Cherry fruit cracking: an understanding of the physiological fundamentals is essential for devising an effective prevention strategy

Rain exposes a vulnerability that develops in cherries as they ripen. To understand cracking, we need to follow the fruit’s growth, the changes in its skin, and what happens when water reaches a weakened area. Current knowledge places the start of the damage at a local level and links its spread to a loss of tissue cohesion. This perspective helps explain why apparently similar fruit can respond differently to the same exposure to water.

Fruit growth and cuticle formation

As the cherry grows, its surface area must increase along with the volume of its flesh. Its growth follows a double-sigmoid curve: after an initial period of active growth, pit hardening coincides with a slowdown in the increase in fruit size; later, cell expansion in the mesocarp drives the final growth phase. During this third phase, the surface begins expanding rapidly again, but the formation of the outer covering can no longer keep pace (Knoche et al., 2004; Alkio et al., 2012).

This covering is the cuticle, a matrix of cutin and waxes deposited on the epidermis. Its formation is concentrated in the early stages and declines before the final expansion phase. As a result, a quantity of material that increases only slightly must cover an increasingly large surface: the amount of cuticle per unit of surface area decreases, and strain builds up.