First Report of Acidovorax citrulli, the Causal Agent of Bacterial Fruit Blotch, on Melon (Cucumis melo) in Guadeloupe (France)

Abstract

HomePlant DiseaseVol. 103, No. 5First Report of Acidovorax citrulli, the Causal Agent of Bacterial Fruit Blotch, on Melon (Cucumis melo) in Guadeloupe (France) PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Acidovorax citrulli, the Causal Agent of Bacterial Fruit Blotch, on Melon (Cucumis melo) in Guadeloupe (France)A. Cunty, C. Audusseau, S. Paillard, V. Olivier, C. François, C. Rivoal, and F. PoliakoffA. Cunty†Corresponding author: A. Cunty; E-mail Address: [email protected]http://orcid.org/0000-0001-8174-587XLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, C. AudusseauLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, S. PaillardLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, V. OlivierLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, C. FrançoisLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, C. RivoalLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this author, and F. PoliakoffLaboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, FranceSearch for more papers by this authorAffiliationsAuthors and Affiliations A. Cunty † C. Audusseau S. Paillard V. Olivier C. François C. Rivoal F. Poliakoff Laboratoire de la Santé des Végétaux, Agence Nationale de Sécurité Sanitaire, 49044 Angers, France Published Online:15 Mar 2019https://doi.org/10.1094/PDIS-10-18-1825-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In March 2015, symptomatic melon (Cucumis melo) plants and fruits were received from the French West Indies Island, Guadeloupe, at the Anses Plant Health Laboratory (LSV). The leaves showed brown necrotic spots surrounding by a chlorotic halo. The fruits presented small and large water-soaked lesions on the rind that did extend into the flesh, and dark brown necrotic spots into the flesh were observed under some of the lesions. The yield loss was estimated at around 50%. Symptoms were first suspected to be associated with the presence of a pathovar of Pseudomonas syringae, but the isolated strain was identified as Acidovorax citrulli and the pathogenicity was confirmed. Because leaf samples were damaged during transport (development of rot), isolations were only performed from lesions on the fruits on modified King’s medium B (mKB) supplemented with cycloheximide (50 mg/liter). A gram-negative, motile, oxidative, nonfluorescent bacterium was isolated (LSV 46.36 and then registered in the French CIRM–Plant Associated Bacteria collection as CFBP 8568). It induced a hypersensitive reaction on tobacco, had a cytochrome c oxidase activity, did not display an arginine dihydrolase activity nor hydrolyze aesculin or gelatin, did not produce levan, used l-arabinose and glucose, but did not use cellobiose and rhamnose. When plated on mKB, the colonies grew at 41°C. The strain CFBP 8568 was compared with the A. citrulli type strain CFBP 4459. Whole cell DNA, extracted by boiling bacterial suspension (1 × 106 CFU/ml) for 10 min at 100°C, was amplified by the duplex polymerase chain reaction (PCR) developed by Bahar et al. (2008). In specific, two fragments of 476 and 279 bp were obtained for both strains, indicating that the strain CFBP 8568 was A. citrulli. The real-time PCR described in appendixes 4 and 6 of the EPPO protocol PM 7/127 (EPPO 2016), which targeted complementary genes, were also applied to the DNA extract and confirmed the previous results. Application of the PCR assay developed by Zivanovic and Walcott (2017) allowed classifying the strain CFBP 8568 in group I. To fulfill all Koch’s postulates, a pathogenicity test was performed. Three melon seedlings (Charentais type) were inoculated by infiltrating a first true leaf with a cell suspension (1 × 107 CFU/ml) of the strain CFBP 8568. The type strain CFBP 4459 was used as a positive control. After 13 days, brown necrotic spots surrounded by a chlorotic halo were observed at the inoculation points for both strains. From those necrotic spots, strains with all the characteristics of A. citrulli (as previously described) were isolated. No symptoms were observed on the stem, which may be because the test was stopped just after the appearance of necrotic leaf spots. To our knowledge, this is the first report of bacterial fruit blotch (BFB) in Guadeloupe. Prophylactic measures and a strong sanitary survey of this crop allowed eradication of the outbreak. Indeed, no symptoms have been reported in 2018. However, this first report of BFB showed that it could represent a threat in Caribbean area, were it was never reported before.