Survival and transmission of Ralstonia solanacearum in aquatic plants of Solatium dulcamara and associated surface water in England¹

An isolated outbreak of brown-rot disease of ware potatoes, caused by Ralstonia solanacearum biovar 2A, was reported for the first time in England in 1992.A second isolated outbreak was detected in 1996 as a result of random testing of ware potatoes for latent infection.Both outbreaks were associated with the use of irrigation water from sources in which infected Solanum dulcamara was found to be growing.Methods involving indirect ELISA, polymerase chain reaction (PCR) and culture on semi-selective media were used to detect R.solanacearum in roots of S. dulcamara.Detection in surface water was possible by direct culture on semi-selective medium and sensitivity of detection could be increased by concentration of the bacterium by centrifugation or filtration.Analysis of both S. dulcamara and surface water showed that the pathogen survived over several years in aquatic roots of the weed host from which it leached into the water.Nearby plants with only terrestrial roots were found not to be infected.R. solanacearum reached detectable levels in the water during warm summer months from June to October in each year when populations as high as lo5