Identification of Lens culinaris ssp. culinaris chromosomes by physical mapping of repetitive DNA sequences

We describe the characterisation and the chromosomal localisation of two repeated DNA sequences, named pLc30 (466 bp long, 64% AT residues) and pLc7 (408 bp long, 61% AT residues), isolated from lentil (Lens culinaris ssp. culinaris) genomic DNA. The pLc30 family is characterised by four internal repeats organised in a head-to-tail orientation, whereas the pLc7 contains many short direct subrepeats. The two families do not share significant sequence similarity. The distribution of these repetitive sequences in different Lens species and in other legumes was investigated. pLc30 is present in all Lens species investigated but absent from other genera examined. In contrast, pLc7 is present also in the genome of other legumes. As determined by FISH, the pLc30 sequence hybridises on six out of seven lentil chromosome pairs, while pLc7 hybridises on one only. The distribution of the nine different hybridisation sites of pLc30 allows the discrimination of all seven chromosome pairs and the construction of a karyotype of L. culinaris ssp. culinaris. Additionally, the combination of simultaneous and successive FISH with pLc7, 5S rRNA, 18S-5.8S-25S rRNA genes, and a telomeric sequence allowed the assembly of a physical map based on lentil karyotype.