西北荒漠带细枝岩黄耆AM真菌与DSE真菌时空分布研究

为探明细枝岩黄耆Hedysarum scoparium根系丛枝菌根真菌（arbuscular mycorrhizae,AM）和深色有隔内生真菌（dark septate endophytes,DSE）定殖特征及其生态地理分布,充分理解菌根共生体在植物生长和植被恢复中的功能,本研究连续3年采集我国西北荒漠带不同样地细枝岩黄耆0-30cm土层土壤样品和根样,不同样地细枝岩黄耆均能被AM和DSE侵染,形成AM典型结构菌丝、泡囊和丛枝,DSE典型结构深色有隔菌丝和微菌核。细枝岩黄耆根系AM真菌定殖高于DSE定殖,但极端干旱条件下DSE定殖优于AM真菌定殖。AM真菌定殖率不同年际间表现为2016年最高,同一年份不同样地,除乌海、沙坡头样地,菌丝定殖率自东向西呈降低趋势。DSE真菌定殖率,在同一样地不同年份：乌海样地2016年定殖率显著高于2015年和2017年,在同一年份不同样地：2015年沙坡头样地DSE菌丝定殖率、总定殖率显著高于其他样地,而2016、2017年鄂尔多斯样地最高。NMDS分析结果显示,AM和DSE真菌定殖不同年际间差异显著。相关性分析表明,AM真菌定殖率与DSE定殖率显著正相关;土壤温度与AM定殖显著负相关;有机碳、速效磷、磷酸酶、湿度与AM定殖显著正相关;DSE菌丝定殖率、定殖强度仅与酸性磷酸酶正相关。本研究比较分析西北荒漠带不同样地AM和DSE定殖与土壤因子的相关性,有助于充分理解菌根共生体在植物生长和植被恢复中的功能和意义。     

河北峰峰矿区深色有隔内生真菌定殖及群落组成

为探明矿区环境深色有隔内生真菌(dark septate endophytes,DSE)生态分布和定殖状况,有效利用DSE真菌资源,促进矿区植被恢复和生态重建。2016年10月采集河北峰峰矿区冬青(Ilex chinensis)和构树(Broussonetia papyrifera)根围0～20 cm和20～40 cm土层土壤样品和根样,采用形态特征结合r DNA ITS序列分析方法研究DSE真菌定殖、群落组成以及与土壤环境因子间的相关性。结果表明:冬青和构树根系均能被DSE高度侵染,形成典型深色有隔菌丝和微菌核结构。微菌核定殖率与土壤速效氮显著负相关。菌丝定殖率与土壤全磷显著正相关。总定殖率与土壤全磷显著正相关,与重金属Zn显著负相关。定殖强度与土壤有机质显著负相关,与土壤全磷显著正相关。共分离鉴定8种DSE,即Acrocalymma vagum、Scytalidium lignicola、Nothophoma quercina、Cochliobolus lunatus、Fusarium acuminatum、Neonectria radicicola、Pyrenochaetopsis indica和Pleosporales sp.。同一植物不同样地DSE群落组成差异显著(P 0. 05)。优势种为Acrocalymma vagum、Scytalidium lignicola和Fusarium acuminatum,分离频率分别达到37.6%、17.43%和11.93%。     

