2011 Research Report to the Michigan Grape & Wine Industry Council

Transcription

1 2011 Research Report to the Michigan Grape & Wine Industry Council Proposal Title: Diagnosis of grapevine virus diseases in Michigan vineyards. Principal Investigator: Name: Annemiek Schilder Mail Address: 105 CIPS, MSU Telephone: Fax: Original goals and objectives for the project: The original objectives for this project in 2011 were: 1) Identify causal agents of virus-like symptoms and grapevine decline in Michigan 2) Establish in-state DNA-based testing capability for grapevine virus and phytoplasma diseases. Literature Review: Virus diseases are widespread in vineyards throughout the world are among the more difficult to detect and identify. Plant viruses are mostly spread via vegetative propagation, although insect and nematode vectors are responsible for the spread of some grapevine viruses. Grapevine viruses can be unrecognized causes of low yields and poor plant growth as well as grapevine decline. Most virus diseases can only be accurately diagnosed by specialized laboratory testing, either via serological methods such as enzyme-linked immunosorbent assay (ELISA) or DNA sequencing (polymerase chain reaction- PCR). These tests are fairly expensive (for example $85-$250 per test, depending on how many viruses are included in the test). For grapevine viruses, most testing is done in specialized private laboratories in California, such as Agri-Analyis in Davis and Eurofins STA in Gilroy, CA. Some common grapevine viruses are grapevine fanleaf virus (GFLV), grapevine leafroll associated viruses (GLRaV-1 through -9), tomato ringspot virus (ToRSV), tobacco ringspot virus (TRSV), grapevine fleck virus (GFkV), grapevine virus A (GVA), grapevine virus B (GVB), Arabis mosaic virus (ArMV), and peach rosette mosaic virus (PRMV), the latter particularly in Michigan juice grapes. Recent surveys in other states have found that several viruses are widespread in grapevines there. For instance, Mekuria et al. (2009a, 2009b) found that grapevine leafroll disease is a significant constraint to sustainable growth of the wine grape industry in Washington state. In a 3-year survey, they detected grapevine leafroll-associated virus (GLRaV) -1, -2, -3, -4, -5, and -9 in different wine grape varieties showing grape leafroll symptoms. Mixed infections of these viruses in different combinations were frequently detected in individual grapevines. GLRaV-3 was most prevalent. The results also revealed the presence of rupestris stem pitting-associated virus, grapevine Virus A, grapevine Virus B, grapevine fanleaf virus and grapevine fleck virus as mixed infections with GLRaVs. A similar survey by Martin et al. (2005) also found Rupestris stem pitting associated virus (RSPaV) and GLRaV-1, -2, and -3 in Washington and GLRaV-1, -2, and -3 in Oregon. When vineyards in the Finger Lakes region of New York were tested, GLRaV-1, -2, and 3 were found in nearly two-thirds of the vineyard blocks (Fuchs et al. 2009). Researchers also found a variety of viruses in surveys of grapevines in Missouri, such as ToRSV, ArMV, GFkV, GVA, 1

