With the fifth and final year of the Canadian Agricultural Partnership Grape & Wine Science Cluster completed, each of the activities has provided a summary update on their research done under the program from 2018-2023. We thank Agriculture & Agri-Food Canada, the British Columbia Wine Grape Council, Grape Growers of Ontario, Ontario Grape and Wine Research Inc., Conseil des Vins du Québec, Nova Scotia Department of Agriculture, and the Grape Growers Association of Nova Scotia, along with our various industry partners, for funding this research. For more information, please contact us.
Activity 2 - Grape and Wine Viruses in British Columbia
Grapevines (Vitis vinifera L.) host the largest number of viruses than any other agriculture crop. Among them, Grapevine leafroll-associated viruses (GLRaVs) and the recently discovered Grapevine red blotch-associated virus (GRBV) cause the most economic impact to the grapevine industry as a result of delayed ripening and reductions in yield and fruit quality. These negative impacts on grapevines are of particular concern to the Canadian wine and grape industry due to the short growing season and an emphasis on production of high quality fruit. Accordingly, the main objectives of this research project were to i) determine the impacts that GLRaVs and GRBV have on plant health and fruit and wine quality in both red and white grape cultivars in BC, ii) evaluate cultural practices that can ameliorate these impacts and iii) identify and control GLRaV-3 and GRBV insect vectors in BC.
Main results achieved from this project are:
- We have determined the significant impact that GRBV has on grapevine health and fruit and wine quality in BC, including reduction of soluble solids of up to 4 °Brix and yield reduction of up to 40% on infected vines. Similarly, we have also determined the impacts that GLRaV-3 has in red and white cultivars. GLRaV-3 reduced soluble solids on red varieties (up to 1.8 °Brix) and affected wine quality; however, its impact was shown to be year dependant. Contrary, GLRaV-3 had no effect on fruit quality parameters on white cultivars.
- We have determined the current status of GPGV throughout vineyards in BC. GPGV is an emerging virus with unknown impacts to grapevine health and fruit and wine quality. Overall, the prevalence of GPGV (46 positive samples out of 468 total samples collected) was 9.8% in BC. The genetic diversity of GPGV isolates from BC was determined by full genome sequencing of seven isolates. All GPGV isolates from BC but two were collected from asymptomatic vines.
- Cultural practices such as crop thinning did not have any effect on reducing the impact that GLRaV-3 and GRBV have on plant health and fruit quality.
- ‘Roguing’, which is the removal of virus infected vines from vineyards and replacing them with virus free certified material, was demonstrated to be a very effective practice to reduce GRBV incidence in BC vineyards. Vineyards where ‘roguing’ was implemented reduced the infection rate from over 10% to less than 1% incidence in five years. Studies on the spread of GRBV showed very low rate of spread in BC.
- An artificial feeding system was successfully developed to screen potential insect vectors present in BC to transmit GRBV. Results from this study showed two species of buffalo treehoppers, Stictocephala basalis and S. bisonia to be able to transmit GRBV under these experimental conditions. These results demonstrate that treehoppers present in BC have the capacity to transmit GRBV.
- Studies on the spread of GLRaV-3 showed the highest rate of infection to occur within the first 0-5 m interval from an infected vineyard block and infected vines decreased as the distance from the nearest virus source increased. Preliminary results for infection rates in relation to vector species and numbers showed mealybug to be more important vectors than scale insects in BC.
- Parasitism rates were determined and species identified. Adult cottony vine scale (CVS) were >80% parasitized by 5 species; the main on being Coccophagus scutellaris. Dr. Gariepy completed DNA extractions from CVS and optimized primers and 91 parasitoids from CVS have been processed and sequenced using the standard DNA barcode primers. Preliminary assessment suggests there may be as many as 9 different species of parasitoids among the samples.
- Rates of parasitism and parasitoid species were then studied in a long-term field trial at SuRDC comparing the neonicotinoid Clutch to the pyrethroid Pounce. Results showed long term effects of these insecticides on parasitism rates and parasitoid species compositions.
Results from this project have demonstrated i) the impact that GLRaV-3 and GRBV have on plant health and fruit quality, ii) have increased awareness among the grape and wine industry on this important issue, and iii) have developed and implemented the first managements strategies to ameliorate these impacts in BC vineyards.
- José Urbez-Torres and Tom Lowery, AAFC Summerland
Activity 3 - Grapevine Virus Diseases and Virus Vector Control
- Expand knowledge on the prevalence and distribution of grapevine leafroll-associated virus (GLRaV) and red blotch virus (GRBV) in Ontario vineyards, the provenance of infected materials and the estimated economic impact of virus infection.
- Investigate the relationship between genotype, symptomology and origin of Grapevine Pinot Gris Virus, especially for Canadian isolates.
- Determine whether GRBV and GLRaV infections spread within vineyards and to adjacent vineyards.
- Document the effect of GLRaV and GRBV alone and in combination on vine cold hardiness, vigour, fruitfulness, yield and fruit and wine quality in different growing season. Study production practices (irrigation, fertilization, crop thinning, pruning) that may enhance fruit quality in GLRaV and GRBV infected vines. Determine minimum thresholds of GLRaV and GRBV infected vines that can impact wine quality.
- Monitor vineyards and surrounding areas for vectors of GRBV and evaluate the ability of potential vector species to transmit GRBV under greenhouse conditions.
- Develop strategies to manage vectors of GLRaVs and GRBV using conventional pesticides and beneficial insect species as biological control agents.
- Develop best management practices for grapevine leafroll and red blotch diseases for Ontario.
Expand knowledge of prevalence of grapevine viruses - Genotype, symptomology and origin of Grapevine Pinot Gris Virus
- We obtained 21 vines from 3 grape growing regions of Canada (13 samples from Ontario, 7 from British Columbia and 1 from Nova Scotia that were previously confirmed by PCR to be infected with GPGV. Total RNA was extracted from the leaf samples and sequenced with Illumina-Miseq in January 2021. The virome data was analyzed in September 2021 and some additional sequencing was done in April 2022 to obtain full-genome sequences of 25 GPGV isolates. Phylogenetic analysis was carried out for full-genomes of 68 GPGV isolates sourced from data banks as well as from other provinces in Canada. Funding for all the HTS testing came from Genome Canada through the project [code 189GRP] entitled “CLEan plAnt extractioN SEquencing Diagnostics (CLEANSED) for Clean Grapevines in Canada".
Spread of GLRV and GRBV
- Petiole samples were collected in 2022 from individual vines in the Chardonnay block that was sampled in 2018-2020 (Chardonnay). Since there was no GRBV detected in the Cabernet franc block that originally included, sampling switched to a Pinot noir block in 2021 and 2022. The Vidal block that was sampled 2018-2021 was not included in 2022 due to poor fungal disease management, making it impossible to find healthy leaves to sample. Samples were submitted to CCOVI lab for testing for GLRV-3 and GRBV.
Effects of infection on vine health and fruit and wine quality
- Fruit was collected from individual vines with GLRaV-3, GRBV and GLRaV-3+GRBV as well as virus free vines at 3 sites (Chardonnay, Pinot noir and Vidal). Yield, cluster number, weight per cluster and average berry weight were determined. Soluble solids, pH and titratable acidity were determined on juice for each vine. Duplicate micro-ferments were conducted with fruit from individual vines. Fermentation kinetics were monitored until MLA was complete. Wine quality parameters (Brix, free and total SO2, malic acid, acetic acid in all wines and anthocyanins and phenolics in Pinot noir and hydroxycinnamic acids in Chardonnay and Vidal) were determined. Vines infected with GLRaV, GRBV and GLRaV+GRBV as well as virus-free vines were sampled monthly at 3 vineyards (Chardonnay, Pinot noir and Vidal) starting in November in 2021 and December in 2022 to determine the effects of solo and combined infections on bud cold hardiness. Vine vigour was evaluated by pruning weights.
- Mealybug and scale were monitored at 4 sites with double-sided tape and trunk counts throughout the growing season to confirm the development of mealybug.
Spread of GRBV and GPGV
- Forty sentinel vines that were confirmed free of GRBV and GPGV by both high throughput sequencing (HTS) and endpoint polymerase chained reaction (PCR) were introduced to two vineyards (one organic and one conventional) that were heavily infected with both GRBV and GPGV. Four months post-introduction, the sentinel vines were relocated to a phytotron. The HTS result 15 months post-introduction revealed widespread infection with grapevine Pinot gris virus (GPGV) among the sentinel vines but did not detect any GRBV. The possibility of an alternative viral reservoir was assessed by testing the most abundant row-middle plants (Medicago sativa, Trifolium repens, Cirsium arvense and Taraxacum officinale), perennial plants in border areas (Fraxinus americana, Ulmus americana, Rhamnus cathartica and Vitis spp.).
Strategies to manage vectors
- Timing of mealybug sprays was determined by developmental stage of the insect.
- The planthopper, Melanoliarus, and buffalo treehopper (Stictocephala bisonia) were collected adjacent to vineyards in the Niagara region and exposed to insecticides (Aceta, Admire, Sivanto Prime, Closer, Pounce) registered for leafhoppers in grapes on grape leaves in Petri-dishes.
Develop best management practicesA questionnaire was conducted with Ontario vineyards to determine:
- If they experienced a change in vine yield and/or sugars associated with virus infection in an affected block,
- If changes occurred, the degree of change if measured or estimated and
- If viticultural practices changed in the affected block in response to the virus infection.
The economic analysis sought to determine which strategies were economically optimal. Simulations were performed to determine the threshold at which point a grower would decide to move from one control strategy to the next as it was more economically optimal. The decision point is met once the current cost of treatment over the life of the vineyard meets or exceeds the costs of next control strategy.
- Justin Renkema and Wendy McFadden-Smith, AAFC Vineland and CCOVI at Brock University
Activity 4 - Evaluation of Viruses
Part I: Impact of key economic grapevine viruses on vine performance and fruit quality
AAFC Team: Debra Moreau (PI), Harrison Wright, Charles Forney, Jun Song, and Shawkat Ali
To evaluate the impact of grapevine leafroll associated virus (GLRaV-3) and grapevine red blotch virus (GRBV) on vine performance and fruit quality, research focused on (a) establishing virus status in selected vineyard blocks, (b) monitoring vine performance parameters of individual GLRaV infected and non-infected vines, (c) evaluating fruit and wine attributes from vines observed in vine performance assessments, and (d) survey virus-confirmed blocks for incidence of insect vectors. A survey of 40 varietal blocks was conducted to establish the status of grapevine viruses in key varieties currently grown in Nova Scotia (NS). Plans to index an additional 10 varietal blocks in 2020 were not possible due to pandemic restrictions that prevented timely access to third party sites and labs for petiole processing. In collaboration with AAFC-SuRDC, CCOVI, and CFIA researchers, AAFC-KRDC efforts also included contributing to NGS screening of existing NS samples and dormant canes collected in 2022 and 2023.
