Susceptibility to Berry Splitting in Several Grape Cultivars

The factors presumed to control the susceptibility to berry splitting caused by rainfall were examined in 6 grape cultivars which were experientially known to differ in their susceptibilty.Judging from the soluble solids contents in juice, the amounts of rainfall during ripening and the proportion of split berries occurring under field conditions, the most susceptible cultivars seemed to be ‘Portland’ and gibberellin (GA)-treated ‘Delaware’, followed by ‘Campbell Early’ and ‘Muscat Bailey A’, while the least susceptible were ‘Kyoho’ and ‘Muscat of Alexandria’, just as predicted from previous observations.Neither the firmness of berries, as measured by a curdmeter, nor their critical turgor pressure exhibited any clear relationship with the susceptibility.The histological observations of berry skin revealed that the thickness of cell wall and the size of cells in the sub-epidermal region were highly related to the susceptibility. Other parameters, including the thicknesses of the cuticlar layer and the epidermal cell wall, and the size of epidermal cells did not show such an obvious relationship.