土层深度和季节变化对保护地西瓜连作土壤中丛枝菌根真菌群落结构的影响

The characteristics of arbuscular mycorrhizal fungal (AMF) community structure in various soil depths and growing seasons of watermelon (Citrullus vulgaris) grown in commercial greenhouses in Daxing of Beijing and Weifang and Laiyang of Shandong, China were investigated using both morphological identification and denaturing gradient gel electrophoresis. The sampled soils had been used for continuous greenhouse production of watermelon for 0, 5, 10, 15, or 20 years. Glomus claroideum was the dominant species in the greenhouse soils planted for 5, 10, and 15 years in Laiyang, while Glomus mosseae and Glomus etunicatum were dominant in the nearby open farmland soil. Sorenson’s similarity index of AMF community composition ranged from 0.67 to 0.84 in the soils planted for 5 years, and from 0.29 to 0.33 for 20 years among the three locations. Spore abundance, species richness, and the Shannon index were highest near the soil surface (0-10 cm) and decreased with soil depth, and higher in June and October than in August and December. Canonical correspondence analysis showed that available P and the number of years that soil had been used for greenhouse production were the main factors contributing to the variance of AMF community composition. It was concluded that the community structure of AMF was mainly influenced by soil available P and planting time of watermelon as well as by soil depth and seasonal variation in the commercial greenhouse.     

长期保护性耕作对丛枝菌根真菌多样性的影响

为了明确我国北方干旱地区长期保护性耕作以及深松对丛枝菌根真菌(AMF)多样性的影响,笔者于2014年在山西省临汾市连续22年实施保护性耕作的长期定位试验基地,针对免耕覆盖(NTS)、深松免耕覆盖(SNTS)及传统耕作(TT)3种处理方式,进行了不同耕作条件下土壤AMF物种丰度、孢子密度、Shannon多样性指数以及AMF侵染率等因素的比较研究。结果显示,长期保护性耕作(NTS和SNTS)共分离鉴定出AMF 7属9种,其中根孢囊霉属(Rhizophagus)和斗管囊霉属(Funneliformis)各2种,球囊霉属(Glomus)、近明球囊霉属(Claroideoglomus)、无梗囊霉属(Acaulospora)、硬囊霉属(Sclerocystis)和隔球囊霉属(Septoglomus)各1种;而传统耕作(TT)共分离鉴定出AMF 6属8种,没有检测到无梗囊霉属。NTS、SNTS和TT处理在不同土层的AMF优势种基本一致,0~40 cm土层为摩西斗管囊霉(Fu.mosseae)和变形球囊霉(G.versiforme),40~80 cm土层为摩西斗管囊霉、变形球囊霉和聚丛根孢囊霉(Rh.aggregatum),80~120 cm土层为聚丛根孢囊霉,120 cm土层以下只有NTS和SNTS处理中存在聚丛根孢囊霉,说明保护性耕作措施促进了AMF向土壤深层发展。NTS和SNTS处理在同一土层的AMF物种丰度、孢子密度和Shannon多样性指数均高于TT处理,SNTS处理高于NTS处理。同一耕作措施不同土层的AMF物种丰度、孢子密度和Shannon多样性指数均随土层加深而逐渐降低;NTS和SNTS处理在小麦各生育期的丛枝侵染率和孢子密度均高于TT处理;各处理在小麦拔节期的AMF侵染率最高,分别为14.9%、16.1%和10.6%,而在收获期的土壤孢子密度最高,分别为111.7个·(100g)~(-1)、125.0个·(100g)~(-1)和90.3个·(100g)~(-1)。研究认为,长期免耕覆盖、尤其深松免耕覆盖,提高了AMF多样性。该研究结果可为中国北方旱作农田生态系统中AMF自然潜力的充分发挥,以及保护性耕作技术的合理应用提供科学依据。     

