Harvest maturity and crop load influence pitting susceptibility and postharvest quality deterioration of sweet cherry (Prunus avium L.)

The objectives of this research were to determine the effects of harvest maturity and crop load level on fruit quality of 'Lapins' and 'Sweetheart'at harvest and after storage. For harvest maturity experiments, harvests occurred when average skin color as described by CTIFL color chips was 4.0, 5.5, or 6.5 for 'Lapins', and 3.0, 4.5 or 5.5 for 'Sweetheart'. With delayed harvest timing, fruits of 'Lapins' and 'Sweetheart', darkened, accumulated soluble solids (SSC) and softened. Respiration rate and titratable acidity (TA) remained relatively unchanged. Fruit of late-harvested 'Lapins' and 'Sweetheart' (skin color of 6.5 and 5.5, respectively) were more susceptible to pitting and showed duller skin color and increased stem browning after storage compared to less advanced fruit from earlier harvests. Fruit harvested at skin color 5.5 and 4.5 for 'Lapins' and 'Sweetheart', respectively, had the best balance between fruit quality attributes and postharvest and shipping quality. For crop load trials, three crop loads were generated on scaffolds 30 days after bloom, establishing fruit densities of 2-3, 5-7, or ›10 fruit spur^-1. Results indicated that crop load level was positively related to yield but inversely related to 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. Regardless of harvest maturity and crop load treatments, FF was negatively correlated with pitting susceptibility of both cultivars. In conclusion, appropriate harvest timing and proper management of crop load can markedly improve fruit quality, resistance to pitting, and storage/shipping quality of 'Lapins' and 'Sweetheart' sweet cherries.