腐霉属的一个新种和二个新记录

本文报告作者1982—1983年在北京和广东一些地区土壤中用已知方法(余永年,1975)分离到的几种腐霉,其中1个新种(Pythium borealis sp.nov.)、2个国内未报道的种(P.oligandrum和P.myriotylum)和1个已知种的变异株(P.ultimum variant)。文中对以上各菌进行了形态学描述。     

The influence ofPythium on the growth of barley seedlings as affected by soil water and inoculum density

Summary Pythium spp. were more abundant in the southerly and more temperature regions of the barley growing region of South Australia than in the drier and hotter north. Populations were more abundant in the top 10 cm than in the 10 to 20 cm soil zone. Eleven species ofPythium were identified from barley crops.P. irregulare appeared to be the most abundant and was one of the most pathogenic species on barley.P. volutum was also highly pathogenic; it had not been recorded in South Australia before. A factorial experiment using ninePythium spp. and four levels of soil water indicated that unlike other species,P. irregulare, P. volutum andP. graminicolum were most pathogenic in soils with a water content close to field capacity. A factorial experiment usingP. irregulare at four levels of soil water and six inoculum levels showed that inhibition of growth in barley seedlings byP. irregulare increased as the level of water in the soil increased. The experiments support the hypothesis that inhibition of growth of barley seedlings byPythium spp. is most severe in the southerly parts of the barley growing area of South Australia particularly where there is a combination of high soil water and high population densities.     

中国腐霉属的水生种类

腐霉属是一个世界广布分类群,迄今为止已报道约100种.它们主要分布于土坡中,条件适合时侵染植物引起病害,造成多种经济植物的重大损失.腐霉也见水中,它们既可寄生于藻类及一些小动物上,也可腐生于动植物残骸上.在研究微生物与水质关系时,腐霉的作用是不可忽视的.在发酵工业上,腐霉可望用于生产多种酶类及转化街族化合物,所以它是一个经济意义较重要的类群.     

Biocontrol of Damping-off Diseases Caused by Rhizoctonia solani and Pythium ultimum with Alginate Prills of Gliocladium virens, Trichoderma hamatum and Various Food Bases

Alginate prills were formulated with the biomass of isolates of Gliocladium virens and Trichoderma spp. and various food bases (wheat bran, corn cobs, peanut hulls, soy fiber, castor pomace, cocoa hulls and chitin). Alginate prills with G. virens (Gl-21) biomass and all food bases except cocoa hull meal significantly reduced the damping-off of zinnia in a soil-less mix caused by Rhizoctonia solani and Pythium ultimum. The prills with bran, soy fiber, castor pomace or chitin resulted in stands similar to those in the non-infested control. In soil, prills with all the food bases and Thrichoderma hamatum (TRI-4) biomass controlled the damping-off of cotton caused by R. solani and gave stands comparable to, or better than, those in the non-infested control soil. Prills with all the food bases resulted in a proliferation of Gl-21 in a soil-less mix and of Gl-21 and TRI-4 in soil. Prills with food bases and TRI-4 biomass reduced the survival of R. solani in infested beet seed to less than 30%, with bran and chitin being the most effective food bases; prills with Gl-21 biomass and all food bases also reduced the survival of R. solani in beet seed, but not as much as did prills with TRI-4 biomass. In prills containing wheat bran, soy fiber or chitin, the biocontrol isolate Th-58 (T. harzianum) was almost as effective as TRI-4, but isolate Gl-3 (G. virens) was less effective. There was no significant interaction between the biocontrol fungus and the food base. The results suggest that the intrinsic properties of a selected fungus isolate are more important than some formulation variables in biocontrol.     

