Pear breeding north of the border
Canada’s pear breeding program has three new fireblight-resistant pears in the pipeline.
Harovin Sundown (tested as HW614) originated from a cross of Bartlett and an unnamed U.S. selection made in 1972. The pear, which is larger than Bartlett, was named and released in 2008.
North America’s two public pear-breeding programs are not very far apart physically—less than 400 miles—but there’s an international border between them that has larger effects than the miles or kilometers would indicate.
“It makes it hard to exchange germplasm, that’s one effect,” said David Hunter.
But it doesn’t much impede the sharing of ideas. “When Richard and I get together, it’s an international meeting of the North American pear breeders,” Dr. Hunter said, jokingly.
Hunter is the pear breeder for Agriculture and Agri-Food Canada, working from his research station at Vineland, Ontario. From nearby Niagara Falls, it’s a straight shot south to Richard Bell’s program at USDA’s Appalachian Fruit Research Station at Kearneysville, West Virginia.
The two programs are quite similar.
Both are located on the moist and humid east side of countries where major pear production is on the arid west side. Between 40 and 50 percent of Canada’s pear production is in the Niagara Peninsula of Ontario, and more than half lies west in British Columbia. But when it comes to farm-gate value, Ontario wins hands down.
Both programs are focused on adding new varieties that will augment the very popular Bartlett while avoiding its problems. The desire is to find varieties with high fruit quality, like Bartlett, that taste similar but harvest earlier or later and store well.
Both are releasing new varieties now and will release more over the next few years. Many of them have spent 30 years or more in the breeding and evaluation process.
New varieties from either program, once they have passed virus-testing protocols in Prosser, Washington, or the Canadian Fruit Inspection Agency in British Columbia, can be sold to growers by nurseries in either country.
In 2008, Hunter released Harovin Sundown, a pear that took over 35 years to develop from a cross made in 1972. Its release was timely and was looked at as a rescue for Ontario pear growers who had just lost their processing market for Bartletts. The processor CanGro, the only processor east of the Rocky Mountains, closed its doors, affecting peach and pear producers in Ontario and western New York.
The goal was to give growers a larger pear that would sell well in fresh markets and at the same time be resistant to fireblight. Sundown pears size up better than Bartlett and produce more fruit. Some glitches have slowed down the commercialization process, so growers have not yet replanted with this new pear. But it’s still on track to become an alternative to Bartlett as more trees become available.
Meanwhile, Hunter has plunged ahead with his release program. In 2009, he applied for Canadian Plant Breeder’s Rights on HW623, an experimental variety that has garnered good reviews from evaluators. Two other new cultivars are going through the Plant Breeder’s Rights process this year. He’s working on the releases and the plant variety protection details. “I’m not at liberty to talk about them now,” he said.
All of the cultivars from Vineland have fireblight resistance at the level of Kieffer, Hunter said—all above 9 on the 10-point USDA scale. The highly susceptible Bartlett is rated 3 to 4.
Sundown rates about 9.3, Hunter said. That means in a fireblight-epidemic year, the tree might take a few strikes, but these seal off and don’t move down the tree. “It’s nothing to worry about,” Hunter said.
Compare that with what happened in one Clapp’s Favorite orchard in a bad fireblight year. “After waiting five years for the tree to come into production, we had blight at blossom time, and by the end of the year the trees were dead. The blight killed five-year-old trees to the ground in one year,” Hunter said.
Hunter took over the Canadian program in 1988, when it was located at Harrow on the north shore of Lake Erie, about 30 minutes southeast of Windsor, Ontario, and Detroit, Michigan. The program there started in the 1960s, and its mission was focused by the fireblight epidemic years in the early 1970s. In the mid-1990s, Hunter was called upon to develop a five-year plan to transfer it all to Vineland. Harrow is still home to the Canadian Clonal Gene Bank, but the breeding work in apples, pears, peaches, and small fruits is now at Vineland.
Harrow Sweet was introduced in the early 1980s. Since he took over the program, Hunter introduced AC Harrow Gold and AC Harrow Crisp in 2002, and then Harovin Sundown in 2008. The first name is a combination of Harrow and Vineland.
The new varieties he’s working on not only have high fireblight resistance and good fruit quality, but one of them is resistant also to pear psylla. Psylla causes some feeding damage on pears, but its major effects are in passing on pear decline disease and creating honeydew that drips onto fruit. Invading microorganisms produce a sooty black residue that greatly reduces fresh market value but leaves the fruit useful for processing.
Other qualities he looks for in pears include precocity, tree size, cold hardiness, and fruit storability.
Hunter said he makes 15 to 20 crosses per year. Each cross of about 200 flowers results in anywhere from 0 to 500 viable seeds, he said, depending on fertility and compatibility issues. But overall, he should have 2,000 or so unique seedlings to test each year.
They’re planted in the greenhouse, he said, and their first test is for fireblight resistance. They are inoculated with high levels of the disease. Seedlings that survive this screening test are planted in the field, and they then have a long juvenile phase—up to 10 years—followed by two to three years of fruiting and propagating tests, followed by more years of testing in the orchard.
Hunter’s research also focuses on orchard management strategies such as improved performance of rootstocks and training systems to meet industry requirements for smaller trees and high-density production for both fresh market and processing varieties.