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

Abstract

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 colony-forming units (cfu) per litre were recorded. Irrigation of potato plants under quarantine

Seasonal Variation of Ralstonia solanacearum Biovar 2 Populations in a Spanish River: Recovery of Stressed Cells at Low Temperatures

“…In 2001, R. solanacearum was detectable by plating in summer and again became nondetectable in November. These results agree with previous studies in the United Kingdom and The Netherlands, where the levels of this bacterium in waterways were usually 10 cells/ ml, dropping below the detection limit when exposed to cold temperatures (12,22). Higher densities (10 3 cells/ml) have been described in the summer in The Netherlands, probably due to the proximity of the sampled sites to industrial plants for potato processing (21).…”

“…An investigation of the population densities of R. solanacearum during the first 2 years of analyses at five sites on a Spanish river associated with an outbreak of bacterial wilt in potato plants has demonstrated that the isolation of this pathogen on solid media is correlated with the water temperature, while previous studies have only suggested a relationship that was not statistically confirmed (12,21). In the analyses of 2000, R. solanacearum began to be detected in river water mostly in early July, when the temperature rose above 14°C.…”

“…It represents the major limitation on the production of solanaceous crops all around the world (17), and it is a destructive pathogen (27), as more plants have been severely affected by wilt disease than by any other bacterial disease (26). In Europe, many reports have demonstrated that R. solanacearum biovar 2 has the unexpected ability to survive in waterways at low temperatures in Northern countries such as the United Kingdom (12) and The Netherlands (21,22). The first report of the detection of R. solanacearum in river ways came from Sweden (35) and was followed by reports of different outbreaks in England in 1992 and 1996 (13) and in The Netherlands (21), Belgium, and France (20,22) in 1995.…”

“…Thus, the isolation of R. solanacearum biovar 2 from contaminated water is generally easy during summer, since the densities of the bacterium are relatively high and the organism is actively multiplying (12,13), but it is difficult during winter (3,4,12,13). This is probably due to the entry of this bacterium into the VBNC state and/or because the low numbers of culturable free-living cells present in the waterways are at or below the detection limits of the techniques used.…”

Ralstonia solanacearum: A new threat to potato production in Serbia

“…Furthermore, the bacterium was not found in any of 134 water samples tested, including those originating from areas in which the bacterium was found in ware potato samples. It is noteworthy that outbreaks of the bacterium in several European countries (UK, The Netherlands, Belgium, France, Spain) during the past two decades have been mostly associated with contamination of surface water used for irrigation, or the use of irrigation water from sources in which infected S. dulcamara was found to be growing (Janse, 1996;Grousset et al, 1998;Elphinstone et al, 1998;Caruso et al, 2000). Furthermore, Urtica dioica has also been reported to be a reservoir of the bacterial wilt pathogen (Wenneker et al, 1999).…”