Good Fruit Grower

July 1

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Grapes grape rootstocks The new Matador, Minotaur, and Kingfisher rootstocks are resistant to aggressive strains of root-knot nematodes. by Melissa Hansen ith the first three root-knot nematode-resistant root- stocks for grapes recently released by the U.S. Depart- ment of Agriculture, grape geneticist Dr. Peter Cousins is concentrating on the next round of resistant rootstocks to give growers options in matching rootstocks to vigor needs. Root-knot nematodes (Meloidognyne spp.) are the primary nematode pest of vineyards across the country and cause more than $1 billion in damage annually, according to Cousins, who's based at USDA's Grape Genetics Research Unit housed in Cornell University's Geneva, New York, experiment station. NEMATODE- RESISTANT Selection PC0458-26 shows promise in the ARS rootstock breeding program led by Peter Cousins. In Washington State, both root-knot and dagger nematodes are the main nematode concerns, but across the country, more acres of U.S. vineyards have root-knot nematodes as the primary root pest than any other root pest, including phylloxera, Cousins said. Vines infested by the microscopic worms yield less and are less efficient at taking up nutrients and water from the soil. His rootstock research currently only screens for root-knot nematodes because of funding and time limitations. Cousins can't say one way or another if the new rootstocks are resistant to dagger or other species of nematodes because they haven't been tested. The need for improved grape rootstocks became apparent in the 1990s after phylloxera, a tiny aphid-like insect that feeds on grape roots, infested vineyards in Napa Valley and other California grape-growing regions. Widely planted rootstocks developed in the 1960s and 1970s were less resistant to phylloxera than expected, and thousands of vine- yard acres had to be removed. Several phylloxera-resistant rootstocks have since been developed. Cousins said that with several phylloxera-resistant rootstocks avail- Bags & Buckets Cherry Bucket 89000 / 89200 Harvest Equipment Picking Bucket 7P104 / 7P105 5250 Amigo Citrus Bag 73500 FC-100 Cordura Bag 73187 / 73393 Padded Bag 73250 able, the priority has shifted to nematode resistance. "Finding root-knot nematode resistance is now the utmost priority of USDA's grape rootstock improvement program." Nematodes have developed into a big problem since growers lost Nemacur (fenamiphos) in 2007 when Bayer Corporation voluntarily pulled its U.S. registration because of association with bird kills. Without Nemacur, grape growers no longer have an effective nematicide for already-established vineyards and only have a few somewhat effective preplant materials. Before the recent USDA releases, a few rootstocks offered root-knot resistance, though not against virulent nematode populations, and they were faulted for other problems, including insufficient phylloxera resist- ance, sensitivity to other pests and diseases, or difficulty of propagation. "But growers are in a much better position now than they were 20 years ago," Cousins said in a phone interview with the Good Fruit Grower. Most Washington grape growers do not use rootstocks, preferring to plant own-rooted material because vines can easily be retrained in the event of winter damage. However, there may be more interest in rootstocks from growers in the future as pest- and disease-resistant rootstocks are developed. New releases The three improved root-knot–resistant rootstocks released in 2010 by Manufactured by Superior Fruit Equipment Also available in cotton Email Web For the dealer nearest you, call us at (509) 662-6065. Wells & Wade Harvest Equipment "When You Want The Best For Your Fruit" 30 JULY 2012 GOOD FRUIT GROWER USDA's Agricultural Research Service are named Matador, Minotaur, and Kingfisher. Matador and Minotaur are full sibling rootstocks, resulting from the hybridization of the 101-14 Mgt rootstock and the 3-1A root- stock selection (a cross of Vitis mustangensis andV. rupestris). Kingfisher came from a cross of the Vitis hybrid rootstock selection 4-12A (V. x champiniiDog Ridge and V. rufotomentosa) with V. riparia. All three have better root-knot resistance than Freedom and Harmony rootstocks and are available from the Foundation Plant Services at the University of California, Davis. Cousins, who joined USDA's research station at Cornell University in 1999, is now part of the Grape Genetics Research Unit at Geneva estab- lished in 2005. The grape genetics unit is part of the National Plant Germplasm System that preserves and safeguards grapes, apples, tart cherries, and vegetables. Access to the germplasm is an essential tool for the breeding of new rootstocks. Through the years, Cousins and his team have screened more than 10,000 rootstock seedlings in their search for nematode resistance. photo by peter cousins, usda

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