西北地区赤霞珠葡萄根际土壤中AM真菌的多样性

对西北地区5个酿酒葡萄赤霞珠（Vitis vinifera L. cv. Cabernet Sauvignon）葡萄园根际土壤060 cm土层的AM真菌空间分布进行了研究。结果表明,葡萄根系可形成丛枝菌根,且侵染率较高,最高达79%; 在西北地区的5个样地中共分离出AM真菌4属22种,其中球囊霉属（Glomus）15种,无梗囊霉属（Acaulospora）4种,盾巨孢囊霉属（Scutellospora）2种,巨孢囊霉属（Gigaspora）1种。5个样地孢子密度大小顺序为: 陕西泾阳（JY）＞山西永济（YJ）＞陕西杨凌（YL）＞宁夏银川（YC）＞甘肃莫高（MG）。各样地葡萄根际土壤中AM真菌种的丰富度不同,陕西泾阳地区最高; 分布于葡萄根际的AM真菌按种类多少排序的属依次是: 球囊霉属无梗囊霉属盾巨孢囊霉属巨孢囊霉属,球囊霉属占据的比例保持着绝对优势; 根内球囊霉、摩西球囊霉、地表球囊霉在不同样地中均为优势菌株,副冠球囊霉,集球囊霉,细凹无梗囊霉是多数样地中的稀有种类。研究表明,葡萄与AM真菌具有良好的共生关系,二者协同进化产生了具有生态环境特异性的菌根真菌多样性; 葡萄根际存在较为丰富的丛枝菌根真菌资源,可供进一步开发利用。     

土壤中芦笋生长最大需磷量对接种丛枝菌根真菌的响应特征

Fertilizer application efficiently increases crop yield, but may result in phosphorus（P） accumulation in soil, which increases the risk of aquatic eutrophication. Arbuscular mycorrhizal fungi（AMF） inoculation is a potential method to enhance P uptake by plant and to reduce fertilizer input requirements. However, there has been limited research on how much P application could be reduced by AMF inoculation. In this study, a pot experiment growing asparagus（Asparagus officinalis L.） was designed to investigate the effects of AMF inoculation and six levels of soil Olsen-P（10.4, 17.1, 30.9, 40.0, 62.1, and 95.5 mg kg^-1for P0, P1, P2, P3, P4 and P5treatments, respectively） on root colonization, soil spore density, and the growth and P uptake of asparagus. The highest root colonization and soil spore density were both obtained in the P1treatment（76% and 26.3 spores g^-1 soil, respectively）. Mycorrhizal dependency significantly（P 〈 0.05） decreased with increasing soil Olsen-P. A significant correlation（P 〈 0.01） was observed between mycorrhizal P uptake and root colonization, indicating that AMF contributed to increased P uptake and subsequent plant growth.The quadratic equations of shoot dry weight and soil Olsen-P showed that AMF decreased the P concentration of soil required for maximum plant growth by 14.5% from 67.9 to 59.3 mg Olsen-P kg^-1. Our results suggested that AMF improved P efficiency via increased P uptake and optimal growth by adding AMF to the suitable P fertilization.     

三种土壤上六种丛枝菌根真菌生长特征和接种效应

以分离于华北、华中和华南3个生态区及法国引进的丛枝菌根真菌为试验菌株,采用三室根箱培养的方法,研究了它们在华北、华中和华南3种典型土壤褐土、棕壤和红壤上的菌根形成、接种效应、磷吸收贡献和根外菌物量情况。结果表明,6种菌株在上述指标上存在显著的种间或生态型差异,土壤与菌株间存在显著的交互作用。6种菌株在3种土壤上都能与玉米形成菌根,在褐土和棕壤上大多数菌株在分离地所在地区土壤类型上的菌根侵染率较高,说明其对该土壤条件的适应性较强;在红壤强酸性土壤条件抑制了菌根真菌的侵染。菌株BEG168、BEG167、BEG151、BEG221和BEG141在褐土上,BEG151和BEG221在棕壤上,BEG168和BEG150在红壤上显著提高了玉米的生物量。在褐土和棕壤上,除BEG150外,BEG168、BEG167、BEG151、BEG221和BEG141能显著促进宿主吸磷;而在红壤上,BEG168和BEG141显著促进了宿主吸磷。若以真菌的根外菌物量作为衡量AM真菌菌株土壤生态适应性的指标,BEG141和BEG167是生态适应性强的菌株,为广幅生态型菌株;菌株BEG168和BEG151次之,前者在棕壤上适应性高,后者在红壤上适应性高。BEG150和BEG221生态适应性较窄,仅适应红壤或褐土,为窄幅生态型菌株。Glomus.etunicatum的两个生态型BEG168和BEG221在土壤生态适应性上差异很大,前者在两种土壤上收集到菌物量,而后者只在褐土上收集到菌物量。土壤条件可以决定丛枝菌根真菌的生长状况和功能。     

