Submitted to: International Bacterial Wilt Symposium
Publication Type: Proceedings
Publication Acceptance Date: 2/8/2002
Publication Date: 1/20/2003
Citation: PROCEEDINGS OF THE THIRD INTERNATIONAL BACTERIAL WILT SYMPOSIUM, FEBR 2-8, 2002, WHITE RIVER, SOUTH AFRICA, P. 90. Interpretive Summary: Screening and certification of pathogen-free propagation materials is a critical process to control ginger wilt disease. Immuno-trapping detection assays and DNA-based identification methods were investigated for screening rhizomes. Cluster analysis show ginger strains from Hawaii form a unique group. This high degree of phenotypic and genotypic uniformity permitted development of a simple detection assay for screening ginger rhizomes prior to field planting.
Technical Abstract: Immunodiagnostic and DNA-based detection assays are needed for screening ginger rhizomes for Ralstonia solanacearum prior to planting in production fields. To determine the general applicability of potentially useful detection assays, representative R. solanacearum strains from a worldwide collection were characterized using reactivity to a panel of monoclonal antibodies (MAbs), bacteriological tests, metabolic profiles, RFLP and AFLP analysis. Ginger strains from Hawaii were serologically indistinguishable from strains representing races 1 and 2, but differed from some race 3 strains from potato. Genetic comparisons using RFLP and AFLP analysis indicated that ginger strains Hawaii formed unique clusters (similarity indices above 0.90) and showed less similarity with strains from tomato, pepper, heliconia, banana, potato and geranium. The relatively high degree of phenotypic and genotypic uniformity among ginger strains in Hawaii permitted development of a simple detection assay using two species-specific antibodies, Ps1 and Ps1a, which reacted with all ginger strains in the collection. MAb reactivity with virulent fluidal colonies as well as heated extracts containing EPS permitted use of a rapid ELISA to distinguish between R. solanacearum and other fluidal EPS-producing contaminants (Enterobacter asburiae and E. cloaceae), which are frequently isolated from ginger rhizomes and overgrow R. solanacearum in culture. A capillary-trapping immunodiagnostic assay was developed to detect R. solanacearum in tissue extracts containing mixed microbial populations. The assay is suitable for detecting the pathogen in wash water from ginger rhizomes and is intended for use in soil assays.