System. Appl. Microbiol. 27, 755–762 (2004) http://www.elsevier.de/syapm Reclassification of the Xanthomonads Associated with Bacterial Spot Disease of Tomato and Pepper Jeffrey B. Jones 1 , George H. Lacy 4 , Hacene Bouzar 2 , Robert E. Stall 1 , and Norman W. Schaad 3 1 University of Florida, Plant Pathology Department, Gainesville, USA 2 Sakata Seed America, Inc., Salinas, USA 3 USDA ARS FDWSRU1301, Fort Detrick, USA 4 Virginia Polytechnic Institute & State University, Department of Plant Pathology, Physiology and Weed Science, Blacksburg, USA Received: May 17, 2004 Summary Four phenotypic xanthomonad groups have been identified that are pathogenic to pepper, tomato, or both hosts. These include groups A and C which are found in Xanthomonas axonopodis pv. vesicatoria, group B found in X. vesicatoria, and group D found in ‘X. gardneri’. We present DNA:DNA hybridiza- tion data in which X. axonopodis pv. vesicatoria group A and C strains have less than 70% DNA relat- edness with each other, with the type strain of X. axonopodis, and with the currently classified species within Xanthomonas and, therefore, should be removed from this species and given species status. We present information that the A strains most closely resemble the strains originally isolated by Doidge in 1921. In an attempt to avoid confusion in nomenclature as stated in Principle 1 of the Bacteriological Code, we propose that the A strains of X. axonopodis pv. vesicatoria be renamed as X. euvesicatoria (ATCC11633 T = NCPPB2968 T = ICMP 109 T = ICMP 98 T ). Use of the euvesicatoria epithet should be re- served for strains originally identified by Doidge, which she designated Bacterium vesicatorium (Ann. Appl. Biol. 7: 407–430, 1921) in the original description when she referred to those strains as being fee- bly amylolytic. The name X. perforans sp. nov. is proposed for the C group of strains previously desig- nated as X. axonopodis pv. vesicatoria (ATCC BAA-983 T = NCPPB 4321 T ). We also propose that ‘X. gardneri’, which has less than 70% DNA relatedness with any of the Xanthomonas species and which has never had taxonomic status, be named X. gardneri (ATCC 19865 T = NCPPB 881 T ) to reflect the spe- cific epithet proposed by Sutic [17] in 1957. Key words: Xanthomonas campostris pv. vesicatoria Introduction Ethel M. Doidge [6] in South Africa originally identi- fied the pathogen causing bacterial spot disease on toma- to (Lycopersicum exculentum Mill.) as Bacterium vesica- torium. In the same year, Gardner and Kendrick [10] also identified a bacterium causing a leaf spot of tomato in Indiana, USA and proposed naming it Bacterium exi- tiosum. However, when they became aware of Doidge’s designation of a similar bacterium on tomato in South Africa, they deferred to her designation because of an ap- parent similarity between the two organisms and her prior publication. Gardner and Kendrick [10] noted one major difference between the strains Doidge isolated and theirs: the bacterium isolated by Doidge [6] was feebly or non-amylolytic, whereas their strains were strongly amy- lolytic. At that time few techniques were available to dif- ferentiate bacteria and this difference was not considered important enough for designating the amylolytic strains as a different species. Both organisms were classified as X. vesicatoria and later as X. campestris pv vesicatoria [8]. In the 1990s, Vauterin et al. [21] and Stall et al. [18] determined that two genetically and phenotypically dis- tinct groups existed within X. campestris pv. vesicatoria; group A and group B. Bouzar et al. [2] confirmed that the A group strains were uniformly negative for starch hy- drolysis and pectolytic activity while the B group consist- ed of strongly amylolytic and pectolytic strains (Table 1). Based on DNA similarities [14, 18, 21], it was evident 0723-2020/04/27/06-755 $ 30.00/0