Effect of brassinosteroids on cherry maturation, firmness and fruit quality

28-Homobrassinolide was applied to early and mid-season maturing cultivars of sweet cherries at the beginning of fruit color change (translucent green to straw) to evaluate effects on maturation time, fruit firmness and other quality parameters. Trials with early season 'Tulare' cherry in Fresno, California, showed that HBR decreased the maturation period based on fruit color and soluble solids, and that treatment with 0.4 and 2 ppm HBR showed a significant increase in stem removal force compared to both the untreated control and the standard gibberellic acid (GA₃) treatment. Trials with 'Tulare' in Madera, California similarly showed that HBR treatment made cherries mature earlier as well as increase stem removal force and fruit firmness compared to the control. Trials in mid-season 'Bing' cherry in Orland, California, showed HBR treatments of 0.4 and 8 ppm advanced cherry maturity and harvest. All applications appeared to increase cherry quality with respect to color parameters and firmness. Trials with 'Bing' cherry in Salem, Oregon showed that 0.4 ppm HBR treatment increased the quality of cherries. HBR treatment with 1, 2, and 8 ppm decreased maturation time as well as possibly increased fruit compared to the control and GA₃ treatment. Trials in mid-season cherries at Oregon State University showed that 0.4 ppm HBR treatment increased cherry quality based on color and firmness in 'Rainier' cherry and that treatment with HBR plus GA₃ increased firmness compared to control without the loss of color associated with treatment of GA₃ alone in 'Rainier' and 'Bing' cherries. No phytotoxicity was observed in any of these studies. A slight increase in 'Lapins' cherry firmness can be seen from application of HBR for both single and two separate 0.4 ppm applications.