Identification ofErwinia carotovorafrom Soft Rot Diseased Plants by Random Amplified Polymorphic DNA (RAPD) Analysis

Erwinia carotovora and pectolytic pseudomonads are the most prevalent bacteria associated with soft rot of plants. A procedure based on random amplified polymorphic DNA (RAPD) analysis was developed to distinguish these bacteria rapidly and easily. Forty bacterial strains isolated from diseased plants in the province of Quebec were used to screen RAPD primers. Two primers were chosen based on cost considerations and on their capacity to discriminate between the bacterial strains. The combination of the two primers was sufficient for adequate distinction of Erwinia carotovora from pectolytic, fluorescent Pseudomonas spp. Furthermore, E. carotovora subsps. atroseptica and carotovora could also be distinguished from each other. To simplify the identification work, a quantitative identification tool was elaborated, based on selected markers produced with the two primers. To verify the RAPD analysis accuracy, 49 additional soft rot bacteria from diseased plants were submitted to the RAPD procedure and all the identifications were in agreement with those produced by standard biochemical tests. In addition, the RAPD analysis correctly identified 25 bacteria from collections outside of Quebec.