Molecular structure and chromosomal localization of major repetitive DNA families in the chickpea (Cicer arietinum L.) genome

Three major repetitive DNA sequences were isolated from a genomic library o f chickpea (Cicer arietinum L.) and characterized with respect to their gen omic organization and chromosomal localization. All repetitive elements are genus-specific and mostly located in the AT-rich pericentric heterochromat in. Two families are organized as satellite DNAs with repeat lengths of 162 -168 bp (CaSat1) and 100 bp (CaSat2). CaSat1 is mainly located adjacent to the 18S rDNA clusters on chromosomes A and B, whereas CaSat2 is a major com ponent of the pericentric heterochromatin on all chromosomes. The high abun dance of these sequences in closely related species of the genus Cicer as w ell as their variation in structure and copy number among the annual specie s provide useful tools for taxonomic studies. The retrotransposon-like sequ ences of the third family (CaRep) display a more complex organization and a re represented by two independent sets of clones (CaRep1 and CaRep2) with h omology to different regions of Ty3-gypsy-like retrotransposons. They are d istributed over the pericentric heterochromatin block on all chromosomes wi th extensions into euchromatic regions. Conserved structures within differe nt crossability groups of related Cicer species suggest independent amplifi cation or transposition events during the evolution of the annual species o f the genus.