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Host Range and Molecular Phylogenies of the Soft Rot Enterobacterial Genera Pectobacterium and Dickeya

First, eighth, and ninth authors: Genome Center of Wisconsin, University of Wisconsin-Madison, 425G Henry Mall, Madison 53706; second author: Department of Biology, Indiana University, 1001 East Third Street, Bloomington 47405-370; third, fourth, and eleventh authors: Department of Plant Pathology, 1630 Linden Dr., University of Wisconsin-Madison, Madison 53706; fourth author: Department of Ornamental Horticulture, Derech Hamakabim, ARO, Volcani Center, Bet Dagan 50250, Israel; fifth and sixth authors: Hancock Agricultural Research Station, N3909 County Rd V, Hancock, WI 54943; and tenth author: Department of Plant Pathology, North Carolina State University, 3419 Gardner Hall, Raleigh 27695-7616.

Pectobacterium and Dickeya spp. are related broad-host-range entero-bacterial pathogens of angiosperms. A review of the literature shows that these genera each cause disease in species from at least 35% of angiosperm plant orders. The known host ranges of these pathogens partially overlap and, together, these two genera are pathogens of species from 50% of angiosperm plant orders. Notably, there are no reported hosts for either genus in the eudicots clade and no reported Dickeya hosts in the magnoliids or eurosids II clades, although Pectobacterium spp. are pathogens of at least one plant species in the magnoliids and at least one in each of the three eurosids II plant orders. In addition, Dickeya but not Pectobacterium spp. have been reported on a host in the rosids clade and, unlike Pectobacterium spp., have been reported on many Poales species. Natural disease among nonangiosperms has not been reported for either genus. Phylogenetic analyses of sequences concatenated from regions of seven housekeeping genes (acnA, gapA, icdA, mdh, mtlD, pgi, and proA) from representatives of these genera demonstrated that Dickeya spp. and the related tree pathogens, the genus Brenneria, are more diverse than Pectobacterium spp. and that the Pectobacterium strains can be divided into at least five distinct clades, three of which contain strains from multiple host plants.