Characterization and Classification ofErwinia chrysanthemiStrains from Several Hosts in The Netherlands

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Abstract
Forty-one strains of the bacterium Erwinia chrysanthemi were characterized using physiological, biochemical, serological, and pathogenicity tests. Strains from The Netherlands originated from Aechmea fasciata, Aglaonema, Cichorium intybus, Dieffenbachia, Kalanchoe blossfeldiana, Philodendron erubescens, Scindapsus pictus, and Solanum tuberosum. Reference strains were from Chrysanthemum morifolium, Dianthus caryophyllus, Dieffenbachia, Philodendron, S. tuberosum, and Zea mays. On the basis of growth on eight different carbon sources, growth at 39 C, and degradation of arginine, we found that four of the seven biovars of E. chrysanthemi occurred among strains from The Netherlands (biovars 2, 3, 5, and 7). Most potato strains and Kalanchoe strains belong to biovar 7; the other potato strains and one from C. intybus belong to biovar 5. Dieffenbachia strains belong to biovar 2, and strains from Aechmea, Aglaonema, Philodendron, and Scindapsus belong to biovar 3. Using seven antisera against three somatic (O) serogroups and three flagellar (H) serotypes of E. chrysanthemi, strains were classified using indirect immunofluorescence. Only serogroup 1 was found among strains from The Netherlands. The most common combination was serogroup 1-flagella type 1 (O1:H1). Strains from Aglaonema, Dieffenbachia, Philodendron, and Scindapsus showed unknown flagella types (O1:H?). Some reference strains from corn and chrysanthemum belong to a unknown serogroup. There was no correlation between serogroup-flagella type and biovar or original host. E. chrysanthemi strains were tested for pathogenicity on K. blossfeldiana ''Calypso'', P. erubescens ''Emerald King'', S. tuberosum ''Bintje'', and Z. mays '' LG11''. All strains were pathogenic for corn and potato. Kalanchoe, cichory, and potato (KCP) strains were not pathogenic on Philodendron; the other strains (from greenhouse crops and corn) were pathogenic. On Kalanchoe only the KCP strains caused infections. Moreover, the KCP strains did not grow at 39 C and showed a much weaker pectolytic activity at 37 C than greenhouse and corn strains. KCP strains of E. chrysanthemi apparently form a separate group, adapted to crops grown under temperate conditions. The need to standardize classification techniques is discussed.