Spring invasion of Heterodera schachtii in sugarbeet; a simulation study     

W. Van Der Werf  R. Rabbinge  W. Heijbroek 《European journal of plant pathology / European Foundation for Plant Pathology》1986,92(1):33-42

A simulation model was developed for the spring invasion of the beet cyst nematode,Heterodera schachtii Schmidt, into sugarbeet roots, according to the state variable approach. This model describes the processes of egghatch, emergence of second stage larvae from cysts, migration to roots and penetration into roots quantitatively, using published data.In 1983 a field experiment was conducted to test this model.H. schachtii cysts were introduced at depths 6–29 cm in PVC-cylinders, buried in the soil. The rooting depth of sugarbeet seedlings, growing in these cylinders, was limited to 5 cm by 50 m mesh nylon gauze. Every 10 days the second stage larvae, which had penetrated into the roots of these seedlings were counted. After 50 days, about 40% of the eggs had hatched. More than 20% of the emerged larvae penetrated if the cysts had been buried undeeply, and only 4% if the cysts had been buried at 29 cm depth.The model predicted the course of penetration into the root during the first 40 days with reasonable accuracy (r²=0.79), but in the 5th period of 10 days the model made an overestimation of more than 100%. Egghatch after 50 days was correctly simulated. The differences in penetration into the root between the model and the experiment might result from an oversimplified simulation of the penetration success or the neglection of mortality of second stage larvae. Detailed experiments should be done to provide better parameters for these factors.Samenvatting Volgens de toestandsvariabele-benadering werd een simulatiemodel ontwikkeld van de voorjaarspenetratie van het bietecystenaaltje. Het model beschrijft aan de hand van literatuurgegevens het uikomen van de eieren, het verlaten van de cyst door de larven, de migratie naar en de penetratie in de wortel.In 1983 werd een veldproef uitgevoerd om het model te toetsen. Cysten vanH. schachtii werden op 5 dieptes tussen 6 en 29 cm ingegraven in PVC-cylinders, welke waren verzonken in de bodem. De bewortelingsdiepte van de suikerbiete-zaailingen die hierin groeiden werd beperkt tot 5 cm door nylon gaas van 50 m maaswijdte. Elke 10 dagen werden de larven geteld die in de wortels van deze plantjes waren gepenetreerd. Na 50 dagen was 40% van de eieren uitgekomen. Meer dan 20% van de gelokte larven penetreerden als de cysten ondiep waren ingegraven, en slechts 4% als de cysten op 29 cm diepte waren ingegraven.Gedurende de eerste 40 dagen werd het verloop van de penetratie in de wortel met redelijke nauwkeurigheid door het model voorspeld (r²=0.79). In de 5e periode van 10 dagen maakte het model echter een overschatting van meer dan 100%. Het uitkomen van de eieren werd correct gesimuleerd. De verschillen in penetratie tussen het model en de proef zouden het gevolg kunnen zijn van een oververeenvoudigde simulatie van het penetratiesucces of van het verwaarlozen van de mortaliteit van de migrerende larven. Betere gegevens hierover zullen moeten komen uit detailproeven.  相似文献   

Heat resistance,biology and prevention of Diehliomyces microsporus in crops of Agaricus species     

Annemarie Van Zaayen  Bernarda Van Der Pol-Luiten 《European journal of plant pathology / European Foundation for Plant Pathology》1977,83(6):221-240

