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1.
Using a leaf disc method, 19 isolates of the poplar rust, Melampsora larici-populina , and one isolate of M.populnea from England were inoculated on to 25 poplar clones belonging to Populus nigra and P.trichocarpa, and hybrids between P. deltoides and P. nigra, P. deltoidesand P. trichocarpa, P.tacamahaca and P.trichocarpa, and P. alba and P. tremula. Disease was scored based on the pustule area and inoculum density. In terms of whether sporulating uredinia formed, the 19 isolates showed seven different patterns to the tested poplar clones. The majority of the rust isolates infected P. nigra P3090 and Vereecken, P.nigra×P. deltoides Casale and Tasman, P. tacamahaca×trichocarpa 36 and Balsam Spire, and P.trichocarpa Blom. Populus trichocarpa×P. deltoides 69039/4 was infected by only three isolates collected from southern England. No visible symptoms appeared on P. alba ×P. tremulaTower and P.trichcarpa×P. deltoides×P. deltoides76028/5 in inoculations with M. larici-populina isolates. Populus alba×P.tremula Tower was infected only by M. populnea. When M. larici-populina isolates were tested using AFLP, no differences were found either between isolates from different geographical regions or between those having narrow spectrum of virulence and those showing wide spectrum of virulence on the tested clones. The results suggest that the UK rust populations possess virulences which were found in races E1, E2, E3 and E4 in continental Europe and that rust having virulence patterns similar to race E4 has occurred in UK poplar plantations since 1996.  相似文献   

2.
In July 1998, a sudden wilt of Star Ruby grapefruit (Citrus paradisi Macf.) occurred in Israel in a region with a warm Mediterranean climate. The wilt of the middle and upper canopy of main limbs was accompanied by gum oozing from the affected branches. The bark of these branches attained a dark colour and the epidermis sloughed off easily revealing a mass of black powder, resulting from copious sporulation of dark conidia. Both the bark and the xylem were intensively colonized with mycelium. The fungus was identified as Scytalidium lignicola Pesante, based on the characteristic mixture of some colourless and dark conidia, produced in branched chains by conversion of the vegetative hyphae. Artificial inoculations induced typical disease symptoms and the fungus was reisolated, thus confirming Koch's postulates. Similar symptoms appeared in Star Ruby interim segments which had been cut and top grafted with various citrus cultivars. This is the first detailed report of pathogenicity of S. lignicola to citrus trees. It is postulated that the disease developed after predisposition of Star Ruby grapefruit trees by comprehensive pruning followed by extremely hot conditions.  相似文献   

3.
Cell suspension cultures were set up from two tomato cultivars, one resistant, (Rio grande) and one susceptible (63.5) toFusarium oxysporum f. sp.lycopersici. Growth rates of the two cell cultures were comparable. Toxicity of fusaric acid, expressed as the fresh weight loss, was analyzed: It was significant in both cases after 10 h, but toxicity was twice as high for 63.5 suspension cells. In the same way, electrolyte leakage caused by fusaric acid was three times more important for 63.5 suspension cells. Moreover, fusaric acid treatment resulted in an acidification of the extracellular medium for 63.5 suspension cells (0.4 pH unit), whereas an alkalization was observed for Rio grande suspension cells (0.2 pH unit). Preliminary experiments suggest that fusaric acid was partially metabolized by Rio grande suspension cells, however, no detoxified forms of fusaric acid were detected either in cells or in culture filtrates. For these two tomato cultivars, the differences in sensitivity to fusaric acid of cultivated cells correspond to the differences in plant susceptibility toFusarium oxysporum f. sp.lycopersici.Abbreviations BAP 6-benzylaminopurine - conductivity - 2,4-D 2,4-dichlorophenoxyacetic acid - EtOAc ethyl acetate - FA fusaric acid - resistivity  相似文献   

4.
In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.  相似文献   

5.
In her fire blight prediction systems, E. Billing (1978, in: P.R. Scott & A. Bainbridge (Eds), Plant disease epidemiology, p. 159–166) has used the parameter potential doublings per day (PD) of the fire blight causing bacterium,Erwinia amylovora. Reconsideration of her calculations of PD revealed, however, that the PD values in Billing's table were underestimated. This leads to overestimation of the duration of incubation periods. A corrected PD table is presented. Sensitivity analyses indicated that day-of-the-year and latitude have little effect on the values in the PD table.Samenvatting Billing maakte in haar systemen waarin de ontwikkeling van bacterievuur wordt voor-speld, gebruik van de parameter potentiële verdubbelingen per dag (=PD) van de bacterievuur veroorzakende bacterieErwinia amylovora. Uit herberekeningen blijkt echter, dat de PD-waarden in Billings tabel onderschat worden. PD-onderschattingen leiden in haar systemen tot overschattingen van de duur van incubatieperioden. Een gecorrigeerde PD-tabel werd samengesteld. Uit gevoeligheidsanalyses bleek dat de dag van het jaar en de breedtegraad een gering effect hebben op de waarden in de PD-tabel.  相似文献   

