic fungi against phytopathogens

Caffeine (1,3,7-trimethixanthine) is a typical purine alkaloid produced in more than 80 plant species. Its biological role is considered to strengthen plant''s defense capabilities, directly as a toxicant to biotic attackers (allelopathy) and indirectly as an activator of defense system (priming). Caffeine is actively secreted into rhizosphere through primary root, and possibly affects the structure of microbe community nearby. The fungal community in coffee plant rhizosphere is enriched with particular species, including Trichoderma family, a mycoparasite that attacks and kills phytopathogens by coiling and destroying their hyphae. In the present study, the caffeine response of 8 filamentous fungi, 4 mycoparasitic Trichoderma, and 4 prey phytopathogens, was examined. Results showed that allelopathic effect of caffeine on fungal growth and development was differential, being stronger on pathogens than on Trichoderma species. Upon confronting, the prey immediately ceased the growth, whereas the predator continued to grow, indicating active mycoparasitism to have occurred. Caffeine enhanced mycoparasitism up to 1.7-fold. Caffeine thus functions in a double-track manner against fungal pathogens: first by direct suppression of growth and development, and second by assisting their natural enemy. These observations suggest that caffeine is a powerful weapon in the arms race between plants and pathogens by fostering enemy''s enemy, and we propose the idea of "caffeine fostering" as the third role of caffeine.     

Rhizosphere Colonization and Control of Meloidogyne spp. by Nematode-trapping Fungi

The ability of nematode-trapping fungi to colonize the rhizosphere of crop plants has been suggested to be an important factor in biological control of root-infecting nematodes. In this study, rhizosphere colonization was evaluated for 38 isolates of nematode-trapping fungi representing 11 species. In an initial screen, Arthrobotrys dactyloides, A. superba, and Monacrosporium ellipsosporum were most frequently detected in the tomato rhizosphere. In subsequent pot experiments these fungi and the non-root colonizing M. geophyropagum were introduced to soil in a sodium alginate matrix, and further tested both for establishment in the tomato rhizosphere and suppression of root-knot nematodes. The knob-forming M. ellipsosporum showed a high capacity to colonize the rhizosphere both in the initial screen and the pot experiments, with more than twice as many fungal propagules in the rhizosphere as in the root-free soil. However, neither this fungus nor the other nematode-trapping fungi tested reduced nematode damage to tomato plants.     

AM Fungal Diversity in Selected Medicinal Plants of Kanyakumari District,Tamil Nadu,India

The association of Arbuscular Mycorrhizal Fungi (AMF) with three medicinally important plants viz., Eclipta prostrata, Indigofera aspalathoides, I. tinctoria collected from three different localities of Kanyakumari District, South India was examined. The study reports the colonization percentage, diversity and species richness of different AM fungi in the rhizosphere of the three medicinal plants and discusses the impact of soil physicochemical characteristics such as soil texture, pH and available macro- and micro nutrient content on AM fungal communities. A total 21 AM fungal species were identified in field conditions of the three plants from three sites. AM fungal species richness, colorization percentage and Shannon index were found to be high in the two Indigofera sp. growing in the hilly areas of Kanyakumari District and were low in E. prostrata collected from the damp regions in the foothills of the three study sites. Five species registered 100% frequency in all the study sites of the three medicinally important plants with Glomus as the dominant genera. The study states that the mean colonization and diversity patterns were dependant on edaphic factors and type of vegetation.