ASSESSMENT OF SUSCEPTIBILITY AND PREVENTION OF CRACKING OF 'SKEENA' SWEET CHERRY

Cracking in cherries can lead to a dramatic economic loss, depending on market conditions at time of harvest. To get a better understanding of this phenomenon, two experiments on the cherry cultivar ‘Skeena’ were set up in Washington State, USA in 2011. In two different locations, cracking susceptibility development of fruit during maturation, as well as influence of gibberellic acid (GA) and a rain-repellent material, RainGard (RG), on maturity and storability were investigated. To determine cracking susceptibility, samples were taken weekly, starting four weeks before harvest. Fruit diameter, weight, and calculated cracking index (CI) showed block-by-block variations. In one site, an exponentially increasing CI was observed with increasing fruit weight, while in the second site fruit weight remained constant and CI decreased seven days before harvest. Different cracking expression between sites was related to precipitation levels, irrigation and fruit growth rates. GA (10 ppm once or twice, 20 ppm once) and RG (7.58 L/ha) were applied separately or in combination starting three weeks before estimated harvest. A significant decrease in postharvest fruit pitting was observed in both sites for GA treated fruit. A general observation was a delay of fruit color development, increase of soluble solids and decrease of acids. Fruit firmness was improved by GA at both sites. Neither RG nor GA reduced cracking susceptibility in our trials.