Summerland cherry breeder Dr. Cheryl Hampson’s objective is to develop cherries that are large, firm, and sweet, have good stems, and are productive.

For the past 50 years, the focus of the program has been on developing self-fertile varieties. Hampson still prefers new varieties to be self-fertile, but if a cultivar has other great attributes, it’s not essential, she says.

“If we continue to adopt dwarfing rootstocks, the non-self-fertile varieties can be quite productive on those rootstocks.”

Whereas self-fertile varieties on some of the smaller rootstocks can overcrop and produce small fruit, the non-self-fertile varieties might be a good fit.

“I feel nervous about throwing away everything that’s not self-fertile because in ten years we might want that,” she said.

Early varieties

The cherry breeding program, which is based at the Pacific Agri-Food Research Center, began in 1936 with the goal of developing cherries with the characteristics of Bing or Lambert that matured earlier, were more resistant to rain cracking, and could be used as pollinizers for those cultivars.

However, the program has produced more late-­maturing cherries than early ones.

Dr. David Lane, breeder from 1974 to 1994, said early-maturing cherries have fewer days on the tree to grow and accumulate carbohydrates, and it proved very difficult to develop early cherry varieties that had high production and fruit quality comparable with later varieties.

To date, the program has released 35 cherry cultivars. Some, such as Lapins, Sweetheart, and Skeena, are widely grown. Not all have been commercial successes, however.

Frank Kappel, breeder from 1994 to 2011, said it’s hard to tell before they are released how well they will perform when grown in larger quantities and run across packing lines. “You don’t get a good feel for that at the breeding program,” he said.

One of the reasons that the Lapins cherry caught on was the willingness of a group of Canadian growers to plant it and work with it.

“I think part of the success of the program has always been that we’ve had innovative growers here who’ve taken these varieties and run with them,” he said. “It was a ­combination of the varieties and these innovative ­growers that saw the potential.”

Lynn Long, Oregon State University Extension educator based in The Dalles, said the program’s cherries have been extremely important to growers in the Northwest who, previously, focused on one variety—Bing.

“It was really the success of the Canadian growers with Lapins that gave people in Oregon, and I think also in Washington, the confidence to plant another variety besides Bing,” he said. “The fact that we were travelling and seeing that growers in other parts of the world, like Spain and Germany, were also using these cherries just reinforced in the minds of the Northwest growers that this was a good step to take.”

Mildew resistance

While Kappel was breeder, the program began looking at incorporating powdery mildew resistance and has been working with Dr. Paul Wiersma, a molecular biologist at Summerland, to develop genetic markers for the trait. Hampson said the emphasis is on finding resistance in late-maturing varieties, which are the most vulnerable to the disease.

Her sources of resistance are not the same as used by Washington State University’s breeding program. Hampson is using the resistant Hedelfingen and Moreau cherries as parents for crosses.

She’s been evaluating a cross of Lapins and Moreau that has mildew resistance, but when it began to fruit, it was too sour and soft to be a commercial variety. The next step is to backcross it with a variety that has good fruit quality, but that’s going to take time.

“The cherry generation time is not short,” she noted.

The more characteristics desired in a cherry—for example, good fruit quality, self-fertility, and disease resistance—the lower the chances of finding it. That means sorting through so many more seedlings to identify promising selections.

“It does raise the bar,” Hampson said.

In fact, Lane says not having to take disease resistance into account has been one of the reasons for the success of the program in the past. The Pacific Northwest has far fewer concerns with little cherry virus or pseudomonas, for example, than growing districts in eastern North America or Europe.

“If you have to deal primarily with resistance or tolerance to diseases, then you don’t have the flexibility to focus on large size and that sort of thing,” he said.

Hampson said she is not focusing exclusively on new late-season varieties because there’s been an upsurge of interest in early to midseason varieties. Larger growers, in particular, want an extended season to keep their workers busy and to keep their customers supplied over a longer period.

Lynn Long, Oregon State University Extension educator in The Dalles, agrees that self-fertility is no longer a necessity with the advent of the size-controlling Gisela and Krymsk rootstocks.

“There are other ways to get productivity besides self-fertile cherries,” he said, “Though it’s nice to have a self-fertile variety because you don’t have to worry about pollinizers, and in years when pollination weather is not what you hoped it would be, it gives you better potential for ­pollination.”

If varieties don’t have to be self-fertile, it might be easier to find new cherries with other important characteristics, said Long, who still sees a need for more new varieties.

“We have not found the perfect cherry yet,” he said. “There’s always some limitation. You’ve got cherries like Lapins and Sweetheart that are very productive, but they tend to pit. You have a cherry like Skeena that ships well, but is very sensitive to rain cracking. You have Regina that’s resistant to rain cracking but not very productive. There’s definitely room out there for finding better cherries.”