Oregon State University scientists are hoping to find ways to improve fruit set and productivity in Regina cherries, a new sweet cherry variety with exceptional fruit quality.

Regina has been the focus of OSU research because of its potential as a fresh market cherry for Oregon growers in the Willamette Valley and The Dalles-Hood River cherry growing regions. The German variety is very large, resistant to rain cracking, and has export potential because it holds up well after three to four weeks of storage.

Data collected by OSU during the 2005 season, in what was considered a rain year, showed less than 5 percent cracking in Regina at the packing house, compared with 55 percent cracking in Bing.

While the late-season variety seems to have much going for it, low yields have been a problem.

Scientists suspect that the low yields are a result of pollination problems and are searching for more compatible pollinizers.

“Regina is called ‘lazy girl’ by Europeans because she doesn’t want to produce,” said Dr. Anita Azarenko, who heads the horticulture department at OSU and is looking for ways to increase its production.

Effective pollination

Azarenko explained that there are many factors that influence effective pollination period—longevity of the ovule, duration of the stigma being receptive, pollen tube growth, and fertility. “But it all boils down to how long do you have to get the ovule fertilized,” she said, adding that effective pollination periods in cherries range from one to two days to about a week. In Washington State, the average for Bing is from four to seven days.

With self-incompatible varieties, like Regina, Bing, Tieton, and others, growers must use pollinizers. When pollinizers are used, time of bloom, compatibility, and pollen viability become issues of importance. Many of the pollinizers that have been recommended for Regina have low viability.

Researchers are looking at the time of bloom and pollen viability of different pollinizers, as well as combinations of pollen, that would give more rapid pollen tube growth. They will also be looking at the duration of pollen tube growth, and placement or distance and density of pollinizers.

Research conducted at OSU by Dr. Roberto Nuñez-Elisea found that Regina productivity, as measured in pounds of fruit per tree, has a relationship to placement of the pollinizer. Productivity fell sharply beyond the second row of trees located next to the pollinizer row.

Some OSU Regina trials have yielded 80 pounds of fruit per tree, with large fruit size, demonstrating that the potential is there for Regina—provided viable, compatible pollen is available.

Azarenko suspects that several sources of pollen may be needed due to Regina’s protracted bloom period.