6.
A wettable powder of prochloraz manganese complex 50% a.i. satisfactorily controlled the four major pathogens ofAgaricus bisporus andA. bitorquis: Verticillium fungicola var.fungicola, the cause of dry bubble,Mycogone perniciosa, the cause of wet bubble,Cladobotryum dendroides, the cause of cobweb disease andV. fungicola var.aleophilum, the cause of brown spots. The results were obtained in trials in trays with theAgaricus species, which were inoculated with the pathogens.The product was not toxic to bothAgaricus species in the effective dosages and the taste of the mushrooms was not affected by prochloraz formulations. Application of 1.5 g a.i. m–2 nine days after casing is preferred, also in view of the residue levels. A 45% emulsifiable concentrate of the product without manganese was slightly toxic to mushrooms in a lower dosage than the wettable poweder.Samenvatting Een spuitpoeder met 50% prochloraz als werkzaam bestanddeel (een prochlorazmangaan-complex) gaf in de teelt van champignons (A. bisporus enA. bitorquis) een uitstekende bestrijding van de vier belangrijkste pathogene schimmels:Verticillium fungicola var.fungicola (de veroorzaker van droge mollen),Mycogone perniciosa (de veroorzaker van natte mollen),Cladobotryum dendroides (spinnewebschimmel) enV. fungicola var.aleophilum (de veroorzaker van bruine vlekken). Deze resultaten werden verkregen in proeven met kisten waarin deAgaricus-soorten, die geïnoculeerd werden met genoemde pathogenen, werden geteeld.Het produkt was voor geen van beideAgaricus-soorten toxisch als het werd toegepast in de werkzame doseringen, en de champignonsmaak werd door het middel niet nadelig beïnvloed. De voorkeur wordt gegeven aan toepassing van 1,5 g werkzame stof per m2, 9 dagen na het afdekken, mede op grond van de gevonden residuwaarden. Een 45% vloeibare formulering zonder mangaan was, in lagere doseringen dan het spuitpoeder, in lichte mate toxisch voor champignons.  相似文献   

