Chromosomal organizations of major repeat families on potato (Solanum tuberosum) and further exploring in its sequenced genome.

One of the most powerful technologies in unraveling the organization of a eukaryotic plant genome is high-resolution Fluorescent in situ hybridization of repeats and single copy DNA sequences on pachytene chromosomes. This technology allows the integration of physical mapping information with chromosomal positions, including centromeres, telomeres, nucleolar-organizing region, and euchromatin and heterochromatin. In this report, we established chromosomal positions of different repeat fractions of the potato genomic DNA (Cot100, Cot500 and Cot1000) on the chromosomes. We also analysed various repeat elements that are unique to potato including the moderately repetitive P5 and REP2 elements, where the REP2 is part of a larger Gypsy-type LTR retrotransposon and cover most chromosome regions, with some brighter fluorescing spots in the heterochromatin. The most abundant tandem repeat is the potato genomic repeat 1 that covers subtelomeric regions of most chromosome arms. Extensive multiple alignments of these repetitive sequences in the assembled RH89-039-16 potato BACs and the draft assembly of the DM1-3 516 R44 genome shed light on the conservation of these repeats within the potato genome. The consensus sequences thus obtained revealed the native complete transposable elements from which they were derived.