菌根真菌对3种兰花幼苗生长作用研究

菌根真菌在兰科植物生活史中具有重要作用。为获得促进兰科植物生长的共生真菌,阐明菌根真菌对兰科植物的作用,本研究对从野生建兰中分离获得的3株共生真菌进行形态学和系统进化分析,并将3株真菌与建兰、硬叶兰和铁皮石斛幼苗在不同浓度燕麦琼脂培养基(OMA)条件下共培养,进行比较研究。结果表明,3株真菌分属于胶膜菌属(Tsc)、角担菌属(Cej3)和蜡壳菌属(Sec),且菌丝和菌落特征存在明显差异;系统进化分析发现,Tsc菌株与Cej3菌株亲缘关系较近,与Sec菌株亲缘关系较远;与兰科植物共培养结果表明,Tsc菌株可在全部OMA浓度条件下与3种兰科植物幼苗建立共生关系,且定殖率均为100%;Cej3菌株和Sec菌株与3种兰科植物在不同OMA浓度条件下定殖时间及定殖率存在差异,且具有一定的专一性;与对照组相比,与真菌共生的兰科植物幼苗的平均鲜重、干重、苗高、根长增长率均明显提高。本研究结果为深入研究兰科植物与真菌共生的分子机制奠定了一定的理论基础,并为兰花种质资源的保护提供了参考。     

基于生态-产业共生关系的林业生态安全测度方法构想

通过对林业生态安全内涵构成的研究和对现有测度方法的比较分析,发现国内外林业生态安全测度研究中存在“就生态论生态”的预警滞后性、评价指标体系及权重设定的主观性、指标体系和特征指数难以优势互补、生态安全性判据缺乏客观依据等问题.为解决这些问题,需要基于生态与产业系统的共生关系研究林业生态安全测度的新方法.首先,研究林业生态安全的压力-状态-影响-响应结构模型和结构方程模型(SEM)的构建方法,从而为评价指标体系的构建和权重的确定提供了理论依据和结构化、定量化方法.然后,通过寻求指标体系和特征指数的有机结合,得出描述林业生态安全演变趋势的性质和程度的特征指数——生态-产业共生度和成熟度.由此提出确定林业生态安全阈值和底线的定量化方法,并建立林业生态安全双特征判断矩阵,从而将林业生态安全度分为3个安全区间、6个安全等级和4个预警级别.最后,综合以上成果,构建了基于生态-产业共生关系的林业生态安全测度方法的整体框架:目标-手段树和技术路线.根据新方法的构建机理,所得出的林业生态安全测度和预警信息具有主观性弱、预测性强、特征指数值的生态经济意义明确、便于追溯问题的原因等技术优势,有利于林业生态安全的监控和管理.     

Mycorrhizal Associations and Their Manipulation for Long-Term Agricultural Stability and Productivity

Summary

Mycorrhizae refer to an association (largely symbiotic) between plants and fungi that colonize the cortical root tissue of most agricultural crops during the period of active plant growth. The contribution of these symbioses to plant growth and soil fertility maintenance has been well-recognized for past several years. In spite of these benefits to agriculture, at present, the realization of the full potential of these fungi has not yet been reached. It must also be recognized that recent research on the possible application of the mycorrhizal symbiosis in agriculture has revealed many gaps in knowledge of fungal biology and ecology. Scientific knowledge on the role of these fungi in plant development and protection, soil stabilization, aggregate formation and creation of nutrient reserves is still limited. For efficient use and manipulation of these fungal symbioses for long-term agricultural stability and productivity, our understanding of their physiology, function and interactions with existing crops and environmental conditions should be improved. Besides, effects of different agronomic practices, application of chemical fertilizers and pesticides on their ecology and function should be elucidated before their successful utilization in agriculture.

This paper presents information on the morphology of different my-corrhizal fungi, their physiology and functions. Methods presently used to produce mycorrhizal inocula, their application in the field, problems to be resolved for their massive exploitation and future research needs have also been described. References have been selected to explain the recent advances in our understanding on these beneficial fungi.     

Symbiotic Associations in Ascidians: Relevance for Functional Innovation and Bioactive Potential

Associations between different organisms have been extensively described in terrestrial and marine environments. These associations are involved in roles as diverse as nutrient exchanges, shelter or adaptation to adverse conditions. Ascidians are widely dispersed marine invertebrates associated to invasive behaviours. Studying their microbiomes has interested the scientific community, mainly due to its potential for bioactive compounds production—e.g., ET-73 (trabectedin, Yondelis), an anticancer drug. However, these symbiotic interactions embrace several environmental and biological functions with high ecological relevance, inspiring diverse biotechnological applications. We thoroughly reviewed microbiome studies (microscopic to metagenomic approaches) of around 171 hosts, worldwide dispersed, occurring at different domains of life (Archaea, Bacteria, Eukarya), to illuminate the functions and bioactive potential of associated organisms in ascidians. Associations with Bacteria are the most prevalent, namely with Cyanobacteria, Proteobacteria, Bacteroidetes, Actinobacteria and Planctomycetes phyla. The microbiomes of ascidians belonging to Aplousobranchia order have been the most studied. The integration of worldwide studies characterizing ascidians’ microbiome composition revealed several functions including UV protection, bioaccumulation of heavy metals and defense against fouling or predators through production of natural products, chemical signals or competition. The critical assessment and characterization of these communities is extremely valuable to comprehend their biological/ecological role and biotechnological potential.     

