Length variation and repetitive sequences of Internal Transcribed Spacer of ribosomal RNA gene, diagnostics and relationships of populations of potato rot nematode, Ditylenchus destructor Thorne, 1945 (Tylenchida: Anguinidae)

Abstract

Abstract Seventy-eight ITS rRNA gene sequences obtained from the potato rot nematode, Ditylenchus destructor, collected across the world from different hosts were compared and analysed. The ITS rRNA gene sequences showed significant length variation between populations. The differences in this rRNA fragment length were due to the presence of repetitive elements in the ITS1, which were characterised by relatively higher rates of substitution changes. Reconstruction of secondary structure for the ITS1 revealed that these minisatellites formed a stem structure. Phylogenetic analyses of ITS rRNA and D2-D3 expansion segments of 28S rRNA gene sequences showed that all studied populations clustered in two major clades: a group of populations having the ITS sequences with the repetitive elements and a group of populations without the repetitive elements in the ITS. We propose to distinguish seven ITS rRNA haplotypes within potato rot nematode populations. PCR-ITS-RFLP diagnostic profiles are presented for these ITS haplotypes and usefulness of recently developed PCR methods with species-specific primers for D. destructor are analysed and discussed.