Histological Study on Skins of Grape Cultivar ‘Olympia’ with Respect to Berry Splitting

Abstract

In vinylhouse-cultured ‘Olympia’ (Vitis vinifera L.×V. labrusca L.), berry growth, especially in diameter, was more rapid than in field-cultured ‘Kyoho’ or ‘Delaware’ during 2_??_4 weeks after veraison when berry splitting was most frequently observed. Almost all berries of ‘Olympia’ split when injuries were made to berry tips by needle, while splitting occurred only in 20_??_30% in ‘Kyoho’ and ‘Delaware’.
Among the 3 groups of experiments in ‘Olympia’, field-cultured berries sprayed withgibberellic acid (GA), field-cultured berries and vinylhouse-cultured berries, the first case resulted in severe berry splitting, followed by the second one. The development of sub-epidermal layers and cells of the berry fairly paralleled the susceptibility to berry splitting but cuticle or epidermal layers did not. Thickness of the layer was increased and radial growth of sub-epidermal cells was excessively enhanced under the susceptible conditions. Pectic substances in the walls of sub-epidermal cells also increased under the susceptible conditions.
Ultrastructural observations on skin surface around the stylar scars showed that long cracks, invisible with the naked eye, were observed most frequently in berries sprayed with GA during berry splitting, followed by field-cultured and vinylhouse-cultured berries. The development of these cracks seemed to determine the susceptibility to berry splitting of this cultivar.