Characterization of Pectobacterium carotovorum subsp. odoriferum causing soft rot of stored vegetables

Pectobacterium carotovorum subsp. odoriferum has been generally considered to have a narrow host range and has been isolated most often from chicory. Research was conducted to identify 91 Pectobacterium spp. strains isolated from different vegetables in Europe, North and South America, Asia, and Africa, and to compare their ability to cause disease in chicory and potato. Among the 91 strains, 22 strains from Europe were identified as P. c. subsp. odoriferum. Based on phylogenetic analysis of 16S rDNA, recA, and rpoS gene sequences, strains isolated from stored vegetables clustered together with the type strain of P. c. subsp. odoriferum and clustered separately from the P. c. subsp. carotovorum isolates. Eleven strains previously identified as P. c. subsp. carotovorum were reclassified as P. c. subsp. odoriferum. All P. c. subsp. odoriferum isolates were able to cause soft rot symptoms on chicory and potato. Moreover, the symptoms on potatoes were more severe at temperatures from 15 to 37 °C with P. c. subsp. odoriferum isolates than with P. atrosepticum or P. c. subsp. carotovorum isolates. Tissue maceration by P. c. subsp. odoriferum isolates was highest at 28 °C, and at that temperature tissue maceration was two-times greater for P. c. subsp. odoriferum isolates than for P. c. subsp. carotovorum isolates. Symptoms on inoculated chicory leaves were more severe with P. c. subsp. odoriferum (regardless of origin) than with other subspecies or species. To our knowledge, this is the first report that P. c. subsp. odoriferum occurs on a wide range of vegetables and has the ability to cause soft rot during potato storage.