连作对马铃薯酚酸类自毒物质及根际真菌群落的影响

为研究连作对马铃薯根际土壤中酚酸类自毒物质及真菌群落的影响,通过收集不同连作季(1季、3季、5季)马铃薯根际土壤,利用高效液相色谱法测定酚酸类物质及Illumina高通量测序技术测定真菌ITS序列,结果表明:(1)连作土壤中检测出丁香酸、香豆酸、对羟基苯甲酸、阿魏酸,连作增强后,pH不断下降,对羟基苯甲酸、阿魏酸含量不...     

木霉菌对几种植物病原菌的拮抗作用

为探明木霉对植物病原菌的拮抗作用效果,筛选出优势菌株,从长沙地区的15种作物根围采集到27份土壤样本,经室内分离、纯化得到28个木霉菌菌株.利用对峙法和稀释法测定了28个菌株对花生立枯病菌、水稻纹枯病菌、水稻恶苗病菌、辣椒炭疽病菌、白术白绢病菌的拮抗作用,得到1株对5种供试病原真菌均有强烈拮抗作用的菌株,经鉴定该菌株为哈茨木霉.对峙培养可观察到,多数情况下,接种后2 d内木霉与病原菌接触,随后覆盖或侵入病菌菌落,抑制其生长,其抑制程度随木霉孢子浓度的降低而减弱.温室盆栽试验发现,哈茨木霉对番茄立枯病防效显著,喷洒高浓度的哈茨木霉分生孢子悬浮液防效可达80%以上,且具有持续防效和刺激作物生长的作用.     

Control of Phytophthora cryptogea in the hydroponic forcing of witloof chicory with the rhamnolipid-based biosurfactant formulation PRO1

Rhamnolipids, extracellular metabolites of Pseudomonas aeruginosa with surfactant properties, proved to be very effective in controlling the spread of brown root rot disease caused by Phytophthora cryptogea in the hydroponic forcing system of witloof chicory ( Cichorium intybus var. foliosum ). The biosurfactant was applied as the product PRO1, a formulation of 25% rhamnolipids in oil. Both an in vitro screening and in vivo experiments in a mini-hydroponic system demonstrated the ability of PRO1 to control brown root rot. A 25  µ g mL⁻¹ rhamnolipids nutrient solution was enough to obtain good control of an artificial infection with a zoospore suspension of P. cryptogea . The biosurfactant PRO1 performed well in a semicommercial system under growers' conditions. A treatment of 25  µ g mL⁻¹ rhamnolipids (100  µ g mL⁻¹ PRO1) reduced the disease incidence significantly in two independent experiments. However, PRO1 was not effective when a mycelial suspension was used as inoculum. Rhamnolipids have good potential to limit the spread of P. cryptogea in the hydroponic forcing system of witloof chicory, and can be used as a preventive measure against brown root rot.     

Relation between cropping frequency of peas and other legumes and foot and root rot in peas

The relation between the frequency of legume crops in a rotation and the root rot severity in pea was examined in a field survey. Additionally, greenhouse experiments were performed with soil samples from legume rotation trials or from farmers' fields. The frequency of pea crops in current rotations proved to be much less than the recommended value of one in six years. The correlation between pea root rot and the number of years that pea or other legumes were not grown on the field under consideration (called crop interval) was weak. Root rot severity correlated better with the frequency of peas or legumes in general over a period of 18 years, but the frequency still explained only a minor fraction of the variation in disease index. Some experimental data pointed to the occurrence of a highly specific pathogen microflora with continuous cropping of only one legume species, but this phenomenon probably does not occur in farmers' fields. In field samples, root disease index for pea correlated well with that for field bean. The survival of resting structures of pathogens such asAphanomyces euteiches probably explains why the frequency of legume cropping has a higher impact than crop interval on root disease incidence. Pea-free periods and legume frequencies have a poor predictive value for crop management purposes.     

Development and evaluation of an enzyme-linked immunosorbent assay for the serodiagnosis of pythiosis in dogs

Pythiosis (caused by the aquatic oomycete Pythium insidiosum) is a devastating and often fatal cause of either severe transmural gastroenteritis or locally invasive subcutaneous disease in dogs living in the southeastern United States. Although early diagnosis is essential for successful treatment, tools available for this task are limited. Therefore, we developed and evaluated an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-P insidiosum antibodies in canine serum. A soluble mycelial extract of P insidiosum was utilized as antigen in the ELISA, which was used to evaluate serum from 43 dogs with pythiosis, 8 dogs with lagenidiosis (another canine oomycosis), 16 dogs with nonoomycotic fungal or algal infections, 22 dogs with nonfungal gastrointestinal or skin disease, and 55 healthy dogs. Results were expressed as percent positivity (PP) relative to a strong positive control serum run on each plate. Medians and ranges for each of the 5 groups were as follows: pythiosis (81.7%, 50.6-98.5%), lagenidiosis (17.3%, 11.3-29.2%), other fungal or algal infections (8.2%, 4.7-15.4%), nonfungal gastrointestinal or skin disease (6.2%, 3.9-20.7%), and healthy dogs (6.7%, 3.0-15.2%). When using a cutoff value of 40% PP, the sensitivity and specificity of the ELISA both were 100%. In addition, ELISA values measured after successful surgical therapy in 2 dogs showed a decrease of anti-P insidiosum antibody concentrations into the normal range as early as 2 months after treatment. We conclude that the ELISA is a sensitive and specific test for the diagnosis of canine pythiosis, and may be a useful tool for monitoring response to medical or surgical therapy.     

