First Report of Bacterial Canker of Walnut Caused by Brenneria nigrifluens in France

Abstract

Since the summer of 2000, vertical oozing cankers have been observed on trunks and branches of Persian walnut trees (Juglans regia). Cvs. Fernor, Chandler, Mayette, and Hartley were the most frequently affected, but cvs. Lara and Franquette could also be affected. Brenneria nigrifluens (synonym Erwinia nigrifluens) (3) was isolated from diseased trees from 13 orchards and nurseries in southwestern (Aquitaine, Périgord, Charentes, and Quercy), southeastern (Grenoble areas), and western (near Angers) France. Cankers were observed on trunks and branches where brown-to-black exudates staining the bark appeared mainly in the summer. Isolations were performed primarily from exudates but also from infected tissues by using King's medium B. Colonies similar in appearance to Brenneria nigrifluens (1) were purified and characterized. Gram reaction, Kovac's oxidase, oxidative-fermentative metabolism, and urease activity were assayed for all isolates. API Biotype 100 kits (BioMérieux, Marcy l'Etoile, France) were used as recommended, except that incubations were at 28°C for 4 days. When compared with the reference strain (French Collection of Plant Pathogenic Bacteria (CFBP) 4998T = National Collection of Plant Pathogenic Bacteria (NCPPB) 564T = American Type Culture Collection (ATCC) 13028T) from California, 14 isolated strains were identified as B. nigrifluens on the basis of physiological and biochemical characteristics. These 14 strains were deposited in the CFBP under Accession Nos. 6746 to 6759. Pathogenicity of three selected strains (CFBP 6746, 6747, and 6758) was confirmed by inoculating branches of 7-year-old walnut trees with 108 CFU of each isolate introduced in wounds (2). The reference strain (CFBP 4998T) and water were similarly inoculated as controls. Two and five months later, necrotic lesions were observed in the inner bark and dark lines were observed in internal wood, but no external cankers were observed on any trees inoculated with the local and reference strains. B. nigrifluens was reisolated from the dark lines in internal wood up to approximately 10 cm from the inoculation site. To our knowledge, this is the first report of this bacterium in France. References: (1) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998. (2) M. Ridé and S. Ridé. Proc. Int. Conf. Plant Pathogenic Bacteria, 4th, 2:957, 1978. (3) E. E. Wilson et al. Phytopathology 47:669, 1957.

Aggressive Emerging Pathovars of Xanthomonas arboricola Represent Widespread Epidemic Clones Distinct from Poorly Pathogenic Strains, as Revealed by Multilocus Sequence Typing

“…Strains of the pathovar are responsible for walnut blight and VOC, a disease that appeared in French walnut orchards in the early 2000s (56,92). MLST and pathogenicity tests showed that only a few closely related sequence types within the pathovar juglandis clonal complex are able to cause typical VOC symptoms, confirming the previous results of Hajri et al (56) based on fluorescent AFLP (f-AFLP).…”

Revisión de técnicas de diagnóstico de Brenneria spp en nogal (Juglans regia)

“…En Europa B. nigrifluens fue identificado en huertas de nogal de castilla. Posteriormente, la bacteria fue detectada en Francia e Italia en plantas jóvenes y árboles adultos (Saccardi et al, 1998;Morone et al, 1998;Ménard et al, 2004;Nelson y Hudler, 2007;Scortichini, 2008;Abeysekara, 2014;Narayanasamy, 2011). En España B. rubrifaciens ha sido reportada en nogales de castilla y en árboles importados de California (González et al, 2002;Nelson y Hudler, 2007).…”

“…En el nogal de castilla Ménard et al, (2004) comprobaron la patogenicidad de tres cepas, al inocular con 10 8 UFC heridas de ramas de 7 años de edad. La cepa de referencia y agua fueron inoculadas de manera similar como testigos.…”

Bark necrosis by Brenneria nigrifluens and other bacteria on walnut plantations in Piedmont: analysis of the disease evolution in the field and isolate characterization by rep-PCR

“…Il patogeno non è nuovo in Italia: descritto per la prima volta su noce nero americano in California (Wilson et al 1957) e segnalato a metà degli anni '90 in Spagna su noce europeo (López et al 1994), fu poi osservato nel nostro Paese proprio in Piemonte (Morone et al 1998) e quasi contemporaneamente in Veneto (Saccardi et al 1998), quindi in Lazio (Scortichini 1999) e in Campania (Carella et al 2003). Comparso poco più tardi in Francia (Ménard et al 2004) e da ultimo in Serbia (Popović et al 2013), le segnalazioni del batterio sono andate intensificandosi nel nostro Paese soprattutto nell'ultimo lustro. Conosciuto in letteratura anglosassone come agente di cancro corticale superficiale (Shallow Bark Canker, SBC) per contrapporlo a Brenneria rubrifaciens (Wilson et al) Hauben et al, agente di cancro corticale profondo (Deep Bark Canker, DBC) allo stato attuale non ancora diffuso in Europa se non in un distretto spagnolo (Gonzá-lez et al 2002), B. nigrifluens rappresenta una minaccia potenziale per la conduzione degli impianti di noce misti e soprattutto in purezza, viste anche le scarse conoscenze sulle condizioni predisponenti alla sindrome e più in generale sulla sua epidemiologia in Italia.…”