RECLASSIFICATION OF XANTHOMONAS

A comprehensive DNA-DNA hybridization study was performed by using 183 strains of the genus Xanthomonas. This genus aas shown to comprise 20 DNA homology groups which are considered genomic species. Four groups corresponded to the previously described species Xanthomonas albiline ans, Xanthomonas fragariae, Xanthomonas oryzae, and Xanthomonas populi . The previously described species Xanthomonas campestris was heteroge neous and was divided into 16 DNA homology groups. One of these groups exhibited a high level of DNA homology with Xanthomonas axonopodis. T he 62 pathovars represented in this study were allocated to appropriat e species. Our results, together with previous taxonomic data, support ed a comprehensive revision of the classification of the genus Xanthom onas. The species X. albilineans, X. fragariae, X. oryzae, and X. popu li are not affected. The type species of the genus, X. campestris (Pam mel 1895) Dowson 1939, is emended to include only the pathovars obtain ed from crucifers (i.e., X. campestris pv. aberrans, X. campestris pv, armoraciae, X. campestris pv. barbareae, X. campestris pv. campestris , X. campestris pv. incanae, and X. campestris pv. raphani). X. axonop odis Starr and Garces 1950 is emended to include 34 former X. campestr is pathovars. The following species names are proposed: Xanthomonas ar boricola sp. nov., including X. arboricola pv. corylina, X. arboricola pv. juglandis, X. arboricola pv. poinsettiicola (type C strains of th e former X. campestris pathovar), X. arboricola pv. populi, and X. arb oricola pv. pruni; Xanthomonas bromi sp. nov. for strains isolated fro m bromegrass; Xanthomonas cassavae (ex Wiehe and Dowson 1953) sp. nov. , nom. rev.; Xanthomonas codiaei sp. nov., including type B strains of the former taxon X. campestris pv. poinsettiicola; Xanthomonas cucurb itae (ex Bryan 1926) sp. nov., nom. rev.; Xanthomonas hortorum sp. nov ., including X. hortorum pv. hederae, X. hortorum pv. pelargonii, and X. hortorum pv. vitians; Xanthomonas hyacinthi (ex Wakker 1883) sp. no v., nom. rev.; Xanthomonas melonis sp. nov.; Xanthomonas pisi (ex Goto and Okabe 1958) sp. nov., nom. rev.; Xanthomonas sacchari sp. nov. fo r strains isolated from diseased sugarcane in Guadeloupe; Xanthomonas theicola sp. nov.; Xanthomonas translucens (ex Jones, Johnson, and Red dy 1917) sp. nov., nom. rev., including X. translucens pv. arrhenather i, X. translucens pv. cerealis, X. translucens pv. graminis, X. transl ucens pv. hordei, X. translucens pv. phlei, X. translucens pv. phleipr atensis, X. translucens pv. poae, X. translucens pv. secalis, X. trans lucens pv. translucens, and X. translucens pv. undulosa; Xanthomonas v asicola sp. nov., including X. vasicola pv. holcicola and X. vasicola pv. vasculorum (type B strains of the Former taxon X. campestris pv. v asculorum); and Xanthomonas resicatoria (ex Doidge 1920) sp. nov., nom . rev., which includes the type B strains of the former taxon X. campe stris pv. vesicatoria. Differentiating characteristics were determined for the new species on the basis of metabolic activity on a range of carbon substrates by using the Biolog GN microplate system.