7.
The prophylactic effect in elm of one treatment with aPseudomonas isolate was monitored in two types of field trials. In one type only natural Dutch elm disease infections were monitored and hence large numbers of trees were necessary due to the low incidence of natural occurring infections. In the other type trees were artificially infected.The large-scale field trials in which only natural infections were monitored, were based on expected annual losses due to Dutch elm disease of approximately 2%. As a result of the Dutch sanitation program, which was based on the prompt removal of every weakened or diseased elm, the actual losses were generally threefold lower. Dutch elm disease incidence was 22–45% lower in the trees treated with aPseudomonas isolate in the year of treatment and the year after. The results of the biocontrol treatment were negatively influenced because on several locations trees were felled that showed initial signs of Dutch elm disease, which probably would have disappeared during the season.The advantage of artificial infections withOphiostoma ulmi was a reproducable development of symptoms and the possibility to maintain diseased trees, at least till the first signs of elm bark beetle breeding. For Commelin elms an increase in symptoms was observed with increasingO. ulmi dose till 3000 conidia per tree; the standard 500 000 conidia used for most experiments was well above this critical value. No decrease in effectiveness of the bacterial pre-treatment was observed with increasingO. ulmi inoculum. Different bacterial treatments suggested that injections at a smaller interval (i.e. more injections per tree) may result in a better prophylactic effect, but the significance of the correlation remained doubtful. A comparison of several elm species and clones showed the importance of the host tree. Prophylaxis as a result of one bacterial treatment was shown repeatedly in Commelin elms; the numbers of trees showing symptoms by the end of the second year were 10 to 85% lower in the bacteria-treated groups in comparison with the controls. Also in one experiment with Belgica elms prophylaxis was observed, resulting in a 84% decrease in the number of trees showing symptoms by the end of the second year after the prophylactic treatment followed by inoculation withO. ulmi. In Vegeta symptom development was only less severe and in field elms (Ulmus carpinifolia) some prophylactic effect was observed in one experiment, but no effect in two others.Samenvatting De mogelijke bescherming tegen de iepeziekte, verkregen door injectie van de boom met bacteriën van het geslachtPseudomonas, werd gemeten in twee soorten experimenten. In het ene soort werden natuurlijke infecties gemeten, waardoor grote proefgroepen nodig waren. In het andere soort werden de iepen kunstmatig geinfecteerd.De grootschalige veldexperimenten waarbij natuurlijke iepeziekte-infecties werden gemeten, waren gebaseerd op een verwachte jaarlijkse uitval van 2%. Als gevolg van de landelijke bestrijdingscampagne bleken de verliezen slechts ongeveer een derde hiervan te zijn. Er kwam minder iepeziekte voor in de metPseudomonas geïnjecteerde bomen in het jaar van injectie en in het jaar daarna. Een storende invloed op de resultaten had het effect dat ook met bacteriën geïnjecteerde bomen soms beginnende symptomen vertonen na infectie metOphiostoma ulmi, symptomen die in de loop van het seizoen soms weer verdwijnen. Als gevolg van de bestrijdingscampagne werden zulke bomen toch geveld.Het voordeel van kunstmatige infecties metO. ulmi was een voorspelbaar verloop van de symptoomontwikkeling en de mogelijkheid om zieke bomen te laten staan tot er iepespintkevers in kwamen. In Commelin iepen bleken de symptomen toe te nemen met een tot 3000 conidiën per boom toenemende dosisO. ulmi. De gebruikelijke 500000 conidiën die in de meeste experimenten werden gebruikt lagen ver boven deze kritische waarde. Er werd geen effect van een toenemende dosisO. ulmi op de effectiviteit van een bacteriebehandeling waargenomen.Uit variaties in de diverse bacteriebehandelingen kwam naar voren dat injecties met een kleinere tussenruimte (dus meer injecties per boom) mogelijk het effect verbeterden, maar de significantie van deze correlatie bleef twijfelachtig.Vergelijken van diverse iepen toont dat soort en kloon type een belangrijke rol speelt bij deze bestrijdingsmethode. Bescherming tegen de iepeziekte als gevolg van een bacteriebehandeling werd diverse malen aangetoond in Commelin iepen; het aantal bomen met iepeziekte-symptomen was aan het eind van het tweede seizoen in de met bacteriën behandelde groepen 10 tot 85 % lager dan in de controlegroepen. Ook in een experiment met Belgica iepen werd een goede bescherming gemeten. In Vegeta werd slechts een verminderde symptoomontwikkeling gemeten en in veldiepen (U. carpinifolia) werd enige bescherming gevonden in één experiment, maar geen effect in twee andere.  相似文献   

8.
Artificial inoculation experiments were carried out at 25°C to determine the effects of inoculum density of Fusarium oxysporum f.sp. ciceris races 0 (Foc-0) and 5 (Foc-5) and susceptibility of chickpea cultivars P-2245 and PV-61 on development of Fusarium wilt. Foc-5 proved much more virulent than Foc-0. Increasing the inoculum density of F. oxysporum f.sp. ciceris caused an exponential reduction in disease incubation period and a monomolecular increase of disease incidence and the area under the disease intensity progress curve. The extent of these effects was highest in the most conducive P-2245/Foc-5 combination and decreased in the less susceptible PV-61 and for the less virulent Foc-0, in that order. For P-2245/Foc-5, the highest disease intensity was attained with 6 chlamydospores g–1 of soil, the lowest inoculum density in the study. One thousand chlamydospores g–1 of soil of the same race were needed to attain a comparable disease intensity in PV-61. Twenty thousand chlamydospores g–1 of soil of Foc-0 were required for maximum disease intensity in P-2245.The disease intensity curves were adequately described by the Gompertz model. Using this model, a response surface for disease intensity was developed, in which the model parameters are expressed as a function of both time from inoculation and inoculum density. This response surface confirmed that the final amount of disease intensity increases in a monomolecular relationship with increasing inoculum density and showed that the relative rate of disease progress increases exponentially with increasing inoculum density of the pathogen.  相似文献   