Intracellular location of NADP+-linked malic enzyme in C3 plants

Ultraviolet light induces anthocyanin biosynthesis in cell cultures of an Afghan cultivar of Daucus carota (Daucus carota L. ssp. sativus). Simultaneous treatment with a fungal elicitor from Pythium aphanidermatum results in an inhibition of the catalytic activity of chalcone synthase (CHS), which in turn correlates with an inhibition of anthocyanin biosynthesis. On immunoblots, one isoenzyme (40 kDa) of CHS disappears upon elicitor treatment. On an mRNA level, only the mRNA for the 40-kDa-CHS is active after treatment with ultraviolet light. After inhibition of anthocyanin biosynthesis by the elicitor the enzyme protein disappears and the CHS mRNA is strongly diminished. This inhibition depends on the concentration of the elicitor. In addition, elicitor treatment leads to an induction of the general phenylpropanoid pathway as well as to the accumulation of 4-hydroxybenzoic acid which is covalently bound to wall polysaccharides of the carrot cells. The possible function of phenylalanine ammonia-lyase in providing precursors for 4-hydroxybenzoic acid is discussed.Abbreviations CHI chalcone isomerase - CHS chalcone synthase - PAL phenylalanine ammonia-lyase - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis We are grateful to Professor K. Hahlbrock (Max-Planck-Institut für Züchtungsforschung, Köln, FRG) for providing us with antisera to CHS and PAL, respectively. This work was supported by a grant from the Deutsche Forschungsgemeinschaft and scholarships from the Friedrich-Ebert-Stiftung (J. G.), the Landesgraduierten-förderungsgesetz Baden-Württemberg (J.-P. S) and the Gerhard-Rösch-Stiftung (D. S.). We thank R. Hofmann for her excellent technical assistance.     

Production and Evaluation of Monoclonal Antibodies for the Detection of Pythium sulcatum in Soil

Monoclonal antibodies (MAbs) were raised against surface antigens from Pythium sulcatum. The immunogens were prepared from salt extractable cell wall protein to produce monoclonal antibodies. The MAbs showed high specificity to seven P. sulcatum isolates among 26 species of soil‐borne fungi. Weak cross‐reactivities were observed with Pythium aristosporum, Pythium myriotylum, and Pythium zingiberum in indirect enzyme‐linked immunosorbent assay (ELISA), but no reaction was obtained in Western blot analysis. The MAbs recognized glycoproteins in cell wall. Pythium sulcatum was detected in naturally infected carrot tissues and soil using indirect competition ELISA.     

Cutaneous Pythiosis insidiosi in calves from the Pantanal region of Brazil

Two cases of cutaneous Pythiosis insidiosi were diagnosed in cattle from the Pantanal region, Brazil. The lesions were observed in the limbs of two 8-month-old beef calves. Close examination showed local swelling and focal ulceration of the skin. Microscopically, there was multifocal granulomatous dermatitis with intralesional Pythium insidiosum hyphae. The diagnosis was based on the morphological aspects, immunohistochemical findings and culture of the etiologic agent. This revised version was published online in June 2006 with corrections to the Cover Date.     

Formulation of the Biocontrol FungusCladorrhinum foecundissimumto Reduce Damping-Off Diseases Caused byRhizoctonia solaniandPythium ultimum

Five isolates ofCladorrhinum foecundissimum, added to soilless mix as 10-day-old fresh bran preparations (1.0% w/w), significantly reduced (P≤ 0.05) damping-off of eggplant and pepper caused byRhizoctonia solanistrain R-23. After 4 weeks of growth, plant stands in the biocontrol-amended, pathogen-infested treatments (>80%) were comparable to those in the noninfested controls. Since plant stands were similar at 2 and 4 weeks, most of the disease was preemergence damping-off. The bran preparations also reduced saprophytic growth of the pathogen, and there was an inverse correlation (r²= −0.94) between saprophytic growth and eggplant stand. Added to soilless mix at a rate of 2.0% (w/w), alginate prill containing 20% fermentor-produced biomass of six biocontrol isolates ofC. foecundissimumreduced (P≤ 0.05) damping-off of eggplant caused byR. solani, but only the prill with biomass of isolates Cf-1 or Cf-2 yielded plant stands (>80%) comparable to that in the noninfested control. As with the bran preparations, there was also an inverse correlation (r²= −0.80) between saprophytic growth of R-23 and eggplant stand with the alginate prills. Alginate prill with biomass of Cf-1 or Cf-2 also reduced (P≤ 0.05) damping-off of eggplant and pepper caused by other isolates (195, NG-2, DPR-1) ofR. solani, but only the stands (>80%) of pepper were similar to that in the noninfested control. Alginate prill formulations ofC. foecundissimum(Cf-1, Cf-2, and Cf-3) also reduced (P≤ 0.05) populations of the pathogen and damping-off of eggplant and pepper caused byPythium ultimum(PuZ3). However, although the plant stands in the treatments were not as high as those in the noninfested controls, they were higher than those in the pathogen-infested controls. The treatments also reduced populations ofP. ultimumin the soilless mix so that there were inverse correlations between the pathogen population and eggplant stand (r²= −0.81) and pepper stand (r²= −0.78). Extruded flour/clay granules containing 5.0% biomass of Cf-1 and Cf-2, added toR. solani-infested soilless mix (2.0%), reduced (P≤ 0.05) damping-off of eggplant and pepper. However, only the Cf-2 treatments resulted in stands (>80%) equal to those in the noninfested controls for the crops after 4 weeks of growth. The influence of bran and alginate prill of Cf-1 or Cf-2 on the spatial spread ofR. solaniand its ability to incite damping-off of eggplant showed that prill with Cf-1 or Cf-2 and bran with Cf-2 were equally effective in reducing the spread of the pathogen from the point source of the inoculum to the center of the flats.     

