摘要:

The EC method for the detection of latent ring‐rot infections (Corynebacterium sepedonicum) consists essentially of an indirect immunofluorescence test and a pathogenicity test on eggplant (EP). When interpreting the results of this method, care should be taken that: (a) eggplants are grown at 21°C. At 28–29°C the detection level of the EP was increased 102to 103‐fold to 105to 106cells ml‐1and latent infections (which may go unnoticed) occurred with 104to 105cells ml‐1; (b) reisolations are made from symptomless eggplants grown at the optimum temperature (21°C) as latent infections can also occur in these plants at concentrations of 102to 103cells ml‐1; (c) potato tuber extracts are tested without freezing or stored freeze‐dried or in a proper protective agent. Freezing at ‐20°C in maceration buffer of cells ofC. sepedonicumandPseudomonas solanacearum(the latter was included for comparison) reduced their numbers by 90–98% after one day. This could easily cause viable cell numbers to drop below the detection level of t

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Des pourritures et flétrissements bactériens dus àErwinia chrysanthemisont inventoriés aujourd'hui sur plus de 25 espèces de plantes cultivées (dont la pomme de terre depuis 1971) et dans de norabreux pays tempérés ou tropicaux. Cette diversité géographique et de gamme d'hôtes mérite des études approfondies. L'espèce bactérienneE. chrysanthemiest subdivisée dans le Bergey's Manual de 1984 en six pathovars:chrysanthemi, dianthicola, dieffenbachiae, paradisiaca, partheniietzeae.Que faire desE. chrysanthemiisolées de pomme de terre, tomate, endive, artichaut? Au lieu de classer les isolats en pathovars, il paraît souhaitable, car simple et fiable, d'adopter le classement en biovars d'après des critères physiologiques de laboratoire mis en évidence ces dernières années, et qui se révèlent discriminants (croissance à 39°C; hydrolyse de l'arginine selon Moeller, de la lécithine et de la gélatine; utilisation des sources de carbone suivantes: cis‐aconitate, D(‐)arabinose, 5‐cétogluconate, inuline, mannitol, mélibiose, raffinose, D(‐)tartrate). Il est également important, avant d'entreprendre une détection par sérologie, de connaître l'appartenance des isolats aux sérogroupes connus (a

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Methods are described for the detection of latent infection byErwinia carotovorassp.atroseptica(blackleg and soft rot),Corynebacterium sepedonicum(ring rot) andPhoma exiguavat.foveata(gangrene) which are regarded as the most important tuber‐borne pathogens of potato. The methods comprise selective media forE. carotovorassp.atrosepticaandP. exiguavar.foveata, indirect fluorescence antibody staining forE. carotovorassp.atrosepticaandC. sepedonicum, and the eggplant test forC. sepedonicumandP. exiguavar.foveata.These are used in Northern Ireland to detect pathogen contamination in nuclear stock mother tubers prior to micropropagation. Marked reductions in disease levels of blackleg have been observed in present pre‐basic stocks raised by micropropagation compared with those previously propagated from stem cuttings. It was found thatPseudomonas stutzeri, a saprophytic contaminant bacterium, can pass through the micropropagation process in a latent f

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Potato tubers are usually contaminated by more than one species or pathovar of soft rot erwinia and, because blackleg incidence is related to the contamination level of seed tubers, the disease potential of seed stocks may be assessed by determining seed‐tuber contamination level. A method is described for identifying and quantifying directly from tubers the three soft rot erwinias commonly associated with potatoes. Replicate lots of 10–15 tubers are peeled by dry abrasion in a commercial potato peeler and the peel weight determined by weighing the tubers before and after peeling. Sap is expressed from the peel, an antioxidant (0.075% dithiothreitol) added, and the sap is dilution‐plated on a diagnostic selective medium (crystal violet pectate [CVP]). After incubating for 24 h at 20°C, the plates are velvet‐replicated onto fresh plates of CVP with or without 35 μg ml‐1erythromycin and incubated for 48 h at 27°C and 24 h at 33.5 or 37°C. Soft‐rot erwinias typically form deep cup‐like cavities on CVP and they can be identified and enumerated according to the pattern of cavity formation. Cavities are formed byErwinia carotovorapv.atrosepticaonly at 27°C, byE. carotovorapv.carotovoraat 27 and 33.5°C but not at 37°C, whereasE. chrysanthemiforms cavities at all temperatures but fails to grow in the presence of erythromycin. Contamination levels can be expressed as the number of different erwinias per

