MOLECULAR METHODS FOR DETECTION AND DISCRIMINATION OF RALSTONIA SOLANACEARUM.
Seal S.E.
Natural Resources Institute, Chatham Maritime, Chatham, Kent ME4 4TB, UK.
In the past decade much research effort has concentrated on the development of improved tests for detection and discrimination of strains within the complex R. solanacearum species. There have been significant advances made in the composition of selective media, antisera production and serological test methodologies, and the development of DNA probes and polymerase chain reaction (PCR) amplification tests.
For rapid diagnosis of R. solanacearum in plant material, serological and PCR tests have been found to be the most suitable. The PCR test has the capability to be more sensitive, specific and rapid than serological methods such as enzyme-linked immunosorbent assays (ELISA) or immuno-fluorescence (IF). However, PCR is also a more costly method in terms of the equipment, consumables and labour required. All these costs are increased further for samples containing high levels of PCR-inhibitory compounds, such as soil and banana tissue extracts, as additional DNA purification steps need to be employed to avoid false negatives. Methods to reduce the cost of PCR will be outlined, and the suitability of PCR for disease diagnosis discussed.
A short overview will also be given on molecular methods for subgroup and strain discrimination. The majority of such methods, like PCR detection tests, require sophisticated laboratory set-ups with stable power supplies, waste disposal systems, and skilled staff. It is considered therefore that their use in developing countries will be most sustainable if regional test centres are set up.