Diversity of arbuscular mycorrhizal fungi in soils of yam (Dioscorea spp.) cropping systems in four agroecologies of Nigeria

The diversity of arbuscular mycorrhizal (AM) fungi in soils under a yam cropping system in four agroecologies of Nigeria was investigated. Soil samples were collected from yam fields at Onne (humid forest, high rainfall area), Ibadan (derived savanna), Abuja (Guinea savanna) and Ubiaja (humid forest, medium rainfall area). Soil characteristics, AM fungi species, spore abundance, Shannon diversity index, species richness and evenness were determined. A total of 31 AM fungi species was isolated from the four agroecologies with a range of 14–20 species found in a single location. Glomus species were the most abundant among AM fungi species with G. geosporum, G. intraradices and G. mosseae occurring in large populations in all locations. Ubiaja, which had a cassava/natural vegetation sequence before yam, had significantly higher spore abundance and species richness than the other locations, which had a yam/legumes or a maize/legume sequence before yam. However, diversity was significantly higher at Abuja, which had a maize/legume sequence with yam, than Ibadan, which had only a yam/legume sequence. The study revealed significant diversity in AM fungal species across agroecologies in yam-growing regions. Further research on the functional consequences of changing composition of AM fungi species across the region is recommended.     

自然再生、非管理、伐光的山毛榉林丛枝菌根真菌的浸染性研究

Clear-cutting,a management practice applied to many beech forests in the North of Spain,modifies microclimate and,consequently,the composition of the understory plant community in the disturbed areas.The objectives of this study were to assess if changes in the understory vegetation caused by altered light microclimate after clear-cutting affect the infectivity of arbuscular mycorrhizal fungi(AMF) on herbaceous plant species in beech(Fagus sylvatica L.) forests naturally regenerating from clear-cutting and to test if the use of bioassays for studying the infectivity of native AMF could provide useful information to improve the management of clear-cut areas.Three nearby beech forests in northwest Navarra,Spain,a region in the northwest part of the Pyrenees,were selected:an unmanaged forest,a forest clear-cut in 1996,and another forest clear-cut in 2001.High stem density in the forest clear-cut in 1996(44 000 trees ha -1) attenuated photosynthetic active radiation(PAR) and impaired the growth of herbaceous species within the ecosystem.The percentage of AMF colonization of plants in bioassays performed on soil samples collected from the forest clear-cut in 1996 was always lower than 10%.In the forest clear-cut in 2001,where soil was covered by perennial grasses,PAR was high and the infectivity of native AMF achieved minimum values in spring and autumn and a maximum value in summer.In contrast,the infectivity of native AMF in the unmanaged forest remained similar across the seasons.Our results demonstrated that changes in the composition of understory vegetation within beech forests strongly affected the infectivity of native AMF in clear-cut areas and suggested that the assessment of the infectivity of native AMF through bioassays could provide helpful information for planning either the removal of overstory when the tree density is so high that it impairs the correct development of herbaceous species or the plantation of new seedlings when high light intensity negatively affects the establishment of shade species.     

Diversity of arbuscular mycorrhizal fungi in red tangerine (Citrus reticulata Blanco) rootstock rhizospheric soils from hillside citrus orchards

