Trends in sweet cherry breeding
This is the first in a series of articles compiled by Lynn Long of Oregon State University Extension from research presented at an International Society for Horticultural Science cherry symposium which he attended in Turkey in 2005.
Public and private cherry breeding programs exist in a large number of Old World countries, including Denmark, the United Kingdom, the Czech Republic, Romania, Estonia, and the Ukraine in Europe, and Japan and China in Asia. Research presenters Drs. Silviero Sansavini and Stefano Lugli of the University of Bologna, Bologna, Italy, mentioned the importance of the cherry breeding programs in North America—especially Summerland, British Columbia, Canada—as an impetus to cultivar innovation.
In the last decade, 120 new varieties have been released by breeders from Europe and Asia. Most of these varieties have one or more outstanding traits that make them noteworthy.
In the last decade, average fruit size has improved from 6 to 8 grams to 9 to 12 grams, and flesh firmness has greatly improved with the elimination of softer varieties as new, firmer varieties have taken their place. Over this period of time, color has also changed, with European breeders releasing varieties that are deeper red verging almost on black. Examples familiar to Pacific Northwest growers are Regina and Attika. Asian breeders are tending towards a bright pinkish-orange blush over a yellow background.
Due to relatively high rainfall in late spring and summer throughout much of Europe, resistance to cracking has been a high priority among breeders with several new varieties exhibiting a cracking rate of only 5 to 10 percent, even with heavy rains. Also notable has been the extension of the ripening window through the release of these new varieties. Ripening dates have been extended one week earlier and two to four weeks later than previously grown varieties.
Compact tree habit, once a high priority among breeders, has been relegated to a secondary pursuit due to irradiation-induced problems such as fruit size and yield reduction, but also because the success of dwarfing rootstocks has decreased the need to manipulate scion size. Similarly, breeding cherries that are resistant to the most important pests and pathogens, such as cherry fruit fly and bacterial canker, has seen little progress.
Despite the great abundance of new releases, especially from Europe, few of these have made their way to the United States. The exceptions, as already mentioned, are Regina and Attika. Others that may be of interest to Pacific Northwest growers include Techlovan from the Czech Republic and Alex from Hungary. Although these varieties are in the United States, several years of evaluation will need to be conducted to determine the potential of these two cultivars for U.S. growers.