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A comparison was made of methods for viroid detection. Molecular hybridization using cDNA is a very sensitive method that can handle large quantities of samples at the same time but it has the disadvantage that only small amounts of the sample can be applied to the nitrocellulose filter. The method therefore can only detect viroid in plants when its concentration is 10–20 ng g‐1of leaves, using32P as a marker system. Bi‐directional electrophoresis can detect viroid in plants when its concentration is 10 ng g‐1of leaves, because it uses larger samples. It does not need hazardous chemicals like32P and formamide, and the reading of the results of the test is less liable to failures because it is based on two criteria (position and intensity of RNA band). The Dutch Plant Protection Service and the Dutch General Inspection Service for Ornamentals therefore use a modified bi‐directional electrophoresis method to detect potato spindle tuber viroid and chrysanthemum stunt viroid, res

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Potato spindle tuber viroid (PSTV) in potato plants was investigated by ‘return’ gel electrophoresis. The experiments were carried out under quarantine conditions in the greenhouse with primarily and secondarily infected plants. The PSTV content in different plant parts was estimated by the intensity of the viroid band in polyacrylamide gel. The results showed a decrease of viroid content from the upper to the lower parts of the plant. In both primarily and secondarily infected plants, PSTV was reliably detected in the top leaves, but less so in the lower leaves. In four out of ten secondarily infected plants, PSTV was found in the roots. In dormant tubers, the bands were more intense with samples obtained from the rose end and the heel than from those obtained from the medullary tissue. With one exception, all 64 tubers from 26 primarily infected plants were infected with P

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Threats from potato spindle tuber viroid (PSTV) to potato breeding and centralized elite seed‐tuber production have been identified in world potato genetic resources. In the UK effective diagnostic testing has proved essential in preventing acquisition. Inoculation of potato nucleic acids to tomato and subsequent viroid detection by polyacrylamide gel electrophoresis (PAGE) has proved a sensitive, but cumbersome, test over 8 years. Additionally, over 2 years,32P‐labelled PSTV cDNA was used to probe denatured sap and nucleic acid extracts: 10‐4of peak viroid concentrations in tissue could be detected. Spurious positives were seen in particular circumstances, but could be avoided. Probing of non‐denatured samples was not as sensitive. Tubers became infected and PSTV was readily detected by PAGE in leaves of potato experimentally inoculated and maintained below 20°C, but the cDNA probe could not detect infection in tuber sprouts growing at 8–10°C in darkness. Otherwise similar green‐leaved sprouts were faintly positive. Detection for all sprouts was unproblematic after movement to 25°C and lig

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

In UK, the tobacco veinal necrosis strain of potato virus Y (PVYN), potato virus A (PVA) and potato virus V (PVV) each occur in the field only in limited ranges of potato cultivars in which they mostly cause mild symptoms or even symptomless infection; little is known about incidence of strain C of PVY (PVYC). The ordinary strain of PVY (PVY°), however, is widespread causing symptoms ranging in severity from very severe through to very mild, depending on cultivar sensitivity/tolerance. During field inspections, very mild potyvirus symptoms may be missed, so inspectors are trained to be particularly vigilant when examining problem cultivars which react in this way. PVA is almost invariably treated, along with PVX, as a mild kind of virus infection, but infections with PVY°, PVYNand PVV are treated as severe with stricter tolerances being applied for them (especially for PVYN) regardless of symptom severity. Wide variation within the same cultivar in the behaviour of variants within the PVY° strain group also sometimes causes difficulties in interpretation at inspection. To detect PVY, PVA and PVV in routine serological testing on potato certification samples, it is necessary to employ specific antisera to each of them. PVYN‐specific monoclonal antibodies can be used in ELISA to distinguish PVYNfrom

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Like other seed‐potato‐producing countries, France has now been using ELISA for many years and this method is now totally integrated into the French laboratory test system. It is applied on an occasional or systematic basis at all stages of genealogical selection, and provides complete satisfaction owing especially to its flexibility. An occasional difficulty has been cross reaction between potato viruses A and Y, and the causes and remedies of this are examined. An ELISA serum production unit was set up in early 1985 to provide for French needs and to allow for the possibility of extension of the method to other pathogens than viru

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The standard ELISA method for detection of PVY in dormant potato tubers was compared with recently developed methods: (1) a hybridization technique, using a complementary DNA‐probe to PVYN; (2) three modifications of ELISA (standard monoclonal, Flegg&Clark polyclonal or monoclonal). Sap of six Dutch cultivars secondarily infected with PVY was subjected to these methods directly after lifting and after six subsequent one‐week intervals during storage at 20°C. During storage the detectability of PVY decreased, irrespective of the diagnostic method applied. However, decrease was less in susceptible than in resistant cultivars. Although the hybridization technique yielded slightly better results than the standard ELISA procedure, it was time‐consuming and involved hazardous reagents. The modifications of ELISA investigated were not, in general, more sensitive than standard

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1987.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY