Identification of Ralstonia solanacearum in potato tubers using protein electrophoretograms
The diagnostic protocol for Ralstonia solanacearum (EPPO A2 quarantine pest) proposed by the European Union (interim test scheme for the diagnosis, detection and identification of Pseudomonas solanacearum (Smith) Smith in potatoes) envisages a screening test for samples of potato tubers followed by, for potentially infected samples, a direct isolation and identification of pure cultures based on pathogenicity test and a phenotypic or genomic fingerprint. Among the phenotypic fingerprints, the analysis of electrophoretic profiles of whole cell proteins has been proposed. Studies were carried out in Italy to assess the reliability of this method. 53 strains of R. solanacearum belonging to different races and biovars, isolated from different hosts and origins were examined. In addition, 18 unidentified bacteria presenting similar morphological characters in culture, but non-pathogenic to tomato or aubergine were included. All tested strains were submitted to a pathogenicity test on tomato or aubergine. Results showed that visual comparison of the electrophoretic profiles (SDS-PAGE) of whole cell proteins could generally distinguish between R. solanacearum strains, and the non-pathogenic or R. solanacearum-like bacteria. Densitometric analysis of the electrophoretograms revealed a main group of strains including 4 sub-groups. One of these subgroup was constituted of potato and tomato strains belonging to race 3 biovar 2 (including all strains of Mediterranean origin). In addition, principal component analysis clearly discriminated two groups: one group containing the isolates belonging to race 2 and 3, biovars 1 and 2; and a second group containing tropical isolates of race 1. R. solanacearum-like bacteria did not form a discrete group but appeared distinct from R. solanacearum. The authors concluded that the electrophoretic profiles of whole cell proteins, combined with pathogenicity tests, is a reliable method for the identification of R. solanacearum on potato tubers.
Stefani, E.; Mazzucchi, U. (1997) Protein electrophoretograms for the identification of Ralstonia solanacearum in potato tubers.
Journal of Plant Pathology, 79(3), 189-195.
EC Commission, 1997. Commission decision 97/647/EC.
Official Journal of the European Communities. L. 273, 1-25.