The success of recent introductions of new apple scion cultivars in the U.S. provides clear evidence that both consumers and the industry are eager for genetic innovations with appealing new fruit quality characteristics. The spectacular commercial impact of ‘Honeycrisp’, developed by the University of Minnesota, is an exciting indicator of this opportunity.
However, developing and delivering a new apple cultivar is slow and inefficient, often requiring more than 25 years. Apple breeders have a hard time predicting which individuals will serve as the best parents and face the daunting challenge of selecting winners from populations of thousands of seedlings after making their crosses.
To efficiently and rapidly deliver superior, commercially successful new cultivars, apple breeding programs need to implement new genetic technologies. Marker-Assisted Breeding (MAB), using DNA diagnostic information, is one such technology, applicable to selecting parents and their offspring for desirable fruit quality traits such as flavor, texture and color, disease resistances, or a range of important horticultural characteristics.
MAB can identify parental combinations that increase the probability of finding the most desirable offspring. Further, MAB ups the efficiency of selecting for target traits at the seedling stage, before plants even flower. This early screening reduces expenditures for planting, maintaining, and testing full-grown plants, an expensive and time-consuming proposition for apple. While this approach has been standard practice in many agronomic crops for years, it had not been applied to apple, or other important rosaceous crops like almond, blackberry, cherry, peach, pear, raspberry, rose and strawberry, until the RosBREED project.
“RosBREED: Enabling marker-assisted breeding in the Rosaceae” was funded by the USDA Specialty Crop Research Initiative. This project was dedicated to the genetic improvement of U.S. rosaceous crops by targeted applications of genomics knowledge and tools to accelerate and increase the efficiency and effectiveness of breeding programs. This multi-state, multi-institutional project focused on five rosaceous crops: apple, peach, strawberry, and sweet and tart cherry.
Within RosBREED, apple breeding programs in Minnesota, New York, and Washington evaluated important parents, their ancestors, and their offspring for a range of fruit quality traits. Evaluating these individuals across these three very different sites added to our understanding of key traits and their interrelationships, making it possible to more efficiently improve them genetically.
RosBREED scientists developed DNA tests to predict apple skin color, fruit firmness, crispness, juiciness, acidity, storability, and storage disorders. These new genetic tests now help identify parents with the greatest likelihood of transmitting favorable traits, as well as pinpointing the best seedlings for further testing. All this reduces the effort and expense of growing out and sorting through thousands of seedlings with unacceptable fruit quality.
Apple breeders can now develop superior cultivars that meet the needs and desires of consumers and producers more efficiently, accurately, and creatively. The impact is already being realized:
- Participating apple breeding programs have applied MAB to choose better parents to create more useful offspring since 2011.
- Over 14,000 seedlings were discarded in 2011 to 2013, prior to field planting, after DNA screening predicted they would have inferior fruit quality or disease susceptibility, thus avoiding resource expenses totaling over $200,000.
- Three graduate students in RosBREED apple breeding programs have received state-of-the-art education in DNA-informed plant breeding.