9.
The antifungal glycoalkaloid -tomatine accumulates in tomato plants and may protect plants from fungal infection. Fusarium oxysporum f. sp. lycopersici, the causal agent of vascular wilt of tomato, produces a tomatinase (FoToml) that degrades -tomatine to the nontoxic compounds tetrasaccharide lycotetraose and tomatidine. Induction of tomatinases and the distribution of FoToml homologs were examined among 30 strains belonging to 16 formae speciales of F. oxysporum. Tomatinase activity was found in 27 strains belonging to 15 formae speciales, but FoToml homologs (>98% sequence identity) were detected in only six strains belonging to four formae speciales. To identify tomatinases other than FoToml, -tomatine-inducible proteins of another tomato pathogen F. oxysporum f. sp. radicis-lycopersici were analyzed by two-dimensional gel electrophoresis. A protein with a molecular mass of 64kDa accumulated in the -tomatine-induced culture filtrates, and the protein had tomatinase activity, degrading -tomatine to lycotetraose and tomatidine.  相似文献   

10.
Culm base samples were collected in August 1984, from winter wheat fields in Groningen, Flevoland and near Wageningen in Gelderland. In contrast to fields in the latter two areas, fields in Groningen were characterized by intensive wheat cultivation and yearly applications of benzimidazole fungicides for eyespot control. Seventy-seven isolates ofPseudocercosporella herpotrichoides were recovered. Forty-three percent of recovered isolates were carbendazim-resistant, all of which originated from fields in Groningen. Resistant isolates were detected among both rye- and wheat-types of the pathogen. Rye-type isolates were identified asP. herpotrichoides var.acuformis and those of the wheat-type asP. herpotrichoides var.herpotrichoides.Samenvatting Monsters van de halmbasis van tarwestro werden in augustus 1984 verzameld van percelen met wintertarwe in Groningen, Flevoland en bij Wageningen in Gelderland. In tegenstelling tot de percelen in de twee laatstgenoemde gebieden, waren de percelen in Groningen gekenmerkt door intensieve tarweteelt en door jaarlijkse bespuitingen met benzimidazool fungiciden tegen de oogvlekkenziekte. In totaal werden 77 isolaten vanPseudocercosporella herpotrichoides verkregen. Drieënveertig procent van de isolaten was resistant tegen carbendazim en alle resistente isolaten waren afkomstig van percelen in Groningen. Resistente isolaten werden zowel bij het rogge- als bij het tarwetype van het pathogeen aangetroffen. Isolaten van het roggetype werden geidentificeerd alsP. herpotrichoides var.acuformis en die van het tarwetype alsP. herpotrichoides var.herpotrichoides.  相似文献   

11.
BACKGROUND: Transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis Berliner (Bt) were first commercialised in 1996. The risk that pests have the potential to evolve resistance to Bt toxins is one of the most serious challenges to this technology. Gene stacking, pyramiding two Bt genes into one variety, is considered to be an effective insect resistance management (IRM) strategy. In this study, insect‐resistant rice expressing two Bt genes was developed by sexual crossing, and then characterised. RESULTS: Homozygous rice lines of two pyramided Bt genes were obtained in the F3 generation. Quantification of Bt toxin showed that protein concentrations of Cry1Ab, Cry1Ac and Cry2A in the two‐gene lines were comparable with their single‐gene parents, while the expression of cry1C gene decreased after gene stacking. Four two‐gene lines showed higher activity to striped stem borer (Chilo suppressalis Walker) than parental lines in the laboratory bioassay. All pyramided lines and their hybrids exhibited excellent efficacy against stemborers and leaffolders in field evaluation, while most pyramided lines had no significant differences from original variety in yield under spraying of insecticide. CONCLUSION: These results demonstrate that the two‐gene lines have commercial potential and could serve as a valuable IRM strategy. Copyright © 2011 Society of Chemical Industry  相似文献   

