Variability in Sweet Cherry Fruit Quality Is Related to Day of Anthesis

The high fruit-to-leaf area ratios and yields possible in modern, high-density sweet cherry orchards based on size-controlling rootstocks make thinning a necessity in most years.  While there are no commercially proven thinning programs for sweet cherry, research is investigating blossom thinning with caustics, as in other tree fruit crops.  In other tree fruit crops, early thinning is optimal, with the best results from thinning before or during bloom.  Towards developing precision thinning strategies we initiated research to identify the relationship between timing of flowering and fruit quality potential.  During the 2009 season, individual flowers of 2 replicate limbs of ‘Bing’ and ‘Chelan’ cultivars, and 3 replicate limbs of ‘Attika’ were labeled on their date of opening.  In total, 2,599 flowers were labeled.  From these flowers, 488 fruit were set, a yield of 18.8 %.  Within each cultivar, all fruit were harvested on the same day and analyzed individually for standard quality parameters.  ‘Bing’ bloomed over 13 days.  Flowers that bloomed on the first, 7^th, and 13^th days yielded  fruit with a mean weight of 9.44 ± 0.83 g, 7.02 ± 0.71 g, and 5.30 ± 0.90 g, respectively.  ‘Attika’ also bloomed over 13 days.  Flowers that bloomed on the first day produced fruit with a mean weight of 9.53 ± 0.63 g.  The smallest fruit were produced by flowers blooming on the 11^th day, producing fruit weighing 7.60 ± 0.93 g.  ‘Chelan’ had the shortest bloom period of the three cultivars, lasting only 10 days.  Flowers that bloomed on the first day produced fruit with a mean weight of 6.58 ± 1.17 g.  Flowers from the 7^th day of bloom produced the smallest fruit for this cultivar with a mean weight of 4.68 ± 1.06 g. For each cultivar, we recorded significant differences in key fruit quality attributes related to flowering date.  This research shows that on unthinned trees, there is greater fruit quality potential in the earliest opening flowers.  Current research is investigating the role of crop density on the relationship between time of anthesis and quality potential.