Of the viruses detected, Grapevine Leafroll associated Virus-3 (GLRaV-3) is the most prevalent, followed by Grapevine Pinot Gris Virus (GPGV), Grapevine Red Blotch Virus (GRBV), Grapevine Leafroll associated Virus-1, then Grapevine Fanleaf Virus. Soil samples were also taken from the same varietal blocks surveyed for virus, to establish the composition of plant parasitic nematodes throughout the wine-grape regions in NS. Lesion, ring, dagger, root knot and pin nematodes were found. In general, nematode numbers may be impacting some NS vineyard blocks but not at serious levels. In most cases, counts were low and remain at levels that do not warrant concern.
Under pandemic restrictions, as an alternative to accessing commercial vineyards, a trial was setup in the research vineyard located at the Kentville Research and Development Centre (KRDC) in late May 2020 to compare both, previously confirmed, GLRaV-3 and GRBV infected plants. Plants infected with GLRaV-3 were compared to non-infected controls in ‘Vidal’ and ‘New York Muscat (NYM)’ while the same was done for GRBV in ‘Marquette’. Over the remaining 3 years of the study, all vines-of-interest were inspected weekly to bi-weekly, photographed, and any observed symptoms recorded. The phenology and physiology (chlorophyll levels, carbon fixation rates, yield, fruit quality and dormant pruning weights) were assessed in both non-infected and infected vines across a number of time points. Grape samples from virus infected and non-infected vines were collected to evaluate the effects of virus infection on grape chemical composition. Must from the grapes was analyzed for sugar, acid and volatile composition, and phenolics assessment. While treatment differences related to virus status were found, the impact on vine performance was nuanced and depended on the year of measurement and cultivar. For cultivars, °Brix values were typically lower in virus-infected vines, but variability was high between vines and this fell short of being significant. Additionally, virus vines showed signs of having lower leaf chlorophyll, but significant differences depended on the cultivar and year. Vidal Blanc and Marquette virus vines had higher fruit acidity levels in 2021. This negative trait has also been associated with better studied virus-infected vinifera cultivars. Unfortunately, there was no NYM fruit and the Vidal Blanc crop load was impacted significantly by the 2022 January freeze event. There was no difference in TA or Brix in the Vidal Blanc as a result of virus status. Similarly, there was no difference in Marquette TA; however, the Brix was weakly significant. Infected (GRBV) Marquette Brix was 24.4 while uninfected vines were 25.8 (p = 0.0542). This was the first time we saw a statistical difference in Brix in this trial. In the past we found infected Vidal Blanc had larger berry size and Marquette and Vidal Blanc had high acid. Results suggest possible fruit composition implications of virus in hybrids, but the collection of data was impacted by: (a) low replication, and (b) the crop load has been highly variable with the freeze damage the KRDC vineyard has sustained over the years. A second major finding was differences in bud viability between virus-infected and virus-free plants in the wake of a winter freeze event in early 2023. Temperatures were cold enough that bud viability in the two more sensitive varieties (New York Muscat and Seyval Blanc) was close to zero, regardless of virus status. However, for the two hardier cultivars (Marquette and Marechal Foch), the vines were only partially damaged and so measuring the impact of virus was possible. For the Marechal Foch, the bud viability of virus-free plants was 28% greater than in virus-infected plants. For Marquette, the buds of virus-free plants were 39% more viable than in virus-infected plants. This is the first time such findings have been found in a hybrid cultivar.
Weekly inspections for known vectors were conducted annually and confirmed very low and localized populations of Grape mealybug (Pseudococcus maritimus). Fruit lecanium scale (Parthenolecanium corni) was observed in commercial sites but did not correlate with leafroll virus status. To date, numbers do not warrant sprays to manage. The potential vector of GRBV, Buffalo Treehopper (Stictocephala alta) was commonly observed in sweeps within laneways. Cane girdling was observed in blocks with confirmed GRBV but insects were not observed feeding. The risk of increased incidence of grapevine viruses is likely linked to infected nursery material, since vector pressure remains very low in Nova Scotia. Local producers support the need for research to develop best practices for virus mitigation. Access to virus-free plant material and knowledge of sustainable vector management tools has become a major priority for our industry, especially given the current virus status and continued expansion in acreage in NS, observed trends in regional climate change, and shifts to organic production systems. Research observations and preliminary trends have been shared with cooperating growers and industry stakeholders in annual reports and presentations to the Grape Growers Association of Nova Scotia, Nova Scotia Department of Agriculture, Canadian Grapevine Certification Network, and AAFC researchers and collaborators working on grapevine viruses across Canada.
Part II: Distribution and impact of emergent and invasive insect pest species in the context of viticultural expansion in Nova Scotia.
AAFC Team: Debra Moreau (PI)
To determine the distribution and impact of emergent and invasive insect pest species in the context of viticultural expansion in Nova Scotia, two objectives were established: (1) to determine the incidence and distribution of Phylloxera and (2) to assess the presence of pest status for other potential endemic and invasive insect threats. Efforts in 2020 were significantly impacted by pandemic restrictions that prevented access to commercial sites. An intensive trial was established in a research vineyard located at the Kentville Research and Development Centre (KRDC). The study focused on understanding the seasonal dynamics in soil emerging phylloxera, based on counts, and how this related to the presence of leaf galls, ambient air and soil temperatures, and vine phenology. Trapping was done using a non-invasive technique with plastic buckets that captures phylloxera nymphs as they emerge from the soil. In 2021, trials were extended to include 4 commercial vineyards. Weekly counts continue to be highly variable within varietal blocks and between varieties. Annual observations showed sustained catches for soil emerging stages to be in mid-June for all varieties assessed and was approximately 1 to 10% of the subsequent summer peak.
Over the duration of the study, both ambient soil and air temperatures were statistically correlated with the soil emergence counts. Soil temperatures between 21 and 25°C at a depth of 30 cm were correlated with the highest emergence levels. These temperatures were consistent with previously reported temperatures for nymph survival (21-28°C). Air temperatures were also significantly correlated with emerging counts but, not unexpectedly, were more variable than soil temperatures. Phenology stages around rapid shoot and inflorescence development and berry development were associated with the highest emergence numbers. Results suggest that phylloxera populations were already established in all the varietal blocks included in this study and counts recorded throughout the sampling period, reflected seasonal dynamics of local populations. Emergence counts for vinifera Chardonnay and Riesling varieties showed comparable trends, whereas, hybrid varieties varied considerably. L’Acadie Blanc consistently showed low emergence and leaf gall counts and highest populations were observed in Marquette, with an approximate 1000 times difference between L’Acadie Blanc and Marquette. General observations of leaf gall presence throughout the entire vineyard showed that phylloxera populations moved throughout the vineyard over the growing season and dispersal was likely facilitated by the direction of prevailing wind patterns, machinery and labourers. A small pilot trial was established to observe the fate of phylloxera in leaf galls after canes were pruned and left on the ground within the vineyard aisles. Of interest, was that phylloxera crawlers exited galls on pruned canes and moved up the walls of the container suggesting that infested prunings could potentially act as a reservoir within the blocks if left within the aisles. What is not known is the distance that crawlers could potentially move and if vines could be reinfested. Dispersal is likely facilitated by prevailing winds. Incidence and overall level of infestations observed each year appear to be on the increase. Although gall presence remains the obvious measure for vineyard managers to use for decision-making as to whether to manage, it is likely an underestimate of the actual population that exists within the vineyard. Leaf gall counts on vines were not found to be significantly correlated with the timing of highest soil emergence counts and the delay may be explained by the gap in time between when active stages emerge from the ground and the time it takes for galls to form on the leaves.
In 2022, wildflower treatments were evaluated for their potential to attract key predator species, like hoverflies, and impact to phylloxera populations. Four species of plant hosts (Daucus carota (wild carrot), Coriandrum sativum (cilantro), Lobularia maritime (alyssum), Thymus serpyllum (thyme)) were established at the head of rows. Species from 7 taxonomic groups of interest (Ichneumonidae, Braconidae, Coccinellidae, Carabidae, Diptera, Neuroptera, Arachnids) were targeted in weekly sampling. Bucket traps were sampled weekly to determine counts of phylloxera emerging from soil and number of winged (alates) and crawlers (aptera). Leaves of vines in panels with traps were assessed for galls. Early findings of visual assessments of wildflowers showed that cilantro attracted the most potential predators, primarily hoverflies. Alyssum was also an attractive host to hoverflies. Generalists like lacewings, spiders, and carabids were also observed on occasion. Thyme was the least visited. Proximity of trap to wildflowers did not seem to suppress pest emergence counts over time. Likely because the wildflower plots had only just been established and size in proportion to the vineyard block would not have been sufficient to be measurable. However, predator counts by wildflower host suggests that cilantro and alyssum may be good candidates for promotion of biological control, if plots of sufficient size. Efforts going forward need to focus on enhancing non-cropping spaces within and around commercial vineyards to develop potential reservoirs of beneficial species that would contribute to pest suppression and management, especially in organic systems. The greatest threat remains for producers of non-conventional production systems, where there are no effective control products available for use on this pest. Further research is needed to evaluate alternative control options.
Monitoring for other invasive and emerging species was done annually. Visual observations for presence of Japanese beetle in vineyards not previously known to have this pest, confirmed the continued spread in distribution. We did not observe Grape Berry Moth larvae in clusters. Various leafrollers were collected and reared, with the majority identified as Redbanded leafroller (Argyrotaenia velutinana), a common Tortricid in Nova Scotia. Malaise trap samples from 2023 are still being barcoded to determine species identification. Monitoring did reveal observed damage in vinifera grapes from spotted wing drosophila (Drosophila suzukii). Typically, this has not been considered a pest of interest in grape and damage may have been a result of multiple factors that included warm, humid temperatures that supported higher populations and fruit (especially thinner-skinned varieties…mostly vinifera) left to hang longer with the favourable Fall conditions. Higher than usual levels of sour rot were observed and may have been affected by the wounds caused by egg-laying that can contribute to development of the disease. Given changing climate trends, spotted wing drosophila should be monitored from veraison and on. Damage was sufficient to cause some growers to want to schedule maintenance sprays but this would present challenges around harvest. Work is needed to determine best timing of management tactic, with a growing interest in incorporating wildflower plots as refuges for beneficial species, especially in organic production systems. As in previous years, specimens and/or images of pest species of interest were routinely received by growers and identified. Commercial vineyard monitoring efforts for other invasive and emerging insect pests included grower education and increasing awareness of potential pests and their associated risks. Newsletters ‘AAFC Pest Update’ were produced and disseminated to growers through the Grape Growers Association of Nova Scotia. Regular communications were ongoing with AAFC, the Canadian Grapevine Certification Network, Grape Growers Association of Nova Scotia, and wine-grape growers and stakeholders.