黄瓜根际细菌J352对大豆根腐病菌的作用

J352是从黄瓜根际筛选到的一株对病原真菌具有拮抗作用的细菌。室内培养结果表明,该菌对大豆根腐镰刀病菌有较强的抑制效果。J352发酵液对2种病原真菌孢子萌发有较高的抑制率;细菌与病原菌共培养后发现真菌菌丝和孢子发生畸变,菌丝和孢子内部均发生原生质体凝聚并出现空洞。与其它供试病原真菌的对峙培养发现,对烟草赤星病菌抑制作用最明显,抑菌率达85.5%。     

Relation between Soil Health, Wave-like Fluctuations in Microbial Populations, and Soil-borne Plant Disease Management

A healthy soil is often defined as a stable soil system with high levels of biological diversity and activity, internal nutrient cycling, and resilience to disturbance. This implies that microbial fluctuations after a disturbance would dampen more quickly in a healthy than in a chronically damaged and biologically impoverished soil. Soil could be disturbed by various processes, for example addition of a nutrient source, tillage, or drying-rewetting. As a result of any disturbance, the numbers of heterotrophic bacteria and of individual species start to oscillate, both in time and space. The oscillations appear as moving waves along the path of a moving nutrient source such as a root tip. The phase and period for different trophic groups and species of bacteria may be shifted indicating that succession occurs. DGGE, Biolog and FAME analysis of subsequent populations in oscillation have confirmed that there is a cyclic succession in microbial communities. Microbial diversity oscillates in opposite direction from oscillations in microbial populations. In a healthy soil, the amplitudes of these oscillations will be small, but the background levels of microbial diversity and activity are high, so that soil-borne diseases will face more competitors and antagonists. However, soil-borne pathogens and antagonists alike will fluctuate in time and space as a result of growing plant roots and other disturbances, and the periods and phases of the oscillations may vary. As a consequence, biological control by members of a single trophic group or species may never be complete, as pathogens will encounter varying populations of the biocontrol agent on the root surface. A mixture of different trophic groups may provide more complete biological control because peaks of different trophic groups occur at subsequent locations along a root. Alternatively, regular addition of soil organic matter may increase background levels of microbial activity, increase nutrient cycling, lower the concentrations of easily available nutrient sources, increase microbial diversity, and enhance natural disease suppression.     

Evaluation of the API 50CH and API ZYM systems for rapid characterization of Clavibacter michiganensis subsp. sepedonicus, causal agent of potato ring rot

API 50CH and API ZYM systems were used to characterize fifty-three strains of Clavibacter michiganensis subsp. sepedonicus from different geographic locations and several reference strains of the same and different species, including other potato pathogens. Clavibacter michiganensis subsp. sepedonicus strains displayed a high level of homogeneity, both in carbohydrate utilization and in enzymatic activity. Using API 50CH and API ZYM it was possible to differentiate C. michiganensis subsp. sepedonicus strains from the remaining taxa analysed in this study, which included representative strains of the other subspecies of C. michiganensis as well as other bacterial pathogens affecting potatoes. Therefore, these systems could be used as an effective method to characterize C. michiganensis subsp. sepedonicus. Such a procedure would constitute an alternative system to the conventional nutritional and physiological identification tests currently included in the official methods employed in the European Union to detect and identify this bacterium. The results obtained with the API systems agreed with the current taxonomic classification of C. michiganensis, clearly separating sepedonicus from the other subspecies belonging to this species.     

Top 20 environmental weeds for classical biological control in Europe: a review of opportunities, regulations and other barriers to adoption

Classical biological control remains the only tool available for permanent ecological and economic management of invasive alien species that flourish through absence of their co‐evolved natural enemies. As such, this approach is recognized as a key tool for alien species management by the Convention on Biological Diversity (CBD), the European and Mediterranean Plant Protection Organization (EPPO) and the European Strategy on Invasive Alien Species (ESIAS). Successful classical biological control programmes abound around the world, despite disproportionate attention being given to occasional and predictable non‐target impacts. Despite more than 130 case histories in Europe against insect pests, no exotic classical biological control agent has been released in the EU against an alien invasive weed. This dearth has occurred in the face of increasing numbers of exotic invasive plants being imported and taking over National Parks, forests and amenity areas in this region, as well as a global increase in the use of classical biological control around the world. This paper reviews potential European weed targets for classical biological control from ecological and socioeconomic perspectives using the criteria of historical biological control success, taxonomic isolation from European native flora, likely availability of biological control agents, invasiveness outside Europe and value to primary industry and horticulture (potential for conflicts of interest). We also review why classical biological control of European exotic plants remains untested, considering problems of funding and public perception. Finally, we consider the regulatory framework that surrounds such biological control activities within constituent countries of the EU to suggest how this approach may be adopted in the future for managing invasive exotic weeds in Europe.     

香菇开放式接种中环境微生物的变化和接种效果

对四个香菇开放式接种场所内不同时间点环境中霉菌和细菌的数量、温度和湿度进行测定,结果表明,在同一测试场所,不同测试时间点环境中霉菌和细菌的数量有所变化。总体上,消毒前和接种结束时环境中霉菌和细菌的数量相对较多,接种开始和接种进行一半时环境中霉菌和细菌的数量较少。各场所环境中的温度、湿度与霉菌和细菌的数量无相关性。消毒前环境中霉菌、细菌数量与菌棒污染率成正相关,相关系数分别为0.83和0.96;接种开始时环境中霉菌、细菌数量与菌棒污染率的相关系数分别为0.64和0.94;接种进行一半和接种结束时环境中的霉菌数量与菌棒污染率无相关性,而这两个时间点细菌数量与菌棒污染率的相关系数分别为0.62和0.88。