Are molecular markers strengthening plant variety registration and protection?

In vegetatively propagated ornamentals, new varieties can be obtained from i.) conventional breeding through crossing and selection or ii.) spontaneous or induced variant types of existing (initial) varieties. Indeed, variant types enlarge the assortment to be produced without the need to alter production systems. However, they inherit the breeding effort needed to create a completely new and profitable variety. Under the rules defined by the UPOV convention of 1991 this new variant type should be considered as an ``Essentially Derived Variety'' (EDV) from the initial variety (IV). Therefore, the breeder of the initial variety might want to claim at least part of the profits acquired by the breeder of the EDV under the form of a royalty. To detect either EDV or fraud, criteria based on plant morphology are insufficient or even not applicable. Here, some case studies are presented to illustrate the possibilities and the limitations of the use of molecular fingerprints in disputes on fraud and essential derivation of ornamental plants. These examples are put in contrast with genetic analysis work that has been performed for the study of phylogenetic relationships, characterization of hybrids and breeders' gene pools. From this framework, it is discussed what benefits molecular markers could provide to plant variety registration and protection of Plant Breeders' Rights.