Erwinia chrysanthemi as a cause of potato blackleg
According to recent evidence, E. chrysanthemi (an EPPO A2 organism) causes blackleg disease of potato, originating from infected seed tubers, indistinguishable from blackleg caused by Erwinia carotovora ssp. carotovora or E. carotovora ssp.·atroseptica (Pérombelon M.C.M. & Kelman A. (1987). Blackleg and other potato diseases caused by soft rot erwinias: proposal for revision of terminology. Plant Disease 71, 283-285). E. chrysanthemi tends to be more important under warmer conditions (over 25°C) and E. carotovora. ssp. atroseptica under cooler conditions. If seed potatoes are produced and tested in the field for blackleg symptoms under the cooler conditions of northern countries, then any blackleg detected is likely to be due to E. c. ssp. atroseptica. However, if these seed potatoes are exported to warmer countries, this bacterium will not be likely to cause blackleg. Conversely, any E. chrysanthemi (or E. c. ssp. carotovora) present on the seed tubers will be less likely to be-affected in the cooler conditions of Northern countries (and so may be overlooked) but may express itself after export to warmer countries. It is concluded that it is useful to distinguish the soft rot erwinias present on seed tubers for export, by direct bacteriological testing (e.g. Pérombelon M.C.M., Lumb V.M. & Hyman L.J. (1987). A rapid method to identify and quantify soft rot erwinias on seed potato tubers. Bulletin OEPP/EPPO Bulletin 17, 25-36).
Sources
Plant Disease 71, pp. 283-285