Grapevine leafroll disease (left; healthy vine at right) is one of several graft-transmissible viral diseases that reduces yield and quality. The New York State Grapevine Certification Program tests vines that are the source of budwood for nursery production at three New York nurseries, and certifies them as 'virus tested', greatly reducing introduction of virus-infected vines to new vineyards.
Photo by Marc Fuchs
By Margaret K. Kelly
Assistant Director – Division of Plant Industry
New York State Department of Agriculture & Markets
The New York State Department of Agriculture and Markets has revived its Grapevine Certification Program after a 40-year hiatus, and NY-certified vines derived from virus-tested, foundation plantings are now available from three New York nurseries. This revived (and improved) program has the most stringent testing protocol at the nursery level in North America, and its reintroduction is just the latest step in a process that started with the establishment of the National Clean Plant Network in the early 2000s.
New York’s three premier grapevine nurseries have worked diligently with the New York State Department of Agriculture and Markets, and Cornell University to bring back New York’s virus certification program. Back in the 1980s the Department had suspended the program due to staff cuts. Scientific technology has marched on in the passing decades. Today much of plant pathology diagnostics uses molecular methods that we just dreamed about in the 1980s. This is especially true with viruses and other systemic pathogens.
What is certification and why is it important?
Certification is a system of monitoring and testing plants for the presence of undesired viral pathogens in combination with isolation and plant maintenance criteria. Initially you start with a plant, in this case a grape scion (or rootstock) that has been tested and determined to be free of viruses of concern. This plant is then the source of vegetative propagation to produce a planting stock.
Certification is essential in these woody perennial crops like grapes and fruit trees where you are planting for a generation. Grapes are susceptible to viruses that can reduce the quantity and quality of the crop - and are passed on down the line during the process of propagation. Without continued testing to confirm that propagation wood is free of viruses of concern, growers get the desired variety but also get any undesired viruses that may be present.
Once even a few infected vines are planted, insect and dagger nematode vectors can feed on infected vines and spread the infection throughout the vineyard. A few infected vines, over several years, can turn into a lot of infected vines. (see Grapevine leafroll virus: an increasing problem in the Finger Lakes, US, and the world)
Historically vineyards were started with cuttings from the vineyard down the road. These woody cuttings are collected in the early winter when there are no leaves present. This also means there were no visual symptoms of viruses present. Vines would be cut and propagated with no warning of the lurking viruses. Even with leaves, viruses can be present with no symptoms showing. Over time, this has led to significant dissemination of viral infections to new plantings.
Woody indexing – the traditional testing technology
Before molecular technology was developed over the past twenty years, the way to determine if a virus was present would be test it on “an indicator plant.” This is a process known as biological indexing where a plant that readily shows symptoms, if infected with a given virus, is used to indicate its presence. These plants include Chenopodium quinoa and some grapes including the rootstock Vitis rupestris St. George and the hybrid LN33, among several others. This was an effective technique for determining if viruses were present and still is today, but it is terribly time consuming. You have to allow time for the virus to develop in the indicator plant and for the plant to exhibit disease symptoms. You have to allow time for the plant to grow. Not to mention you need staff and facilities to grow, maintain and monitor them.
New molecular testing methods have reduced costs and delays
Marching forward, grape growers and nurseries asked to have New York’s certification program be brought back. Having this conversation in the 2000s is very different as the new molecular technology affords new opportunity. This means working smarter and in turn faster. Today we are using laboratory methods such as ELISA (enzyme-linked immunosorbent assay) and PCR (polymerase chain reaction) techniques that provide results that are better than the time-consuming biological indexing. Testing takes hours or days, not years.
The New York State Certification Program
New York’s program is nursery-focused. Nurseries bring in foundation, virus-tested, clean budwood (scion) and cutting (rootstock) material (called “G1” material) from Foundation Plant Services at UC-Davis in Davis, CA or the Clean Plant Center-Northwest at the University of Washington in Prosser, WA. These two clean plant centers maintain foundation (G1) vines and are part of the National Clean Plant Network (NCPN). Cornell University in Geneva is also part of NCPN but there is no G1 foundation vineyard in New York. The G1 vines are the “cleanest” of the “clean”, and many are derived from tissue-cultured material that was produced after therapeutic treatments to eliminate existing viruses.
Given the limited availability of G1 virus-tested, clean vines, nurseries need to bulk up this material to produce the desired planting stocks and respond to the growers’ demands. This is done in increase vineyard blocks (referred to as “G2 blocks”). Once in the New York nursery, the growers maintain the increase vineyard blocks planted with the G1 material in isolation from grapes that are not certified – both cultivated and wild. These G2 vineyard sites were screened for dagger nematode levels prior to planting to minimize spread of viruses vectored by nematodes. Insect pests such as mealybugs and soft scale insects are managed since they can vector leafroll viruses, and G2 vines are grafted on nematode-tolerant rootstocks.
