A PSEUDOAUTOSOMAL RANDOM AMPLIFIED POLYMORPHIC DNA MARKER FOR THE SEX-CHROMOSOMES OF SILENE DIOICA

The segregation pattern of an 810-bp random amplified polymorphic DNA (RAPD) band in the Fl and backcross generations of a Silene dioica (L. ) Clairv. family provides evidence that this molecular marker is locat ed in the pseudoautosomal region (PAR) of the X and Y chromosomes. The marker was found through a combination of bulked segregant analysis ( BSA) and RAPD techniques. Recombination rates between this pseudoautos omal marker and the differentiating portion of the Y chromosome are 15 % in both generations. Alternative explanations involving nondisjuncti on or autosomal inheritance are presented and discussed. Chromosome co unts provide evidence against the nondisjunction hypothesis, and proba bility calculations argue against the possibility of autosomal inherit ance. This constitutes the first report of a pseudoautosomal DNA marke r for plant sex chromosomes.