Issue link: https://read.dmtmag.com/i/386317
12 OCTOBER 2014 GOOD FRUIT GROWER www.goodfruit.com tree fruit pathologist, a postdoctoral researcher was to be hired to do the disease management work, which will be a three-year project. The scientist, based at the Tree Fruit Research and Extension Center in Wenatchee, will also develop extension programs to disseminate results of the research and supporting work done by other scientists. Alternative pollinizers Dr. Stefano Musacchi, WSU horticulturist, and Karen Lewis, WSU extension specialist, are heading the alterna- tive pollinizer aspect of the research, which will be a five- year project. Manchurian was adopted as a pollinizer by Washington apple growers in the 1980s to provide cross-pollination in solid blocks of commercial apple varieties. This elim- inated the need to manage another commercial variety in high-density apple orchards and, as crab apples need little space to grow, they could be planted between the other trees. Manchurian was one of few crab apples that bloomed early enough to pollinate the earliest blooming commercial apples. It is estimated that Manchurian is planted in 60 to 75 percent of the state's commercial apple orchards at a rate of 5 to 10 percent of the total trees. Lewis and Musacchi got a head start on the project last spring when they visited nurseries around the country, including J. Frank Schmidt & Son Company in Boring, Oregon, which has a large collection of crab apple germ plasm. They bought some trees, which they're growing in pots in Wenatchee for evaluation. Any alternative to Manchurian would need to be com- patible with Washington's commercial apple varieties, be attractive to bees, and bloom annually. Lewis said they'll be looking for early, mid-season, and late-blooming crab apple trees to pollinate Washington's range of commer- cial varieties. WSU's WA 38, for example, is a late bloomer. They'll also need to look at pollen viability and pol- len-tube growth in the alternative crabs. The fertiliza- tion process begins after pollen is deposited on a flower stigma. Male gametes from the pollen are transported through a pollen tube that grows from the pollen grain down through the flower style to the ovary where the ovule is fertilized, resulting in fruit set. Research by Dr. Keith Yoder and Leon Combs at Virginia Tech suggests that Manchurian might not be the most efficient pol- linizer because of slow pollen tube growth. "We absolutely think there are more efficient polliniz- ers," Lewis said. Scientists at Virginia Tech are unable to work on the project, so Musacchi's research associate, Sara Serra, will go to Virginia Tech to learn how to do the pollen-tube growth work. "We'll build capacity in Washington," Lewis said. "In the long run, it's very exciting that we're going to be able to do that." Willett said that while the disease-control portion of the work is important to resolve the short-term problem, the efforts of Musacchi and Lewis will be extremely valu- able to Pacific Northwest apple growers in the future. • A Manchurian crab apple tree showing signs of twig dieback on the lower part of the trunk, a canker in the center, and black fruiting bodies on the upper part of the trunk. PHOTO COURTESY OF CHANG-LING XIAO