12.
Sterol biosynthesis inhibitors that inhibit the yeast-hyphae conversion inOphiostoma ulmi suppressed Dutch elm disease development in two elm clones. After curative treatment with fenpropimorph-sulphate of 27 Vegeta elms which had previously been inoculated withO. ulmi, 25 trees did not show disease symptoms by the end of the second season. All 41 control trees, inoculated withO. ulmi only, were clearly diseased. In an experiment with Commelin elms three fenpropimorph salts and thiabendazole were compared. Injection of the trees three weeks after inoculation withO. ulmi gave by the end of the second season no symptoms of Dutch elm disease in any of the trees injected with fenpropimorph-phosphate or thiabendazole, and in most trees injected with fenpropimorph-acetate or-sulphate. Similar treatments with the free base of fenpropimorph and fenpropidin-sulphate were less effective due to insufficient uptake of the fenpropimorph emulsion and phytotoxicity of fenpropidin-sulphate, respectively. Injection of fenpropimorph-sulphate or thiabendazole six weeks after inoculation withO. ulmi did not result in significant differences from the control group inoculated withO. ulmi only.Fenpropimorph-phosphate and-sulphate completely suppressed Dutch elm disease upon injection of only 7.5 or 10 g per tree (average tree diameter 28 cm). Residue analyses showed only a slow decrease in concentration of the fungicide over two growing seasons and an apparent transport into the new annual ring, other prerequisites for a possible future use for control of Dutch elm disease.Samenvatting De iepeziekte kan onderdrukt worden door sterolbiosyntheseremmers die de overgang vanOphiostoma ulmi van de gistvorm in de hyfevorm remmen. Aan het eind van het tweede seizoen na een curatieve behandeling van 27 Vegeta iepen met fenpropimorfsulfaat bleken 25 bomen geen symptomen van iepeziekte te vertonen. Alle controlebomen, die alleen metO. ulmi geïnoculeerd waren, waren duidelijk ziek. In een proef met Commelin iepen werden drie fenpropimorfzouten en thiabendazool vergeleken. De zouten werden drie weken na de inoculatie metO. ulmi geïnjecteerd. Aan het eind van het tweede seizoen vertoonden geen van de bomen die met fenpropimorffosfaat of thiabendazool geïnjecteerd waren en slechts enkele bomen die met fenpropimorfacetaat of-sulfaat geïnjecteerd waren iepeziektesymptomen. Behandelingen met fenpropimorf (vrije base) en fenpropidinsulfaat werkten minder goed door de slechte opname van de fenpropimorfemulsie en de fytotoxiciteit van fenpropidin. Injectie met fenpropimorfsulfaat of thiabendazool zes weken na inoculatie leidde niet tot significante verschillen met de controlegroep die alleen metO. ulmi geïnoculeerd was.Een dosis fenpropimorffosfaat of-sulfaat van 7.5 of 10 g per boom met een gemiddelde boomdiameter van 26 cm bleek de iepeziekte volledig te kunnen onderdrukken. Uit residue-onderzoek bleek dat de concentratie van het fungicide gedurende de twee groeiseizoenen slechts langzaam afnam en dat het middel naar de nieuwe jaarring werd getransporteerd, twee voorwaarden voor een toepassing op praktijkschaal van fenpropimorf voor de bestrijding van de iepeziekte.  相似文献   

13.
转cry1Ab基因粳稻对稻纵卷叶螟成虫产卵行为的影响   总被引：1，自引：1，他引：0  
为评价转cry1Ab基因粳稻(KMD1和KMD2)对稻纵卷叶螟Cnaphalocrocis medinalis(Guenée)成虫产卵行为的影响,采用"Y"型嗅觉仪和笼罩以及田间试验等方法对稻纵卷叶螟成虫对转基因水稻的趋性以及其产卵选择性进行了研究,并利用固相微萃取和GC-MS技术测定了这2种Bt水稻及其对照亲本秀水11挥发物的组成及其相对含量。结果表明,稻纵卷叶螟成虫在"Y"型嗅觉仪和小型笼罩内对Bt水稻和对照亲本的选择性差异不显著,而在大型笼罩和田间条件下均显著趋向于在非转基因水稻上产卵,其中大田中稻纵卷叶螟在KMD1、KMD2和对照中的百叶卵量分别为2.20±1.28、1.00±0.77和5.60±2.16粒。水稻挥发物的组成及其相对含量在Bt水稻及其对照亲本之间差异不显著。表明相对于Bt水稻,在田间条件下稻纵卷叶螟成虫趋向于在非转基因水稻产卵,而水稻挥发物可能不是引起这种行为趋性的直接原因。  相似文献   

14.
The coding sequences in RNA2 for the coat proteins (CP) of strawberry latent ringspot virus (SLRSV) were modified and amplified using polymerase chain amplification reactions (PCR) to facilitate their expression inAgrobacterium tumefaciens-transformedNicotiana tabacum Xanthi-nc. The coding sequences for the smaller capsid protein (S, 29kDa) and that for the theoretical precursor of L and S (P, 73kDa) had ATG initiation codon sequences added at the 5-proximal Ser/Gly (S/G) cleavage site in the unmodified sequence. The sequence coding for the larger of the two proteins of mature SLRSV capsids (L, 44kDa) had an ATG codon added at its 5 S/G site and a TAG stop codon sequence added at the 3-proximal S/G site. The P, L and S proteins were expressedin planta to a maximum concentration of 0.01 % of total extractable proteins but did not assemble into virus-like particles. When challenged by mechanical inoculation with virus particles or viral RNA, and compared with control plants, tobacco plants (primary transgenic clones or S1 and S2, kanamycin-resistant seedlings) expressing the virus capsid subunits separately, or their precursor, decreased the accumulation of SLRSV particles in inoculated leaves and fewer plants became invaded systemically. In experiments in which the roots of seedlings were exposed to SLRSV-carrying vector nematodes (Xiphinema diversicaudatum), SLRSV was detected in the roots of non-transformed control tobacco plants (6/20) and in transgenic tobacco expressing the L protein (7/40), but not in any of 25 tobacco plants expressing the S protein or in 35 expressing the P protein. This is the second example of CP-mediated resistance to virus inoculation by nematode vectors.  相似文献   