- Debra Moreau, AAFC Kentville
Activity 5 - Cold Hardiness in Eastern Canada
Growing grapes in cold climates has several challenges to overcome. Cold injury to grapevines is an important problem, especially at the northern limits of culture where extensive damage to bud and cane tissues can result in severe economic losses. The main objective of this project is to improve knowledge of grapevine cold hardiness for hardy and semi-hardy hybrid and Vitis vinifera cultivars as well as to provide methods to reduce cold injury under climatic conditions of eastern Canada in order to support the development of the wine industry. To help understand cold resistance in grapevines, methods and models for evaluating bud resistance have been developed and utilized for several years. Following previous works, CRAM has set up a network of eleven vineyards across Quebec to monitor bud cold tolerance by means of Differential Thermal Analysis (DTA) during the winter and spring. The Low Temperature Exotherm (LTE) for each studied varietal can be derived in from DTA in order to demonstrate bud cold tolerance. The grape varieties that are followed from November to May are rustic hybrids, Frontenac, Marquette, St-Pepin, Frontenac blanc and Petite Perle. Then, from April on, V. vinifera (Chardonnay, Vidal and Pinot noir) are added. Three years of LTE monitoring in Quebec demonstrated that there was great variability in LTE values between vineyards and grape cultivars. In addition, rustic hybrid cultivars do not seem to follow a standard curve of acclimation/maximum hardiness/deacclimation that is usually observed for V. vinifera. The LTEs are more variable during the winter and closely follow local temperature variations. Most notably, maximum hardiness was only attained at the end of February.
Winter protection methods have been developed to use concomitantly with tender and semi-hardy wine grapes that are less resistant to the cold in the northern regions. The use of geotextiles to protect semi-rustic and non-rustic vines is increasingly used in Quebec though without specific knowledge for optimal installation and outcome. The project evaluates three types of geotextiles (Hibertex 2.2 mm, Hibertex 3mm and Texel Arbo Pro) and four moments of installation/withdrawal (early installation/early withdrawal, early/late, late/early and late/late). Three grape varieties were followed: Vidal, Chardonnay and Pinot noir. The trials are carried out in five vineyards across Quebec. A first site was evaluated in the fall of 2018 and the data was collected during the 2019 season. We can note that the geotextiles influence the environment under them, keeping the temperature around the vines significantly higher than outside, especially in very cold weather and when a snow cover is present. The temperatures under the geotextiles, the timing of phenological stages and the yield components were not influenced by the type of geotextiles. The timing of installation and removal had a small impact on the yield and yield component depending on the year, site and cultivar. In some condition, an early installation/early removal treatment had a higher cluster number/vine than the late installation/late removal treatment. Higher yield/vine was also observed in some conditions on the late installation/late removal compared to the late installation/early removal treatment.
Several management practices can modulate the resistance to cold or vine acclimation, such as leaf removal, fertilization, pruning, training systems and rootstocks. Rootstocks can directly affect the biochemistry of grafts and tolerance to freezing or can affect cold tolerance indirectly by acting on the vigour of the vine and shade from the canopy. The effects of grafting for rustic grape varieties on various parameters have been monitored for several years. Thirty combinations including six grape varieties (Frontenac, Frontenac blanc, Frontenac gris, Marquette, Adalmiina, Baltica) and five root systems (pied franc, 3309, Riparia Gloire, 101-14, SO4) were studied. This study has demonstrated that rootstocks may affect cold-hardy hybrids in different ways and some of them showed higher potential than others for use under eastern North American conditions. Our results obtained for Frontenac, Frontenac blanc and Marquette did not show a significant effect of rootstock on bud survival, vine physiology during the spring nor for the remainder of the season but the grapevine vigor was affected by rootstock, where lower vigor was observed with Riparia Gloire. For vine varieties known to have magnesium deficiencies, such as Frontenac, the use of rootstock 3309 reduces this deficiency. Rootstocks may also affect some yield components and fruit composition parameters, but the effect of growing season (vintage) is predominant. The significant impacts of grafting on fruits are on wine appreciation where higher aromas were noted on wines produced with grapes on grafted vines compared to own-rooted vines. The wines made from own-rooted vines were the least popular. Thus, the results of this project allow us to propose the use of certain rootstocks, such as 3309 and 101-14, which are well adapted to soil and climatic conditions. Some growers have already asked nurserymen to prepare hybrid plants with these rootstocks. In the coming years, the use of rootstocks with hybrids could increase. Growers will be able to use the results of this project to select the desired rootstock.
- Caroline Provost, Centre de Recherche agroalimentaire de Mirabel (CRAM)
Activity 6 - Grape & Wine Grapevine Hardiness
After Carl Bogdanoff retired in 2021, Dr. Ben-Min Chang resumed the activities under the supervision of Dr. Kevin Usher.
Objective 1: Evaluation & modification of vineyard management practices
In this objective there are four multi‐year field experiments.
Expt 1 (planted in 2017) – The aim of this study is to investigate whether rootstocks affect vine cold hardiness. Merlot were grafted on eight rootstocks (101-14, 110R, 3309C, 5C, Ramsey, Riparia gloire, Schwarzmann, and SO4) in 2017. The experimental block was drip irrigated three times a week. The rootstock treatments did not affect yield, juice Brix, juice pH, juice TA, and cold hardiness under frequent irrigation. The potential small rootzones that are created by frequent irrigation might reduce the effects of rootstock treatments.
- Expt 2 (initiated in 2019) – Early season deficit irrigation enhanced vine hardiness but reduced yield in 2019 trial. However, the 2020 trial was then canceled due to COVID restriction. Despite the fact that the experiment was terminated, the results suggested that early season management can affect cold hardiness later in the dormant season. The cool and wet early season in 2022 might explain why vines became less hardy during the 2022/2023 winter (The lethal temperature was about 2°C higher than 2021/2022 winter).
- Expt 3 (initiated in 2021) - Effects of irrigation/fertigation treatments on vine senescence and hardiness. This experiment, with irrigation/fertigation treatments ranging from 50% to 150% of conventional irrigation rate, were repeated in 2022–2023 season. Bud break rate, photosynthesis measurements, leaf senescence, berry composition, yield, pruning weights and bud hardiness measurements have been and will continue to be collected till May 2023. Bud damages were widely spread in the Okanagan valley due to December 21-22, 2022, cold snap. The budbreak rate will be assessed in early May 2023. The results in 2021 trial showed the irrigation treatments did not affect budbreak rate. The budbreak rate could be interpreted as survival rate after a significant cold snap event. However, the minimum air temperature during the cold snap did not reach the lethal temperature in December 2021. Thus, the effects of irrigation treatment might be masked by buds without any winter damage. The budbreak rate of 2022 season will be analyzed. On the other hand, the yield, berry weight, juice pH, and juice TA were associated with amount of irrigated water.
- Expt 4 (initiated in 2021) - Effects of post-harvest defoliation on bud hardiness. The aim of this experiment is to simulate an early hard frost event and explore its effect on bud hardiness. The second year trial in 2022 was compromised by the early November frost event.
Objective 2: Regular posting of varietal bud hardiness measurements and development of predictive bud hardiness models
Due to low staffing in the 2022 season, we collected samples from only south Okanagan valley. Varietal bud hardiness measurements from 36 Okanagan Valley vineyard sites have been made every two weeks from late October to early April. This data is posted to the BCWGC, the BCGA and to local growers, and is used to verify and improve the predictive bud hardiness models that have been developed for eight widely grown cultivars. However, the cold snap on December 21-22, 2022, caused severe bud death. We obtained aberrant Low Temperature Exotherm measurements after the cold snap. The data was not used in constructing the model. Dr. Wolkovich of UBC had developed an online dashboard based on the model. The assessment of cold hardiness will be continued to the next Sustainable CAP project by Dr. Ben-Min Chang (pending cluster and activity approval). The report of cold hardiness forecast will be resumed in 2023 winter.
Objective 3: The investigation of grapevine phloem hardiness
As this objective had been completed, no further action was taken.
Objective 4: The investigation of grapevine root hardiness
Much of the proposed goals for this objective have also been completed.
Objective 5: The examination of grapevine diseases and novel vineyard management practices on winter hardiness
Bud hardiness were measured from late fall to early spring for all field experiments in Activities 2, 6, 11, 21, & 22.
Objective 6: Surveying local vineyards to develop new varietal winter hardy clones
New assessment will be conducted. Six vineyards in Kelowna and Lake Country areas had been surveyed for surviving vines after the cold snap in December 2021. The surviving vines could be isolated as a winter damage resistant new clone. Unfortunately, no obvious survivors stood out in the surveyed vineyards while the environmental variations can make significant differences. For example, some vines with stunted growth could be observed in the survey. Initially, these vines were considered as cold damaged vines. The rest of healthier vines were identified as potential winter survivors. In fact, the stunted growth might be related to Pinot curl leaf symptom due to cool weather in the spring of 2022. To select winter damage resistant clones or mutants efficiently, we can utilize new technologies (e.g. gene sequencing) for screening before entering field comparison trial.
- Ben-Min Chang, AAFC Summerland
Activity 7 - Grapevine evaluation and cold hardiness program
This activity was a collaborative project between program leads Dr. Jim Willwerth (Brock University/Cool Climate Oenology and Viticulture Institute (CCOVI), St. Catharines, ON) (Vote 10) and Dr. Harrison Wright (AAFC, Kentville Research and Development Centre (KRDC), Kentville, NS) (Vote 1). Activity 7 had five objectives:
- To study the impact of rootstock on cold tolerance and fruit quality of wine grapes (Vote 10);
- To study the impact of Abscisic Acid (ABA) analogs on wine grape hardiness and performance (Vote 10);
- To coordinate wine grape bud hardiness survey work in Ontario, British Columbia and Nova Scotia (Vote 1);
- To study factors that influence wine grape bud hardiness (Vote 1);
- To install and study a Chardonnay clone trial in Nova Scotia to act as a satellite site to similar work ongoing in Ontario (Vote 1).
