Retro transposon-markers: an overview of the recent progress in Citrus germplasm

Citrus is a commercially important genus of the family Rutaceae and widely cultivated fruit crop in the world. Retro transposons are the most abundant class of transposable elements and they outnumber the genes in the eukaryotic genomes. Repetitive sequences make up a large part of the genome, up to 80% in certain species. Dozens or even hundreds of copies of members of some transposon families can be present in a single genome. Transposons can serve as a very rich source of identifiable polymorphisms. In this revised, several retro transposon-based marker systems such as SSAP, IRAP, REMAP and RBIP have been developed and discuss their use to visualize the genetic diversity generated by retro transposon in Citrus germplasm. Sequencing of the recent draft genome represents a valuable resource for understanding and improving of retro-transposons regions in Citrus germplasm. Therefore, sequences information of retro-transposons regions should exhibit more phylogenetic informative sites, which must be received more attention in future research in Citrus germplasm. Consequently, retro transposons integration markers are ideal tools for rapid characterization of Citrus and its related genera. This approach could be efficiently employed for conservation and management of Citrus germplasm genetic resource.