Evaluating Clonal Diversity in ‘Merzifon Karası’ (Vitis vinifera) for Yield, Cluster Characteristics, and Millerandage Index

This study examined clonal variation in Vitis vinifera L. cv. ‘Merzifon Karası’, a Turkish wine grape. Thirty-two clones were evaluated for key growth and enological characteristics, including cluster structure, berry attributes, yield components, millerandage index, and berry skin color. Considerable variability was observed in cluster weight (95.8–254.1 g), berry weight (0.64–3.06 g), and millerandage index (1.35–9.77), highlighting the importance of clonal selection for optimizing fruit set, cluster compactness, and overall vineyard performance. Promising clones, such as F13/29, K11/27, and H20/24, combined high yield, well-formed clusters, and low millerandage indices, whereas clone K13/10 exhibited exceptional uniformity in fruit set, achieving the lowest millerandage index. Incorporating berry skin color characteristics further identified K11/27, F13/29, and K13/10 as particularly favorable for both productivity and winemaking quality due to their dark berries, consistent fruit set, and well-formed clusters. These findings illustrate the potential of targeted clonal selection to enhance sustainable viticulture and improve fruit quality in ‘Merzifon Karası’.