Identifying grapevine (Vitis vinifera L.): a comprehensive approach using morphology, sugar analysis, and ISSR markers, illustrated with Taferialte cultivars

The exploration of indigenous grapevine diversity in Morocco has been limited, primarily due to the considerable number of local cultivars with subtle distinctions and the associated challenges in identification and characterization. This research, centered in northwestern Morocco, conducted a survey to gather leaf and bunch samples from vineyards, along with their corresponding GPS coordinates. Three cultivars with similar names (Taferialte kahla, Taferialte hamra, and Taferialte chahba) were morphologically described using both quantitative and qualitative descriptors established by the international organization of vine and wine. These descriptors covered leaf morphology, as well as the size and weight of berries and bunches. The must sugar content was determined using the sulfuric phenol method, and the identity of the cultivars was established using six inter simple sequence repeat (ISSR) markers. The survey successfully identified 29 indigenous grapevine cultivars based on local appellations. Despite the similarity in names, morphological descriptions revealed inevitable similarities among the three cultivars. For instance, the leaves displayed a pentagonal shape with three slightly open lobes and teeth on both convex sides, with a subtle difference in anthocyanin pigmentation. Notably, distinct differences were observed in berry color, size, and pip number. The sugar content, approximately 18%, was moderate compared to that of the reference stocks, which was attributed to environmental conditions. While the observed similarities suggested a potential relationship between the three cultivars, the use of 6 ISSR primers produced 178 bands, 93.82% of which were polymorphic. This conclusively demonstrated that the three cultivars are distinct, having only 64% similarity. This study provides valuable insights into Moroccan indigenous grapevine cultivars, underscoring the need for conservation to safeguard their unique characteristics.