Genetic determination of seed origin is of high interest for the certification of forest reproductive material. PCRRFLP offers a simple and straightforward technique for mutation detection in PCR products and is therefore a method of choice whenever large sets of specimen have to be genotyped. To evaluate the method's reproducibilty we performed a ring test study and compared the results of six independent centers with those obtained in our own reference laboratory. 94.9% of the submitted and interpretable restriction patterns were identical among all study participants, corroborating the high reliability of PCR-RFLP. On the other hand, some participants encountered substantial difficulties to yield sufficient PCR product for subsequent analysis. The percentage of sample-primer combinations non-genotyped for this reason ranged from 1.2 to 49 %. Thus we conclude that PCRRFLP is a suitable tool in seed certification as long as (a) optimization of PCR procedure is carried out individually for each laboratory and (b) internal quality control is performed by integration of DNA standards with known restriction patterns into each analysis.
