Xanthomonas arboricola pv. corylina
2004; Wiley; Volume: 34; Issue: 2 Linguagem: Catalão
10.1111/j.1365-2338.2004.00716.x
ISSN1365-2338
Tópico(s)Phytoplasmas and Hemiptera pathogens
ResumoEPPO BulletinVolume 34, Issue 2 p. 179-181 Diagnostic protocols for regulated pests†Free Access Xanthomonas arboricola pv. corylina First published: 10 September 2004 https://doi.org/10.1111/j.1365-2338.2004.00716.xCitations: 5 European and Mediterranean Plant Protection Organization PM 7/22(1) Organisation Européenne et Méditerranéenne pour la Protection des Plantes AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Specific scope This standard describes a diagnostic protocol for Xanthomonas arboricola pv. corylina Specific approval and amendment Approved in 2003-09. Introduction Bacterial blight of hazelnut was described for the first time in the USA (Oregon) in 1913 on Corylus maxima. Subsequently, the same disease has been reported also on C. avellana, the most important hazelnut-producing species, in the following European countries: Italy, France, Netherlands, Russia (southern), Serbia and Montenegro, Switzerland, Turkey and United Kingdom (EPPO/CABI, 1997). Outside Europe, it has been recorded on C. avellana in Algeria, USA (Oregon, Washington), Canada (British Columbia), Chile, Australia (Victoria, Western Australia). It can also cause damage to C. pontica and C. colurna. The bacterium has a narrow host range, infecting only Corylus spp. Greatest losses on C. avellana cultivars are seen in 1–4 year-old orchards, where up to 10% of mortality has been recorded. Identity Name: Xanthomonas arboricola pv. corylina (Miller et al.) Vauterin et al. Synonym: Xanthomonas campestris pv. corylina (Miller et al.) Dye Taxonomic position: Bacteria, Gracilicutes, Proteobacteria Bayer computer code: XANTCY Phytosanitary categorization: EPPO A2 list no. 134 Detection There are no diagnostic techniques (i.e. ELISA, IFAS, PCR) specifically developed for routine detection of X. a. corylina. No standardized antisera have been produced, nor have any selective or semiselective bacterial culture media been developed that might help the isolation procedure. Consequently, rapid detection of the pathogen is not possible and diagnostic procedures have still to rely on the observation of disease symptoms, microscopical examination of the symptomatic tissues, isolation from the plant using common media for xanthomonads, pathogenicity and confirmation tests. Disease symptoms Symptoms can be observed both in the nursery and in the field (Web Fig. 1). In the nursery, bud dieback and necrosis of the shoot tips can be noticed in spring on twigs over one-year old. Later, the shoots may wither completely. If the pathogen does not girdle the twig, it can cause cankers 10–25 cm long. The leaves show oily polygonal lesions which may subsequently coalesce. In the field, dieback of buds and new lateral shoots, and cankers along the twigs, are frequently observed in spring and summer. The fruits show typical ‘black heel’ symptom and browning. The involucre of the shell frequently shows oily lesions. Hazelnut organs that show symptoms of bacterial blight are: leaf (tiny angular necrotic lesions), shell (round or elongated black necrotic lesions), involucre of the shell (oily or necrotic round spots 2–4 mm in diameter), lateral twigs (partial or total dieback), twig (partial or total dieback, longitudinal canker mainly developing from a bud), branch (longitudinal canker), sucker (longitudinal canker). Microscopic examination Small pieces of tissues (1–2 mm) showing symptoms of bacterial blight (i.e. oily or necrotic spots on leaves or on the involucre of the shell) are cut and put in a drop of sterile physiological saline (SPS; 0.85% NaCl in distilled water) on a microscope slide, covered with a cover-slip and examined with a phase-contrast microscope. Observation of abundant bacterial cells diffusing from the plant tissue indicates presumptive bacterial blight infection. Isolation Isolation of the pathogen from symptomatic leaves is often difficult. Pieces of tissue (1–2 mm × 2–4 mm) taken from the margin of the lesion are crushed in a sterile mortar containing 3 mL of SPS. After 15 min, an aliquot of 100 µL is spread onto GYCA medium (glucose 10.0 g; yeast extract 5.0 g; calcium carbonate 30.0 g; agar 20.0 g; distilled water to 1.0 L) or onto YPGA medium (yeast extract 5.0 g; bacto peptone 5.0 g; glucose 10.0 g; agar 20.0 g, distilled water to 1.0 L; pH 6.5–7.0), to be preferred to YDC for the primary isolation. The plates are incubated at 25–27 °C for 3–4 days. Mucoid, yellow-pigmented colonies 2–3 mm in diameter with round margin are selected for the pathogenicity and confirmation tests. For propagative material not showing symptoms, no methods have been standardized. The buds that harbour the pathogen during winter as well as during the growing season (Gardan & Devaux, 1987) are presumably the best candidate organs for checking the presence of the bacterium. The same isolation procedures