生防放线菌Snea253代谢产物的理化性质

研究了温度、pH值及光对该菌株发酵液中活性物质稳定性的影响,并利用捷克8溶剂系统纸色谱及纸电泳方法对该菌株发酵液中活性物质的理化性质进行鉴定.结果表明:该发酵液中杀线虫活性物质对温度较敏感,超过50℃活性逐渐下降,过高温度则失活;该活性物质光稳定性强,在中性偏碱性环境较稳定;经Doskochilova溶剂系统层析和纸电泳初步确定该物质属于碱性水溶性物质.     

青霉菌snf 44-1代谢产物对不同植物线虫的影响

室内测定了一株青霉菌snf 44-1的发酵代谢产物对番茄根结线虫（Meloidogyne hapla）、大豆胞囊线虫（Hreterodera glycines）、甘薯茎线虫（Ditylenchus destructor）的影响作用.发酵液对不同种类的线虫抑制作用有所差别,不同稀释倍数的发酵液对同种线虫的处理和无菌水处理有梯级差异.     

南方根结线虫生防镰刀菌菌株筛选

采用镰刀菌处理南方根结线虫2龄幼虫(J2)和卵以评价生防菌对南方根结线虫的杀线活性.从东北和华北等地区采集土样分离获得452株镰刀菌,采用南方根结线虫生防因子筛选体系进行活性菌株的筛选,获得14株对该线虫有高杀线活性的镰刀菌.菌株snef242和snef332的菌悬液对南方根结线虫J2有较强的杀死作用,校正死亡率达91.99%、91.35%;菌株Snef332、snef242和snef143的发酵液对卵囊孵化相对抑制率分别达86.61%、86.19%、85.36%;菌株snef109、snef332、Snef408和snef143的发酵液对南方根结线虫J2活性均有不同程度的抑制作用,其中菌株Snef109对线虫的抑制率最高,可达94.7%.经继代培养结果表明:菌株Snef332杀线能力遗传稳定性较很高,在南方根结线虫生防领域具有较大潜力,适宜作为南方根结线虫的生防因子加以开发利用.     

阿维菌素对南方根结线虫的生物活性

采用直接触杀法测定了阿维菌素对南方根结线虫的杀线活性。结果表明,1.8%阿维菌素EC对南方根结线虫具有很强的杀线活性,其LC50为1.48mg/L,而10%噻唑膦GR的LC50为13.90mg/L,表明1.8%阿维菌素EC对南方根结线虫的杀线活性明显高于对照药剂10%噻唑膦GR,具有广阔的应用前景和开发价值。     

苘麻提取物对南方根结线虫的活性

[方法]为寻找环境友好型杀线虫剂,测定了不同溶剂苘麻提取物对南方根结线虫的生物活性,对甲醇提取物进行生物碱粗分离,并对杀线虫活性强的碱水层进一步用极性从小到大的溶剂萃取,同时进行生物活性检测.[结果]12个萃取组分中氯仿与甲醇体积比为4∶1(A5)和1∶2(A8)两组分具有极强杀线虫活性,干粉质量浓度125g/L时,A5组分48h的线虫校正死亡率达100％,A8组分达932％.[结论]可对A5和A8组分进一步分离纯化和生物活性追踪.     

茼蒿甲醇提取物不同萃取组分对南方根结线虫发育的影响

采用液-液分配法对茼蒿甲醇提取物进行了萃取分离,得到石油醚、三氯甲烷、乙酸乙酯、正丁醇、水等5种不同萃取组分;采用室内培养和盆栽试验的方法,研究了5种萃取组分对南方根结线虫发育的影响。结果表明:茼蒿甲醇提取物水萃取组分对南方根结线虫胚胎发育和胚后发育的抑制作用最强。1%茼蒿甲醇提取物水萃取组分处理后264h,仅有15%的卵完成胚胎发育;胚后发育历程、初侵染、初产卵日分别推迟4、5、9d,雌虫产卵量显著降低。     

不同药剂复配对南方根结线虫增效作用

[目的]筛选对南方根结线虫高效低毒的药剂。[方法]采用浸泡杀线虫法测定9种药剂对南方根结线虫的毒力,选活性较高的单剂进行交互复配,测定其联合毒力。[结果]甲氨基阿维菌素苯甲酸盐对2龄幼虫和卵囊的毒力最强,LC50值分别为2.51、10.50 mg/L;甲氨基阿维菌素苯甲酸盐与噻唑膦复配的共毒系数为141.59,阿维菌素与噻唑膦复配的共毒系数为159.37。[结论]单剂以甲氨基阿维菌素苯甲酸盐活性最高,复配剂以噻唑膦与阿维菌素、甲氨基阿维菌素苯甲酸盐复配效果最佳。     

