Evolutionary Trends of Different Repetitive DNA Sequences During Speciation in the

The presence and distribution of two simple sequence repeats (SSRs), three highly repetitive sequences from rye, and the 5S rDNA have been investigated in 3 rye cultivars and 10 wild-related species of the genus Secale. The following conclu-sions can be drawn in addition to detailed knowledge of the sequence content of chromatin in each accession studied: (1) Every species is unique in either or both the complement and chromosomal distribution of the six repeated sequences an-alyzed. (2) These sequences reveal multiple landmarks along all the rye chromo-somes arms. (3) High polymorphism as well as heterozygosity between homo-logues in the distribution of the (AAG)5 and (AAC)5 was revealed in the outbreeding species of the Secale strictum complex. (4) It is possible to deduce trends in the complexity of repetitive DNA during the evolution of the genus. A possible evolu-tionary pathway that accounts for the present-day Secale species is presented. The genus Secale includes cultivated rye and between 4 and 11 wild species, de-pending on the criteria used for specie