西北沙区梭梭根系深色有隔内生真菌等微生物时空分布及对根际土壤环境的响应

为揭示西北沙区不同时空尺度梭梭Haloxylon ammodendron根系深色有隔内生真菌（dark septate endophyte,DSE）分布规律及其环境驱动机制,分别于2019年7月、9月和12月在安西极旱荒漠国家级自然保护区和民勤连古城国家级自然保护区采集根系和土壤样品,根据真菌形态学特征、组织化学等方法,研究了梭梭根系DSE真菌定殖规律、定殖特征及其与土壤环境因子间的相互关系。结果表明,DSE真菌在自然生境梭梭根系广泛定殖,形成具有时空异质性的典型暗色有隔菌丝和微菌核结构。梭梭根系DSE真菌定殖受季节和空间分布影响,其中总定殖率在生长旺季7月最高（85.6%）,且菌丝隔间距显著大于9、12月;安西样地菌丝定殖率（71.5%）和总定殖率（85.6%）显著高于民勤样地（40.7%,60.0%）,但民勤样地微菌核直径显著高于安西样地。相关性分析表明,DSE定殖率及形态特征受土壤理化性质影响,温度、有效磷是影响DSE真菌定殖率的主要土壤因子,湿度和碱解氮是影响DSE真菌定殖形态的主要土壤因子。相比空白土壤,梭梭根际革兰氏阳性细菌含量、土壤脲酶活性以及安西样地有效磷含量均更高,预示其对荒漠土壤具有改善作用。本研究对梭梭DSE真菌时空分布和影响因素的系统性调查有助于为荒漠化治理和生态恢复提供依据。     

深色有隔内生真菌（DSE）研究进展

<正>深色有隔内生真菌(dark septate endophytes,DSE)不是一个科学的分类单元,而是泛指一群定殖于植物根内的小型土壤真菌,包括功能和分类关系都不确切的多种真菌。这类真菌的定殖模式在不同植物中是相似的,一般特征是菌丝颜色较深、具     

荒漠沙蒿根围AM真菌和DSE的空间分布

2009年7月在内蒙古黑城子北、多伦县城东和正蓝旗元上都遗址3个样地分别从0-10 cm、10-20 cm、20-30cm、30-40 cm和40-50 cm 5个土层采集沙蒿(Artemisia sphaerocephala)根围土壤和根样,系统研究了沙蒿根围AM真菌和DSE(Dark septate endophytes)的空间分布及与土壤因子的相关性。结果表明,沙蒿根系能被AM真菌高度侵染形成典型的I-型(Intermediate type)丛枝菌根,并发育形成泡囊和丛枝结构, 并与DSE形成良好的共生关系,样地生态条件和采样深度对AM真菌分布和活动有显著影响。黑城子样地孢子密度最高,元上都样地泡囊定殖率最高,不同样地间丛枝、菌丝、总定殖率和DSE定殖率无显著差异。孢子密度峰值出现在0-10cm表层土,并随土壤剖面深度增加而降低;泡囊定殖率峰值出现在10-20cm土层;AM真菌其他结构定殖率及DSE定殖率在各土层间差异不显著或变化无规律。孢子密度与AM真菌不同结构定殖率无显著相关性,与各土壤因子极显著正相关。泡囊定殖率与脲酶和碱性磷酸酶极显著负相关,与酸性磷酸酶显著负相关。菌丝定殖率、总定殖率及DSE定殖率与各土壤因子均无显著相关性。土壤碱解N和有机C与脲酶、酸性磷酸酶和碱性磷酸酶极显著正相关;土壤速效P与碱性磷酸酶极显著正相关,与脲酶显著正相关。对沙蒿根系AM真菌和DSE真菌分布和定殖规律的研究,可进一步明确AM真菌和DSE的生态功能,为利用菌根生物技术促进荒漠植被恢复和生态重建提供依据。     

