The spliced leader RNA gene array in phloem-restricted plant trypanosomatids (Phytomonas) partitions into two major groupings: epidemiological implications

The arbitrary genus Phytomonus includes a biologically diverse group of kin etoplastids that live in a wide variety of plant environments. To understan d better the subdivisions within the phytomonads and the variability within groups, the exon, intron and non-transcribed spacer sequences of the splic ed leader RNA gene were compared among isolates of the phloem-restricted me mbers. A total of 29 isolates associated with disease in coconut, oil palm and red ginger (Alpinia purpurata, Zingibreaceae) were examined, all origin ating from plantations in South America and the Caribbean over a 12-year pe riod. Analysis of non-transcribed spacer sequences revealed 2 main groups, I and II; group II could be further subdivided into 2 subgroups, IIa and II b. Three classes of spliced leader (SL) RNA gene were seen, with SLI corres ponding to group I, SLIIa to group IIa, and SLIIb to group IIb. Two isolate s showed some characteristics of both major groups. Group-specific oligonuc leotide probes for hybridization studies were tested, and a multiplex ampli fication scheme was devised to allow direct differentiation between the 2 m ajor groups of phloem-restricted Phytomonas. These results provide tools fo r diagnostic and molecular epidemiology of plant trypanosomes that are path ogenic for commercially important flowers and palms.