寡雄腐霉防治大棚草莓病害试验初报

草莓灰霉病、黑霉病、白粉病是大棚草莓的主要病害,近年来随着草莓栽培面积的不断扩大,病害也逐年加重,严重影响着草莓的质量和产量,制约着草莓业的发展。化学杀菌剂在草莓上的使用,不仅造成环境污染,还会影响草莓食品安全。寡雄腐霉是一种广谱性的微生物杀菌剂,可防治多种真菌性病害,且无污染、无公害、     

钩状木霉菌的生物学特性及对腐皮镰刀菌的抑菌机理研究

从兰花根际中分离出一株木霉菌株LAN2B-1,对其进行形态学鉴定和ITS序列分析,确定菌株为钩状木霉菌Trichoderma hamatum.该菌株菌落生长的最佳条件为PDA培养基、碳源为甘露醇、pH 5、温度25℃～30℃,暗处理有利于菌落生长,但氮源对菌落生长影响不显著.木霉菌发酵液的抑菌活性和作用机理研究表明,钩...     

戊菌唑

理化性质：戊菌唑属于三唑类杀菌剂。戊菌唑原药质量分数≥95％;外观为无色结晶粉末;熔点：57．6～60．3℃;蒸气压：0．17mPa（20℃）,0．37mPa（25℃）;     

肟菌酯

理化性质：肟菌酯属甲氧基丙烯酸类杀菌剂。纯品外观为无味白色至灰色结晶粉末;熔点：72.9℃;沸点：约312℃;蒸气压（25℃）：3.4×10^-6Pa;在水中溶解度（25℃）：0.61mg/L,     

苯醚菌酯

理化性质：苯醚菌酯属甲氧基丙烯酸甲酯类杀菌剂,是我国具有自主知识产权的新农药。纯品外观为白色粉末。熔点：108℃～110℃：蒸气压（25℃）：1．5×10^-6Pa;溶解度（g／L,20℃）：水中3．60×10^-3,甲醇中15．56,乙醇中11．04,二甲苯中24．57,丙酮中143．61;分配系数（正辛醇／水）：3．382×10^4（25℃）;在酸性介质中易分解;对光稳定。化学名称：（E）-2-[2-（2,5-二甲基苯氧基）-苯基]-3-甲氧基丙烯酸甲酯;结构式：     

Rhizosphere Competence of Pythium oligandrum

ABSTRACT The associations of Pythium oligandrum with the root cortex, rhizoplane, and rhizosphere were measured with 11 crop species. This work was expedited by the use of a semiselective technique for isolation of P. oligandrum from soil and plant material. Cortical colonization of roots by P. oligandrum was not detected, and the rhizoplanes of the roots of most crops were free of the fungus. However, P. oligandrum was detected in large quantities with every crop tested when roots with adhering soil (rhizosphere soil) were assayed. Different crop species and cultivars of cantaloupe, cauliflower, and tomato varied in rhizosphere densities of P. oligandrum, but rhizosphere population densities of the fungus were consistently higher than in nonrhizosphere soils with plants grown in P. oligandrum-infested sterilized potting mix or an unsterilized mineral soil. After transplanting tomatoes into potting mix infested with P. oligandrum, increases in CFU occurred over time in the rhizosphere but not in the nonrhizosphere soil. In trials on delivery methods of inoculum of P. oligandrum, the rhizosphere populations of tomato plants grown in potting mix were about sixfold higher compared to seed-coat treatments when ground, alginate pelleted oospores were applied to seedlings growing in plug containers prior to transplanting or to pots containing potting mix before direct seeding.     

寡雄腐霉生防机理及应用研究进展

寡雄腐霉是一种重要的微生物农药,因其对病原菌具有广谱、高效的防治特性及对作物具有促生长和增产等特点被广泛关注。本文从寡雄腐霉对植物病原菌抗性、诱导植物产生诱导系统抗性、促进植物生长等方面对其生防的分子机理和信号转导的研究进展进行了综述,总结了寡雄腐霉在防治植物病害方面的应用,并对研究和应用过程中存在的问题及解决途径提出展望。     

Factors affecting the control of Pythium ultimum damping-off of sugar beet by Pythium oligandrum