Soon after its introduction the mushroom speciesAgaricus bitorquis, which is immune to virus disease and prefers a warm climate, was threatened by the competitorDiehliomyces microsporus, false truffle. This fungus also likes warmth, and used to occur in crops ofA. bisporus.Mycelium and ascocarps were grown on several nutrient media. Optimum temperatures for mycelial growth were 26°C and 32°C, with a slight depression at 30°C. In trials in isolated growingrooms strain Somycel 2.017 ofA. bitorquis was generally used since it appeared to be highly sensitive to the competition of false truffle. Inoculation with mycelium, ascocarps or ascospores ofD. microsporus nearly always resulted in the presence of the competitor and in decreased mushroom yields. Even ten spores per m² causedD. microsporus. The time of inoculation was most important: irrespective of the kind of inoculum, inoculation only resulted in both false truffle and yeild loss, if applied from spawning until a few days after casing. Inoculation at a later date could result in false truffle, but yield was not decreased.As germination in vitro of ascospores failed, even after addition of various triggers, ascospore suspensions were treated at various temperatures for several periods. Then mushroom growing trays spawned with Somycel 2.017 were inoculated with the treated suspensions giving 7–11×10⁷ spores/m². The ascospores could not withstand 85°C for 0.5 h, 80°C for 1 h and 70°C for 3 h. Spontaneous incidence of false truffle, however, could not always be prevented and interfered with the results of these trials. It is possible that the thermal death-point of the ascospores is below 85°C. Fruiting bodies and ascospores did not survive peak-heating at the beginning and cooking out (compost temperature 12 h at 70°C) at the end of a crop. After cooking out, however,D. microsporus could still be present in the wood of trays and contaminate a following crop if no wood preservative was applied.Yield of Somycel 2.017 was reduced by the competition ofD. microsporus much more than yeilds of other strains ofA. bitorquis. The least sensitive were the highly productive strains Horst K26 and Horst K32.The effects of fungicides onD. microsporus in vitro and in growing trials did not correspond. The fungicides tested so far could not prevent or controlD. microsporus. Growing of less sensitive strains ofA. bitorquis together with sanitary measures early in the crop and at the end of the crop, however, can prevent the competitor. failure to turn up of false truffle. To understand the discrepancy between the in vitro effects of several fungicides and their effect in inoculated mushroom trays, the rate of adsorption of benomyl in the substrate and probably the interrelationships between antagonists andD. microsporus require further research. Other strains ofA. bitorquis than Somycel 2.017 appeared to be less sensitive to the competition. Among these, highly productive strains Horst K26 and Horst K32 will not be hindered byD. microsporus if the following precautions are exercised: cooking out at the end of a crop (compost temperature 70°C for 12 hours), followed by treatment of the wood with SPCP; protection by hygiene early in the crop, i.e. covering of the compost by a thin plastic sheet during mycelial growth followed by a quick execution of casing.Samenvatting De teelt van de warmteminnende champignonsoortAgaricus bitorquis, die immuun is voor virusziekte, werd al spoedig na introductie bedreigd door de eveneens warmteminnende concurrentDiehliomyces microsporus, valse truffel. Deze schimmel kwam vroeger voor in teelten vanA. bisporus; de sporen zouden een temperatuur van 82°C gedurende 5 uur kunnen overleven (Lambert, 1932). Tabel 1 geeft de myceliumgroei op verschillende voedingsbodems en de vorming van vruchtlichamen (Fig. 1A, B) weer. De optimale temperaturen voor myceliumgroei waren 26°C en 32°C, met een licht depressie bij 30°C (Fig. 2). Proeven in geïsoleerde teeltruimten werden voornamelijk uitgevoerd met Somycel 2.017, een ras vanA. bitorquis. Inoculatie met mycelium, vruchtlichamen en/of ascosporen vanD. microsporus, al of niet in reincultuur gekweekt, leidde vrijwel steeds tot de aanwezigheid van de concurrent in de geïnoculeerde teeltkisten (Fig. 1C, D), waarbij vruchtlichamen met ascosporen (Fig. 1E) gevormd werden en tot een reductie van het aantal champignons. Tien sporen per m² waren al voldoende omD. microsporus te doen aanslaan (Fig. 3). Het tijdstip van inoculatie bleek van groot belang te zijn: onafhankelijk van de aard van het inoculum leverde dit slechts zowel valse truffel als oogstreductie op, indien het werd aangebracht in de periode vanaf enten tot enkele dagen na het afdekken (Tabel 2 en Fig. 4). Inoculatie op latere tijdstippen kon wel tot valse truffel leiden, maar niet tot oogstreductie.Aangezien de kieming van ascosporen in vitro slechte resultaten opleverede, ook na toevoeging van diverse stimulantia, werden ascosporensuspensies in vitro gedurende verschillende tijden bij verschillende temperaturen behandeld; vervolgens werden teeltkisten met de behandelde suspensies geïnoculeerd (7 tot 11×10⁷ sporen/m²). De kisten waren tevoren geënt met Somycel 2.017. Een aantal proeven wees uit, dat de ascosporen 1/2 uur 85°C, 1 uur 80°C en 3 uur 70°C, niet overleefden (Tabel 3). Het spontaan optreden van valse truffel kon echter niet altijd worden voorkomen en beïnvloedde de uitkomsten van deze proeven. Daarom is het mogelijk, dat de sporen al bij een lagere temperatuur worden gedood Vruchtlichamen en ascosporen werden gedood door het uitzweten aan het begin van een teelt en door het doodstomen aan het einde van een teelt (composttemperatuur 12 uur 70°C) maar de schimmel bleek in het laatste geval wel over te kunnen blijven in het hout van teeltkisten als er vervolgens geen houtontsmettingsmiddel werd toegepast.Somycel 2.017 leed verhoudingsgewijs meer schade door concurrentie vanD. microsporus dan enkele andere rassen (Tabel 4 en. 5). Inoculatie met ascosporen bleek bij de minst gevoelige en meest produktieve rassen Horst K26 en Horst K32 slechts te gelukken in extreem droge compost; bij Somycel 2.017 daarentegen zowel in compost met een laag als met een hoog vochtgehalte. Inoculatie met mycelium veroorzaakte meer valse truffel en meer schade naarmate de compost natter was (Tabel 5).De werking van een aantal fungiciden in vitro (Tabel 6) en in teeltkisten (Tabel 7) stemde niet overeen. Aangezien de tot nu toe getoetste fungicidenD. microsporus niet kunnen voorkomen of bestrijden, moet preventie van deze concurrent worden gezocht in het telen van weinig gevoelige rassen vanA. bitorquis in combinatie met hygiënische maatregelen vroeg in en aan het eind van de teelt.  相似文献   

