Heterogeneity of Xanthomonas campestris pv. hederae strains from araliaceous hosts

Xanthomonas campestris pv. hederae (synonym X. hortorum pv. hederae) strain s (59 total) were collected from plants in the araliaceae family. Strains w ere isolated from Hedera helix, Schefflera arboricola, Brassaia actinophyll a, and Polyscias spp. from Florida, California, Hawaii, and New Zealand. Al l strains produced yellow mucoid growth; hydrolyzed esculin, starch, casein and gelatin; were pectolytic; produced urease; and grew on minimal media c ontaining asparagine. All bacterial strains were pathogenic on H. helix (En glish ivy), B. actinophylla (dwarf schefflera), and Polyscias fruticosa (mi ng aralia). No differences in symptomatotogy were detected among strains; h owever, severity of symptoms usually was greatest on the host of origin. In planta growth rates of representative strains isolated from H. helix, B. a ctinophylla, and Polyscias spp. also were compared among these three hosts. In all cases, populations grew more rapidly when strains were inoculated t o their original host species. All 59 bacterial strains were compared by 95 -carbon source GN microplate, fatty acid methyl ester (FAME), and restricti on fragment-length polymorphisms (RFLP), with the pulse-field gel electroph oresis method, analyses. All three analyses grouped strains into two distin ct groups that correlated with the host of origin. Using metabolic profiles , 75% of the H. helix strains were separated from strains isolated from Bra ssaia and Schefflera and 95% of the Polyscias strains. FAME analysis separa ted strains into two distinct groups, with 96% of the H. helix strains plac ed in one group. RFLP analysis placed all of the H, helix and Schefflera st rains in one group, as well as 33% of the Brassaia strains, whereas the oth er group contained all of the Polyscias strains and the remainder of the Br assaia strains. It is apparent that the pathovar hederae is made up of hete rogeneous populations that can be separated by biochemical, pathological, g enetic, and physiological analyses into two groups that are closely associa ted with the host of origin.