Vote 10. Objective 1 and 2. Objectives within this activity included:
1) Gain in‐depth understanding of scion‐rootstock combinations to optimize vine performance with respect to production, cold tolerance and fruit/wine quality using certified nursery material; and
2) Elucidate relationships between different grapevine genotypes, cold tolerance, dormancy and associated cold hardiness‐related metabolites in their biochemical and physiological responses as well as improving hardiness through Abscisic Acid (ABA) analogs.The effects of clone x rootstocks on vine performance, cold hardiness and fruit composition have now been evaluated for multiple seasons using cultivars, Chardonnay, Pinot noir, Merlot, Cabernet franc and Sauvignon blanc. We have found some specific impacts of clone x rootstock on cold hardiness with Cabernet franc but the differences are not as evident as previous work with Sauvignon blanc and Riesling. Furthermore, dehydrin proteins were measured for 2 seasons and while these individual proteins varied over dormancy there were no clear indications that dehydrins were associated with greater hardiness. Climate conditions over dormancy did impact clone x rootstock hardiness, winter survival as well as cold hardiness metabolites such as dehydrins. In addition, clone and rootstock can impact vine size, yields, crop loads and some primary fruit chemistry. In some cases with rootstock it appears to be related to advances in maturity that may be related to overall vigour and crop size. Clone and rootstock interactions cannot be ignored through the findings of this research activity. This research is quite novel with respect to being able to demonstrate that clone, rootstock and their interactions can impact vine performance, production and cold tolerance. The research from this activity has successfully demonstrated that selection of plant material is very important with respect to sustainable production in vineyards and quality.
For objective 2:ABA analogs can improve and maintain dormancy in multiple cultivars including cold tender V. vinifera as well as hybrid cultivars over multiple years of study. However, there can be some seasonal effects to how well ABA analogs maintain dormancy and some analogs may perform more consistently in this regard. Molecular studies involving ABA during key periods of cold acclimation, deacclimation and reacclimation phases revealed unique changes to some cold hardiness related genes and those associated with dehydrins and starch and carbohydrate metabolism. In conclusion, our understanding of genotype and environment on cold hardiness dynamics and respective changes at the biochemical and molecular level are invaluable for understanding how to improve the trait of cold hardiness and identifying more freeze resilient grapevines. In addition, ABA analogs continue to demonstrate promise as a cold hardiness promoter and helping to maintain dormancy. Applications of these molecules may lead to improved hardiness throughout dormancy and reduce the vine’s susceptibility to lose hardiness later in dormancy. This may be very beneficial in terms of mitigating the effects of temperature fluctuations that commonly occur during Canadian winters and for greater freeze tolerance for tender V. vinifera cultivars or varieties very susceptible to cold deacclimation such as V. riparia-based varieties such as Marquette.
For objective 3 (bud hardiness survey)
The coordinated bud hardiness survey conducted at locations throughout Canada served a dual purpose. Having researchers and technicians in such a wide array of commercial vineyards provided an excellent opportunity to observe vineyards and to engage growers on the topic of vine hardiness as well as other research questions. Additionally, years of temperature and bud hardiness data are needed from diverse regions and years in order to accurately model vine bud hardiness performance. This analysis is ongoing and will be used to create new metrics assessing the risks associated with growing particular cultivars under different climate change models. This information was particularly informative in the final year of the project when a combination of the warmest winters on record in Nova Scotia followed by one of the coldest low temperature events resulted in widespread winter damage.
For objective 4 (factors associated with hardiness)
Bud viability assessments provided the basal levels needed to assess the impact of severe weather events and other factors. A multitude of studies examined the influence of factors such as crop load, vine balance and harvest timing on vine hardiness. Despite often being listed as a factor, no evidence that crop load impacted hardiness was found in two hybrid cultivars and fruit composition was only moderately influenced. Harvest timing did have some influence on hardiness, but only when the crop load was heavy. Multiyear and multi-cultivar wood sugar and water content data demonstrated that these variables are dynamic while the vine is dormant and provided insights into how the vine balances hardiness and dormancy with the need to resume growth in the spring.
Finally, for objective 5 (Chardonnay clone trial)
Despite setbacks, a satellite Chardonnay trial that used a subset of clones used in its Ontario counterpart was installed in the final year of the project. If the site responds favourably to the 2023 freeze damage, this will be a source of further collaboration between Ontario and Nova Scotia in future years.
- Harrison Wright and Jim Willwerth, AAFC Kentville and CCOVI at Brock University
Activity 8 - Canopy Management to reduce disease pressure
As a first step, leaf removal in the cluster zone was evaluated for its effect on downy mildew. The following five practices of leaf removal in the cluster zone were: on 1) one side of the row at nouaison (BBCH 17); 2) two sides of the row at nouaison ; 3) one side of the row at veraison (BBCH 27); 4) two sides of the row at veraison; 5) no leaf removal (control). Microclimate and fungicide penetration were monitored within the fruit zone. The effect of leaf removal was evaluated based on disease progress and disease at harvest. Overall, lower disease severity was observed when leaves were removed on both sides of rows and when leaves were removed at nouaison. For most year and sites, significantly lower diseases severity was observed in plots where leaves were removed on both sides of rows at nouaison than in plots were leaves were not removed. No effect on airborne inoculum and within canopy temperature and relative humidity were observed. However, solar radiation and wind speed (aeration) were higher in the plots with leaf removal. The most important effect in terms of disease development was a decrease in the duration of leaf and berry wetness. Fungicide penetration was higher in plots were leaves were removed on both sides of rows.
As a second step, we studied the effect of leaf removal in the cluster zone on disease management. The following fungicide application schemes were evaluated:
- A calendar-based scheme, with fungicides applied at predefined times;
- A calendar-based scheme with leaf removal at fruit set on both sides of the rows;
- A disease risk-based scheme with disease risks estimated according to the phenological stage (vine receptivity) and weather conditions in the vineyard;
- A disease risk-based scheme with disease risks estimated as in treatment 3 with leaf removal at fruit set on both sides of the rows;
- A disease risk-based scheme with disease risks estimated according to the phenological stage and weather conditions (microclimate) in the canopy (grape cluster zone) with leaf removal at fruit set on both sides of the rows;
- A control without fungicide applications. In all the plots with leaf removal, leafing was repeated about 3-4 weeks after the first leaf removal done at fruit set in order to avoid the grapevine compensation.
In conclusion, leaf removal in the cluster zone as a method of controlling the main grapevine diseases alone has not made it possible to significantly reduce the development of diseases as well as yield losses in terms of both quantity and quality. However, when leafing was combined with tools for estimating disease risks, particularly when risks were estimated from weather conditions in the microclimate (cluster zone), this practice made it possible to significantly reduce the number of fungicide treatments while maintaining the yields. The results obtained tend to demonstrate the importance of integrated pest management and the effect of methods which alone do not provide acceptable control but which when combined make it possible to achieve an acceptable level of control while reducing the use synthetic fungicides.
A cost-benefit analysis vas conducted for anthracnose management since we have collected data on fungicide reduction in plots with and without leaf removal. In the plots without leaf removal a total of 11 fungicide applications were made at a total cost of $1543/ha (product and labor). In the plots with leaf removal but without consideration of microclimate change due to leaf removal, the total cost (product and labor) was $ 2018/ha and $ 1738/ha, for manual and mechanical leaf removal, respectively. In the plots with leaf removal and consideration of the microclimate the total cost (product and labor) was $1748/ha and $1468/ha, for manual and mechanical leaf removal, respectively. Therefore, if we consider only the benefits of leaf removal on anthracnose management, leaf removal is profitable. Other benefits of leaf removal include better management of several diseases, grape quality, potential reduction of fungicide treatments, and increased ecological services. However, leaf removal also has its share of disadvantages including sunburn and the demand for skilled labor.
- Odile Carisse and Caroline Provost, AAFC CRDH and Centre de Recherche agroalimentaire de Mirabel (CRAM)
Activity 9 - Optimization of grape production in Eastern Canada
Climate is the most important element when growing grapes in cool to cold areas such a s those found in Eastern Canada. Although several practices are in place to increase crop quality and productivity, many unknowns remain regarding this industry. Understanding how climate affects berry quality is an essential step to better understand cold-climate terroir and how to optimize the relationship between growing conditions and grape varieties to then optimize wine quality.
In this study, we demonstrated varietal differences between five grape varieties grown in Eastern Canada. These findings can guide grape growers in their selection and provide them with insight about how to blend those varieties to optimise wine quality.
We then demonstrated the impact of temperature on the accumulation of organic acids, sugars, amino acids, bound aroma and phenolic compounds of L’Acadie blanc berries, as well as on the microbiota present on the leaf and the berries of this variety. We showed that high temperature during early berry development as well as exposure to light during the same period impacts berry composition for the whole season, with positive impact on volatile phenols, but low impact on organic acids.
Through our study of the terroir of Île d’Orléans, QC and Gaspereau Valley, NS, we found that L’Acadie blanc is a good fit for the growing conditions historically experienced in Île d’Orléans, whereas the conditions found in Gaspereau Valley are closer to the temperature requirement for the accumulation of terpenes in Riesling.
Many other aspects of grape quality remain to be explored, using this dataset and future data, to accurately define the relationships between terroir, varieties and wine quality. Future work will focus on continuing this work. We will also focus on the development of innovative approaches to improve berry quality.
-Karine Pedneault, Université Sainte-Anne
Activity 10 - Water and Nutrient management strategies for grapevines and health promoting natural products
This study aimed to investigate the use of Soil Water Retention Technology (SWRT; U shape membranes installed 50 cm deep in both sides of a newly established vine row) and biochar-compost mixture inter-row applications to improve soil water holding capacity and reduce competition for water and nutrients between grape vine and cover crops. The impact of various management strategies such as vermicompost, vermicompost tea, and Stella Maris (seaweed extract) application rate, method, and frequency of application on grape yield, fruit quality, plant nutritional status, and plant and/or soil health was investigated. SWRT has the potential to enhance water usage efficiency in sandy soils, according to the research findings. Biochar-compost increased soil C and N levels while also increasing soil water retention capacity. Cover cropping improved carbon sequestration and nitrogen supply in vines. The use of foliar vermicompost tea improved fruit quality and reduced the requirement for powdery mildew spray. Under-vine vermicompost application increased yield as well as soil C and N concentrations. Foliar use of seaweed extract improved grapevine resistance to environmental stressors.
- Mehdi Sharifi and Francisco Diez, AAFC Summerland and Perennia Agriculture and Food Inc.
Activity 11 - Grape & Wine Nitrogen Management
Nitrogen directly impacts grape quality by affecting vine vigour, fruit set and maturation, crop load and pressure from diseases and insects. The impact of fruit nitrogen content on fermentation is through the yeast's requirements for ammonium and amino acids for growth, and as a byproduct amino acids are metabolized by the yeast into flavours and aromas which influence wine quality. We examined how soil and foliar N applications influence the ratios of YAN components (ammonium and 20 alpha amino acids) in grapes and how they impact fruit and wine quality. Application of foliar nitrogen in two commercially important varieties (Pinot gris and Cabernet Sauvignon) resulted in up to a two-fold increase in fruit nitrogen content and had an impact on amino acid profiles. These results were consistently achieved over four years. Fermentation studies indicate that the differences in fruit amino acid profiles and total nitrogen content from treatments applied in the field trials impacted fermentation and wine quality.