Application of Pythium oligandrum to a soil-based compost as a mycelial suspension (5 × 10² CFU g⁻¹ of dry compost) and oospore alginate pellets (10⁵ oospores/g of dry compost) controlled pre- and postemergence damping-off of sugar beet caused by Pythium ultimum to a level similar to metalaxyl seed treatment. Oospore seed treatments and aqueous suspensions of oospores applied to compost failed to control disease. Problems in the use of P. oligandrum oospore inocula for the control of damping-off were highlighted. It was shown that treatment of oospores with cellulase (20 g L⁻¹) increased germination approximately three-fold in comparison to untreated spores. Untreated and cellulase pretreated oospores were subsequently evaluated as seed treatments for their ability to control damping-off of sugar beet. The highest rate of pretreated oospores (10⁴ oospores/seed) gave levels of emergence and establishment in infested compost that were not significantly different from the uninfested controls, whereas seed treatment with untreated oospores gave no significant reduction in disease. In a trial carried out in a controlled environment to assess the effect of pH (4.5–8.0), P. oligandrum (10⁴ cellulase pretreated oospores/seed) was shown to control pre- and postemergence damping-off of sugar beet at pH 7.0 and 7.5 only.     

Biological control of Pythium ultimum–induced damping-off by treating cress seed with the mycoparasite Pythium oligandrum

Incorporation of the aggressive mycoparasite Pythium oligandrum into a carboxymethyl cellulose-based seed coating decreased damping-off of cress seedlings by Pythium ultimum in both naturally infested soil and artificially infested sand. This effect is attributed to the germination of P. oligandrum oospores on the seed surface with subsequent generation of a protectant mycelium around the seedling.
P. oligandrum oospores survived storage periods of 10—20 weeks at zero relative humidity both on glass slides and within seed coatings. The mycoparasite also survived an 18–month burial in natural soil, probably in the form of oospores.
The implications of these observations for biocontrol of seedling diseases by P. oligandrum are discussed.     

Pelleting of seed with the antagonist Pythium oligandrum for biological control of damping-off

Pythium oligandrum oospores, incorporated in clay carrier, survived a commercial seed-pelleting process to give protection against damping-off in sugar beet and cress induced by Pythium ultimum , together with damping-off in carrot caused by Mycocentrospora acerina.
It is suggested that field scale evaluation of P. oligandrum as a biocontrol of fungally incited seedling diseases is now both feasible and desirable.     

Control of damping-off in cress and sugar-beet by commercial seed-coating with Pythium oligandrum

Seeds of cress and sugar-beet were coated with oospores of Pythium oligandrum using commercial seed-pelleting or film-coating procedures. Following either procedure approximately 10⁴ oospores were recovered from both seed types, achieving 75.94% of the targeted dose. Oospore germination (9.19%) was unaffected by the coating treatments. Both types of treatment reduced damping-off of cress caused by P. ultimum in artificially infested sand and potting compost and by Rhizoctonia solani in artificially infested sand. In some cases, the level of control was equivalent to fungicide drenches. In general, pelleting of P. oligandrum on cress gave better control than film-coating treatments. P. oligandrum also reduced damping-off of sugar-beet in soil naturally infested with Aphanomyces cochlioides and Pythium spp. Control was equivalent to that achieved with hymexazol fungicide seed-coating treatments and was related to the inoculum potential of A. cochlioides in the soil; neither standard hymexazol coatings nor P. oligandrum treatments gave control at high inoculum potentials. P. oligandrum was not rhizosphere competent on cress or sugar-beet.     

Interactions Between the Mycoparasite Pythium oligandrum and Sclerotia of the Plant Pathogen Sclerotinia sclerotiorum