IgE-bearing cells in bronchoalveolar lavage fluid and allergen-specific IgE levels in sera from RAO-affected horses     

Künzle F  Gerber V  Van Der Haegen A  Wampfler B  Straub R  Marti E 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2007,54(1):40-47

Recurrent airway obstruction (RAO) is a common condition in stabled horses characterized by small airway inflammation, airway neutrophilia and obstruction following exposure of susceptible horses to mouldy hay and straw and is thus regarded as a hypersensitivity reaction to mould spores. However, the role of immunoglobulin E antibodies (IgE) in the pathogenesis of RAO is unclear. We hypothesized that the number of cells with receptor-bound IgE in bronchoalveolar lavage fluid (BALF) and IgE levels in serum would be higher in RAO-affected than in healthy horses living in the same environment. Therefore, IgE-positive (+) cells were identified by immunocytochemistry on cytospins from BALF and counted. IgE levels against the mould extracts Aspergillus fumigatus (Asp. f.) and Alternaria alternata (Alt. a.) and the recombinant mould allergen Aspergillus fumigatus 8 (rAsp f 8) were measured by enzyme-linked immunosorbent assay (ELISA) in the sera of seven RAO-affected and 22 clinically healthy mature horses housed in the same conventional stable environment. After correcting for the number of neutrophils, there were no significant differences in IgE+ cells on cytospins from BALF between both groups of horses (5% versus 7%, P > 0.1). Serum IgE levels against the mould extracts were significantly higher in RAO-affected than in clinically healthy horses [median = 119 versus 66 relative ELISA units (REU), P < 0.05]. Furthermore, significantly more RAO-affected than healthy horses had detectable serum IgE against the recombinant allergen rAsp f 8 (4/7 and 3/22, respectively, P < 0.05). Age had no significant effect on BALF cell ratios or on specific serum IgE levels. These results show that high IgE levels against mould antigens are associated with RAO under controlled environmental conditions but ranges of mould-specific serum IgE levels overlapped too much between diseased and clinically healthy animals to be of any diagnostic value. Further studies are needed to assess whether IgE-mediated reactions contribute to the pathogenesis of RAO.  相似文献   

Water balance estimates of evaporation from ponded rice fields in a semi-arid region   总被引：1，自引：0，他引：1  