Precision management of nitrogen in vineyards is used to improve consistency in grape quality and vine growth throughout a vineyard block. Identifying areas with low or high nitrogen status in grapevines is challenging when done on a large scale. It takes grapevines more than one season to adjust to changes in nitrogen availability. In the second year of the field nitrogen trials work on developing imaging tools to predict nitrogen status began. Using different imagers (red edge, RBG, infrared, lidar) and techniques (NADR, cloud point) with an aerial drone we identified eleven indices with significant correlations to nitrogen status in grapes and leaves. Additionally, using three-dimensional modelling we developed a method to image the sides of the vine canopy instead of the narrow top which provided more accuracy.
The work conducted in this activity provides new tools and an understanding of nitrogen management in both the vineyard and winery. This will improve the sustainable use of nitrogen fertilizer in vineyards and reduce the requirement for using diammonium phosphate (DAP) for winemaking.
Objective 1: Soil and foliar nitrogen (N) application to determine the impact on and relationships among amino acid profiles, yeast assimilable nitrogen content, fruit quality, bud hardiness and flavonoids (pigment and tannin)
Two foliar nitrogen application trials with Pinot gris and Cabernet Sauvignon were completed in industry vineyards. Five treatments were applied (three rates of fertigated N or two rates of late foliar N) , vine and fruit measurements were collected and fruit from both trials was harvested and used for winemaking in objectives 4 and 5. Chemical analysis of the fruit is almost complete. The remaining samples are from the final season. Results from all three years of the field trials show significant differences (up to two-fold differences) in berry nitrogen and amino acid content among treatments without affecting vine vigour or general berry composition (sugar and acid). Different amino acid profiles were recorded among treatments which should result in different flavour profiles in the wines. There were no differences in bud hardiness or vine vigour among treatments which indicates the elevated N content was not detrimental. To increase fruit yeast assimilable nitrogen later in the season to avoid vigour and herbaceaousness its recommended that 2% urea can be applied two or three times at two to three week intervals starting at 10o Brix.
Objective 2: Evaluate the effectiveness of N application to alleviate leaf roll virus symptoms of reduced yield and maturity
This objective was completed in 2021. We concluded that fertilizing with nitrogen does not impact virus symptoms of delayed maturation or reduced yield.
Objective 3: Spectral imaging and precision management for vineyard N status using UAVs (drones)
Pinot Gris and Cabernet Sauvignon vineyard blocks (two different sites) were imaged using a UAV with multispectral, infrared and RGB cameras. Multiple flights were conducted each year. At the same time, direct multispectral measurements of leaves were taken and leaf samples were analyzed for N status and pigments. Nitrogen and pigment analysis of leaves and fruit are complete. During the project, there were environmental challenges for aerial imaging which included smoke, wind and proximity to wildfires. Despite these challenges, we were able to develop models for predicting vine N status with an acceptable level of accuracy. Using NADIR and point cloud imaging, 11 indices were significant for predicting vine N status remotely. The data was correlated to both leaf colour and directly to the nitrogen status (nitrogenous compounds) which is a step forward compared with the industry standard methods of inference through using leaf colour alone.
Objective 4: Evaluate soil applied N with late foliar N application in the field for impacts on wine quality including amino acid profiles, fermentation kinetics, sensory evaluation, wine protein content and compounds related to N metabolism
Wines were produced from the field trials conducted in objective 1. Chemical analysis of the current wines including amino acids and ammonium, nitrate and other compositional components are almost complete. Sensory trials will be conducted on the 2022 wines after they have been in the bottle long enough to reduce bottle shock and for maturation. Varietal differences in response to foliar N application in the field are present and treatment effects on N content in the finished wines indicate quality differences are present. Amino acid content in the must and wine from foliar N treatments was elevated which coincides with the elevated yeast assimilable nitrogen content evaluated in objective 1. Sensory evaluation of wines from previous years indicate less vegetative and more fruity characteristics with foliar N applications. Yeast assimilable N was elevated enough with foliar N application to complete fermentation without supplemental DAP additions while maintaining or enhancing wine quality.
Objective 5: Determine the influence that amino acid composition and diammonium phosphate additions have on wine flavour, aroma profiles and fermentation kinetics
This objective has been partially met. Investigation of amino acid composition and its influence on quality in Pinot gris and Cabernet Sauvignon is almost complete. Amino acid analysis of the 2022 vintage will be completed shortly. We have significant differences in amino acid profiles and we will investigate the sensory impact on 2022 wines when we complete the sensory analysis. Fermentation kinetics were not affected by treatments.
Objective 6: Evaluate YAN requirements in icewine and high sugar musts with respect to recent findings on yeast nutrition such as biotin, pantothenic acid and other vitamin requirements
This objective was deferred. We harvested grapes for icewine trials to be conducted this fiscal year but due to time constraints and a shortage of student help we were not able to complete this component before the end of the project. We would like to continue this work in the new fiscal year since it is partially done.
- Kevin Usher, AAFC Summerland
Activity 12 - TanninAlert: improving red wine quality and consumer acceptance
Over the last decade, the increasing popularity of red wines has driven consumer market growth in Ontario and Canada. Red wine, both foreign and domestic, represents 53% ($4.17 billion) of the $7.85 billion of wine sales in Canada in 2020 (Statista, 2021). However, foreign imports still dominate the red wine market, representing 73% ($3.04 billion) of the red wine sold in Canada ($4.17 billion) in 2020 (Statista 2021). Similar trends are reported in Ontario. Given the overall trend of increased red wine consumption in Ontario and Canada, there is a tremendous opportunity for domestic growth in red wine sales and production. Strategic initiatives that are focused on developing product and process innovations to improve quality are the key to meeting consumer demands and subsequent growth of the industry.
The main objective of the overall Tannin project is to improve Ontario red wine quality by ensuring grape phenolic ripeness is incorporated into harvest decisions. Tannins are one of the most defining components of the quality of red wine. Understanding how to best manage winemaking techniques based on tannin values in the fruit are important steps towards improving red wine quality. This project is developing a unique precision oenology tool for winemakers that measures the maturation of red grapes based on tannin development, specifically “TanninAlert”. The tool analyzes tannin concentration in skins and seeds, separately, for red grapes to evaluate phenolic levels in these grapes. The values are bench marked against tannin measurements from Ontario red grapes collected over the past eight years between 2015-2022 and available in a database of skin and seed tannin. Red winemaking guidelines based on tannin concentrations will also be available from the TanninAlert database.
In this past year, the skin and seed tannin values during ripening and at harvest in 2022 were determined for Pinot noir, Cabernet franc, Cabernet sauvignon, Merlot, Syrah, Gamay for addition into the TanninAlert database. Histogram plots of tannin distribution, grouping the tannin into low, medium and high skin and seed tannin values based on the 33rd and 66th percentile of the distribution, are available for all red varieties tested including Pinot noir, Cabernet Franc, Cabernet Sauvignon, Gamay, Merlot and Syrah. All red varieties were also grouped together and presented as one histogram for seed tannin and one histogram for skin tannin so that tannin values could be compared across all varieties. The tannin commercial testing service, based on these distribution values, was launched by CCOVI in October of 2022 in partnership with CGCN and OGWRI.
Tannin management techniques for winemaking in 2022 for Merlot and Syrah tested different amounts of extra small oak chip preparations (Arobois) during the fermentation to determine if tannin extraction and stabilization was improved compared to a control. There was no benefit with respect to tannin extraction and stabilization for the treatments tested at the six month post-fermentation time point for either variety tested.
The tannin stability of wines made in 2021 was also completed in 2022 for Merlot and Syrah. The Merlot treated with Flash Détente continued to have the highest tannin value at the 6 month testing timepoint compared to the control with no treatment. The wines that contained a mix of fruit not treated with flash detent and treated with flash détente had tannin values midway between the control and the 100% treatment. Tannin stability was retained over the 6 month testing trial which was a significant finding as many of the tannin trial treatments over the course of this program did not show stability over time. For Syrah, a liquid tannin addition to maintain tannin in wine was trialed post fermentation and post filtration compared to a control wine with no liquid tannin addition. Tannin stability was only found in the wines that had tannin added post filtration. The tannins appeared to drop out of solution if they were added post fermentation but pre-filtration.
The extractable tannins in the Gamay wines of 2021 were below the detectable level in the wines using the MCP assay so tannin stability tests could not be run.
Due to COVID 19 restrictions with concerns with aerosol transmission of COVID 19, no sensory or consumer tests could be performed in 2022 on wines from prior years.
- Debra Inglis, CCOVI at Brock University
Activity 13 - Improving wine quality through mixed and sequential fermentation with indigenous yeasts
Winemaking is a burgeoning industry in Nova Scotia, with many new opportunities to create regionally distinctive products. While commercial yeasts are usually added to grape juice to induce wine fermentation, many native yeasts reside naturally on grape skins and can noticeably influence wine flavour (the “microbial terroir”). There is therefore recent interest in natural, or spontaneous, fermentations that forgo the addition of commercial yeast and rely on native yeasts to produce wines that are more representative of the local region. Although a lack of control over the end product makes natural fermentations somewhat risky, this can be reduced by using both indigenous (native) and commercial yeasts simultaneously (mixed fermentation), or by allowing the native yeasts to ferment initially, followed by commercial yeast to ensure completion of the fermentation process (sequential fermentation). This project aimed to 1) document and characterize the native yeasts in Nova Scotia vineyards, 2) determine their influence on wine quality, alone or in combination with commercial yeast, and 3) grow and store promising native yeast strains to produce mixed starter cultures that can provide the benefits of native yeasts without the risks of fully natural fermentations.
Grape samples were collected from eight Nova Scotia vineyards over multiple years and used for spontaneous (natural) fermentations. Yeasts were also cultured from these grapes and characterized with respect to their fermentation properties. Promising indigenous yeasts were then utilized in both mixed and sequential fermentations with a commonly used strain of commercial yeast. The flavour and aroma of the products of these fermentations were assessed by a wine tasting panel to link the quality of the final products to the occurrence of specific native yeasts. Indigenous vineyard yeast communities were also characterized by next generation DNA sequencing technology before and after spontaneous fermentation, as well as across vineyards and across sampling years, allowing for more informed selection of promising indigenous yeast strains.
The isolated indigenous yeasts exhibited a wide diversity of fermentation properties (e.g., tolerance to alcohol and sulphur dioxide). Wines made with the indigenous yeast Saccharomyces uvarum, and wines made with non-Saccharomyces yeasts had alcohol and acid levels that were slightly lower, and sugar levels that were slightly higher, than wines fermented with commercial yeast. A native yeast collection and data base have been established for future research and to allow wine makers access to this resource.
