Optimizing preharvest application rate of gibberellic acid (GA3) and homobrassinolide (HBR) to improve shipping quality of sweet cherry (Prunus avium L.)

The objectives of this research were to evaluate the effects of GA(3) application rates (25, 50, and 100 ppm) and a new compound homobrassinolide (HBR) (1 ppm) on harvest and shipping quality of three late-season cultivars grown in the US Pacific Northwest. Foliar applications of GA(3) were applied to 'Lapins' and 'Sweetheart' and HBR to 'Sweetheart' and 'Skeena'. All treatments were applied at straw color. Fruit were harvested when they attained a predetermined CTIFL color score: 'Lapins' at similar to 5; 'Sweetheart' and 'Skeena' at similar to 4. Results demonstrated that GA3 increased FF, reduced pitting susceptibility and limited stem browning (SB) after cold storage for 'Lapins' and 'Sweetheart'. The improved FF and shipping quality, however, did not follow a rate response to GA(3) and was optimized at 25 ppm. GA(3) delayed harvest timing (slowed color development), but the harvest delay did not correspond to improvements in fruit size for either cultivar. GA3 had no consistent effect on soluble solid content (SSC%), titratable acidity (TA%), skin darkening, or moisture loss (ML%) for either cultivar at harvest or following 4 weeks of storage at 0 degrees C. HBR at 1 ppm increased FF of 'Sweetheart', but did not affect fruit color, fruit size, SSC, TA, pitting susceptibility, skin darkening, SB, or ML of 'Sweetheart' and 'Skeena' at harvest or following 4 weeks of storage at 0 degrees C. Positive effects of HBR on FF warrant greater evaluation.