Dr. Alireza Rahemi (Morehead State University, Kentucky)
The Ontario wine industry contributes approximately $5.5 billion annually to Ontario’s economy. However, cold temperatures remain one of the most significant challenges facing grape growers in the province. While the details of how growers manage vineyards under these conditions are beyond the scope of this article, both active and passive protection strategies play essential roles.
Active protection methods (i.e. wind machines) are typically implemented during cold events to reduce heat loss from vine tissues and prevent damage. In contrast, passive protection methods involve long-term cultural practices applied well in advance of cold events. Among these, one of the most important and cost-effective strategies is the use of cold-hardy cultivars and rootstocks.
Although the inherent winter hardiness of a grape cultivar is genetically determined, rootstocks can influence how vines respond to seasonal temperature changes.
There is increasing research that the selecting the appropriate scion–rootstock combination can significantly influence the cold hardiness of the vine. Ideally, such combinations promote earlier acclimation in the fall, enhancing winter survival, and delayed de-acclimation in the spring, reducing the risk of damage from late frosts.
Based on this concept, researchers at the University of Guelph thought that rootstocks derived from native species (Vitis riparia) adapted to southern Ontario’s variable winters may help regulate the timing of acclimation, thereby enhancing overall vine resilience.
To explore this potential, a research project was initiated to determine whether native grape rootstocks can improve a cultivar’s tolerance to harsh winter conditions, ultimately supporting the development of cold-resistant grapevines resulting in reduced cold injury and enabling vinifera grapes to be grown in non-traditional grape growing areas.
In 2012, approximately 900 native Vitis riparia grapevine selections were collected from woodlots from across Ontario, including regions in Brant, Elgin, Middlesex, Norfolk, and Oxford counties, as well as locations spanning from Windsor to Kingston (Figure 1). These selections were propagated and evaluated for their suitability as cold-hardy rootstocks at the Simcoe UofG research station (Figure 1b).
Figure 1 a) Map of locations where native Vitis Riparia were collected b) Evaluating cold hardiness and drought tolerance at the Simcoe research station. (Source: Rahemi)
Eight of the top-performing clones as the promising cold-tolerant rootstocks (Simcoe #34, #89, #123, #517, #634, #659, #732, and #802), along with a control (Riparia Gloire de Montpellier, RGM), were grafted with Pinot Noir (Clone 828) in 2016. These vines were planted at two sites: the Simcoe Research Station (Simcoe, ON) (Figure 2) and Burning Kiln Winery (St. Williams, ON), and have been evaluated annually for yield, Ravaz index, fruit and wine quality, as well as freezing tolerance. In 2025-2026, Cool Climate Oenology Viticulture Institute (CCOVI) tested the vines to ensure that they are true to type using whole genome sequencing. Additionally, the vines have been screened for key viruses, including Red Blotch Virus, Leafroll Virus (types 1–4), Fanleaf Virus, and Pinot Gris Virus and plans are also in place to establish to add clean plant material from some of these rootstocks to the Canadian Grapevine Certification Network grape repository at Brock University.
Figure 2 Brayden Lafleur showing the Planting of top-performing clones on Pinot Noir at the Simcoe Research Station.
Continued monitoring and research are essential to fully understand the potential of these rootstocks. Ongoing collaboration among the University of Guelph, CCOVI-Brock University, and OMAFA specialists will be critical to advancing this work and ensuring that the most promising selections are made available to growers as soon as possible.
Finally, I want to acknowledge colleagues we have lost over the course of this work, especially Dr. Helen Fisher (University of Guelph) and Phil Ryan (OSCWGA), both of whom played pivotal roles in guiding and supporting this project.
This work continues to be supported by a collaborative team of faculty, specialists, and staff from multiple institutions, including Dr. John Cline (University of Guelph), Dr. Sudarsana Poojari, Dr. Ping Liang, and Dr. Jim Willwerth (CCOVI/Brock University), Dr. Adam Dale (University of Guelph), Dr. Alireza Rahemi (Morehead State University), Dr. Wendy McFadden Smith and Kathryn Carter (Ontario Ministry of Agriculture, Food and Agri-business), as well as Brayden Lafleur (University of Guelph/Brock University) and Torin Boyle (University of Guelph), Dr. Andrew Reynold (formerly CCOVI/Brock University)and Nik Antunovich (Burning Kiln winery).
We also gratefully acknowledge the Ontario Agri-Food Innovation Alliance, Ontario Grape and Wine Research Inc. (OGWRI) and the Ontario South Coast Wineries and Growers Association (OSCWGA) for providing funding for this project.
Dr. Helen Fisher- Initiated this rootstock project, and her research continues on with the Legacy Project