Wine tasting scores (based on flavour, texture and aftertaste) for wines produced with an indigenous species of Saccharomyces followed by commercial wine yeast after either seven or 14 days were generally somewhat better than the score for the commercial yeast alone, although the differences were not statistically significant.
Important attributes of these wines included light flavour, sweet, crisp and apple taste. Scores for wines fermented with three non-Saccharomyces indigenous yeasts followed by a commercial yeast at 4 and 7 days were also higher than that score for the commercial yeast alone. Although again, the differences were not statistically significant. Important attributes included strong flavour, bitter and pungent tastes in some cases.
Scores for wines made using mixtures of indigenous Saccharomyces yeasts and commercial yeast at different ratios were more variable. Favorable descriptors included sweet, light flavour, pear, and citrus, although some bitter and pungent attributes noted in some treatments. Scores for the mixed fermentations were slightly higher than for the commercial yeast alone, but one of the yeast mixtures resulted in wines with an average score that was significantly higher that that of the commercial yeast alone.
The next generation DNA sequencing of vineyard yeasts showed strong shifts from non-fermentative yeasts in the pre-fermentation musts to dominance by either Saccharomyces cerevisiae (the same species as used commercially) or its native relative, Saccharomyces uvarum. The DNA data also shows that although yeast communities within a vineyard differed from year to year, this was not as great as the variation among different vineyards. Although we had expected that yeast communities in vineyards with organic management would be more diverse than in conventional vineyards, this difference was not statistically significant. However, there were large differences in the groups of yeasts inhabiting organic and conventional vineyards, mainly related to the types of non-fermentative yeasts present.
We have characterized Nova Scotian indigenous vineyard yeasts in terms of their diversity, fermentative properties and the taste and aroma of the wines they can produce. We found that specific mixtures of indigenous and commercial yeasts can result in wines with sensory attributes superior to those made with commercial wine yeast alone. This is a promising result, which together with our other data, will allow local winemakers to begin utilizing the native yeasts found in their vineyards to create distinctive wines with qualities reflecting the Nova Scotia wine making region.
- Lihua Fan and Gavin Kernaghan, AAFC Kentville and Mount Saint Vincent University
Activity 14 - Improving sparkling and still wine quality: preventing high volatile acidity, honey off-flavour and other faults through Canadian yeast isolates
In wines, a limited amount of “sweet/honey” flavour contributes to the complexity of wine, but at high levels, is considered a fault (Campo et al. 2012). It has been observed by sparkling producers in Canada Ontario that sparkling wines in Ontario produced with Pinot noir grapes (susceptible to sour rot) can have an obvious “sweet/honey” flavour. With sparkling wine production on the rise across Ontario, it is critical that this issue is addressed. Two specific aroma compounds identified in wine that cause this “sweet/honey” off-flavour are Ethylphenyl acetate (EPhA) and Phenylacetic acid PhAA (Campo et al. 2012). Both compounds were reported to contribute to “sweet/honey” off-flavour in wines made from grapes that contain some sour rot (Campo et al. 2012). It is unclear as to when these problem compounds originate, and the direct linkage to sour rot development in grapes. It could be that the grapes have high levels of the precursor, and the sour rot microbial complex acts on the precursor contributing to the “sweet/honey” off-flavour when sour rot develops in the fruit. Alternatively, commercial yeast could be forming these compounds during fermentation when acetic acid levels are high in the starting must (such as when sour rot grapes are present) through esterification reactions with other fermentation metabolites.
PhAA is a plant-growth regulator so it could possibly be produced in grapes susceptible to sour rot as a growth response to an alteration of the surface of the grapes. No studies to analyze the grapes before, and after, sour rot to measure the precursor PhAA and the metabolite EpHA have been carried out. We hypothesize that these compounds are high in grapes as they begin to break down internally from sour rot, and then are transferred to the must and ultimately the wine. Studies have not been carried out on Ontario varieties in Canada prone to sour rot used in red table wines and sparkling wines (Pinot noir). Consumer threshold levels have been identified in wines made from the Portuguese red grape variety Trincaderia. However, the “sweet/honey” off- flavour also appears to be increased by the common nitrogen additive Diammonium phosphate (DAP) during fermentation and lees aging. It is essential we test grapes harvested for sparkling wine that are known to be susceptible to sour rot, for the precursor and the metabolite (Torrea et al. 2011, Campo et al. 2012). The thin-skinned Pinot noir is particularly susceptible to sour rot, widely planted across Canada and in Ontario and used in sparkling wine production.
One way to improve quality and further provide a sense of regional identity to Canadian wine is through the use of locally isolated yeast. Inglis has been characterizing a natural yeast isolated from the skin of local Icewine grapes in Ontario, CN1. Although the yeast was not a sufficiently strong yeast to ferment above 9% v/v ethanol in Icewine, it has proven beneficial for appassimento wine production in that it is a low producer of the oxidative compounds acetic acid, ethyl acetate and acetaldehyde while also offering a favorable, unique flavor profile to the wines and over 16%v/v ethanol. This project has the opportunity to fully characterize the commercial potential of locally isolated yeasts, one of which is already known to produce lower levels of acetic acid, acetaldehyde and ethyl acetate during fermentation. This yeast also appears to consume large quantities of acetic acid during the fermentation, and may further reduce the formation of “sweet/honey” off-flavour. Applications of this yeast may extend beyond appassimento wine production to still red wine production, sparkling base wine production and a specific application to reduce negative impacts from a percentage of sour rot fruit on overall wine quality.
The overall objectives of this project are to identify if two “sweet/honey” off-flavours from ethyl phenylacetate (EPhA) and phenylacetic acid (PhAA) are present in Pinot noir grapes because of sour rot infection, as well as in sparkling and still wines fermented from those grapes. Test consumer acceptance of the compounds in red and sparkling wines, and test if natural indigenous yeast isolates from Canadian vineyards can remove the compounds along with acetic acid. Furthermore, an indigenous yeast isolated from an Ontario vineyard will be trialed for commercial scale red wine production.
- Quantify EPhA, PhAA, ethyl acetate and acetic acid levels from clean and sour rot infected fruit in grapes prior to harvest to measure baseline values of taint and precursor compounds in grapes. Produce
- Pinot noir sparkling and still red wines with varying amounts of sour rot to determine if the taint compounds EPhA, PhAA, ethyl acetate and acetic acid are present.
- Determine the potential of the indigenous yeast isolated from Ontario to reduce acetic acid, EPhA and PhAA in sparkling and still red wines.
- Establish the consumer detection and the consumer rejection threshold levels of EPhA and PhAA associated with “sweet/honey” off-flavour in Pinot noir sparkling and still red wines to determine at what concentrations the compounds affect wine quality.
- Differentiate and describe sparkling wines made from grapes with varying sour rot levels fermented with a standard commercial yeast versus the Brock isolated yeast.
- Assess the commercial application of the Brock isolated yeast CN1 for fermenting appassimento wines
Both still red wines and sparkling wines were made in 2019 and 2020 as per previous reports. Still wines from 2019 and 2020 were already analysed for the standard juice and wine chemical analysis including acetic acid and ethyl acetate following standard procedures of enzyme kit (Megazyme) for acetic acid and GC FID for ethyl acetate. The 2020 sparkling wines were disgorged in June 2022 and laboratory analysis of these wines were completed in 2022-2023. The two “off-flavour” compounds EPhA and PhAA were measured in the sparkling wines after disgorging using the GC MS method developed in prior years. Sensory analyses of the sparkling wines has not been completed yet due to COVID-19 restrictions and challenges associated with COVID, as it was dependent upon the health and safety guidelines of the Brock University Research Ethics Committee.
Commercial fermentations of Cabernet franc appassimento wine were trialed with the active dry culture of the CN1 yeast at Pilitteri winery whereas paste formulations of CN1 were also completed with Cabernet franc, Merlot and Corvina appassimento juice in the fall of 2021. All wine replicates were placed into individual barrels for aging at the winery (24 in total) in 2022. After one year in barrel, sufficient wine from each treatment (10L) was transferred to CCOVI for bottling in 2023 and future study. Wines were sulfited, bottled and all chemical analysis of the wines was completed in 2023. No sensory evaluation of the wines was performed as it was not scheduled within this project and there was insufficient time after bottling was completed.
- Belinda Kemp, CCOVI at Brock University
Activity 15 - Unearthing the impacts of plant-parasitic nematodes on grapevine health and productivity
Plant-parasitic nematodes (PPNs) are important components of vineyard soil ecosystems, with several species of root-knot (Meloidogyne sp.), root-lesion (Pratylenchus sp.), dagger (Xiphinema sp.) and ring (Mesocriconema sp.) nematodes known to be significant pests of grape vines grown in most major grape-growing regions of the world. The impacts of PPNs on grapevine health in the Okanagan and other cool climate growing regions in Canada are less well known. Vineyards generally harbour multiple species of PPNs and research to assess the interaction of multi-species PPN assemblages with other biotic and abiotic stresses under field conditions would greatly improve current understanding of the overall impacts of PPNs on grapevine health and vineyard productivity. More specifically, better knowledge of the distributions of PPN species among vineyards would improve understanding of the overall importance of PPNs to vineyard health in Canada; improved knowledge of PPN spatial distributions within vineyard blocks would facilitate the development of improved sampling strategies for diagnostic purposes. As well, analysis of factors governing spatial variation in PPN populations would enhance fundamental understanding of factors driving spatial variation in broader soil biological processes, and the influences of agricultural practices on those populations and processes.
Objectives of the proposed research:
- Determine the distribution of key species of plant-parasitic nematodes (PPNs) in relation to soil health indicators in representative Okanagan vineyards
- Assess spatial co-variation of PPN populations with vine water stress and the incidence of trunk and crown gall disease.
- Use controlled-inoculation of field micro-plots to experimentally determine effects of key PPN species on vine growth and incidence and expression of disease complexes.
- Determine the presence and abundance of key PPN species in representative vineyards in Nova Scotia.
Methodology and Results:
Objective 1 - distribution of key species of plant-parasitic nematodes (PPNs) in relation to soil health indicators in representative Okanagan vineyards.
There was no significant activity on this objective in 2022 as it was completed in 2021.
Deliverable Publication: Forge, T., Munro, P., Midwood, A.J., Philips, L., Hannam, K., Neilsen, D., Powers, T., and Zasada, I. 2021. Shifting prevalence of plant-parasitic nematodes in orchards and vineyards of the Okanagan Valley, British Columbia. Plant Health Progress. Published Online: 24 Mar 2021, https://doi.org/10.1094/PHP-10-20-0079-RS.
Objective 2 - spatial co-variation of PPN populations with vine water stress, vine decline symptoms in virus-infected and virus-free grapevines, and the incidence of trunk and crown gall diseases.