2 GLRaV-1 and GLRaV-3 (Milkus et al. 1999; Milkus, 2001). Some French hybrids and American cultivars were 100% infected with GLRaV-3. No formal virus survey had been conducted in Michigan vineyards however there is preliminary evidence that grapevine viruses are causing problems. Tobacco ringspot virus was detected in table grapes at SWMREC about 10 years ago. Diagnostic testing by AgriAnalysis, Inc. to determine the causes of vine decline and virus-like foliar symptoms during the 2009 growing season led to the discovery of grapevine leafroll-associated virus 3 and rupestris stempitting-associated virus in commercial vineyards in Michigan. Leaf reddening and yellowing symptoms are common in Michigan, but the cause was not known. While most common grapevine viruses have not been reported in Michigan before, they are widespread in other grape-growing areas and as such, not expected to be of concern to regulatory agencies. However, there is a need to determine the causes of vine decline and virus-like symptoms in Michigan vineyards so growers can start understanding and managing these problems. Results and Conclusions In 2011, 174 leaf samples from symptomatic grapevines in 30 vineyards or plots on 12 farms (including research sites), representing 40 different cultivars were tested by ELISA for 12 different viruses. Of these, 41% were positive for one or more viruses, including Grapevine leafroll viruses 1, 2, 3, 4-9; Grapevine fleck virus, Grapevine fanleaf virus, and Tobacco ringspot virus. Some vines had mixed infections with up to four viruses. Grapevine fanleaf virus, a nematode-vectored virus, and GLRaV-4-9 (a mealybug/scale-transmitted virusgroup) were detected for the first time in Michigan in Grapevine leafroll viruses can cause chronic infections that reduce yield and fruit quality, whereas tobacco ringspot virus and grapevine fanleaf virus may cause vine decline and death. These results emphasize the importance of using virus-tested planting material and also suggest that soil and weed testing may be useful to assess potential risk from nematode-transmitted viruses prior to planting. Time line This project was conducted from January 1 until December 31, 2011 and represents year 2 of a 2- year project. Work accomplished during period (2011) including methods (by Objective) 1) Identify causal agents of virus-like symptoms and grapevine decline in Michigan In late summer and fall of 2011, 174 leaf samples were taken from symptomatic vines in a total of 30 vineyards or plots on 12 farms (including research sites), representing 40 different cultivars. An effort was made to screen the variety trials at the Northwest Michigan Horticultural Research Center in Traverse City and the Southwest Michigan Horticultural Research and Extension Center in Benton Harbor to facilitate a fair comparison of cultivars in these trials since virus-infected vines may not yield or mature as well as healthy vines. Samples were taken from vines exhibiting virus-like symptoms or general decline. Some samples were also taken from potted vines maintained in an MSU greenhouse. All samples were tested by ELISA for the following 12 viruses: Grapevine leafroll viruses (GLRaV-1, GLRaV-2, GLRaV-3, GLRaV-4-9 [represents five virus strains in a combined kit]), Grapevine fleck virus (GFkV), Grapevine virus A (GVA), Grapevine virus B (GVB), Arabis mosaic virus (ArMV), Grapevine fanleaf virus (GFLV), Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), and Peach rosette mosaic virus (PRMV). Of the 174 samples tested, 72 (41%) tested positive for one or more of the following viruses: GLRaV-1, GLRV-2, GLRaV-3, GLRaV4-9, GFkV, TRSV or GFLV (Table 1), which was a higher detection rate than in There were some suspect samples with intermediate values as 2

3 well. Some vines had mixed infections by up to four (and possibly five) viruses! It is well known that simultaneous infection by multiple viruses can significantly increase severity of symptoms. Cultivars Pinot Noir, Riesling, Lagrein, Albarino, Chancellor and Vignoles showed multiple virus infections (Table 2). Grapevine fanleaf virus (a nematode-transmitted virus) and GLRaV 4-9 (mealybug or scale-transmitted viruses) were detected for the first time in Michigan in the 2011 survey. GLRaV-3 was predominant among the leafroll viruses (similar to other regions), followed by GLRaV-2 and the GLRaV-4-9 group. GLRaV-1 was detected in only one vine and suspected in another. Peach rosette mosaic virus and tomato ringspot virus were not detected in 2011 even though they were found (in different vineyards) in Michigan in Grapevine fleck virus is not known to cause symptoms except in Vitis rupestris. When samples tested negative this may have been due to low virus titer in response to warm weather, crowngall, physical injury, fungal trunk diseases, nutrient deficiencies, herbicide injury or other pathogens that could not be detected with the available tests. A B C Fig. 1. A) Tobacco ringspot virus in Riesling vine, B) Typical leafroll symptoms on grapevine in southwest Michigan. C) Poor ripening of fruit on grapevine leafroll-infected vine (fruit on neighboring healthy vines was ripe). In addition, unusual symptoms were noted on two single Niagara vines in two commercial vineyards (Berrien and Van Buren County): leaves looked shiny and leathery and somewhat misshapen or wrinkled (Fig. 2). Peach rosette mosaic virus was suspected but the ELISA test only showed GLRaV-3 in one of the samples. It is not known whether GLRaV-3 is responsible for the symptoms. These vines will be re-tested in Most infections, particularly with grapevine leafroll viruses, were likely introduced into Michigan vineyards with the planting material. However, some growers also commented that leafroll infections appeared to be spreading from infected blocks to adjacent vineyards, which is a possibility as mealybug and scale have been found on grapevines in Michigan before. Tomato and tobacco ringspot viruses naturally occur in Michigan soils and grapevines could have also become infected by dagger nematodes transmitting these viruses from weeds (e.g., dandelions) or a previous fruit crop. Soil tests for nematodes are recommended prior to planting, and growers should also consider having weeds tested for TRSV and ToRSV as indicators of the potential for infection. This survey indicates that Michigan is similar to other US grape-growing regions in terms of the types of grapevine viruses present and emphasizes the importance of using virus-tested planting material whenever possible. It also supports National Clean Plant Network activities to produce clean grapevine nursery stock which will benefit all grape growers in the long run. 3

