by Sally Colby
Tim Martinson, senior extension associate at Cornell University, wants grape growers to be aware of the efforts made starting in the mid 2000s to improve the production and dissemination of virus-tested plant material to nurseries and producers throughout the United States.
Martinson, who has served as the director of the Northern Grapes Project and is involved with the National Clean Plant Network, says that the New York State Department of Agriculture and Markets is revitalizing its grapevine certification program. The program has been dormant since the early 1990s, but New York grapevine nurseries are investing in the effort to improve propagation practices.
“This renewed effort started with the National Clean Plant Network in the 2008 Farm Bill, which provided support and coordination of efforts of five grape clean plant centers across the United States,” said Martinson. “Plant material resulting from this effort is now making its way from foundation blocks to nursery.”
Martinson says that the problem is that there’s a long list of viruses that affect grapevines, some more serious than others. “Once the plant has a virus, there is no cure,” he said, “and they spread within the vineyard.”
These viruses arrived over time through propagation material. “Historically, in the grape industry, there’s a lot of self-propagation,” said Martinson. “Growers collected material from production and propagated their own vines. When nurseries came on later, they collected vines from customers, and continue to do that today.”
One factor that contributed to the problem is the way in which material is collected – when vines are dormant in winter. “If you have a block of mixed varieties or you come across a big vine with lots of wood, you collect a lot of wood from that,” said Martinson. “Chances are it’s bigger because it’s an off-type vine, so there have been problems with collections being true-to-type. And even if you see leaf symptoms during the growing season, you may not see them during the dormant season, so the only way to get around that is to mark the vines beforehand and avoid collecting from those that had symptoms, which generally wasn’t done.”
Martinson says that modern virus and vector identification started in the 1970s. “We had woody indexing and indicator plants before that,” he said, “but our ability to detect viruses started with ELISA tests (enzyme-linked immunosorbant assay) and has continued with DNA. Vectors weren’t always identified.”
The long history of grape production in the east foreshadowed the virus issue. From 1800s to the 1960s, native Labrusca types were dominant. Those grapes often carried the virus but showed no symptoms. From the 1940s through the 1970s, French hybrid varieties from various sources became popular. “Then the new hybrids from Cornell and other breeding programs were introduced,” said Martinson. “In the 1980s, widespread V. vinifera plantings in the east took hold.”
With each change in variety, there was more plant material from a wider area. In the 1970s, some of the issues associated with viral diseases became evident in the Finger Lakes region of New York. “One of the challenges of producing clean plants in the east is that we have such a wide range of variety from different species, unlike the western industry, which is mostly based on Vitis vinifera,” said Martinson. “We have all sorts of germplasm from all sorts of places, and that makes it a longer list of varieties and a wider range of genetics.”
Martinson says that the initial virus issues started in the 1970s in the newly popular French hybrids including Vidal blanc, Chelois, Baco Noir, DeChaunac and Ventura. He noted that most of these varieties are no longer grown. With a combination of market drop and diseased vineyards, the Finger Lake region lost about 2,000 acres of production over ten years.
The National Clean Plant Network (NCPN) is a national network of clean plant centers, scientists, regulators and educators from universities, departments of agriculture and the USDA with a focus on providing healthy planting stock to nurseries and growers. Participating crops include fruit trees, grapes, berries, hops, citrus, roses and sweet potatoes. Martinson says that the program is part of the 2008 Farm Bill, and is the first time the USDA has been involved in pathogen diagnosis and elimination in vegetative propagation of plants such as grapes.
NCPN grapes clean plant centers are located at Cornell, Florida A&M, Missouri State, UC Davis and Washington State Prosser. Martinson says that the system is a long-term investment by the federal government to produce a long-term benefit.
“When imported selections arrive at a clean plant center, they don’t know the phytosanitary status of the grapes,” said Martinson. “The first step is diagnostics, which involves lab work, DNA testing and woody indexing (grafting buds onto plants). This takes about two years. If they’re clean, they can be released to the next step, and if not, they go through virus elimination which involves meristem culture and takes a minimum of two years, and then retesting.”
From there, clean material goes to foundation service mother blocks where bud wood and cuttings are distributed. The process is lengthy, and it takes three to four years before there is sufficient bud wood to be distributed. Plant material is also mist-propagated in the greenhouse, which takes one year, which allows more vines to be established sooner. Plants are grafted, then planted in the field, and are in full production after two to four years. Each vine at full production can produce about 50, two to three bud cuttings for own-rooted vines.
Throughout the process, including the growing out phase, nursery mother blocks are closely monitored for signs of virus. Martinson noted that it’s a lengthy process to get plants from the initial stage to vineyard-ready. “It takes two to six years for diagnosis and therapy,” he said. “Six years if you need to generate a new plant and test it; then another three to five years in the mother block, three to four years for the nursery blocks, then to production. The full process, from import to commercial vineyard, is ten to seventeen years.”
Martinson says that although the process is time-consuming, grape growers will see more virus-free material available in the future. “There are a lot of benefits to the certification process,” he said. “Improved cleanliness of the planting material, improved fruit quality and yield and better productive lifespan of vineyards.”
Nurseries will have to make a significant investment to certify plant material, so growers can expect to pay more for vines. However, economic returns for the grower include reduced losses due to poor vine establishment, increased profitability; which should help growers avoid penalties for poor fruit quality associated with inferior fruit from infected vines.