贵州栽培笃斯越橘DSE真菌、AM真菌与ERM真菌空间分布研究

为探明贵州省栽培笃斯越橘根系深色有隔内生真菌（dark septate endophytes,DSE）、丛枝菌根（arbuscular mycorrhiza,AM）真菌与欧石南菌根（ericoid mycorrhiza,ERM）真菌的定殖及地理分布情况,揭示共生真菌在栽培笃斯越橘生长中的地位,本研究在贵州省笃斯越橘主栽区麻江县、凤岗县和高坡乡分别选取主栽品种圆蓝、粉蓝、奥尼尔和莱格西的根样及根围土样,观测不同地区不同品种根样DSE真菌、AM真菌和ERM真菌的定殖结构和定殖率,并测定土样土壤理化性质,分析不同真菌与土壤因子相关性。结果表明,3个地区的4个笃斯越橘品种均有DSE真菌、AM真菌和ERM真菌定殖,栽培笃斯越橘能与3类真菌形成共生关系,平均定殖率分别为61.11%、25.55%和22.50%。DSE真菌定殖率：高坡（62.50%）>麻江（61.66%）>凤岗（59.16%）;AM真菌定殖率：凤岗（34.14%）>麻江（25.83%）>高坡（16.66%）;ERM真菌定殖率：高坡（35.00%）>凤岗（20.00%）>麻江（12.5%）。相关性分析表明,DSE真菌中的菌丝与微菌核的定殖率呈负相关,AM真菌的总定殖率及定殖强度与微菌核的定殖率呈极显著正相关,与DSE真菌菌丝的定殖率呈负相关。ERM真菌总定殖率与DSE真菌菌丝的定殖率及AM真菌定殖强度呈极显著正相关,与DSE真菌总定殖率呈显著正相关。土壤有效磷与DSE真菌和ERM真菌总定殖率呈显著正相关,与AM真菌定殖率呈显著负相关。土壤铵态氮与DSE真菌中微菌核结构定殖率及AM真菌定殖率呈极显著正相关,与ERM真菌定殖率呈极显著负相关。土壤pH值与DSE定殖强度呈显著负相关,与ERM定殖强度呈极显著正相关。本研究分析比较贵州省3个笃斯越橘种植基地不同品种栽培笃斯越橘DSE真菌、AM真菌和ERM真菌的定殖及其与土壤理化性质之间的相关性,为贵州省栽培笃斯越橘的管理和发展提供技术基础和理论依据。     

蒙古沙冬青根围AM和DSE真菌与土壤因子的相关性研究

于2012年6月对银川、沙坡头、民勤3个样地的蒙古沙冬青(Ammopiptanthus mongolicus)根围采集5个土层(0~10、10~20、20~30、30~40、40~50cm)的土样和根样,研究了蒙古沙冬青根际AM和DSE真菌空间分布以及土壤因子的生态作用,以阐明沙冬青与土壤真菌的共生关系,为利用共生真菌资源促进沙冬青生长和荒漠植被恢复提供依据。结果表明:(1)沙冬青根系能被AM和DSE真菌高度侵染,共生程度和生态分布具有明显空间异质性。(2)沙坡头样地AM真菌总定殖率最高,民勤DSE定殖率最高,但不同样地菌丝、泡囊、丛枝和定殖强度无显著差异;同一样地不同土层AM真菌总定殖率和DSE定殖率无显著差异。(3)相关性分析表明,AM真菌总定殖率与土壤速效P显著正相关;泡囊定殖率与有机质显著正相关,与速效P极显著正相关;定殖强度与总球囊霉素(TEG)显著正相关,与碱解N和速效K极显著正相关;DSE定殖率与易提取球囊霉素(EEG)极显著正相关,与碱解N显著正相关。(4)通径分析表明,土壤有机质、EEG和速效K是通过直接作用影响AM真菌总定殖率和DSE定殖率。     

沙冬青与伴生植物深色有隔内生真菌定殖规律及其与土壤因子的相关性

为了探明荒漠环境深色有隔内生真菌(dark septate endophytes, DSE)生态分布和定殖状况, 于2013年7月从宁夏银川、沙坡头和甘肃民勤地区采集沙冬青(Ammopiptanthus mongolicus)及其伴生植物根围0-10、10-20、20-30、30-40、40-50 cm共5个土层土壤样品和根样, 研究了DSE空间定殖规律及其与土壤因子的相关关系。结果表明: 沙冬青和伴生植物根系能被DSE侵染, DSE分布和定殖具有明显的空间异质性, 并与土壤因子密切相关。沙冬青DSE微菌核结构紧凑, 呈团块状, 而伴生植物DSE微菌核零散分布。同一样地, 沙冬青DSE菌丝定殖率、定殖强度和总定殖率较伴生植物高, 而沙冬青和伴生植物微菌核定殖率无显著差异。不同样地, 沙冬青和伴生植物微菌核定殖率无显著差异, 沙冬青DSE菌丝定殖率、定殖强度和总定殖率为沙坡头>银川>民勤; 伴生植物DSE菌丝定殖率、定殖强度和总定殖率为银川>民勤>沙坡头。通径分析和主成分分析表明, 土壤有机质、总球囊霉素、磷酸酶和速效钾是西北荒漠环境中DSE定殖的主要影响因子。     