15.
In recent years in the Netherlands a second mushroom species,Agaricus bitorquis, which prefers higher temperatures thanA. bisporus and is less susceptible to certain diseases, is often commercially grown.Verticillium fungicola var.fungicola, the causal agent of dry bubble, is responsible for considerable damage in crops ofA. bisporus. InA. bitorquis, however, dry bubble has hardly been noticed, but brown spots due toV. fungicola var.aleophilum resulted in inferior mushroom quality. The latter variety also caused brown spots ina. bisporus, but to a minor degree. In variety Les Miz 60 ofA. bisporus, however, it also induced fruit-body deformation in a way different from dry bubble. Verticillium psalliotae, isolated fromA. bitorquis in England, induced more confluent brown spots inA. bitorquis. In the netherlands, where moreA. bitorquis is grown than in other countries,V. psalliotae has not yet been encountered in crops ofA. bitorquis. V. psalliotae, which has a high temperature optimum for mycelial growth, likeV. fungicola var.aleophilum andA. bitorquis, did not infectA. bisporus in our trials.Artificial infection ofA. bisporus orA. bitorquis could not be accomplished with the following related and/or fungicolous fungi:Verticillium lamellicola, V. fungicola var.flavidum, V. biguttatum, Nectriopsis tubariicola, Acremonium crotocinigenum andAphanocladium album.Samenvatting Vooral in Nederland wordt sinds een aantal jaren naastAgaricus bisporus ook de warmteminnende champignonsoortAgaricus bitorquis geteeld, die minder vatbaar is voor bepaalde ziekten. TerwijlVerticillium fungicola varfungicola in de teelt vanA. bisporus droge mollen en daardoor veel schade veroorzaakt, komen in de teelt vanA. bitorquis geen droge mollen voor maar wel bruine vlekken, die tot kwaliteitsverlies en dus schade leiden. De vlekken bleken veroorzaakt te worden doorV. fungicola var.aleophilum. Deze schimmel veroorzaakte ook inA. bisporus bruine vlekken, hoewel in minder ernstige mate, maar in het ras Les Miz 60 vanA. bisporus bovendien misvormde champignons, die wel op droge mollen leken, maar daaraan niet gelijk waren.OokV. psalliotae, in Engeland geïsoleerd vanA. bitorquis met vlekken, veroorzaakte wat meer samenvloeiende, bruine vlekken inA. bitorquis. In Nederland, waar meerA. bitorquis geteeld wordt dan in andere landen, isV. psalliotae nog niet aangetroffen in teelten vanA. bitorquis. InA. bisporus kon geen kunstmatige infectie worden verkregen metV. psalliotae, die net alsV. fungicola var.aleophilum enA. bitorquis warmteminnend genoemd zou kunnen worden.Met de volgendeVerticillium-achtige of van paddestoelen geïsoleerde schimmels kon evenmin op kunstmatige wijze een infectie worden opgeroepen inA. bisporus ofA. bitorquis: Verticillium lamellicola, V. fungicola var.flavidum, V. biguttatum, Nectriopsis tubariicola, Acremonium crotocinigenum enAphanocladium album.  相似文献   

16.
Induction of germination of microsclerotia by exudates from plant roots may be important for the control ofV. dahliae. Laboratory experiments with root observation boxes were carried out to assess the influence of root tips of seven crop species and cultivars on the germination of microsclerotia ofVerticillium dahliae in soil under controlled conditions. The root density of crops was measured in a field experiment. The results of the laboratory experiments and the field experiment were combined to estimate the total effect of crops on the population of microsclerotia in the field. Germination of microsclerotia was stimulated by all crops compared to a control without a crop. Among crops, roots of potato cvs Element and Astarte had a larger stimulation effect on microsclerotia than that of potato Ostara, pea, flax, sugar beet or onion. The number of hyphae per microsclerotium decreased with distance from the root surface regardless of the crop species or cultivar. Differences in root densities, in the affected root zones and in the stimulation effect on germination of microsclerotia caused large differences among crops in the effect on the population of microsclerotia in the soil. However, growing a rop with the special purpose to reduce the level ofV. dahliae inoculum in the soil is an inefficient control measure, because only a small part of the total soil volume is affected by roots and the number of hyphae per microscleroium affected is too low.Abbreviations MS microsclerotia, microsclerotium  相似文献   