T. Talsma  A. Van Der Lelij 《Agricultural Water Management》1976,1(1):89-97

Evaporation from ponded rice grown on fine-textured soils was calculated using a simple water balance equation, and compared with pan evaporation measured at a regional meteorological station. Crop/pan (E_r/E_p) evaporation ratios showed seasonal trends, with values generally exceeding unity during the mid- to late-season ponding period. Mid-summer ratios of E_r/E_p for two experimental fields were not significantly different from those reported in a previous study using a different experimental technique, but were higher on a third. On the average, evaporation over the whole ponding period equalled that from a Class A pan. The assumption that the infiltration or seepage term of the water balance may be neglected for fine-textured soils would seriously overestimate E_r on one of the three experimental sites.  相似文献   

High vegetative compatibility diversity of Cryphonectria parasitica infecting sweet chestnut (Castanea sativa) in Britain indicates multiple pathogen introductions     

A. Pérez-Sierra  P. Romón-Ochoa  C. Gorton  A. Lewis  H. Rees  S. Van Der Linde  J. Webber 《Plant pathology》2019,68(4):727-737

Chestnut blight, caused by Cryphonectria parasitica, was identified in Devon, UK, in December 2016. Intensive surveys detected the disease at further sites in Devon (seven), Berkshire (one), Dorset (one), Derbyshire (four) and a cluster of eight sites in southeast London. Over 570 survey samples were tested, and 227 were positive for C. parasitica by isolation and real-time PCR. A total of 227 isolates were tested for mating type, and 197 screened for vegetative compatibility group (VCG) and compared with VCGs known from mainland Europe. The same isolates were also screened for the presence of Cryphonectria hypovirus 1 (CHV-1). Eleven VCGs were identified within the UK population. Five corresponded to already known European VCGs but six were unique. The European VCGs mainly came from the Devon, Dorset, Berkshire and Derbyshire disease outbreaks, whilst unique VCGs were almost exclusively from the southeast London cluster. Both mating types were detected, but only one mating type was present at each site, with the exception of a single Devon site. Perithecia of C. parasitica were never observed at any site. CHV-1 was found in seven isolates from three different locations and was always subtype-I, which has limited hypovirulence. Therefore, although CHV-1 is associated with C. parasitica at some outbreaks, it probably has limited impact on virulence. The diversity of VCGs and their distribution at outbreak sites, together with findings of CHV-1, suggests C. parasitica has been introduced to the UK multiple times over at least two decades through international plant trade.  相似文献   

Polyunsaturated fatty acids modulate the properties of the sex steroid binding protein in goldfish     

G. Van Der Kraak  S. Biddiscombe 《Fish physiology and biochemistry》1999,20(2):115-123

This study examines the effects of nonesterified fatty acids on the properties of the sex steroid binding protein (SSBP) in the plasma of goldfish (Carassius auratus). Scatchard analysis revealed a single class of high affinity (Kd 1.89±0.20 nM), low capacity (Bmax 302±17 nM) binding sites for [3H]17-estradiol in female goldfish plasma. The SSBP bound 17-estradiol and testosterone with similar affinity but had much lower affinity for estriol, 17,20-dihydroxy-4-pregnen-3-one and cholesterol. Nonesterified fatty acids inhibit the binding of [3H]17-estradiol to the SSBP as a function of dose, degree of unsaturation and fatty acid chain length. Polyunsaturated fatty acids (PUFAs) such as arachidonic acid (C20:4), eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6) strongly inhibit the binding of [3H]17-estradiol to the SSBP. By comparison, saturated fatty acids such as heptadecanoic acid (C17:0), palmitic acid (C16:0) and stearic acid (C18:0) were without effect. Scatchard analysis and Lineweaver-Burk plots showed that PUFAs act through a competitive mechanism whereby they reduce the affinity but have no effect on the binding capacity of the SSBP. Collectively, these studies suggest that in addition to their roles as metabolic energy sources and as precursors to eicosanoids, PUFAs can be potent modulators of steroid hormone interactions with the SSBP in goldfish plasma.  相似文献   

Makregeln gegen den Maifäfer     

Der Rönigliche Dberförfter Solf 《European Journal of Forest Research》1865,9(1):394-396

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Beilage III     

Direftorium des landm. Rreisbereins Cruftus  Direftorium des landm. Rreisbereins Schmarzmöller  Direftorium des landm. Rreisbereins Cruftus  Der landm. Rreisberein zu Dresben S. Siegel 《European Journal of Forest Research》1859,3(1):45-48

