Variety identification in vine grafting is important not only in the case of the scion but also in the rootstock. The choice of the rootstock variety can be decisive due to its compatibility with certain soil types and interactions with the scions.
Usually vine varieties are identified by morphological characteristics such as leaf shape and size, as well as type and density of the hairs on the stem tips and leaves, thus requiring the presence of green tissue. Since rootstocks are traded as cuttings, their identification by morphological properties based on green tissue is naturally not possible.
By extraction of the genomic DNA of the variety sample to be investigated and a RAPD reaction (randomly amplified polymorphic DNA) with this DNA as template, the given variety can be determined with this PCR-based random amplification of DNA fragments and their subsequent gel electrophoretic separation, or the unintentional mixing of different batches can be checked.
This is important, for example, for post-control cultivation within the framework of the "Rebenpflanzgutverordnung" (Vine Plant Material Directive), where samples of rootstocks are tested for their correct classification of varieties. DNA samples from cuttings from rootstock mother plantations are isolated and tested for identity and purity.