Millerandage and flower abscission in ‘Grillo’, ‘Frappato’ and ‘Nero d’Avola’ grapevines: Some probable causes

Some Sicilian cultivars, in particular vintage, showed a high percentage of flower abscissions and shot berries. In this paper, to understand these phenomena, some aspects of the flower morphology of three Sicilian cultivars (two black: ‘Nero d’Avola’ and ‘Frappato’; and one white: ‘Grillo’) was studied. The number of stamens, ovule adherence to the ovary wall and pollen germination were evaluated using standard light microscopy. At harvest, seed number was counted on 30 berries per cultivar. The percentage of six stamens was lowest in ‘Frappato’ and highest in ‘Grillo’. The ovule adherence to the ovary wall was highest in ‘Frappato’ and lowest in ‘Nero d’Avola’. The percentage of pollen germination and seed number was high in ‘Frappato’ while low in ‘Grillo’. Five or six stamens were found in all cultivars. These results could partially explain the different bunch density in ‘Nero d’Avola’, ‘Grillo’ and ‘Frappato’.