MOLECULAR CHARACTERIZATION AND PHYLOGENETIC ANALYSIS OF 16S rRNA FROM A NEW "CANDIDATUS LIBERIBACTER" STRAIN ASSOCIATED WITH ZEBRA CHIP DISEASE OF POTATO (SOLANUM TUBEROSUM L.) AND THE POTATO PSYLLID (BACTERICERA COCKERELLI SULC)

The full-length 16S rRNA gene region of a new "Candidatus Liberibacter" strain was PCR- amplified from tubers of potato plants showing zebra chip (ZC) disease symptoms and also from the potato psyllid [Bactericera (= Paratrioza) cockerelli Sulc], the presumptive vector of the ZC disease causal agent. Sequences of the amplicons from ZC diseased potato and potato psyllids were 100% identical but differed from "Ca. L. asiaticus" (Las) and "Ca. L. africanus" (Laf) by 4% and from "Ca. L. americanus" (Lam) by 6.0-6.3%. Neighbor-joining analysis placed the ZC disease-associated sequences in a monophyletic clade consisting of all known "Ca. Liberibacter" spp., positioned in the tree basal to a node shared exclusively by Las and Laf but proximal to a node shared by Lam and all other "Ca. Liberibacter" spp. Here we present evidence for the association between a new "Candidatus Liberibacter" strain and ZC disease in field samples. The relationship of this Liberibacter to the other Liberibacter bacteria detected in psyllids, potato and other solanaceous crops as well as in citrus remains to be determined.