The approach and methodology for this objective involved analyzing population densities of plant-parasitic nematodes in key field experiments being managed by CGCN-funded collaborators as follows:
Relationships with irrigation scheduling and vine water relations:
This field experiment was established by AAFC collaborators Pat Bowen & Carl Bogdanoff at SuRDC in 2018. The initial objective was to determine effects of alternative irrigation scheduling protocols on ring nematode (Mesocriconema xenoplax) population densities, vine growth parameters, and relationships between nematode population densities and vine growth parameters. Sampling and analyses of nematode populations in all 60 plots was initiated in spring of 2018, and was repeated in May and October of each year thereafter. However, the irrigation treatments and vine water relations ceased in 2020 due to Covid-19, and the two collaborators retired in 2021. Nonetheless, analyses of nematode populations in all plots carried on from 2018 through 2022. As the irrigation treatments ceased in 2020, statistical analyses are proceeding to relate plot-to-plot variation in nematode population densities to plot-to-plot variation in indicators of vine vigour.
Statistical analyses to date indicate a positive relationship between ring nematode population densities averaged over the entire study period and vine trunk cross-sectional areas. The maximum and range of population densities observed at the site are not very high relative to population densities observed in some vineyards (e.g. Forge et al. 2021).
Relationships with compost amendments and incidence of crown gall:
Two separate field experiments were established by UBC-Okanagan collaborators Tanja Voegel and Louise Nelson, with Ph.D. student Portiaa McGonigal, at Westpoint vineyard in southeast Kelowna. The objective of both experiments was to determine if surface application of composts to vine rows affects population dynamics of plant-parasitic nematodes, and through collaboration to analyze relationships between nematode population densities and incidence of crown gall, vine growth and fruit quality parameters. The first experiment was initiated in spring of 2019 using a randomized complete block design with three different compost treatments and a non-treated control applied to plots within in each of six replicate blocks. The three compost treatments were: GlenGrow municipal compost from the City of Kelowna (GG), Superior Peat’s Weston blend compost (SP), and winery waste compost (WW) produced by the collaborating winery. All composts were surface-applied to the vine row at a bulk rate estimated to provide the same amount of organic matter: 6.12 Mg organic matter/ha vineyard. The second experiment was initiated in a different part of the same vineyard in spring of 2020, and involved application of GG and SP composts in comparison to mounding of soil and non-treated control plots.Composite soil samples were taken from each plot for nematode analyses at the time of project initiation and in spring and fall of each year thereafter. Sampling procedures and methods for nematode analyses were the same as those used routinely in the PI’s lab and described in previous publications (e.g. Forge et al. 2019).
Detailed methodology and results information from this section is being withheld to avoid potential conflicts or difficulties during future manuscript publication.
Objective 3 - controlled-inoculation of field micro-plots to experimentally determine effects of key PPN species and mixtures on incidence and expression of disease complexes.
While root-lesion nematodes (Pratylenchus species) are widespread in BC vineyards, greenhouse experiments conducted in previous years indicated that Pratylenchus penetrans, the most common species on most other cool-temperate horticultural crops such as apple and cherry, is not able to parasitize V. vinifera grapevines. In 2022, work to identify the species from BC vineyards indicated that most vineyards have P. neglectus rather than P. penetrans. New cultures of P. neglectus from vineyards, for use in future experiments, have been established at SuRDC.
The nematology lab is collaborating with the grape pathology program (Dr. Urbez-Torres, Ph.D. student Jared Hrycan) via contributing to greenhouse experiments and a field microplot experiment to test the influence of ring nematodes on expression of trunk diseases. The greenhouse experiments were conducted in previous years. The field microplot experiment was inoculated and planted in early 2021. Winter injury incurred during the winter of 2021-22 was rated after bud break in early June of 2022. Chi-square analyses indicated that a greater proportion of nematode-inoculated vines (44%) died over winter than non-inoculated vines (19%).
Objective 4 - presence and abundance of key PPN species in representative vineyards in Nova Scotia.
There was no activity associated with this objective in 2022 as work on it was completed in 2021.
Deliverable publication: Forge, T., Munro, P., Wright, H. & Moreau, D. 2022. Plant-parasitic nematodes in Nova Scotia vineyards. Phytoprotection, 102(1), 15–20. https://doi.org/10.7202/1088485ar.
- Tom Forge, AAFC Summerland
Activity 16 - Novel approaches to IPM strategies for climbing cutworm in grapevines
- Deborah Henderson, Kwantlen Polytechnic University
Activity 17 - Grape & Wine Leafhopper Management
Leafhoppers are economically important pests of grapes in Canada. Feeding by nymphs and adults causes the death of individual leaf cells that results in reduced photosynthetic activity, depletion of stored carbohydrate, and delayed fruit ripening. Damage varies between regions and locally due to several factors, including production practices (e.g. organic vs. conventional; hybrid versus vinifera), climate, and the abundance of natural enemies. Control is currently achieved largely with applications of broad-spectrum insecticides, but there is growing interest in alternatives that contribute to sustainable or organic production. This final industry report presents findings from the 2018-2023 CGCN-AAFC (CAP program) leafhopper project (#17) that investigated some of the more promising alternative management strategies for leafhopper control. These included 1) identification and biology of Anagrus parasitoids of leafhopper eggs including their alternate summer and winter hosts and involving several sub-objectives, 2) evaluation of the efficacy of new insecticides, 3) assessment of leafhopper antifeedants, and 4) effect of deficit irrigation on leafhopper populations.
As summarized below, significant progress was made on this project in spite of the many delays and difficulties. Some of the notable discoveries/progress include:
- Discovery of a new species of Anagrus egg parasitoid from willow.
- Development of genetic DNA libraries for the identification of Anagrus parasitoids and their leafhopper hosts.
- New tritrophic relationships determined for Anagrus species, their leafhopper hosts, and the leafhopper host plants.
- Characterized effectiveness of foliar oil sprays and the influence of sprayer technology on levels of leafhopper control.
- Determined the female:male sex ratio for A. daanei in BC.
- Identified new insecticides that are highly effective against leafhoppers.
- Identified fungicides and surfactants that effectively deter leafhopper feeding in the laboratory and in the field.
- Successfully modelled leafhopper and scale development in relation to temperature and grape phenology stages.
- Publication of technical bulletins, industry presentations, and updated insect and mite chapter of the BC grape production guide for grapes.
Numerous considerable difficulties were encountered during the conductance of this project, including most importantly the pandemic that resulted in restrictions that hampered research and contact with colleagues and growers. COVID spawned the need to adjust research activities, alter staffing of students, and to change budgets. The heat dome impacted field work in BC over one summer, and there were several staff changes and retirements as well. In spite of these many and serious obstacles, most of the objectives were fully or largely completed. Delays caused a need to conduct additional research over the final year of the project with some data analysis and preparation of reports and papers still to be completed. In all this research has made a significant contribution to our knowledge of Anagrus parasitoids of leafhoppers and their associations with specific leafhopper hosts and the winter and summer plant hosts of those leafhoppers. Molecular sequencing has led to the development of accurate and rapid testing for the identification of many species of Anagrus parasitoids and leafhoppers. A species of Anagrus new to science was identified in BC by the North American expert on the taxon, Dr. S. Triapitsyn. Research has quantified that a whole region of coastal BC is largely devoid of insect pests, including leafhoppers, other than occasional yellowjacket problems affecting ripening fruit. The reason for this absence requires explanation.
Insecticide lab bioassays identified several novel insecticides that are highly effective against leafhoppers, and replicated field spray trials with horticultural oils demonstrated that with good leaf coverage these materials can be very effective for the control of leafhoppers. Contributing also to organic or sustainable production of grapes, laboratory feeding choice test bioassays and field trials found that certain surfactants and the fungicide Sirocco were highly deterrent to leafhopper nymphs and could provide effective control in the field. Initiation of research to model stages of leafhopper population development based on temperature and grape phenology models will help producers to implement various controls as part of a comprehensive leafhopper management program. From previous and current research these measures include timing of early season removal of basal leaves, application of oils or insecticides timed against peak numbers of 1st or 2nd generation nymphs, and optimum timing of surfactants or fungicides that act also as effective leafhopper feeding deterrents.
This project contributed considerably to our knowledge of leafhoppers and their Anagrus parasitoids and the development fine-tuning of techniques and protocols that will contribute to future studies. Molecular diagnostics will help with research on these pests and their most important natural control agents, while the lab protocols developed to accurately evaluate the efficacy of insecticides or the deterrent effects of materials will assist in future studies involving these or other insect pests. Presentations and scientific manuscripts are forthcoming upon completion of diagnostic tests and statistical analyses.
- Tom Lowery, AAFC Summerland
Activity 18 - Mitigation of infestations of multi-coloured Asian lady beetle (MALB)
This project is complete as of 2020. Please refer to Year 3 Cluster updates.
- Wendy McFadden-Smith, CCOVI at Brock University
Activity 19 - Using ground cover to control soil bourne pathogens in grapevines
The role of groundcover in pathogen control is largely unknown, yet it is well known plants can alter the composition of soil fungal communities. Increasing the biodiversity of Canadian vineyards above ground may have advantages beyond pathogen suppression, including improved nutrient retention, improved soil structure, reduced herbivory. These ecosystem services will become increasingly important as growers experience the effects of future climate regimes. Although grape growers are eager to exploit cover crops as biofumigants there is insufficient evidence to recommend particular crops or combinations. We will test the role of plant identity in cover crops in viticulture on the incidence and abundance of common trunk fungal diseases.
- Assess existing ground cover management/disease incidence in the Okanagan wine growing region
- Develop ground cover mixes (and management) that reduce root disease
- Test and monitor common vine diseases in commercial vineyards
This research will identify groundcover mixes and management to reduce pathogens in grapevine and promote low input, sustainable viticultural practices. Building on current work which shows that the identity of groundcover mix has significant effects on the abundance of vine pathogens and beneficials, this project represents the next step: translating experimental findings into robust industry practices.
Our study found brassica cover crops to increase species evenness which is inconsistent with current literature. We found no significant difference in effect on diversity metrics among different brassica species. There was no effect on the soil fungal community composition, soil nematode abundance, or AMF spore abundance between brassicas and the control or among brassica species. From the results of this study, we can suggest there would be no detriments to using these brassica species as cover crops in a vineyard. Although the brassica species used are non-mycorrhizal, they do not appear to suppress the AMF population. Additionally, they are not able to host ring nematodes. Shepherd’s purse and white mustard in particular show potential for controlling the PPN population. Regarding other benefits expected from using plants with biofumigant properties, more research should be done on the functional changes in the soil rather than only species diversity and composition. The only possible negative result is that all brassica species used appear capable of being colonized by Ilyonectria. However, more research needs to be done to understand this interaction and if it would be detrimental in a vineyard. The results from this study provides evidence that brassica cover crops are a safe cover crop choice for vineyards. Although the beneficial effects may be smaller than desired, there is potential for suppression of soil-borne pathogens using brassica cover crops without the need for incorporation. Future studies should focus on maximizing these beneficial effects as well as studying the interactions between the cover crop and the cash crop under field conditions.
