for example, an expensive trial has to be organised to observe a single character- istic when the absence or presence of that characteristic can also be shown in a molecular marker test. An example is the presence of cytoplasmic male sterility in Brassica crops. To observe this in the field, a replanting of the plants in a second year is necessary, where a PCR test will give the desired result in a matter of days. Also, some disease resistance char- acteristics can be observed using marker techniques. The idea behind this is that if there is a ‘one to one’ relation between the vis- ually observed or measured characteris- tic and the molecular result, UPOV allows the use of a molecular test. The same reasoning is used in the allowance to use molecular techniques in the management of reference collections. If a clear relation can be shown between the molecular fingerprints and the mor- phological features, a molecular test may be used to manage the reference collec- tion; to decide on close varieties for inclu- sion in the growing trial or to discard varieties from common knowledge as potential comparing varieties. Examples of this approach are the maize and potato DNA databases. In these cases, molecu- lar distances and morphological distances are compared and, in combination, safety thresholds are established. IS THIS ENOUGH? In the Netherlands, we are of the opin- ion that for a strong sustainable Plant Breeders’ Right system, more is needed. Not only will breeding techniques develop and produce more new varieties, the set of varieties of common knowledge will grow dramatically as a result of that. Breeding activities take place world- wide and, as a result, a broad diversity of types and varieties is available. Seed companies operate on a worldwide basis so the introduction of new varieties is not confined to certain regions or countries. One of the major challenges in DUS testing is to ensure that new plant variety applications do not presently exist and are clearly distinct from all other varie- ties of common knowledge. The quality of the DUS decision therefore depends largely on the available information on the common knowledge varieties, the subsequent management of the variety collection and design of the DUS trials that contain an acceptable and workable number of comparing varieties without missing any relevant variety of common knowledge as a reference. RISKS IN THE CURRENT DUS SYSTEM It is almost impossible to have and main- tain a full overview of common knowl- edge. The rapid development of new varieties due to intensive molecular assisted breeding and increased global character of the plant breeding industry, makes it an already hard and soon impos- sible task to keep track of common knowl- edge in living form in seeds or plants. In addition, the sending of plant material around the world for testing purposes is subject to phytosanitary requirements that sometimes make it impossible to import samples. We also need to consider that there is a relative subjectivity of the variety description. For several mainly quantita- tive characteristics, the variety descrip- tion –- which is the ID of a variety in the current system and fully based on phenotype –- is influenced by climate and other environmental factors, which vary by geographical location. So, variety descriptions received from other exami- nation offices (EO) are of limited utility and reliability. As more breeding takes EUROPEAN-SEED.COM I EUROPEAN SEED I 11 place in other climate zones, the variety description (and photographs) that are provided by the breeder in the form of a Technical Questionnaire might differ from the expression at the EOs that are responsible for the DUS tests. This can result in the selection of wrong compar- ing varieties with the potential result that trials have to be repeated in additional year(s) with relevant comparing varie- ties. These external environmental fac- tors hamper the usefulness of comparing variety descriptions. SOLUTION TO OVERCOME THE RISKS DNA profiles, available in well-organized databases with DNA data of varieties of common knowledge, are considered as objective and are a valuable tool to guar- antee the efficiency and quality of DUS tests in the near future. There are no restrictions on the number of varieties of common knowledge that can be added in such DNA database. And there are no restrictions on phytosanitary regula- tions as DNA can be exchanged instead of whole plants/seeds.