Sweet cherry fruit cracking mechanisms and prevention strategies: A review

Sweet cherry (Prunus avium L.) is highly perishable and is greatly affected by orchard management and environmental conditions, such as excess rainfall before harvest. Rain-induced cracking is the major cause of crop loss in sweet cherry in most production areas of the world. Advances in understanding the physiological and molecular mechanisms involved in cracking physiology in combination with orchard management strategies to limit cherry cracking are discussed. The current opinions to explain fruit cracking is that the process initiates with water uptake by the fruit surface that results in localised bursting of cells that release malic acid into the apoplast. This results in swelling of the epidermis and weakening of the epidermal and hypodermal cells until macroscopic fruit cracking. This review focusses on management strategies such as rain cover protection, mineral sprays, anti-transpirants and growth regulators. Tree responses to growth regulators and biostimulants vary with cultivar, application frequency, concentration and type, making it hard to generalize their effects. New approaches to limit cracking are presented, including the development of tolerant cultivars, candidate mineral sprays, biostimulants and technologies for rainwater removal such as orchard air-blast sprayers or creating downwash by helicopters.