Pea Ty1-copia group retrotransposons: transpositional activity and use as markers to study genetic diversity in Pisum

The variation in transposition history of different Ty1-copia group LTR ret rotransposons in the species lineages of the Pisum genus has been investiga ted. A heterogeneous population of Ty1-copia elements was isolated by degen erate PCR and two of these (Tps12 and Tps19) were selected on the basis of their copy number and sequence conservation between closely related species for further in-depth study of their transpositional history in Pisum speci es. The insertional polymorphism of these elements and the previously chara cterised PDR1 element was studied by sequence-specific amplification polymo rphism (SSAP). Each of these elements reveals a unique transpositional hist ory within 55 diverse Pisum accessions. Phylogenetic trees based on the SSA P data show that SSAP markers for individual elements are able to resolve d ifferent species lineages within the Pisum genus. Finally, the SSAP data fr om all of these retrotransposon markers were combined to reveal a detailed picture of the intra and interspecies relationships within Pisum.