Improved Nutrient Uptake and Growth of Maize in Response to Inoculation with Thiobacillus and Mycorrhiza on an Alkaline Soil

Most plant nutrients are optimally available when soil pH is close to neutral. In this experiment the effects of Thiobacillus and Mycorrhiza on nutrient uptake and grain yield of maize were studied on an alkaline soil as a factorial experiment with randomized complete blocks design. Treatments consisted of Mycorrhiza fungi (M): inoculated (m₁) and noninoculated (m₀), Thiobacillus (T): inoculated (t₁) and noninoculated (t₀), and sulfur (S) (S₀, S₁: 250, and S₂: 500 kg ha^?1). Inoculation of Mycorrhiza, Thiobacillus, and S application decreased soil pH and increased grain yield and seed oil content. The lowest soil pH and the greatest S content were obtained from the combination of Thiobacillus and 500 kg ha^?1 S. Inoculation of Thiobacillus and S application significantly decreased root colonization. The greatest iron (Fe) content was in the combination of Mycorrhiza inoculation and 500 kg ha^?1 S. Grain P content significantly increased with Mycorrhiza inoculation and S application. The greatest grain yield obtained from combination of Thiobacillus with 500 kg ha^?1 S.     

稻鸭共生中鸭的放养密度及作用效果研究

在稻田中放养鸭子的密度为10只/667 m2、20只/667 m2和30只/667 m2,根据试验田的面积,将110只巢湖麻鸭随机分为4组,经58 d的稻鸭共生试验表明:稻鸭共生技术具有良好的稻田除虫、除草和防水稻病害效果。在稻田中放养鸭子20只/667 m2具有良好的鸭只生长情况和最高的水稻产量,为最佳放养密度。     

鸭粪提取物对水稻纹枯病菌的影响及其有效成分分析

为探明稻鸭共养模式抑制水稻纹枯病发生的原因,以稻鸭共养模式的鸭粪提取物为研究对象,对其抑菌活性及有效成分进行了测定和分析,以期为水稻纹枯病生物防治提供新的途径。结果表明:鸭粪乙醇提取物对水稻纹枯病菌有抑制作用,24h内最高菌丝生长抑制率和EC50分别为88.64%、26.11mg·mL-1;鸭粪乙醇提取物经萃取分离得到石油醚和乙酸乙酯两种组分,其中石油醚组分抑菌效果较弱,乙酸乙酯组分抑菌能力较强,其对水稻纹枯病菌抑制率为89.70%,EC50为15.52mg·mL-1;对乙酸乙酯组分进行硅胶柱层析分离得到5种流份,其中第2流份有显著抑菌活性,在24h和48h内对水稻纹枯病菌的抑制率分别为89.58%和80.36%。GC-MS分析表明,鸭粪的抑菌物质主要为酚酸类和含硫醇有机物质,进一步纯化和鉴定有待研究。     

丛枝菌根真菌提高植物非生物胁迫耐受性研究进展

丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF或AM真菌)是一种在土壤中广泛存在的有益真菌,能与地球上80％左右陆生植物根系共生形成丛枝菌根结构.AM真菌能通过与宿主植物交换碳源,促进宿主植物对N和P等无机营养元素的吸收,提高植株生产力和抵抗非生物胁迫的能力.全球气候变化和化肥农药的使用...     

The endophytic fungus Piriformospora indica protects wheat from fusarium crown rot disease in simulated UK autumn conditions

The root endophytic fungus Piriformospora indica (Sebacinacea) forms mutualistic symbioses with a broad range of host plants, increasing their biomass production and resistance to fungal pathogens. This study evaluated the effect of P. indica on fusarium crown rot disease of wheat, under in vitro and glasshouse conditions. Interaction of P. indica and Fusarium isolates under axenic culture conditions indicated no direct antagonistic activity of P. indica against Fusarium isolates. Seedlings of wheat were inoculated with P. indica and pathogenic Fusarium culmorum or F. graminearum and grown in sterilized soil‐free medium or in a non‐sterilized mix of soil and sand. Fusarium alone reduced emergence and led to visible browning and reduced root growth. Roots of seedlings in pots inoculated with both Fusarium isolates and P. indica were free of visible symptoms; seed emergence and root biomass were equivalent to the uninoculated. DNA was quantified by real‐time polymerase chain reaction (qPCR). The ratio of FusariumDNA to wheat DNA rose rapidly in the plants inoculated with Fusarium alone; isolates and species were not significantly different. Piriformospora indica inoculation reduced the ratio of Fusarium to host DNA in the root systems. The reduction increased with time. The ratio of P. indica to wheat DNA initially rose but then declined in root systems without Fusarium. With Fusarium, the ratio rose throughout the experiment. The absolute amount of FusariumDNA in root systems increased in the absence of P. indica but was static in plants co‐inoculated with P. indica.     

Lipopolysaccharides from Commensal and Opportunistic Bacteria: Characterization and Response of the Immune System of the Host Sponge Suberites domuncula

Marine sponges harbor a rich bacterioflora with which they maintain close relationships. However, the way these animals make the distinction between bacteria which are consumed to meet their metabolic needs and opportunistic and commensal bacteria which are hosted is not elucidated. Among the elements participating in this discrimination, bacterial cell wall components such as lipopolysaccharides (LPS) could play a role. In the present study, we investigated the LPS chemical structure of two bacteria associated with the sponge Suberites domuncula: a commensal Endozoicomonas sp. and an opportunistic Pseudoalteromonas sp. Electrophoretic patterns indicated different LPS structures for these bacteria. The immunomodulatory lipid A was isolated after mild acetic acid hydrolysis. The electrospray ionization ion-trap mass spectra revealed monophosphorylated molecules corresponding to tetra- and pentaacylated structures with common structural features between the two strains. Despite peculiar structural characteristics, none of these two LPS influenced the expression of the macrophage-expressed gene S. domuncula unlike the Escherichia coli ones. Further research will have to include a larger number of genes to understand how this animal can distinguish between LPS with resembling structures and discriminate between bacteria associated with it.