新疆沙冬青AM和DSE真菌的空间分布

2012年6月从新疆阿图什市选取康苏、膘尔托阔依(阳)、膘尔托阔依(阴)和上阿图什4个样地,采集新疆沙冬青(Ammopiptanthus nanus)根围0—10、10—20、20—30、30—40和40—50cm5个土层土壤样品,研究了新疆沙冬青AM和DSE真菌定殖规律以及土壤因子的生态作用。结果表明,AM和DSE真菌平均总定殖率分别为83.2%和53.22%,说明AM和DSE真菌能与新疆沙冬青根系形成良好共生关系。AM和DSE真菌具有明显空间异质性,AM总定殖率最大值在20—30cm土层,样地间表现为康苏=上阿图什膘尔托阔依(阳)膘尔托阔依(阴);DSE土层间无规律性变化,样地间为膘尔托阔依(阳)膘尔托阔依(阴)康苏上阿图什。相关性分析表明,AM菌丝、泡囊和总定殖率与DSE定殖率极显著负相关,AM定殖强度与DSE菌丝和总定殖率显著负相关,丛枝定殖率与DSE菌丝和总定殖率极显著正相关,说明两者间存在生态位竞争。土壤速效P、总球囊霉素和酸性磷酸酶与AM总定殖率极显著正相关,pH与AM总定殖率显著负相关;脲酶与DSE极显著正相关,pH和碱解N与DSE显著负相关。     

北方两省农牧交错带沙棘根围AM真菌与球囊霉素空间分布

2009年7月在内蒙古和河北两省农牧交错带沙棘(Hippophae rhamnoides L)集中分布区选取3个典型样地,分别从0-10cm、10-20cm、20-30cm、30-40cm和40-50cm土层采集沙棘根围土壤样品,研究了沙棘根围AM真菌与球囊霉素空间分布及与土壤因子的相关性。结果表明,沙棘能与AM真菌形成良好的疆南星型(Arum-type)丛枝菌根。AM真菌定殖率和孢子密度与样地生态条件密切相关。大梁底村和多伦东样地AM真菌不同结构定殖率及孢子密度无明显差别,但均显著高于黄柳条村样地,只在大梁底村发现丛枝定殖;孢子密度在3个样地均随土层加深而降低,不同结构定殖率在大梁底村随土层加深而降低,其他2个样地无明显变化规律;AM真菌最高定殖率和最大孢子密度均出现在0-30cm浅土层。根围土壤总球囊霉素(TEG)和易提取球囊霉素(EEG)含量在3个样地均随土层加深而降低。相关性分析表明,孢子密度与菌丝定殖率、泡囊定殖率和总定殖率极显著正相关。AM真菌菌丝、泡囊和总定殖率与土壤pH值、有机C、碱解N和速效P含量、脲酶和碱性磷酸酶活性极显著正相关,丛枝定殖率与土壤碱解N含量和脲酶活性显著正相关。多元线性回归方程表明,AM真菌不同定殖结构和土壤因子对TEG和EEG含量贡献不同,对于TEG:菌丝>孢子>泡囊;有机C>速效P>酸性磷酸酶>pH值,对于EEG:泡囊>孢子>菌丝;有机C>速效P。结果建议,AM真菌孢子密度、菌丝定殖程度和土壤球囊霉素含量在一定程度上能综合反应土壤AM真菌群落、有机C动态和养分循环进程,可以作为土壤质量及功能评价的新指标进一步深入研究。     

Atypical morphology of dark septate fungal root endophytes of<Emphasis Type="Italic"> Bouteloua</Emphasis> in arid southwestern USA rangelands

