RAIN-INDUCED FRUIT CRACKING OF SWEET CHERRIES .1. INFLUENCE OF CULTIVAR AND ROOTSTOCK ON FRUIT WATER-ABSORPTION, CRACKING AND QUALITY

The physiology of cracking, water uptake and quality of three sweet cherry cultivars that differ in their susceptibility to cracking were studied. Cracking appeared to be related more to the rate of water uptake than to the total amount of water that was accumulated. The less susceptible cultivars, ''Ulster'' and ''Sam'', appeared to obtain their cracking resistance by displaying a slower rate of water uptake and thereby having a greater period to accumulate the damaging quantities of water prior to cracking rather than by tolerating more water once absorbed. It is evident from this study that cultivaral differences in cracking are closely associated with indirect effects that the fruit osmotic potential and skin permeability have on the rates of water accumulation. Fruit from the more cracking-susceptible cultivar ''Van'' on F.12/1 rootstock accumulated more water and underwent more cracking than fruit from Colt rootstock. Fruit moisture content, fruit transpiration rates, fruit size and firmness, however, failed to help explain the cultivar difference in cracking propensity.