Within-plant variability in blueberry (Vaccinium corymbosum L.): maturity at harvest and position within the canopy influence fruit firmness at harvest and postharvest

For blueberry, harvest readiness is based on skin color, with fruit being considered ready to pick when the berry skin reaches 100% blue coverage. The extended bloom period for the blueberry inflorescence and uneven developmental rates can yield fully blue fruit that are widely different in physiological maturity, at any given harvest date. The objective of this study was to determine the inherent variability in the firmness of a synchronized cohort of blueberry fruit and the effects of harvest delay and position within the canopy on fruit characteristics at harvest and after refrigerated storage. During two consecutive seasons, the harvest canopy of 'Duke' and 'Brigitta' was divided into two regions as east (E) and west (W) sides. Fruit of a specific developmental stage from each side were either harvested when reaching 100% blue coverage (ripe fruit: B100) or allowed to stay on the plant for six additional days (over-ripe fruit: B100+6). Despite the narrow period of time elapsed between harvests of ripe and over-ripe fruit, variation in firmness was extensive, with decreases up to 24%, depending on year and cultivar. The six days of additional development were enough to increase the amount of soft and very soft fruit at harvest and after storage, demonstrating the importance of frequent harvests to improve firmness at final destinations. Both the percentage of blue fruit at each harvest date and total fruit produced were higher on the E side of the plant. Year-to-year variation in firmness exceeded that caused by the imposed treatment, which highlights the need to understand the environmental factors contributing to fruit softening. This is the first report on in-plant fruit variability for blueberry and its effect on postharvest performance.