Effects of Preharvest Applications of 1-Methylcyclopropene on Fruit Firmness in Southern Highbush Blueberry

Fruit firmness was evaluated in southern highbush blueberry (Vaccinium corymbosum L.) cultivars after preharvest treatments with sprayable 1-methylcyclopropene (1-MCP). Two cultivars, 'Star' and 'Sweetcrisp', were sprayed with 1-MCP at a rate of 160 mg/L at five or nine days prior to harvest. Treatments were applied as a split plot cultivar x treatment design with three blocks. Berries were harvested when fully blue and measured for firmness using a Bioworks FirmTech II firmness tester (Bioworks, Inc., Wamego, KS). There were significant differences in firmness for both cultivars and treatments (P<0.05) but not for the cultivar x treatment interaction (P=0.089). For all treatments, 'Sweetcrisp' fruit were significantly firmer than 'Star' fruit. The untreated control was not significantly different from the nine day preharvest 1-MCP treatment (P=0.808), and the two preharvest 1-MCP treatments were not statistically different from one another (P=0.058), but the untreated control had firmer berries than the five day preharvest 1-MCP treatment (P=0.011). Postharvest application of 1-MCP is commonly used to inhibit ethylene production and ripening and thus maintain firmness in other climacteric fruits such as apple, but has recently been found to increase ethylene production and fruit softening in rabbiteye (Vaccinium virgatum Aiton) blueberry. The results of this study suggest that 1-MCP application five days prior to harvest may decrease postharvest fruit firmness of southern highbush blueberries.