Sample collection for virus testing
Staff from the New York State Department of Agriculture and Markets collect leaf samples for regular ongoing testing so that an increase vineyard block (G2) at the nursery is continually monitored catching any virus introductions before they are disseminated via propagation to the planting stocks sold by the nursery. New York has established a system to test 25% of all vines in the mother block each year. In the course of four years 100% of the vines in the mother block will be tested. At the nursery level, this represents the most frequent testing program in North America.
Samples for testing are submitted to Dr. Marc Fuchs’ virology lab at Cornell AgriTech, in Geneva, NY. Leaves arrive with just a sample number so that no one in the lab knows where the vines originated. Some viruses of grape are more readily detected in the spring (tomato ringspot virus, tobacco ringspot virus and grapevine fanleaf virus) versus the fall when grapevine leafroll-associated viruses and grapevine red blotch virus are optimally detected. Table 1 shows a list of viruses that are tested for and the timing of sample collection. Because of distinct optimal times for testing, samples are taken twice per year – once in the spring and then again in the fall. An increase vineyard (G2) is the endowment, the treasure to be protected. We monitor and test these vines to know they do not have viruses.
Table 1. Grapevine viruses of significance in New York and their testing schedule
Removal of infected vines
If any vines are found to test positive for any of the viruses listed in Table 1 in a G2 increase vineyard, they are removed, along with vines adjacent to the infected vine. This reduces the likelihood that neighboring vines that are infected but not tested (or test negative shortly after infection) will be propagated and introduced to production blocks.
Nursery production blocks, which are derived from G2 material and the final step in delivering planting stocks to growers, are visually inspected and tested based on symptoms, as appropriate. In New York, these certified commercially available vines were propagated directly from G2 vines that are on a continual rotation of testing. Testing G2 vineyard blocks on this cycle puts testing close to the end product.
Grapevine red blotch virus, identified and found to be common in North America only in the mid 2010s, gave a lot of growers a crash course in viruses and the role of certification. In New York we were pleased to learn that we do not have the vector (three-cornered alfalfa hopper) of this virus present in vineyards in our state. As we all get more knowledgeable about viruses questions growers need answered include: How do you know these vines do not have viruses? When were these vines (or their sources) tested for viruses? What viruses were they tested for? Red blotch?
New York’s certification program is focused on the viruses that cause diseases of economic concern (Listed in Table 1). These viruses cause reduced Brix levels, reductions in yield and alterations of fruit juice chemistry. The New York State Department of Agriculture and Markets serves as an objective third party to monitor and sample vines in these G2 vineyard blocks for virus introductions. We have updated our regulations related to the voluntary testing of plants to be in line with the current technology and terminology.
This all costs money. The cost of the program is projected to be covered by a $0.50 charge to the nurseries – and the nurseries will have to cover the additional costs to them of maintaining the G2 increase vineyard blocks. But the extra cost will be worth it for growers.
At the end of the day the economics are clear – especially since Cornell Agricultural Economists Dr. Miguel Gomez and his graduate student at the time Dr. Shadi Atallah (now Associate Professor, University of Illinois-Urbana-Champaign) crunched the numbers for us. Their study concluded:
- uncontrolled grapevine leafroll disease on Cabernet franc vineyard in the Finger Lakes ranged from $10,000 to $17,000 per acre over 25 years (this was in 2012)
- Paying a premium of 25% for certified virus-tested planting material is financially rewarding, although it may not initially appear to be an attractive alternative.
The objective of New York’s Grapevine Certification Program is to make certified, good quality grapevines that are derived from New York-grown G2 virus-tested vines available to growers. New York nurseries are now offering those grapevines.
This represents the final step in a 14-year process since the establishment of the National Clean Plant Network to produce clean, virus-tested ‘G1’ vines, establish new ‘G2’ increase vineyard blocks at three New York nurseries, and finally to propagate and sell New York-certified vines to their customers.
Virus-tested Certification Program Participating Nurseries
Amberg Grapevines LLC
2399 Wheat Road
Clifton Springs, NY 14432
Double A Vineyards Inc.
10277 Christy Road
Fredonia, NY 14063
Hermann J. Wiemer Vineyard
3962 Route 14
Dundee, NY 14837
Margaret Kelly is assistant director of the Division of Plant Industry, New York State Department of Agriculture and Markets, based in Albany, NY.