Issue link: https://read.dmtmag.com/i/45659
approved for planting by several U.S. government agen- cies, growers haven't planted it since, up to now, plum pox virus has not spread in the United States. Scorza is particularly concerned about the California dried plum industry. It produces 99 percent of America's dried plums and 60 percent of all the dried plums in the world. Yet the industry is based on one cultivar, Improved French, making it vulnerable to disease and pest outbreaks. Should plum pox ever come to America and not be contained by quarantine and eradication of infected trees—as was done in Pennsylvania, Michigan, and New York—the industry might need to turn to HoneySweet as a parent for new resistant cultivars. Scorza believes the variety he created would be called on in such an emergency. Meanwhile, the Kearneysville scientists are using Fas- Track to improve trait quality for the California dried plum industry. They are working on a five-year project that started in September 2009, collaborating with Uni- versity of California pomologist and extension specialist Theodore DeJong. According to information on the university's Web site, Horticulturist Ralph Scorza pollinates plum flowers while geneticist Ann Callahan measures sugar content and molecular biologist Chris Dardick measures fruit size. FasTrack allows scientists to pollinate flowers and evaluate fruit from the same plants in the greenhouse year round. tree and inserted into the plum cultivar BlueByrd. Srini- vasan produced 196 transgenic plum plants that are bushlike shrubs that produce flowers continually, like tomatoes. Flowers and fruit at various stages of maturity are on the bush at the same time, often in the first year. "In our breeding work now, we are tied to a season," Scorza said. "We work like crazy in a short window in spring to make our crosses, and then hope frost doesn't wipe them out. Then we plant the seeds and wait three to six years to see the fruit. "With trees that are always flowering, we can make crosses any time. We never have to stop. It just makes it go so much faster." The plants are being grown in green- houses, so work can go on year round. These plants also do not require a dormant, or chilling, period. The transgenic trees can be crossed with normal trees that have disease resistance, sweetness, and other desir- able fruit quality traits. But the trees will bear mature fruit in one year, allowing early evaluation of fruit quality. The transgenic plants are themselves not suitable for orchard production—although they might be of interest to growers using high tunnels, to home gardeners, to growers in the tropics, or to people growing houseplants. In the final step of the breeding process, the trees that will be selected for use as commercial cultivars won't carry the ECF gene, will flower normally, and will be no different than trees produced by traditional breeding processes. Greater speed FasTrack, Scorza said, meshes well with other new breeding tools. By identifying molecular markers, for example, breeders can determine whether plants carry desirable traits without waiting for fruit to develop. Those that don't can be weeded out early, reducing the amount of space devoted to seedlings in test plantings. But the fruit still has to be tasted—the proof of the pudding. Without FasTrack, after using markers, it still takes three to six years to see fruit, compared with one year for FasTrack. Scorza sees lots of reasons why speed is important in plant breeding. He believes the American stone fruit industry is vulnerable, especially to plum pox, which has devastated the industry in Europe. More and more, there are threats from invasive diseases and insects, for which we have no defense, and climate change is also putting stress on existing fruit varieties, he said. "We can't wait 20 or 30 years," he said. www.goodfruit.com Scorza developed the plum variety HoneySweet, which is immune to plum pox, but it contains a gene from the plum pox virus itself that was introduced using genetic engineering techniques. While it has been "more than 10 different lines of plum tree have set fruit within the first 14 months of growth. These trees are con- tinually flowering, and several rounds of pollination have produced fruits at different stages of maturity—with flow- ers, immature fruit, and mature fruit on the same plant." Dr. Albert Abbott, who works with molecular markers at Clemson University, is part of the project, as is Dr. Jayson Harper, an agricultural economist at Penn State. • GOOD FRUIT GROWER NOVEMBER 2011 39 stephen ausmus