Ohne Zusammenfassung  相似文献   

Identification of barley yellow mosaic virus by immuno-electron microscopy in barley but not in Polymyxa graminis or Lagena radicicola     

Willem G. Langenberg  Derk Van Der Wal 《European journal of plant pathology / European Foundation for Plant Pathology》1986,92(3):133-136

Samenvatting Gerstegeelmozaïekvirus (BaYMV) werd in een perceel wintergerst (cv. Igri) gevonden by Wittem in Limburg, Nederland. Het virus werd met immuno-elektronen-microscopie geïdentificeerd in bladweefsel als BaYMV. In de wortels van geïnfecteerde planten werden alle vormen die van de schimmel-vector (Polymyxa graminis Led.) bekend zijn aangetroffen nl. cystosori, plasmodia en zoosporangia. Inwendig kon geen BaYMV worden aangetoond of waargenomen inPolymyxa ofLagena spp.Cooperative investigation of the ARS, USDA, the Nebraska Agricultural Experiment Station, and the Plant Protection Service, Wageningen. Research conducted under Project 21-12. Published as Paper No. 7787, Journal Series, Nebraska Agricultural experiment Station. Mention of a trademark or proprietary product does not constitute a guarantee or warranty by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.  相似文献   

Accessions of Australian Nicotiana species suitable as indicator hosts in the diagnosis of plant virus diseases   总被引：2，自引：0，他引：2  

P. Van Dijk  F. A. Van Der Meer  P. G. M. Piron 《European journal of plant pathology / European Foundation for Plant Pathology》1987,93(2):73-85

When screening the genusNicotiana for sensitive and differential hosts for a group of mechanically transmissible plant viruses with narrow host ranges, development of systemic symptoms was alsmost exclusively observed in species of three closely related sections of the subgenusPetunioides. These species wereN. miersii (sectionAcuminatae),N. bigelovii andN. clevelandii (Bigelovianae) andN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata andN. rotundifolia (Suaveolentes). Except forN. benthamiana andN. clevelandii, which are already known for their large virus ranges, they are new experimental hosts that appeared very useful for detection of viruses and for differentiation of viruses that closely resemble each other in host range. Accessions of the same species often varied largely in local and systemic viral response. EspeciallyN. benthamiana-9,N. miersii-33 andN. occidentalis-37B (code numbers given by Tobacco Research Laboratory, Oxford, N.C., USA) are recommended for routine inoculation tests. The sensitiveSuaveolentes species mentioned are native to the arid parts of Australia. Collections of these species deserve attention in studies on virus diseases of unknown etiology where experimental hosts are lacking.Samenvatting In het genusNicotiana werden vatbare, gevoelige en differentiële toetsplanten opgespoord door toetsing van vooral de collectie van het Tobacco Research Laboratory (Oxford, N.C., VS) met een aantal virussen waarvoor weinig of geen bruikbare toetsplanten bekend waren. Systemische reacties werden bijna uitsluitend in soorten van drie nauw verwante secties van het subgenusPetunioides waargenomen. Deze soorten warenN. miersii (sectieAcuminatae),N. bigelovii enN. clevelandii (Bigelovianae) enN. benthamiana, N. cavicola, N. ingulba, N. occidentalis, N. rosulata enN. rotundifolia (Suaveolentes). Behalve voor virusvermeerdering bleken deze soorten ook zeer geschikt te zijn voor differentiatie van virussen of virusstammen met een bijna gelijke waardplantenreeks.Collectienummers van één en dezelfde soort konden sterk in lokale en systemische reactie verschillen. VooralN. benthamiana-9,N. miersii-33 enN. occidentalis-37B kunnen voor routine-inoculaties worden aanbevolen. Met uitzondering vanN. benthamiana enN. clevelandii zijn de genoemde soorten of genotypen nieuwe experimentele waardplanten voor de virologie. De soorten die van de sectieSuaveolentes worden genoemd, zijn inheems in de woestijnachtige gebieden van Australië. Verzamelingen daarvan verdienen nadere aandacht bij de diagnostiek van virusziekten waarvoor nog geen experimentele waarplanten voorhanden zijn.  相似文献