Interactions of Gliocladium virens with Rhizoctonia solani and Pythium ultimum in Non-sterile Potting Medium

Interactions of Gliocladium virens with Pythium ultimum and Rhizoctonia solani under simulated in vivo conditions were observed microscopically. Different types of propagules of the three fungi were paired on nitrocellulose membranes and incubated at 25°C in non-sterile potting medium in Petri dishes for 1-5 days. Alginate-wheat bran prill were used as carriers for G. virens. Prill inoculated with G. virens and pre-incubated in potting medium for 3-5 days before placement on membranes did not inhibit the germination of Pythium sporangia, but subsequent Pythium growth was markedly stunted and distorted, with some hyphal collapse and cytoplasmic leakage. G. virens had no visible effect on older Pythium mycelium. Two to 5 days' growth of G. virens caused cytoplasmic leakage of Rhizoctonia mycelium, prevented secondary branching of hyphae and occasionally coiled around Rhizoctonia hyphae. Prill that were newly colonized by G. virens, but not prill pre-incubated for 3 or 5 days, stimulated the growth of Pythium mycelium and sporangia, Rhizoctonia mycelium and unprimed monilioid cells, probably by supplying nutrients. The timing of the interactions and their specificity for the different pathogen propagules were consistent with the production of gliotoxin by G. virens. This view was supported by in vitro experiments, in which pathogen propagules were incubated in a range of concentrations of gliotoxin in potato dextrose broth. Pythium sporangia and mycelium were inhibited by 1 or 2 μmg ml^-1, but Rhizoctonia monilioid cells and mycelium required 3-5 μmg ml^-1 for inhibition. At the lowest effective concentrations the inhibition was sometimes reversible, but propagules were killed at high concentrations of gliotoxin.     

Survival, root colonisation and biocontrol capacities of Pseudomonas fluorescens F113 LacZY in dry alginate microbeads

Cells of Pseudomonas fluorescens F113 LacZY were encapsulated in alginate and their survival and ability to colonise sugar beet were evaluated. To assess survival, the formulation, composed of dry alginate microbeads of 300- to 700-μm diameter, was stored 1 year at 28±2 and 4±2°C and then tested against pathogenic fungi Pythium ultimum and Rhizoctonia solani in in vitro inhibition experiments. The same material was also used as inoculant for protection of sugar beet against Py. ultimum in microcosm experiments. The results obtained indicated that, although drying alginate beads resulted in a significant reduction of bacterial viability, the use of microbeads enabled a satisfactory level of root colonisation and protection, at least under microcosm conditions. The capability of the encapsulated cells to produce the antifungal metabolite 2,4-diacetylphloroglucinol (Phl) was not significantly affected by 12 months storage. Journal of Industrial Microbiology & Biotechnology (2001) 27, 337–342. Received 07 September 2000/ Accepted in revised form 08 May 2001