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New cherry variety PC7903-2 will be released this year. Photo courtesy of Lynn Long, OSU

New cherry variety PC7903-2 will be released this year. Photo courtesy of Lynn Long, OSU

Cherry growers around the world are planting new varieties—a decision made more difficult with the increasing number of choices. Growers in the Pacific Northwest are predominantly planting new selections from breeding programs based in Canada, Germany, and Washington State University.

The WSU breeding program has the greatest number of varieties in commercial production in the Northwest and plans to release three more selections this year.

From about three decades of breeding, more than ten varieties have already been made available commercially. These include Cashmere, Chelan, Index, Tieton, Benton, and Selah—each a hybrid developed by Dr. Tom Toyama. This program has, since 2004, been active again after about a 20-year hiatus with funding from the Washington Tree Fruit Research Commission and Oregon Sweet Cherry Commission.

Chelan, the earliest-ripening variety from the WSU breeding program,was released by Dr. Ed Proebsting in the early 1990s. It is typically harvested 10 to 12 days before Bing or Van. Chelan belongs to pollen compatibility group III and blooms 2 to 4 days before Bing. Compatible pollinizers with good overlap of bloom with Chelan in Prosser, where the program is based, are Lapins, Index, and Black Tartarian. Chelan fruit have excellent firmness and are moderate size, averaging 24 to 26 mm diameter (8 to 10 g). To achieve good fruit size, aggressive dormant pruning is recommended due to the productive and precocious nature of the variety. Chelan produces well on Mazzard rootstock but shows incompatibility on Mahaleb. Chelan demonstrates good rain-cracking resistance and also exhibits excellent resistance to powdery mildew infection to the foliage. This variety has become well accepted among the official buyers who purchase fruit for supermarket chains. However, the flavor tends to be very mild, and in a consumer taste trial conducted by Oregon State University scientists, Chelan was last among five early to midseason varieties in overall consumer acceptance (Figure 1).

Tieton is a premium quality dark sweet cherry that ripens 6 to 9 days before Bing and produces a very large and attractive cherry averaging 28 to 31 mm in size. Fruit firmness is excellent, but rain-cracking potential is high, similar to Bing. The tree is unproductive on seedling rootstocks and recommended to be grown on a dwarfing, productive rootstock such as Gisela 5. Tieton is self-sterile and sets good crops with Bing as a pollinizer. A high pollinizer density is recommended to set good crops of Tieton (10 percent is often insufficient). As with Chelan, the flavor is mild, and Tieton was ranked fourth out of five by consumers (Figure 1).

Two recent WSU introductions, Benton and Selah, have also caught the interest of growers. Benton is a midseason cherry (harvested 1 to 3 days before Bing) that produces moderately large (27 to 29 mm), very firm fruit that are less susceptible to rain-cracking than Bing. Bloom time is moderately late—approximately 4 to 5 days after Bing or Van—and the flowers are self-fertile. Benton has a very pleasant sweet/acid flavor that ranked second only to Bing in the consumer taste trial (Figure 1).

Selah ripens about 8 to 12 days after Bing, producing very large (28 to 31 mm) fruit that are very firm. The flowers are self-fertile, and the tree produces a moderate crop of fruit in loose clusters. The rain-cracking potential is similar to Bing.

New selections

The three new selections slated for release this year are:

—PC8007-2, an early season dark sweet cherry that ripens with, or just before Tieton. Fruit are slightly smaller than Tieton but have a better flavor and therefore, may be more readily accepted by consumers. This is a self-sterile variety, but Bing is compatible as a pollinizer and should overlap bloom.

—PC7903-2, which ripens 3 to7 days after Bing and produces a very large and very firm cherry. Both soluble solids (sugars) and acidity are very high in this cherry. It is self-sterile and blooms midseason. Bing is a compatible pollinizer.

—PC7147-9, a self-fertile, dark, sweet cherry of moderate productivity that ripens about two weeks after Bing, around the time of Lapins. It also produces fruit that is very firm and large. It blooms late—three to four days after Bing and is self-fertile.

Revived

These are likely to be the last releases of the Toyama-bred dark sweet cherries from the WSU program. Importantly, the next generation of sweet cherries for the Northwest industry is under development, as the revived sweet cherry breeding and genetics program at WSU-Prosser has two crossing seasons complete.

The goals of the new program are to develop a full-season series of cherries that exceed current varieties for a range of characteristics. Targeted traits of the program include self-fertility, large size, excellent flavor, high firmness, and resistance to rain-cracking and powdery mildew.

Another important goal of the program is developing and utilizing genetic tools to improve its efficiency (e.g., marker-assisted selection to eliminate small-fruited selections in year 1 rather than year 5).

Flavor

Fruit flavor is often a low-ranked criterion of sweet cherry breeding programs (probably because it is a subjective characteristic, and, therefore, difficult to evaluate). However, much can be learned from other tree fruit industries where fruit size and color became the most important selection criteria and flavor was nearly ignored.

With increased planting and production of sweet cherry worldwide, producers will need to offer varieties that provide consumers with a positive eating experience throughout the season, thereby encouraging repeat buying. Research shows that if a consumer is displeased with a cherry product, they will not make a second purchase for six weeks.

To this end, consumer acceptance of current sweet cherry fruit produced in the Northwest was evaluated in 2005. Consumer response to five early to midseason (Figure 1) and five mid- to late-season varieties (Figure 2) was evaluated. Santina, one of the early cherries, came from the Canadian cherry- breeding program in British Columbia, as did the late varieties Lapins, Skeena, and Sweetheart. The German-bred Regina is rapidly gaining popularity among Oregon growers, mainly because of its large size, resistance to cracking, and ability to produce blemish-free fruit.

Figure 1 suggests that there may be need for more flavorful cherries in the early season, one to two weeks before Bing. In this early to midseason trial, Bing and Benton both ranked very high among consumers for sweetness and tartness, while Chelan, Santina, and Tieton ranked very low for one or both of these components.

All of the tested cherries in the mid- to late-season trial seemed to be acceptable to consumers. Once again, however, the two varieties ranking highest in sweetness and tartness, Bing and Sweetheart, were ranked number one and number two. From this trial, it is clear that the Pacific Northwest consumer prefers a cherry that has a strong balance between sweetness and tartness.