Phenotypic traits of berries and seeds of Sicilian grape cultivars (Vitis vinifera L.)

•Black and white Sicilian cultivars showed large differences in phenotypic traits of berries and seeds.•White cultivars were characterized by the highest berry and seed weight, but the lowest number of seeds per berry.•Stummer’s index varied due to variation of seed width, which was influenced by seed number.•A linkage between berry and seed traits was found for the diversity of the genetic pool of Sicilian cultivars of Vitis vinifera L.