除草剂对南方根结线虫存活的影响

在离体恒温条件下,研究了7种蔬菜田常用低毒除草剂对南方根结线虫(Meloidogyne incognita)存活的影响,并进行了除草剂盆栽防效试验.结果表明:常用喷施剂量处理后,所有供试除草剂对南方根结线虫2龄幼虫(J2)及卵囊内卵的孵化均有不同程度的致死作用,其中以33%二甲戊乐灵EC和48%氟乐灵EC效果最为明显.并对这2种除草剂进行盆栽防效试验,结果表明:48%氟乐灵EC防效优于33%二甲戊乐灵EC,接近阿维菌素,并且覆膜的防效优于不覆膜.     

氯化苦与阿维菌素混用对南方根结线虫的室内活性评价

[目的]评价氯化苦与阿维菌素混用对南方根结线虫的室内防治效果。[方法]采用广口瓶熏蒸法和凹玻片密闭熏蒸法测定氯化苦与阿维菌素联合对南方根结线虫的毒力。[结果]广口瓶熏蒸试验和凹玻片密闭熏蒸试验表明,氯化苦和阿维菌素的4种不同用量混用均对南方根结线虫表现出增效作用,对南方根结线虫的校正死亡率均分别达到85%和93%以上。[结论]氯化苦与阿维菌素混用对南方根结线虫有良好的控制作用。     

曲霉发酵液对烟草根结线虫的作用

室内测定了一株曲霉发酵液对烟草根结线虫优势种群南方根结线虫（Meloidogyne incognita）2龄幼虫、卵囊和散卵粒孵化的影响。不同稀释浓度发酵液的处理和无菌水处理有显著差异,发酵液的1倍液以上浓度与10μtg／ml涕灭威的防效相当,对2龄幼虫的致死率在90％以上,对卵囊和散卵粒孵化的抑制率在95％以上。     

酸类化合物对南方根结线虫的作用方式

[方法]采用室内离体测定方法,测定3种酸类化合物对南方根结线虫2龄幼虫毒力、死亡时间、运动行为、个体发育及体液外渗作用方式影响。[结果]3种化合物对2龄幼虫毒力大小为甲酸>乙二酸>柠檬酸,死亡时间长短为甲酸<乙二酸<柠檬酸,3种化合物均可抑制2龄幼虫运动行为和个体发育,并导致2龄幼虫体液外渗。[结论]供试化合物通过抑制线虫的运动、发育、促进线虫体液外渗等作用,破坏其正常生理代谢功能,致使线虫死亡。     

4种杀线虫剂对南方根结线虫的室内活性测定

通过藏红T染色法,确定线虫染色时间,并测定4种常规药剂对南方根结线虫的室内活性。结果显示,染色1 h后,线虫的染色率达到100%。1.8%阿维菌素EC和40%灭线磷EC对南方根结线虫具有良好的活性,LC_(50)值分别为14.926 3 mg/L和15.306 8 mg/L;40%辛硫磷EC和200 g/L丁硫克百威EC活性较差。     

10%虫胺磷GR对人参榕根结线虫病的防效

利用10％虫胺磷GR对人参榕根结线虫病进行了防治试验。结果表明,10％虫胺磷GR66-7mg／L药液灌根或者配制成含200g／m^3的毒土,可有效地防治人参榕根结线虫病。     

球孢白僵菌Snf907发酵液对番茄根结线虫病的控病效果及防御酶活性影响

研究球孢白僵菌Snf907不同浓度发酵液对番茄幼苗期南方根结线虫病(Meloidogyne incognita)的室内防效,并测得处理后番茄幼苗根内几种主要寄主防御反应酶系PAL、POD、PPO、SOD和可溶性蛋白PRO活性的动态变化.结果表明:不同浓度的发酵液对根结和卵囊的抑制率均明显高于对照,其中原液和5倍稀释液达到80%以上.不同浓度发酵液处理后番茄幼苗根部的PAL、POD、PPO、SOD活性均高于对照,PRO活性显著增加.显示了球孢白僵菌在促进植物生长方面的潜能.     

