Harvest Timing, Crop Load, and Preharvest GA3 Application Affect Postharvest Quality of ‘Lapins' and ‘Sweetheart' Sweet Cherries

Sweet cherries transported over long distances often arrive at distant markets with significant fruit quality issues, such as pitting, flavor loss, color darkening, and stem browning. Influences of preharvest factors on storage/shipping quality of late-maturing sweet cherry cultivars have not been fully investigated. The objectives of this research were to determine the effects of harvest timing, crop load level, and preharvest GA₃ application on fruit quality of ‘Lapins’ and ‘Sweetheart’ at harvest and after storage.  As harvest timing was delayed, fruit of ‘Lapins’ and ‘Sweetheart’, darkened, accumulated soluble solids (SSC) and softened, while respiration rate and titratable acidity (TA) remained relatively unchanged. Fruit of late-harvested ‘Lapins’ and ‘Sweetheart’ (skin colors of 7 and 6 according to ctifl color chips, respectively) were more susceptible to pitting and showed duller skin color and increased stem browning after storage than less advanced fruit from earlier harvests. To achieve optimum postharvest quality under our conditions, harvest of ‘Lapins’ and ‘Sweetheart’ cherries should coincide with skin colors of 5.5 and 4.5 (ctifl color chips), respectively. Crop load level was positively related to yield but held an inverse relationship with fruit quality. Fruit from high crop load treatments were smaller and had lower SSC, TA, and fruit firmness (FF) at harvest and greater incidence of pitting following storage. Preharvest GA₃ applied at 25, 50, and 100 ppm increased FF at maturity, reduced pitting susceptibility, and limited stem browning after cold storage. Fruit size, SS and TA were not consistently improved by GA₃. Pitting resistance and FF were optimized at 25 ppm; no additional benefits were observed at higher rates. Regardless of harvest timing, crop load, and GA₃ treatments, FF was negatively correlated with pitting susceptibility of both cultivars. Interestingly, 2 weeks of cold storage at 0 °C alone increased FF of all fruit, including untreated controls. In conclusion, appropriate harvest timing, proper management of crop load, and preharvest GA₃ application can markedly improve fruit quality, resistance to pitting, and storage/shipping quality of  ‘Lapins’ and ‘Sweetheart’ sweet cherries.