WSU Sweet Cherry Breeding Program
The goal of the WSU Sweet Cherry Breeding Program is to develop new high quality sweet cherry cultivars with high consumer appeal, suitable for growing in the Pacific Northwest region of the United States. The project has 6 main breeding objectives, each of which represents new cultivar targets, or ideotypes, for different market segments. The program has recently evolved into 3 phases. Phase 1 includes making crosses, planting own-rooted seedlings in the field and evaluating the fruit. Phase 2 includes replicated trials of grafted advanced selections on 3 locations, both on-station and on-farm in Washington and Oregon. Phase 3 contains replicated trials of elite selections on grower-cooperator orchards in Washington and Oregon prior to release. The genotypes in phases 2 and 3 represent potential new cultivars that fit into the desired target market segments. Of particular interest is the genotype in Phase 3, which belongs to the early ripening market class. This advanced selection has similar harvest timing to the current market leading cultivar in that category, i.e. ‘Chelan’. In addition, the fruit is larger and firmer than fruit from ‘Chelan’ without GA application and is also self-fruitful and may not require bees for pollination. In phase 2 there is an advanced selection that fits the target market category for mechanical harvesting. This genotype is later, firmer, and has a lower pedicel retention force than ‘Selah’, the current leading cultivar in that market class. Growers have indicated interest in testing this selection in planar training systems to assess yield potential and mechanical harvestitibility. DNA information is routinely used in the program to improve breeding efficiency and reduce costs. Genetic tests for self-fertility and fruit size ensure that only parents with a high probability of producing large fruited and self fruitful progenies are used in crosses. The tests also help to eliminate inferior seedlings so only seedlings that have favorable alleles for desired traits are planted in the field. The latest innovation in the program is the implementation of bar coding to improve accuracy of tree labeling and data recording in the laboratory. We are making progress towards establishing marker-locus-trait (MLT) associations for other traits including fruit firmness, soluble solids content, flesh/skin color, titratable acidity, pedicel retention force, bloom date, maturity date and powdery mildew resistance. These MLT tags will be deployed once very reliable, robust genetic tests are available.