Pythium oligandrum Drechsler is a mycoparasite which parasitizes hyphae of many fungal species. A detailed study of the interactions between P. oligandrum and the sclerotia of the plant pathogen Sclerotinia sclerotiorum (Lib.) de Bary is presented. Pythium oligandrum was present in Danish soils at concentrations between 4 and 26 cfu g^–1 soil. An increase in the natural population of P. oligandrum by addition of P. oligandrum zoospores to a soil reduced the ability of sclerotia of S. sclerotiorum to germinate myceliogenically and the sclerotia were colonized internally by P. oligandrum. This colonization and reduction of germination of sclerotia were also seen when sclerotia and P. oligandrum were incubated together in water. Small sclerotia were significantly more susceptible to parasitism by P. oligandrum than large sclerotia, and increasing the incubation time caused a further reduction in the germination ability of the sclerotia. P. oligandrum was able to pass through its entire life-cycle from zoospores to oogonia both with sclerotia as sole nutrient-source and in water containing exudates from the sclerotia. The cell wall degrading enzymes N-acetyl--D-glucosaminidase (NAGase), endo-chitinase, protease, -glucanase, -glucosidase and cellobiohydrolase were detected in culture filtrates of P. oligandrum cultivated with S. sclerotiorum. These findings suggest that P. oligandrum has a potential to reduce the survival of S. sclerotiorum sclerotia present naturally in soils, through mycoparasitic activity.     

Induction of transient ethylene and reduction in severity of tomato bacterial wilt by Pythium oligandrum

Pythium oligandrum (PO) is a mycoparasite on a wide range of fungi and suppresses diseases caused by fungal pathogens when colonizing the rhizosphere. PO and its cell wall proteins (CWPs) have elicitor activity that induces defence responses in plants. The potential of a mycelial homogenate of PO to suppress bacterial diseases was studied in roots of tomato ( Lycopersicon esculentum cv. Micro-Tom) inoculated with Ralstonia solanacearum . PO-treated plants showed enhanced resistance to R. solanacearum and reduction in severity of wilt symptoms. As ethylene often acts as one of the signal molecules for induced resistance, its production following treatment of tomato roots with the mycelial homogenate or CWP of PO was measured. The level of ethylene in PO- and CWP-treated plants was transiently elevated six- to 11-fold at 4–8 h after treatment, followed by high expression of three basic ethylene-inducible defence-related genes ( PR-2b , PR-3b and PR-5b ). Analysis of PR-5b gene expression in the leaves of PO- and CWP-treated plants suggested that PR gene expression was induced systemically. The expression of LeERF2 and LeETR4 , which confer an ethylene-dependent signalling pathway, was also significantly accelerated by such treatments. These results indicate that PO has the potential to control bacterial wilt disease and that CWP may play an important role in the induction of resistance to R. solanacearum accompanying the activation of the ethylene-dependent signalling pathway.     

Ultrastructural and Cytochemical Aspects of the Interaction Between the Mycoparasite Pythium oligandrum and Soilborne Plant Pathogens

ABSTRACT The interaction between the oomycete Pythium oligandrum and various soilborne oomycete and fungal plant pathogens (P. ultimum, P. aphanidermatum, Fusarium oxysporum f. sp. radicis-lycopersici, Verticillium albo-atrum, Rhizoctonia solani, and Phytophthora megasperma) was studied by light and electron microscopy in order to assess the relative contribution of mycoparasitism and antibiosis in the antagonistic process. Scanning electron microscope investigations of the interaction regions showed that structural alterations of all pathogenic fungi and oomycetes (except for Phytophthora megasperma) occurred soon after contact with the antagonist. Light and transmission electron microscope studies of the interaction region between the antagonist and P. ultimum revealed that intimate contact between both partners preceded a sequence of degradation events including aggregation of host cytoplasm and penetration of altered host hyphae. Localization of the host wall cellulose component showed that cellulose was altered at potential penetration sites. A similar scheme of events was observed during the interaction between P. oligandrum and F. oxysporum f. sp. radicis-lycopersici, with the exception that complete loss of host protoplasm was associated with antagonist invasion. The interaction between P. oligandrum and R. solani resulted in an abnormal deposition of a wall-like material at potential penetration sites for the antagonist. However, the antagonist displayed the ability to circumvent this barrier and penetrate host hyphae by locally altering the chitin component of the host hyphal wall. Interestingly, antagonist cells also showed extensive alteration as evidenced by the frequent occurrence of empty hyphal shells. In the case of Phytophthora megasperma, hyphal interactions did not occur, but hyphae of the plant pathogen were damaged severely. At least two distinct mechanisms appear to be involved in the process of oomycete and fungal attack by P. oligandrum: (i) mycoparasitism, mediated by intimate hyphal interactions, and (ii) antibiosis, with alteration of the host hyphae prior to contact with the antagonist. However, the possibility that the antagonistic process may rely on the dual action of antibiotics and hydrolytic enzymes is discussed.