Archivio Journal of Plant Pathology

Abstract:

Brenneria nigrifluens and B. rubrifaciens are the causal agents of shallow bark canker and deep bark canker, respectively, of walnut trees. Both diseases and their etiological agents have been described in Europe where they can cause serious economic losses. Since there are no effective measures to control bark cankers caused by these bacterial pathogens, rapid, specific and sensitive detection methods are required. However, there are only few selective media and molecular detection protocols for these bacterial species, which hinders and delays their detection and identification. The aim of this contribution is to select and describe in detail the methods utilised and/or developed in several laboratories in the framework of COST 873. The PCR protocol for B. nigrifluens was appropriate for both diagnosis and identification, but showed sensitivity problems, probably due to the high content of phenolic compounds of bark tissues, requiring the optimisation of DNA extraction protocols. For analyses of symptomless walnuts, it will be also necessary to increase the sensitivity of the assay, or develop new PCR protocols. The information is very limited for B. rubrifaciens diagnosis or detection from naturally infected samples, because the bacterium still has a very restricted distribution. On the contrary, the number of techniques available for B. nigrifluens and B. rubrifaciens identification is quite large, including physiological, biochemical, pathogenicity and PCR tests, as well as fatty acids or MALDI-TOF analyses, which have shown an appropriate specificity.