- Miranda Hart, University of British Columbia-Okanagan
Activity 20 - Crown Gall Disease of grapevines: identification, bio-control and sustainable management strategies
Crown gall of grapevines, caused by the bacterium Allorhizobium vitis, is an economically important disease in grape-growing regions with a continental climate, particularly in those where winter freezing occurs. Crown gall significantly reduces plant vigor and the disease may cause partial or complete vine death, especially in young vines, resulting in significant economic losses for the grapevine industry. The disease is found in many vineyards in BC and ON and seems to be on the increase, likely due to introduction of A. vitis through contaminated nursery stock. The pathogen can also be present in vineyard soil, enters the vine through wounds in plant roots and trunks caused by winter freezing and survives systemically in grape plants. Galls can be formed in trunks or even in 1-year-old canes.
We have developed a methodology to quantify the abundance of A. vitis in nursery stock in an earlier study but have previously only tested the methodology on a small number of samples from different nurseries. Currently, there is no chemical or biological control commercially available for crown gall.
The objectives of this study were:
- Testing of dormant grapevine nursery stock for abundance of A. vitis
- Isolation of potential biocontrols for A. vitis from vineyards in British Columbia and Ontario
- Evaluation of potential biocontrols to prevent crown gall in a greenhouse assay
- Evaluation of organic amendments to prevent or suppress crown gall in a greenhouse assay
- Evaluation of compost treatments to suppress crown gall in a commercial vineyard
- Evaluation of organic amendments to prevent crown gall in an experimental vineyard
We found that most ready-to plant grapevine material originating from national and international nurseries that sell vines to Canadian growers harbors crown gall causing bacteria. Unfortunately, it is not known where in the propagation process the infection occurs, and therefore no recommendations for nurseries can be made. However, we found that the bacterial threshold for disease development is high (>5,000 bacteria), which means that plants with bacteria may not develop disease after planting. Emphasis of growers needs to be placed on avoiding vine injuries in the early years after planting by using viticultural management practice that lead to less freeze injuries (good site selection, less water and fertilizer in fall).
We also found that hilling up around the graft union prevented the development of galls, but more data, including economic analyses, are needed and will be done in future research. Soils are likely already infected with crown gall bacteria, due to earlier planting of contaminated nursery material, but it is not known how long bacteria stay in the soil. Biocontrol will be the most important tool to prevent disease in newly planted vines, and we found bacterial and fungal strains that inhibited the growth of A. vitis in-vitro. We were not successful to show biocontrol using these organisms in greenhouse experiments but have made advances in establishing greenhouse assays for future biocontrol assays. In future research, emphasis will be placed on testing more biocontrols in-planta form different sources, including wild grapes and biocontrols found by other researchers. We also established a collection of locally isolated A. vitis strains, the first of its kind in Canada, which will be helpful when treatment options are explored. Compost treatments had no effect on crown gall incidence, but improved soil health and influenced nematode populations. Crown gall bacteria in the soil were greatly reduced at the end of 2022, compared to high numbers in 2017, independent of treatments.
- Louise Nelson, University of British Columbia - Okanagan
Activity 21 - From nursery to vineyard: Implementation of effective management strategies against grapevine trunk disease in Canada
The long term economic viability of the grapevine industry relies on healthy planting material and effective disease management strategies in vineyards. Grapevine trunk diseases (GTDs) are considered one of the main biotic factors limiting both yield and vineyards’ lifespan worldwide (Gramaje et al. 2018). Studies conducted by the Plant Pathology laboratory at the Summerland Research and Development Centre (SuRDC) since 2010 have significantly contributed to a better understanding of the current status of GTDs in British Columbia (BC), laying the foundation for the development of effective control strategies (O’Gorman et al. 2015; Úrbez-Torres et al. 2014a, 2014b, 2015). However, contrary to most grape-growing countries around the world, neither cultural practices nor registered products (chemical or biological) are currently available to control GTDs in Canada. Therefore, the main objective of this research project was to develop and implement sustainable management strategies against GTDs in both young and mature vineyards as well as at the nursery level. This project investigated cultural practices such as best pruning time to reduce GTDs infection and also focused on potential environment-friendly biological control options. Additionally, this research aimed to demystify the role that abiotic and/or biotic stress factors, such as water stress and nematodes play on GTDs development in young vineyards. The ultimate goal of these studies aims to provide scientific-based information to Canadian growers about best planting and growing conditions to minimize the impact of GTDs.
Research conducted in this project and based on Droplet Digital PCR™ technology, allowed us to develop a rapid, accurate and sensitive molecular tool for the detection and absolute quantification of GTDs fungi present in ready-to-plant nursery stock. We implemented this technology in assessing the health status of domestic and international grapevine nursery material sold in Canada. Overall results showed all plant material evaluated to be infected with at least one fungus associated with GTDs. However, fungal abundance varied between sections (roots, base of the rootstock, graft-union, and scion) within the same plant, between plants within the same nursery and between nurseries. This study is the first of its type worldwide and will assist to identify inoculum sources as well as management strategies to mitigate infections at the nursery level. With such high levels of infection reported, it can be hypothesized that the presence of these fungi in the ready-to-plant nursery material may not directly imply the death of the plant or otherwise viticulture in Canada would not exist in its current form. It is possible that these fungi act as latent pathogens in nursery plants, transitioning from endophytic to pathogenic under abiotic and/or biotic stress conditions (Hrycan et al. 2020). Work conducted in this project under greenhouse and natural field conditions has shown abiotic stress factors such as water stress to play a direct role on favoring fungal growth and disease development in young vines. This represents critical information since long periods of higher than usual temperatures and corresponding water stress are becoming more prevalent across BC grape-growing regions due to climate change.
Work conducted in this project has identified for the first time effective locally sourced biological agents (BCAs) to be used as pruning wound protectants to control GTDs. Seven species in the Trichoderma genus, including two novel species for the scientific community, were fully characterized. Laboratory, greenhouse and field trials have been completed and results from these studies showed high efficacy of three of these Trichoderma spp. as BCAs. Locally-sourced Trichoderma spp. from BC showed similar or better control when applied as pruning wound protectants than commercial BCA and chemical fungicides. In addition, our laboratory has generated required field data to advance the registration of the first commercial products (biological and chemical) for the control of GTDs in Canada. Furthermore, studies to investigate the use of remedial surgery as a cultural practice in BC to mitigate infection were completed. Results showed 100% vine survival and return to economically sustainable production two to three years after treatment.
Despite the difficulties and work limitations experienced due to the pandemic restrictions during 2020 and most of 2021, all objectives scheduled in the project have been successfully completed. Results from this project are of significant importance as they bring the first management options for Canadian grape growers to control and mitigate the impacts caused by GTDs.
- Jose Urbez-Torres, AAFC Summerland
Activity 22 - Grape & Wine Terroir and Precision
A summary of the work conducted for Activity 22, by objective:
GIS update and soil carbon survey:
The green house gas (GHG) emission due to human activities is one of the major drivers causing climate change. The GHG emission in agricultural sector is not fully understood. In the Interior BC, while the precipitation is the limiting factor of grape production, the viticultural production in BC relies on irrigation. The irrigated water can increase overall carbon fixation in this semi-arid environment. Thus, the viticultural practices in the Okanagan valley might contribute to GHG reduction. This study aims to find the correlations between soil carbon and all other vineyard characteristics we had collected in the GIS vineyard database. In this study, we analyzed the soils sampled from vineyards and natural (native) sites throughout the Okanagan Valley. Analyses included total and microbe-available carbon, cation exchange capacity, and plant nutrients. We analyzed additional 70 samples in 2022. The main findings from samples analyzed to date were: zero-tillage viticulture practices, common in BC, are not depleting soil C; and there is a strong relationship between soil C and soil texture regardless of vineyard management practices. These findings reveal the importance of considering soil texture in setting soil C sequestration targets for vineyards. A new map layer of potential carbon storage capability in a vineyard could be generated.
Interactive effects of seasonally timed water stress and cluster exposure:
This study evaluated the effects of water stress and cluster exposure on fruit composition in a Merlot vineyard. A two-way randomized complete block design experiment was conducted in a commercial vineyard in 2019 and 2021. Severe water stress was applied from fruit set to veraison or to harvest. The other milder water stress was applied all season as the control. In this nearly North-South oriented vineyard, high fruit exposure treatment was achieved by removing leaves at the east (80% leaf removal) and the west (50% leaf removal) side of the fruiting zone. The low fruit exposure treatment removed only 20% of the leaves on the east side. The results showed the irrigation treatment didn’t affect cluster exposure. Leaf removal effectively exposed more clusters. The variations of juice Brix, pH and TA can be observed in berry samples taken from the surface of the clusters. This suggested light exposure, as a result of leaf removal, berry location in a cluster, or cluster location in a canopy, can affect juice composition. However, at harvest, no significant differences were observed among irrigation and cluster exposure treatments in yield, clusters per vine, cluster weight, berries per cluster, berry weight, juice Brix, juice pH, and TA. The study suggested direct sunlight exposure might change juice compositions of those exposed berries in the cluster. However, there might be limited effects of irrigation and fruit exposure practices on juice compositions at whole vine level.
Drone based imaging to guide precision management of irrigation and nitrogen:
Drone flight missions were performed in 2022 growing season for the irrigation trial conjugated with Activity 6. The preliminary results showed infrared (IR) thermal images have strong correlation with gas exchange activities of grape vines. The IR images capture the higher operational temperature of leaves when there is limited or no stomata opening. The reduced stomata conductance and transpiration means lower latent heat flux flowing out of the canopy. This experiment demonstrated the potential of using UAV-based platform for fast water stress detection in a large area. This technology might help irrigators to identify failed irrigation devices or help vineyard managers to determine irrigation timing. In the latter case, a well-irrigated plot might be the reference for detecting water stress in a commercial operation. Flight missions were performed in 2022 for the nitrogen trial conjugated with Dr. Kevin Usher’s activity. The hyperspectrum and IR images had been processed. Detailed nitrogen concentration information will be available soon for regression analysis.
Drone and ground based imaging to diagnose grapevine diseases:
Drone flight missions were conducted in the 2022 growing season. The processing of images is still in progress due to the large mass of data for point cloud analysis.
- Pat Bowen, AAFC Summerland
Thank you to our funding Partners: