Y-CHROMOSOME SPECIFIC MARKERS AND THE EVOLUTION OF DIOECY IN THE GENUS SILENE

Sex determination in plants has been most thoroughly investigated in S ilene latifolia, a dioecious species possessing heteromorphic sex chro mosomes. We have identified several new Y chromosome linked RAPD marke rs and converted these to more reliable sequence characterized amplifi ed region (SCAR) markers by cloning the RAPD fragments and developing longer primers. Of the primer pairs for seven SCARs, five amplify a si ngle, unique fragment from the DNA of male S. latifolia. Two sets of p rimers also amplify additional fragments common to males and females. Homology between the X and Y chromosomes is sufficient to allow the am plification of fragments from females under less stringent PCR conditi ons. Five of the SCARs also distinguish between the sexes of closely r elated dioecious taxa of the section Elisanthe, but not between the se xes of distantly related dioecious species. These markers will be usef ul for continued investigations into the evolution of sex, phylogeneti c relationships among taxa, and population dynamics of sex ratios in t he genus Silene.