17.
A virus isolated from lettuce (Lactuca sativa), endive (Cichorium endivia), witloof chicory (C. intybus), and spinach (Spinacia oleracea), and from some weeds was shown to be beet western yellows virus (BWYV) by its host range, particle morphology and serology. It resembled previously described European isolates but differed from American strains in its inability to infectBeta vulgaris, Brassica pekinensis andRaphanus sativus. The most useful host for routine indexing wasCrambe abyssinica. Virus particles in purified preparations stained with uranyl acetate were isometric, ca. 27 nm in diameter. Purified virus reacted with antiserum to an American strain of BWYV in infectivity neutralization gel diffusion and serologically specific electron-microscopy tests.The field reaction to BWYV of cultivars of lettuce, otherLactuca species and someCichorium species was investigated and differences in symptom expression were observed. On the basis of observations during two seasons BWYV appeared to be widely distributed but seemed of minor economic importance to lettuce growing. It may be a potentially important pathogen of endive and chicory.Samenvatting Reeds gedurende enkele jaren trekt in Nederland een vergelingsziekte van sla (Fig. 1 en 2) de aandacht. In 1977 en 1978 werd de ziekte nader bestudeerd en ook waargenomen in andijvie, witlof (Fig. 3) en spinazie. Uit zieke planten van deze vier gewassen en uit de onkruiden herderstasje en kruiskruid, groeiend in de buurt van de zieke sla, kon doorMyzus persicae op persistente wijze een virus worden overgebracht. Het werd op grond van zijn waardplantenreeks (Tabel 1), deeltjesmorfologie (Fig. 4A) en serologie (Fig. 4B) herkend als het in de USA beschreven beet western yellows virus (BWYV).Het Nederlandse virus komt overeen met in andere landen gerapporteerde Europese isolaten van het virus, maar verschilt van Amerikaanse doordat het niet in staat is om biet, chinese kool en radijs te infecteren. Daarom is voor het virus door Bos en Ashby (1978) de Nederlandse naam slavergelingsvirus ingevoerd. De meest geschikte indicatorplant voor routinetoetsing isCramble abyssinica (Tabel 2). De reactie van herderstasje varieert al naar individu van nagenoeg letaal tot vrijwel symptoomloos (Fig. 5).In gedeeltelijk gezuiverde preparaten bleken de deeltjes bolvormig te zijn en ca. 27 nm in diameter (Fig. 4A). Zulke preparaten reageerden met antiserum tegen een Amerikaanse stam van het virus (BWYV) in toetsen die gebruik maken van infectieneutralisering, gel-diffusie en serologisch-speciefieke elektronenmikroskopie. Bij laatstgenoemde techniek werd een fraaie deeltjesklontering waargenomen (Fig. 4B), die ontbrak na incubatie van gezuiverd virus met een antiserum tegen het niet verwante kersebladrolvirus (Fig. 4C).Bij veldwaarneming in 1977 van 20 slarassen, waarbij tot 60% van de planten van één ras werden aangetast, bleken twee rassen niet of weinig vatbaar (Tabel 3). Bij inoculatie in de kas bleken ze echter volledig vatbaar. In 1978 werd een aantal soorten en rassen vanCichorium enLactuca blootgesteld aan natuurlijke en aan kunstmatige infectie. BehalveC. intybus Groenlof IVT waren allen vatbaar, ookL. sativa Gallega de Invierno,L. serriola enL. virosa.Het virus lijkt algemeen voor te komen. Meestal is de infectiegraad niet hoog. Vanwege de lange incubatieduur in sla is het virus in dat gewas bij de hier toegepaste teeltwijze waarschijnlijk van geringe betekenis. Het lijkt echter een potentieel belangrijk pathogeen voor andijvie en witlof.Guest research worker, Plant Diseases Division, DSIR, Private Bag, Christchurch, New Zealand, with financial assistance from the International Agricultural Centre, Wageningen, and Ministry of Education and Science, The Hague.  相似文献   

