Good Fruit Grower

May 1

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Fruit drop is not simple to manage ROOTSTOCK – VARIETIES – POLLINATION Quality from the Start APPLES Aztec Fuji® (DT2 variety) Blondee® Brookfield® Gala Buckeye® Gala Cameo® brand Granny Smith Honeycrisp Joburn Braeburn™ JonaStar® Jonagold Kumeu Crimson® LindaMac® It® Red Delicious POLLENIZERS Indian Summer Manchurian CHERRIES Attika® Benton™ Bing Redcort® Ruby Jon® Ruby Mac™ Mariri Red™ Braeburn Morning Mist™ Early Fuji Smoothee® Golden Spartan Morren's® Jonagored Supra™ Mt. Blanc Ultima™ Gala Zestar!® S Mt. Evereste EbonyPearl™ BlackPearl™ Kootenay™ BurgundyPearl™ Lapins Chelan™ PEARS Bartlett Pearleaf Snowdrift Early Robin® Rainier RadiancePearl™ Hudson Regina Sam Selah™ Columbia Red Anjou™ Forelle Concorde™ Comice PEACHES Allstar Autumnstar® Blazingstar Golden Russet Bosc® Blushingstar Glowingstar Brightstar™ Redhaven Coral Star Redstar Earlystar™ Elberta Red Clapp's Favorite Red Sensation Bartlett Seckel Risingstar Starfire Flamin' Fury® Series PF-19-007 PF-7 PF-24-007 PF-17 PF-35-007 PF-25 PF Lucky 13 Varieties listed may not reflect current inventory. REPRESENTATIVES Leonard Aubert Jim Adams Hood River, Oregon Washington State (541) 308-6008 (509) 670-7879 Larry Traubel Rick Turton Cedaredge, Colorado Kelowna, B.C. (970) 856-3424 (250) 860-3805 Rey Allred Payson, Utah Montmorency D'Anjou Pinedale Ruby™ Rainier Skeena™ Sweetheart Tieton® Van White Gold Thinning in spring and stopping preharvest drop are two sides of the same coin. by Richard Lehnert cientists have made great progress in recent years homing in on answers to mysteries surrounding why apples fall off trees—so they can help growers make more do it when there are too many on the trees in the spring or to stop them from doing it before harvest. One leading figure in this work is Dr. Steve McArtney, a North Carolina State University horticulturist who is the South- east Apple Specialist for that university working jointly with University of Georgia, Clemson University in South Carolina, and the University of Tennessee. He spoke at several state horticultural shows this winter, including those in Michigan and New York. "Every apple grower knows that warmer temperatures and, in some cases, cloudy weather during the thinning period can increase the activity of a chemical thinner," McArtney said. "But have you ever wondered about the processes occurring in an apple tree under those conditions that ultimately result in increased thinner activity? Why is it that an application of NAA soon after bloom will cause the fruit to drop, but application of the same material just before harvest will have the exact opposite effect, causing the fruit to stick?" During the Great Lakes Fruit, Vegetable, and Farm Market Expo in Grand Rapids, Michigan, in December, McArtney recog- nized the work of his colleague Dr. Rongcai Yuan, who died of cancer in April of 2010, only 45 years old. Born in China and with a doctorate from University of Massachusetts, Yuan directed a lab and graduate students at the Alson H. Smith, Jr., Agricultural Research and Extension Center in Winchester, Virginia. Dr. Rongcai Yuan made important contributions to understanding fruit abscission processes. He died a year ago of cancer at age 45. Molecular techniques McArtney said that Yuan was the first to use molecular techniques to quantify how treatments with the chemicals NAA (napthaleneacetic acid), ReTain (aminoethoxyvinyl- glycine), and 1-MCP (1-methylcyclopropene), and shading alter the expression of genes controlling natural fruit drop. "This approach identified changes in the expression of more than 700 genes, many of (801) 465-2321 Larry Lutz Nova Scotia Ephrata, Washington | WILLOW DRIVE NURSERY, INC. 1-888-54-TREES 26 MAY 1, 2012 GOOD FRUIT GROWER which are involved in regulation of photosynthesis, carbohydrate metabolism and transport, auxin transport, and ethylene biosynthesis," he said. Yuan was the first to observe that when NAA and ReTain are combined to stop pre - (902) 680-5027 harvest drop, the rate of ReTain, a costlier chemical, can be cut in half. McArtney has confirmed, and recommends, the best treatment for maintaining fruit firmness while delaying harvest dates of up to three weeks on spur Red Delicious is a half rate of ReTain plus 20 parts per million NAA. Full rates of both can delay harvest four weeks. Yuan and his graduate student Hong Zhu also worked with fruit thinning. They found the chemical NAA works in much the same way as shading (as on cloudy days). "Shading and NAA result in remarkably similar changes in carbohydrate and hormone metabolism," McArtney said. "Dr. Yuan's research into the mechanisms responsible for fruit drop in apple reveal a close relationship between carbohydrates, various plant hormones, and enzymes responsible for cell wall breakdown in the fruit cortex and fruit abscission zone. The con- tributions he made in this area of research are significant and will provide insight and direction for those of us who are trying to manage the fruit drop process for years to come," he added. • Photo by steve mcartney

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