Native grasses of semi-arid rangelands of the southwestern USA are more extensively colonized by dark septate endophytes (DSE) than by traditional mycorrhizal fungi. Roots of dominant grasses ( Bouteloua sp.) native to arid southwestern USA rangelands were prepared and stained using stains specific for fungi (trypan blue) and for lipids (sudan IV). This revealed extensive internal colonization of physiologically active roots by atypical fungal structures that appear to function as protoplasts, without a distinguishable wall or with very thin hyaline walls that escape detection by methods staining specifically for fungal chitin. These structures were presumed to be active fungal stages that progressed to form stained or melanized septate hyphae and microsclerotia characteristic of DSE fungi within dormant roots. The most conspicuous characteristic of these fungi were the unique associations that formed within sieve elements and the accumulation of massive quantities of lipids. This interface suggests a biologically significant location for carbon transfer between the plant and fungus. The continuous intimate association with all sieve elements, cortical and epidermal cells as well as external extension on the root surface and into the soil indicates that they are systemic and considerably more prevalent than previously thought. A fungal network associated with a mucilaginous complex observed on the root surface and its potential role in root function in dry soil is discussed. It is suggested that those fungi that non-pathogenically and totally colonize plant cells be classed as systemic endophytic fungi (SEF). This would refine the broad designation of DSE fungi. The potential mutualistic benefit of SEF for native plants in arid ecosystems based on the extent of lipid accumulation and its apparent distribution is discussed.     

Seasonality of vesicular-arbuscular mycorrhizae in sedges in a semi-arid tropical grassland

Vesicular-arbuscular mycorrhizal (VAM) colonization and spore numbers in the rhizosphere of Cyperus iria L. and C. rotundus L., growing in a semi-arid tropical grassland, was studied during the 1993 and 1994 monsoons. In addition, climatic and chemical properties of the soils were determined in order to investigate their influence on mycorrhizal variables. VAM fungal association in the sedges was confirmed by plant- and root-trap culture techniques. The soil nutrients exhibited seasonal variations, but were highly variable between years. Intercellular hyphae and vesicles with occasional intraradical spores characterized mycorrhizal association in sedges. Dark septate fungi also colonized roots of sedges. Temporal variations in mycorrhizal colonization and spore numbers occurred, indicating seasonality. However, the patterns of mycorrhizal colonization and spore numbers were different during both the years. The VAM fungal structures observed were intercellular hyphae and vesicles. Changes in the proportion of root length with VAM structures, total colonization levels and spore numbers were related to climatic and edaphic factors. However, the intensity of influence of climatic and soil factors on VAM tended to vary with sedge species.     

福廷瓶头霉与马尾松的共生特征

深色有隔内生真菌（dark septate endophyte,DSE）广泛定殖于植物根系,对促进植物生长、提高植物抗逆能力具重要作用。本研究从马尾松Pinus massoniana根系分离到一株DSE,于无菌条件下研究了此菌与马尾松的共生特征,研究结果表明：基于形态学和分子生物学分析,此菌被鉴定为福廷瓶头霉Phialocephala fortinii,在PDA培养基25℃培养条件下,此菌不产孢,菌丝深色、具隔,最适培养基为PDA。此菌与马尾松根系共生体的形成过程可划分为3个时期,即侵入前期：接种后2d,新生菌丝向马尾松根系定向生长并开始接触根系,但未侵入根系内部;侵入期：接种后4d,菌丝与马尾松根系接触侵入根内并在根系皮层细胞间扩展延伸;形成期：接种后6d,菌丝继续在马尾松根系内扩展并形成富含脂类物质的微菌核。接种福廷瓶头霉显著增加了马尾松生物量的积累（P<0.05）,并影响了其根系发育。接种后,马尾松主根生长受限,侧根生长显著提高（P<0.05）,侧根长度较未接种处理增加了112.87%。被侵染根系的根毛数量减少,并由大量根外菌丝包裹。以上结果对进一步揭示DSE与宿主的共生机理有一定指导意义。     