18.
The nematode species Longidorus attenuatus, L. elongatus, L. macrosoma and Paralongidorus maximusare economically important pests to the viticulture industry due to their ability to vector two nepoviruses (Raspberry Ringspot Virus and Tomato Black Ring Virus) to grapevines. In Germany, these species occur in vineyard soil with other non-vector but morphologically similar longidorid species, L. helveticus, L.profundorum and L. sturhani. Species-specific primers were designed from ribosomal DNA for all seven species to facilitate taxonomic identification for non-specialists. Primers were assessed for their reliability by screening, where possible, a number of populations of each species. Furthermore, their selectivity and sensitivity were determined when challenged with closely related longidorid species and general nematode communities typical of vineyard soil. A multiplex approach using a common forward primer combined with species-specific reverse primers enabled three target nematode species to be detected in the same PCR reaction. All primers were highly specific, detecting all nematode developmental forms from disparate populations and were sufficiently sensitive to detect a single target nematode within a whole nematode community typical of a vineyard soil comprising of a range of non-target species. Given their specificity, sensitivity and reliability, these diagnostic primers should be of great benefit to both phytosanitary/quarantine services related to the viticulture industry and also as a decision management tool for growers.  相似文献   

19.
Stems of the susceptible Early Sam and resistant Novada carnations were inoculated with a conidial suspension ofFusarium oxysporum f. sp.dianthi. Stem segments of either cultivar were sampled regularly and used for determination of fungal growth and for microscopical investigation.Early Sam showed typicalFusarium wilt symptoms and its stems were colonized intensively. The observed vascular browning appeared to be caused by discolouration of primary walls of infected vessels and surrounding cells. Vessels were rarely occluded with gel. Cell wall degradation led to the formation of stem cavities. Hyperplasia of xylem parenchyma was not seen.In Novada, fungal colonization remained low throughout the experiment. Macroscopic symptoms were absent except for longitudinal bursts in the stem, which appeared to be caused by hyperplasia of xylem parenchyma bordering infection. Vascular gelation occurred in the infected tissues, causing some vascular browning also. Xylem vessel regeneration was observed in the hyperplastic layer. Cavities were not formed, and wall discolouration was rare. Vascular gelation is considered part of theFusarium wilt resistance mechanism. It is followed by xylem vessel regeneration, which expresses a general plant response to vascular dysfunction rather than being part of the resistance mechanism.Although of different origin, vascular browning as such occurs in both susceptible and resistant interactions. In breeding for resistance, care should hence be taken with the current use of browning as an indication of disease.Samenvatting Anjers van de vatbare cultivar Early Sam en de resistente cultivar Novada werden geïnoculeerd met een conidiënsuspensie vanFusarium oxysporum f. sp.dianthi. Van beide cultivars werden regelmatig stengeldelen geoogst om deze microscopisch te onderzoeken en om de schimmelgroei te bepalen.Early Sam vertoonde de voor deze verwelkingsziekte kenmerkende symptomen en werd intensief gekoloniseerd. Aan het vaatweefsel waargenomen bruinkleuring bleek veroorzaakt te worden door verkleuring van de primaire wanden van geïnfecteerde vaten en de hen omringende cellen. Zelden trad er in de vaten gomvorming op. Celwandafbraak veroorzaakte de vorming van holten in de stengel. Hyperplasie van het houtparenchym werd niet waargenomen.In Novada bleef de schimmelgroei gedurende het hele experiment beperkt. Macroscopisch waren er enkel lengtescheuren in de stengel te zien, die veroorzaakt bleken te worden door hyperplasie van aan de infectie grenzend houtparenchym. In het geïnfecteerde vaatweefsel optredende gomvorming veroorzaakte ook enige bruinkleuring. In het hyperplastische weefsel werd regeneratie van houtvaten waargenomen. In de stengel werden geen holten gevormd, en verkleuring van de celwanden kwam weinig voor. De vorming van gommen in de houtvaten maakt waarschijnlijk deel uit van het resistentiemechanisme. De daarop volgende houtvatregeneratie is eerder een algemene reactie van de plant op vaatverstopping dan een deel van het resistentiemechanisme.Vaatverbruining, zij het van verschillende oorsprong, komt voor in zowel vatbare als resistente interacties. Om die reden moet men in de resistentieveredeling bij de anjer voorzichtig zijn met het gebruik van bruinkleuring als ziekteïndicatie.  相似文献   

20.
Colombian datura potyvirus (CDV) was detected in about 300 plants of tomato Cabrion in one greenhouse in the Netherlands. Virus identification was based on host range and symptomatology, aphid transmission, electron microscopy and serology. Evidence was obtained that the tomato plants were infected by viruliferousMyzus persicae that acquired the virus from a CDV-infectedBrugmansia plant present in the same greenhouse.  相似文献   

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