and the bacterial culture media can be used as above, with 1–3 buds per mortar. Identification Table 1 shows the biochemical characteristics of X. a. corylina which are helpful in the identification of isolates. For growth on SQ medium (Lee et al., 1992), isolates are streaked onto SQ medium (succinic acid disodium salt 10.0 g; quinic acid 5.0 g; K2HPO4 1.5 g; (NH4)2SO4 1.0 g; agar 15.0 g; distilled water to 1 L; pH 7.2–7.5). After autoclaving, 7.5 mL of autoclaved 20% MgSO4·7H2O solution is added. The plates are incubated for 4–6 days at 28 °C and the diffusion of a deep green colour around the bacterial streak is considered as a positive reaction. Table 1. Biochemical characteristics of Xanthomonas arboricola pv. corylina Characteristic Reaction Characteristic Reaction Utilization of: Presence of oxidase – –l-arabinose + Esculin hydrolysis + –d-arabinose + Starch hydrolysis + – glucose + Growth at 35 °C + – galactose + Tobacco hypersensitivity + (after 48 h) – mannose + Growth on SQ medium + – sucrose + – maltose + – trehalose + – cellobiose + – glycerol + –l-xylose – –d-xylose – – rhamnose – – lactose – – raffinose – – adonitol – – mannitol – – inuline – – sorbitol – – dulcitol – – erythritol – Pathogenicity test Inoculation of buds, from October to June, is the most suitable method for confirming the pathogenicity of isolates suspected to be X. a. corylina (Gardan & Devaux, 1987). Bacteria grown for 48 h on GYCA medium are suspended in SPS to an optical density corresponding to 1 × 108 cfu mL−1. The buds are pricked with a sterile needle, and 10 gL of the bacterial suspension is placed on the wound. Symptom development can vary according to the month of inoculation. However, appearance of a necrotic lesion should be expected from 14 days to one month after inoculation. A positive control (i.e. pathogenic strain) should be included in the test. Inoculation through wounds along the twig is less successful. Reference material The X. a. corylina type-strain NCPPB 935, isolated in Oregon (US) from C. maxima, proved weakly pathogenic to C. avellana and deviated phenotypically and genotypically from other X. a. corylina strains obtained from C. avellana (Scortichini et al., 2002). For comparison purposes, it is recommended to use NCPPB 2896, isolated from C. avellana and showing the typical characteristics of the pathovar. Possible confusion with similar species X. a. corylina is genetically similar to but pathogenically distinct from the other X. arboricola pathovars: celebensis, fragariae, juglandis, poinsetticola type C, populi and pruni. Comparison with such pathovars for detection purposes are merely indicative. Requirements for a positive diagnosis The procedures for detection and identification described in this protocol should have been followed. The presence of X. a. corylina is suspected when the colony morphology on the bacterial culture media and the confirmatory tests are those typical of the pathovar. Final confirmation requires a pathogenicity test on C. avellana cultivars by artificial inoculation. Report on the diagnosis A report on the execution of the protocol should include: • results obtained by the recommended procedures • information and documentation on the origin of the infected material • a description of the disease symptoms, if any are evident on the sample • a table with the tests performed and the results obtained in comparison with those of the reference strain • comments as appropriate on the certainty or uncertainty of the identification. Further information Further information on this organism can be obtained from: M. Scortichini, Istituto Sperimentale per la Frutticoltura, Via di Fioranello, 52.1-00040 Ciampino Aeroporto (Roma), Italy. Tel. +39 0679348147; Fax +39 0679340158; E-mail: mscortichini@hotmail.com Footnotes 1 The Figures in this Standard marked ‘Web Fig.’ are published on the EPPO website http://www.eppo.org. Acknowledgements This protocol was originally drafted by: M. Scortichini, Istituto Sperimentale per la Frutticoltura, Ciampino Aeroporto (Roma) (IT). References EPPO/CABI (1997) Quarantine Pests for Europe, 2nd edn. CAB International, Wallingford (GB). Google Scholar Gardan L & Devaux M (1987) La bactériose du noisetier (Xanthomonas campestris pv. corylina): biologie de la bactérie. Bulletin OEPP/EPPO Bulletin 17, 241– 250. Wiley Online LibraryGoogle Scholar Lee YA, Hildebrand DC & Schroth MN (1992) Use of quinate metabolism as a phenotypic property to identify members of Xanthomonas campestris DNA homology group 6. Phytopathology 82, 971– 973. CrossrefCASWeb of Science®Google Scholar Scortichini M, Rossi MP & Marchesi U (2002) Genetic, phenotypic and pathogenic diversity of Xanthomonas arboricola pv. corylina strains, question the representative nature of the type strain. Plant Pathology 51, 374– 381. Wiley Online LibraryWeb of Science®Google Scholar Citing Literature Volume34, Issue2August 2004Pages 179-181 ReferencesRelatedInformation
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