Efficacy of a Chitin-Based Water-Soluble Derivative in Inducing Purpureocillium lilacinum against Nematode Disease (Meloidogyne incognita)

Plant-parasitic nematodes cause severe economic losses annually which has been a persistent problem worldwide. As current nematicides are highly toxic, prone to drug resistance, and have poor stability, there is an urgent need to develop safe, efficient, and green strategies. Natural active polysaccharides such as chitin and chitosan with good biocompatibility and biodegradability and inducing plant disease resistance have attracted much attention, but their application is limited due to their poor solubility. Here, we prepared 6-oxychitin with good water solubility by introducing carboxylic acid groups based on retaining the original skeleton of chitin and evaluated its potential for nematode control. The results showed that 6-oxychitin is a better promoter of the nematicidal potential of Purpureocillium lilacinum than other water-soluble chitin derivatives. After treatment, the movement of J2s and egg hatching were obviously inhibited. Further plant experiments found that it can destroy the accumulation and invasion of nematodes, and has a growth-promoting effect. Therefore, 6-oxychitin has great application potential in the nematode control area.     

Strong repellency of the root knot nematode,Meloidogyne incognita by specific inorganic ions

Simple inorganic salts of the ions K⁺, NH ₄ ⁺ , Cs⁺, NO ₃ ^– , and Cl^– are strongly repellent to infective second-stage larvae of the root knot nematode,Meloidogyne incognita. Some of these salts are known to be beneficial to plant growth. The results suggest a new means of plant protection.     

Nematicidal Volatiles from Bacillus atrophaeus GBSC56 Promote Growth and Stimulate Induced Systemic Resistance in Tomato against Meloidogyne incognita

Bacillus volatiles to control plant nematodes is a topic of great interest among researchers due to its safe and environmentally friendly nature. Bacillus strain GBSC56 isolated from the Tibet region of China showed high nematicidal activity against M. incognita, with 90% mortality as compared with control in a partition plate experiment. Pure volatiles produced by GBSC56 were identified through gas chromatography and mass spectrometry (GC-MS). Among 10 volatile organic compounds (VOCs), 3 volatiles, i.e., dimethyl disulfide (DMDS), methyl isovalerate (MIV), and 2-undecanone (2-UD) showed strong nematicidal activity with a mortality rate of 87%, 83%, and 80%, respectively, against M. incognita. The VOCs induced severe oxidative stress in nematodes, which caused rapid death. Moreover, in the presence of volatiles, the activity of antioxidant enzymes, i.e., SOD, CAT, POD, and APX, was observed to be enhanced in M. incognita-infested roots, which might reduce the adverse effect of oxidative stress-induced after infection. Moreover, genes responsible for plant growth promotion SlCKX1, SlIAA1, and Exp18 showed an upsurge in expression, while AC01 was downregulated in infested plants. Furthermore, the defense-related genes (PR1, PR5, and SlLOX1) in infested tomato plants were upregulated after treatment with MIV and 2-UD. These findings suggest that GBSC56 possesses excellent biocontrol potential against M. incognita. Furthermore, the study provides new insight into the mechanism by which GBSC56 nematicidal volatiles regulate antioxidant enzymes, the key genes involved in plant growth promotion, and the defense mechanism M. incognita-infested tomato plants use to efficiently manage root-knot disease.     

Polyenic Antibiotics and Other Antifungal Compounds Produced by Hemolytic Streptomyces Species

Streptomyces are of great interest in the pharmaceutical industry as they produce a plethora of secondary metabolites that act as antibacterial and antifungal agents. They may thrive on their own in the soil, or associate with other organisms, such as plants or invertebrates. Some soil-derived strains exhibit hemolytic properties when cultivated on blood agar, raising the question of whether hemolysis could be a virulence factor of the bacteria. In this work we examined hemolytic compound production in 23 β-hemolytic Streptomyces isolates; of these 12 were soil-derived, 10 were arthropod-associated, and 1 was plant-associated. An additional human-associated S. sp. TR1341 served as a control. Mass spectrometry analysis suggested synthesis of polyene molecules responsible for the hemolysis: candicidins, filipins, strevertene A, tetrafungin, and tetrin A, as well as four novel polyene compounds (denoted here as polyene A, B, C, and D) in individual liquid cultures or paired co-cultures. The non-polyene antifungal compounds actiphenol and surugamide A were also identified. The findings indicate that the ability of Streptomyces to produce cytolytic compounds (here manifested by hemolysis on blood agar) is an intrinsic feature of the bacteria in the soil environment and could even serve as a virulence factor when colonizing available host organisms. Additionally, a literature review of polyenes and non-polyene hemolytic metabolites produced by Streptomyces is presented.