Root colonization, abundance of spores and hyphae, as well as species diversity of arbuscular mycorrhizal (AM) fungi were analyzed in citrus orchards along an altitudinal gradient. The citrus trees were heavily colonized (50.87–77.45%) by native AM fungi. In citrus orchards located at <600 m above sea level (asl), we recorded more extensive hyphal and arbuscular colonization, and higher spore and hyphal length density. AM fungal colonization, spore density, and hyphal length density were closely correlated with edaphic factors such as available phosphorus, pH, and organic matter. A total of 18 AM fungal species belonging to 3 different orders, Archaeosporales (1 species), Diversisporales (7 species) and Glomerales (10 species), were identified on the basis of spore morphological characteristics. In orchards located at higher altitudes (≥700 m asl), we observed a significant decrease in species richness and Shannon–Wiener index values. However, in all of the surveyed orchards, Glomus aggregatum, Funneliformis mosseae and Rhizophagus intraradices were the dominant species. Isolate frequency and relative abundance of AM fungi exhibited clearly distinct distribution patterns among taxonomic families. Canonical correspondence analysis revealed that the AM fungal community structure was significantly influenced by environmental factors, especially altitude, pH, soil moisture, and available nitrogen. Our data indicated that environmental factors are important in determining AM fungal root colonization, propagule numbers, and species diversity in citrus orchards.     

Response of soybean cultivars toward inoculation with three arbuscular mycorrhizal fungi and Bradyrhizobium japonicum in the alluvial soil

The aim of this study was to assess the comparative efficacy of three arbuscular mycorrhizal fungi (AMF) combined with cultivar specific Bradyrhizobium japonicum (CSBJ) in soybean under greenhouse conditions. Soybean seeds of four cultivars namely JS 335, JS 71-05, NRC 2 and NRC 7 were inoculated with three AM fungi (Glomus intraradices, Acaulospora tuberculata and Gigaspora gigantea) and CSBJ isolates, individually or in combination, and were grown in pots using autoclaved alluvial soil of a non-legume cultivated field of Ajmer (Rajasthan). Assessment of the data on nodulation, plant growth and seed yield revealed that amongst the single inoculations of three AMF, G. intraradices produced the largest increases in the parameters studied followed by A. tuberculata and G. gigantea indicating that plant acted selectively on AMF symbiosis. The dual inoculation with AMF + CSBJ further improved these parameters demonstrating synergism between the two microsymbionts. Among all the dual treatments, G. intraradices + B. japonicum brought about the largest increases in the studied characteristics particularly in seed weight per plant that increased up to 115.19%, which suggested that a strong selective synergistic relationship existed between AMF and B. japonicum. The cv. JS 335 exhibited maximum positive response towards inoculation. The variations in efficacy of different treatments with different soybean cultivars indicate the specificity of the inoculation response. These results provide a basis for selection of an appropriate combination of specific AMF and Bradyrhizobium which could further be utilized for verifying the symbiotic effectiveness and competitive ability of microsymbionts under field conditions of Ajmer region.     

铅胁迫下接种AM真菌对龙葵根际土壤微生物群落代谢特征的影响

为从微生态角度探索接种AM真菌对铅污染根际土壤微生物群落代谢特征的影响,以摩西管柄囊霉（Funneliformis mosseae）和幼套近明囊霉（Claroideoglomus etunicatum）为接种菌剂,在温室盆栽条件下以Pb⁴⁺含量为0 mg·kg^-1、200 mg·kg^-1、400 mg·kg^-1和800 mg·kg^-1土壤种植龙葵（Solanum nigrum）10周后采集根际土壤,采用Biolog微平板法测定龙葵根际土壤微生物群落的代谢变化。结果表明：1）微生物平均代谢活性（AWCD）随铅浓度增加呈降—升—降趋势;接种AM真菌显著提高了铅胁迫下根际土壤微生物的AWCD值,仅中浓度（400 mg·kg^-1）下未达显著差异。2）中浓度铅处理能显著提高根际土壤微生物对糖类及其衍生物、氨基酸类、脂肪酸和脂类及代谢产物类四大类碳源底物利用能力;接种AM真菌,高浓度（800 mg·kg^-1）铅处理显著提高了根际土壤微生物对氨基酸类底物的利用能力。3）铅胁迫下接种AM真菌提高了根际土壤微生物多样性指数,在中浓度下丰富度指数、Shannon-Wiener多样性指数、Simpson优势度指数均达显著水平。4）主成分分析显示,代谢产物类在PC1和PC2中种类最多,分别为6种和4种;糖类及其衍生物在PC3中种类最多（5种）。5）在铅胁迫和接种AM真菌共同作用下,微生物碳源利用主要受铅浓度调节,并且二者对微生物碳源利用具有显著交互效应。综上可知,接种AM真菌能够提高铅胁迫下龙葵根际土壤微生物多样性指数,增强根际土壤微生物对碳源底物的利用能力。该研究为进一步探究AM真菌强化植物联合修复技术提供了依据。     

