Problematiche e approcci metodologici per l’identificazione di varietà essenzialmente derivate.

Essentially derived are those varieties (EDV) obtained from an initial protected one (IV) that, although distingui- shable from the IV, conform strictly to it in the expression of essential characteristics. Many breeding methods are available for the derivation process and particularly modern biotechnological approaches which allow a fast and accurate development of these genotypes. Such procedures impair the rights acquired by the breeder of the protected IV who, if demonstrates the genetic conformity between original and new variety, can claim the dependence of the latter. Therefore, a crucial requirement to solve disputes on illegal derivation is the definition of a genetic similarity threshold, between IV and the new variety, above which essential derivation is suspected. Molecular markers are ef- ficient tools for measuring genetic similarity and their adoption in disputes regarding the derivation process has been recommended. Similarity thresholds can be identified according to three approaches: “calibration principle”, “tail principle” and “pedigree principle”. The first one is based on previous knowledge of the similarity between unrelated and closely related (hence essentially derived) genotypes. The second, which does not require pedigree information, sets the threshold at a given percentile of the similarity distribution of a reference population of unrelated genotypes. The threshold limit defined by the third approach is founded on the a priori definition of breeding techniques that lead to essentially derived varieties. Critical aspects of the different procedures are discussed. A similarity exceeding the threshold value is not, however, a conclusive demonstration of the dependence from the IV. La