Seasonality of root fungal colonization in low-alpine herbs

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungal colonization of Alchemilla glomerulans, Carex vaginata, Ranunculus acris ssp. pumilus and Trollius europaeus growing in low-alpine meadows in the Finnish subarctic were studied at different times during the growing season. Fungal colonization was correlated to soil soluble phosphorus (P) concentration. The influence of flower bud removal on fungal colonization was investigated in A. glomerulans, C. vaginata and R. acris and the correlation between AM and DSE colonization was studied. The fungal colonization patterns were found to be species-specific. R. acris maintained a relatively high rate of fungal colonization throughout the summer, while the rates of colonization of T. europaeus were lower and decreased towards the end of the season. A. glomerulans had constant arbuscular and vesicular colonization throughout the summer, but hyphal and DSE colonization declined towards the end of the season. C. vaginata did not form arbuscular mycorrhiza, but was colonized by DSE fungi and hyaline septate hyphae throughout the season. The soil soluble P concentration showed some seasonal variation, but was also highly variable between the study sites. Bud removal decreased arbuscular colonization of R. acris, but no unique effects were seen in any other parameters or the other species studied. The root fungal parameters correlated with soil P in some species at some sites, but no consistent trend was found. DSE colonization was positively correlated with root vesicular and hyphal colonization in some cases. The differences in fungal colonization parameters may be related to species-specific phenologies.     

Colonization process of the root endophytic fungus Heteroconium chaetospira in roots of Chinese cabbage

Dark septate endophytic fungi (DSE) may have an important functional relationship with host plants, but these functions and the colonization process remain unknown. We made microscopic observations of the growth of an endophytic hyphomycete in Chinese cabbage roots to understand its colonization process. This hyphomycete was Heteroconium chaetospira, a suspected DSE. Three weeks post inoculation, some hyphae became irregularly lobed and formed microsclerotia within host epidermal cells of healthy plants. In stunted plants, hyphae formed closely packed masses of fungal cells within host epidermal cells, but conidiophores rarely broke through the cell walls to produce conidia. Received: December 7, 2000 / Accepted: November 20, 2001     

新疆药用植物天山雪莲及红景天内生真菌的分离与初步鉴定

本文采用常规组织块分离法及直接克隆测序的方法初步鉴定了新疆天山地区代表性的两种药用植物天山雪莲和红景天根内可培养及不可培养的内生真菌。从两种药用植物根中共分离获得34株内生真菌,除7株鉴定为镰孢菌属Fusarium外,其余菌株均具有暗色、有隔菌丝,不产生孢子;从形态上看,属典型的深色有隔内生真菌（dark septate endophyte,DSE）。采用直接克隆测序的方法,从两种植物的根中共获得143个真菌克隆子。依据核糖体内转录间隔区（internal transcribed spacer,ITS）序列鉴定多数克隆子归属于柔膜菌目Helotiales及格孢腔菌目Pleosporales,与已知的DSE如背芽突霉属Cadophora、瓶头霉属Phialocephala、瓶霉属Phialophora以及Leptodontidium等有90%以上的核苷酸序列相似性。该结果显示DSE在天山雪莲和红景天根部内生真菌中占优势,暗示其可能参与了宿主植物对高寒、强辐射环境的生态适应。     