High colonization by native arbuscular mycorrhizal fungi (AMF) of rubber trees in small-holder plantations on low fertility soils in North East Thailand

Rubber tree is a very important crop in Thailand, representing an essential source of income for farmers. In the past two decades, rubber tree plantations have been greatly expanding in unfavorable areas, where climate conditions are difficult and soil fertility is very poor. To optimize latex yields, mineral fertilizers have been widely used. A better understanding of the roles of the biological compartment in soil fertility is essential to determine alternative management practices to sustain soil fertility and optimize latex yields. Arbuscular mycorrhizal fungi (AMF) are widely recognized as beneficial for plants, mainly through their role in improving plant nutrient uptake. The objective of this study was to assess the AMF populations in rubber tree plantations and the impact of both soil characteristics and plantation age on these communities. Our results showed that all rubber trees were highly colonized, regardless of the soil structure and nutrient contents. AMF colonization was not affected by the age of the trees, suggesting that maintaining the symbiosis is likely to be beneficial at all stages. A better understanding and management of the microbial communities would contribute to maintaining or restoring soil fertility, leading to a better tree growth and optimized latex yield.     

Spatial distribution of arbuscular mycorrhizal fungi, glomalin and soil enzymes under the canopy of Astragalus adsurgens Pall. in the Mu Us sandland, China

To measure and manage plant growth in arid and semi-arid sandlands, improved understanding of the spatial patterns of desert soil resources and the role of arbuscular mycorrhizal (AM) fungi is needed. Spatial patterns of AM fungi, glomalin and soil enzyme activities were investigated in five plots located in the Mu Us sandland, northwestern China. Soils to 50 cm depth in the rhizosphere of Astragalus adsurgens Pall. were sampled. The study demonstrated that A. adsurgens Pall. could form strong symbiotic relationships with AM fungi. Arbuscular mycorrhizal fungal status and distributions were significantly different among the five studied plots. Correlation coefficient analysis demonstrated that spore density was significantly and positively correlated with soil organic carbon (SOC), soil acid phosphatase and to two Bradford-reactive soil protein (BRSP) fractions (P < 0.01). Colonization of arbuscules and vesicles were positively correlated with protease activity. The BRSP fractions were also significantly and positively correlated to edaphic factors (e.g. SOC, available nitrogen, and Olsen phosphorus) and soil enzymes (e.g. soil urease and acid phosphatase). The means of total BRSP and easily extractable BRSP were 0.95 mg g⁻¹ and 0.5 mg g⁻¹ in all data, respectively. The levels of BRSP in the desert soil were little lower than those in native and arable soils, but the ratios of BRSP to SOC were much higher than farmland soils. The results of this study support the conclusion that glomalin could be an appropriate index related to the level of soil fertility, especially in desert soil. Moreover, AM fungal colonizations and glomalin might be useful to monitor desertification and soil degradation.     

Use of Trichoderma spp. and arbuscular mycorrhizal fungi to increase soil beneficial population of bacteria in a nectarine commercial orchard: Effect on root growth,nutrient acquisition and replanting disease

The aim of the present experiment was to evaluate the effect of commercial Trichoderma and arbuscular mycorrhizal fungi (AMF)-based bio-fertilizers on nectarine root growth, nutrient acquisition and replanting disease. The experiment was performed from 2008 to 2012 in an A. mellea-infected nectarine orchard subjected to the following treatments: 1) untreated control; 2) AMF-biofertilizer applied at planting (120 kg ha^?1) and every year in spring and autumn at the rate of 6 kg ha^?1; 3) Trichoderma spp applied at planting (5 g plant^?1) and every year (in April, May and September) at 2.5 kg ha^?1. AMF bio-fertilizers decreased root diameter and increased root survivorship. Leaf phosphorus concentration increased in AMF bio-fertilizers plots, while no significant treatments effects were observed on other leaf nutrient concentration. Although biofertilizer application did not affect soil microbial population, at the end of the trial (2012) the application of Trichoderma alone increased the population of the fungus.