Isolation and Characterization of Brenneria quercina, Causal Agent for Bark Canker and Drippy Nut of Quercus spp. in Spain

Abstract

The drippy nut disease of oak was first described in California in 1967 and, since then, the causal agent has not been reported in any other area. This study describes for the first time in Europe the isolation of Brenneria (Erwinia) quercina from bark canker in addition to drippy bud and drippy nut in Quercus ilex and Q. pyrenaica. The bark canker and drippy bud symptoms were not previously described as caused by this bacterium. No fungal pathogens were associated with any of the symptoms. Physiological and biochemical characterization identified the pathogenic isolates from Spain as belonging to B. quercina, similar to the reference strain CFBP 1266. Fatty acid profiles of the Spanish isolates also were similar to the strain of B. quercina from California. Serological analysis by indirect immunofluorescence and enzyme-linked immunosorbent assay using polyclonal antisera against the reference strain of B. quercina and one Spanish oak isolate revealed some antigenic heterogeneity between isolates of different origins. Pathogenicity tests demonstrated that the Spanish isolates were able to reproduce internal symptoms of necrosis and acorn exudation in Q. ilex and Q. pyrenaica and suggest that B. quercina may be associated, among other causes, with the oak decline syndrome affecting Spanish oak forests.

Caracterización fenotípica y genotípica de aislados españoles de Erwinia amylovora.

“…They may be due to the basal media used, since we changed the standard one by a modification of the Ayers basal medium, which consists in a higher concentration of the bromothymol blue. This has been recently reported to give more reliable results when applied to Brenneria (Erwinia) quercina (Biosca et al, 2003). We observed that strains of E. amylovora are able to hydrolize aesculin, unlike previous reports (Paulin & Samson, 1973;Verdonck et al, 1987), but in agreement with the more recent results of Rijckaert (1994), cited in Hauben et al (1998).…”

“…API 20E tests (bioMérieux, Marcy-l'Étoile, France) were applied to all E. amylovora strains according to the manufacturer's instructions, but the incubation temperature was 26ºC and the results were registered after 48 h. For the API 50CH tests (bioMérieux, Marcy-l'Étoile, France) the manufacturer's recomendations were also followed except for the basal medium that was replaced by a modification of the Ayers medium (Ayers et al, 1919), as described by Biosca et al (2003). The galleries were incubated at 26ºC…”

“…Estas discrepancias probablemente se deben a la utilización de un medio basal distinto ya que, en nuestro trabajo, el medio provisto por el fabricante se ha sustituido por el medio basal de Ayers, modificado con mayor concentración del indicador (Biosca et al, 2003). La utilización del sistema API 50CH también ha puesto de manifiesto la capacidad de E. amylovora para hidrolizar esculina, en desacuerdo con estudios anteriores (Paulin y Samson, 1973;Verdonck et al, 1987) pero en coincidencia con otro más reciente de Rijckaert (1994), citado en Hauben et al (1998).…”

Detection of Bacterial and Phytoplasmal Pathogens

“…For the identification of strains of Brennaria (Erwinia) quercina causing bark canker and drippy bud and nut disease in Quercus ilex and Q. pyrenaica, the API System was applied. The API 20E and API 20NE systems showed that all Spanish isolates of B. quercina had similar biochemical characteristics and resembled the reference strain CFBP 1266 (Biosca et al 2003).…”

Conservation of holm oak (Quercus ilex) by in vitro culture

“…and Biscogniauxia mediterranea (Hypoxylon mediterraneum), also implicated in the decline. The presence of the bacterium Brenneria quercina has also been found to be associated with Quercus decline in Spain 14 years ago (Biosca & al., 2003).…”