西北旱区甘草深色有隔内生真菌物种多样性及空间分布

为探明西北旱区甘草Glycyrrhiza uralensis根系深色有隔内生真菌（dark septate endophytes,DSE）生态分布和定殖状况,于2018年7月分别从甘肃安西、民勤和宁夏沙坡头地区采集甘草不同灌丛范围0-10cm和20-30cm土壤和根系样品,系统研究不同样地甘草灌丛内外DSE生态分布及其与土壤因子的相关性。结果表明,不同样地甘草均能被DSE高度侵染,形成典型深色有隔菌丝和微菌核结构。不同样地DSE定殖率差异显著,安西DSE总定殖率（43.34%）显著低于民勤（90%）和沙坡头（88.34%）样地。相关性分析表明,DSE定殖率主要与土壤速效磷、有机碳和碱性磷酸酶显著相关。共分离鉴定11属13种DSE,即Acrocalymma vagum、Alternaria longissima、Alternaria chlamydospora、Alternaria chlamydosporigena、Paraphoma chrysanthemicola、Darksidea alpha、Niesslia aemula、Tricharina ochroleuca、Acremonium nepalense、Fusarium solani、Preussia sp.、Leptosphaeria oraemaris和Ulocladium sp.。其中Acrocalymma vagum是甘草根系DSE优势菌种,为民勤和沙坡头共有种,而安西样地DSE物种多样性最高,共7种。主成分分析表明,安西DSE物种组成在0-10cm和20-30cm不同灌丛范围存在显著差异;单因素方差分析显示,安西和沙坡头DSE菌丝定殖率在距主干0-10cm显著高于20-30cm,说明荒漠环境灌丛覆盖对DSE真菌群落存在显著影响。方差分解结果表明,DSE定殖受样地空间分布、灌丛覆盖和土壤因子共同影响（74.91%）,而DSE种类组成更多依赖于样地异质性（84.46%）和土壤养分（87.82%）的作用。研究不同荒漠环境DSE定殖和群落组成差异,有助于充分理解DSE在旱区植物生长和植被恢复中的功能和意义。     

The co-occurrence of ectomycorrhizal,arbuscular mycorrhizal,and dark septate fungi in seedlings of four members of the Pinaceae

Although roots of species in the Pinaceae are usually colonized by ectomycorrhizal (EM) fungi, there are increasing reports of the presence of arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi in these species. The objective of this study was to determine the colonization patterns in seedlings of three Pinus (pine) species (Pinus banksiana, Pinus strobus, Pinus contorta) and Picea glauca x Picea engelmannii (hybrid spruce) grown in soil collected from a disturbed forest site. Seedlings of all three pine species and hybrid spruce became colonized by EM, AM, and DSE fungi. The dominant EM morphotype belonged to the E-strain category; limited colonization by a Tuber sp. was found on roots of Pinus strobus and an unknown morphotype (cf. Suillus–Rhizopogon group) with thick, cottony white mycelium was present on short roots of all species. The three fungal categories tended to occupy different niches in a single root system. No correlation was found between the percent root colonized by EM and percent colonization by either AM or DSE, although there was a positive correlation between percent root length colonized by AM and DSE. Hyphae and vesicles were the only AM intracellular structures found in roots of all species; arbuscules were not observed in any roots.     

ROOTS OF METAL HYPERACCUMULATING POPULATION OF THLASPI PRAECOX (BRASSICACEAE) HARBOUR ARBUSCULAR MYCORRHIZAL AND OTHER FUNGI UNDER EXPERIMENTAL CONDITIONS

Thlaspi praecox (Brassicaceae) is a recently discovered metal hyperaccumulating plant species colonized by arbuscular mycorrhizal fungi (AMF). The identity and diversity of the AMF colonizing its roots have not been determined so far. Therefore, T. praecox was inoculated with an indigenous fungal mixture from a metal polluted site and grown in original polluted soil/ commercial substrate mixtures (i.e., 100%, 50%, and 25%). Low to moderate mycorrhizal frequencies (F = 33–68%) and only rare arbuscules were observed. Densities of vesicles and microsclerotia, typical structures of dark septate endophytes (DSE), were greater in pots with 100% original polluted soil. In contrast, the highest diversity of fungal genotypes was observed in the roots from 25% polluted soil/ commercial substrate mixture, with the lowest soil concentrations of Cd, Zn, and Pb. The sequences obtained corresponded to Glomus species (Glomeromycota), to putative DSE Phialophora verrucosa and Rhizoctonia sp. and to some other fungi from Asco- and Basidiomycota, that are known to associate with plants, namely Capnobotryella sp., Penicillium brevicompactum, Rodotorula aurantiaca and Rodotorula slooffiae. This is the first report of DSE occurrence in roots of hyperaccumulating T. praecox, a promising candidate for phytoextraction.