4 Table 1. ELISA positive grapevine samples listed by county in Michigan in County locations Total number samples Number Percentage Positive positive* Positive samples by virus (suspects in parentheses) GLRaV- GLRaV- GLRaV GFLV TRSV GFkV GLRaV- 1 Allegan % Berrien % (1) - - (3) 5 Ingham** % (1) (1) Jackson % 1 (1) (1) - 3 Kent Leelanau % (1) 1 (1) - 3 Oakland Van Buren Total % 1(1) (1) 11 (2) 1 (2) 2 (3) 32 (1) *Some samples contained more than one virus (up to four confirmed viruses) suspects included. ** These are potted vines used for experiments in the MSU greenhouse. Table 2. Grapevine samples with mixed viral infections in Michigan in Viruses present in same sample (suspects in parentheses) Grape variety GLRaV-1 GLRaV-2 GLRaV-3 GLRaV-4-9 GFLV GFkV Pinot Noir (commercial farm) X X X (X) X Riesling (commercial farm) (X) X Lagrein (MSU variety trial) X X X Lagrein (MSU variety trial) X X Albarino (MSU variety trial) X X Chancellor (MSU potted vines) X X Vignoles (MSU potted vines) X X Vignoles (MSU potted vines) X X Table 3. ELISA-positive grapevine samples listed by cultivar in Michigan in locations with positives/ Viruses detected in these cultivars GLRaV- GLRaV- GLRaV- GLRaV- Variety infected vines vines tested GFLV TRSV GFkV Albarino VT 2 2/3 1 1 Cabernet Franc F 2 4/4 4 Chambourcin F & VT 1 4/8 4 Chancellor P 1 3/ (1) Chardonel F 1 1/1 1 Einsett F 1 1/1 1 LagreinVT 2 9/ Leon Millot F 1 1/1 1 Malbec VT 1 1/1 1 Mars F 1 1/1 1 Merlot F + VT 2 4/7 4 Niagara F + P 2 4/7 4 Pinot Meunier VT 1 1/1 1 Pinot Noir F 2 17/ Riesling F 2 4/15 (1) 4 2 Semillon VT 2 1/2 (1) Shiraz VT 1 1/1 1 Vignoles P 1 3/5 3 3 *F=Commercial farm; VT=Variety trial, P=potted plants in MSU greenhouse. 4

5 2) Establish in-state DNA-based testing capability for grapevine virus diseases. Due to a lack of matching funds (see Funding Partnerships below), we focused on ELISA testing of vines rather than conducting DNA (PCR)-based tests. However, under the MDA Specialty Crops Block grant in 2012, we will conduct PCR-based tests for grapevine yellows phytoplasmas on frozen petiole samples from the 2010 and 2011 surveys. Communication Activities, Accomplishments and Impacts The results of this research were shared with grape growers and other stakeholders at the following meetings: Great Lakes Expo in December 2011 and the Northwest Orchard and Vineyard Show in January 2011 and This study has greatly improved awareness of virus diseases of grapes in Michigan and has already aided grower decision making regarding ailing vines and reducing virus spread. Through the survey, we also were able to provide fresh plant material as a positive control for ELISA tests sold by Agdia, Inc., a leading diagnostic company. Fig. 2. Niagara vine with shiny, leathery leaves due to unknown cause. Research publications resulting from this project We will submit a scientific publication on this research to an appropriate journal (e.g., Plant Disease) in We are also working on a fact sheet on grapevine viruses (Schilder, Brown- Rytlewski, and Gillett) that will be published by MSU Extension in 2012 and will also be placed on the MSU grape website (grapes.msu.edu). Funding partnerships After a proposal for matching funds had been submitted to the Viticulture Consortium East in January 2011, we were notified that the program had been eliminated. However, we obtained funds from the MDA Specialty Crop Block grants for virus testing of grapes and blueberries in Michigan in 2012 so that we can continue to provide diagnostic support for grape growers in Michigan and re-test a number of suspect vines from the 2011 survey. References Fuchs, M., T. E. Martinson, G. M. Loeb, and H. C. Hoch Survey for three major leafroll disease-associated viruses in the Finger Lakes vineyards of New York. Plant Dis. 93: Martin R. R., K. C. Eastwell, A. Wagner, S. Lamprecht, and I. E. Tzanetakis Survey for viruses of grapevine in Oregon and Washington. Plant Dis. 89: Mekuria, T. A., A. V. Karasev, R. R. Martin, and R. A. Naidu. 2009a. First report of grapevine leafroll-associated virus-3 in six wine grape cultivars in Idaho. Plant Disease 93:11 (1218). Mekuria T. A., M. J. Soule, S. Jarugula, R. A. Naidu. 2009b. Current status of grapevine viruses in Washington State vineyards. Phytopathology 99:S83 Milkus, B. N. Incidence of four nepo viruses in Missouri vineyards Am. J. Enol. Vitic. 52 (1): Milkus, B. N., R. N. Goodman A survey of Missouri vineyards for the presence of five grape viruses. Am. J. Enol. Vitic. 50(1):