Viticulture – Breeding & Cultivar Evaluation Session

Assessing Fresh-Market Potential of Vitis × Muscadinia Wide Hybrids through Consumer Sensory Analysis

Charlie Sims, Renee Threlfall,* Margaret Worthington, Penny Perkins-Veazie, Pat Conner, Jeff Bloodworth, Asli Odabasi, Haley Russo, and Jordan Slayden

*University of Arkansas, 2650 N. Young Ave, Fayetteville, AR, 72704, rthrelf@uark.edu

The genus Vitis has two subgenera, Vitis and Muscadinia. Muscadinia are uniquely flavored grapes grown across the Southeast United States that are resistant to many pathogens that affect Vitis grapes grown worldwide. A 33-person team from 12 institutions is investigating Vitis × Muscadinia wide hybrids for enhanced disease resistance and quality (USDA NIFA SCRI #2024-51181-43236). In 2025, 20 fresh-market Muscadinia and Vitis × Muscadinia hybrid grape genotypes (cultivars and breeding selections) from grape breeding programs in AR, GA, and NC were evaluated in a consumer study at the University of Florida, Gainesville. The grapes were evaluated for visual, texture, and taste attributes by four consumer sensory panels (n = 130 per panel) with five genotypes per panel as well as physical and composition attributes of the grapes. Panelists were also asked demographic questions and grape consumption and purchasing habits. For this consumer panel, 65% were female, 53% were aged 22 to 34, 45% had a graduate degree, 95% had consumed bunch grapes, and 71% had consumed Muscadine, with 28% consuming four to 10 times per year with 53% likely to purchase. Genotype affected all physical and composition attributes. Berry weights ranged from 2.8 to 18.1 g. For soluble solids/titratable acidity ratio, 12 of the 20 genotypes were within the ideal range of 16 to 70. Mighty Fine had the highest flavor and overall liking and Altus had the highest appearance liking (both new University of Arkansas System seeded Muscadine grapes released in 2023), JB12-12-A14-29 (Gardens Alive! seedless selection) had highest skin texture liking, and AM-303 (University of Arkansas System selection) had highest pulp texture liking. This consumer study provided information to assist the goal of the project to introduce disease-resistant cultivars with enhanced fruit quality for a more resilient United States grape industry.

Funding Support: USDA NIFA SCRI #2024-51181-43236

Alexandra Gunn | Stephanie Bilek | Ryan MacIntrye-Newell | Benjamin Voss |James Willwerth*

Evaluating ABA Analogues to Improve Dormancy Maintenance and Cold Hardiness in Multiple Grapevine Cultivars

Alexandra Gunn, Stephanie Bilek, Ryan MacIntrye-Newell, Benjamin Voss, and James Willwerth*

*Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada, jwillwerth@brocku.ca

Erratic winter temperatures increasingly threaten grapevine cold hardiness by disrupting dormancy and accelerating deacclimation, raising the risk of freeze injury in cool climate viticulture. Since abscisic acid (ABA) plays a central role in regulating dormancy and cold acclimation, ABA‑based plant growth regulators may offer a promising strategy to enhance winter resilience. However, rapid degradation of natural ABA in plant tissues limits its effectiveness, leading to development of longer-lasting ABA analogues with greater biological activity. From 2017 to 2023, we evaluated the efficacy of two ABA analogues: 8′‑acetylene ABA and tetralone ABA. Exogenous applications of each analogue were applied postharvest at 1.00, 0.50, and 0.25 g/L in Vitis vinifera Merlot and the interspecific Vitis hybrid Marquette. Treatments were compared with S‑ABA and an untreated control. Cold hardiness and deacclimation dynamics were assessed using differential thermal analysis, budbreak timing was recorded based on the first visible leaf tips, and fruit composition at harvest was analyzed for soluble solids, pH, and titratable acidity. Across the six dormant seasons, ABA analogues variably enhanced cold tolerance and improved resistance to deacclimation, particularly under late‑winter conditions. Budbreak was consistently delayed in Marquette, while responses in Merlot were more variable among seasons. Overall, 8′‑acetylene ABA and tetralone ABA were effective in promoting and maintaining cold hardiness and delaying budbreak, while S‑ABA did not influence dormancy maintenance or budbreak timing. Treatment effects on fruit composition were minimal even in seasons with significant delay in budbreak. These results demonstrate that ABA analogues have potential as tools for extending dormancy and reducing cold‑related risk in grapevines. Their efficacy is influenced by genotype and seasonal conditions, highlighting the need for adaptive management strategies and further evaluation under laboratory and commercial production settings.

Funding Support: Ontario Grape and Wine Research Inc., Canadian Grapevine Certification Network, Agriculture Agri-Food Canada Sustainable CAP Agri-Science Cluster, OMAFRA’s Marketing and Vineyard Improvement Program

Hava Delavar | Harlene Hatterman-Valenti*

Genetic Analysis of Budbreak and Cold Hardiness in an Interspecific Grapevine F₁ Population Using rhAmpSeq markers

Hava Delavar and Harlene Hatterman-Valenti*

*North Dakota State University, 1360 Albrecht Blvd. Loftsgard Hall 470-E, 470-E, Fargo, ND, 58105, h.hatterman.valenti@ndsu.edu

Cold hardiness and deacclimation play crucial roles in grapevine survival and productivity in cool and cold climates. Although midwinter cold tolerance has long been used to assess cultivar suitability, increasing temperature fluctuations associated with climate change have accentuated the importance of deacclimation behavior and budbreak timing in determining frost risk. A better understanding of how these traits vary within populations and how they are genetically controlled is needed to improve grapevine adaptation to cold stress and dormancy release. An interspecific F₁ population resulting from a cold-hardy Vitis riparia parent and the cold-sensitive Vitis vinifera cultivar Fresno Seedless was evaluated in Fargo, ND, using an alpha-lattice design with three replications. Genotyping was conducted using rhAmpSeq markers, resulting in 1235 polymorphic loci, of which 642 were retained after quality filtering for linkage map construction. The genetic map consisted of 19 linkage groups corresponding to the grape genome and spanned 1023 cM, with an average marker interval of 1.62 cM. Cold hardiness was evaluated using differential thermal analysis, revealing wide variation in lethal temperature exotherm values among progenies. Genotypes exhibiting greater cold hardiness during midwinter were not consistently those with greater tolerance to spring frost, indicating that midwinter hardiness alone does not predict frost vulnerability. Substantial variation was observed in both deacclimation behavior and budbreak progression within the population. When integrated with the high-density genetic linkage map, these phenotypic data provided insight into the genetic architecture underlying cold hardiness and budbreak in grapevine. This study represents a foundational step toward improving selection strategies for grapevine breeding programs targeting cold and variable environments.

Funding Support: VitisGen3

10:40 am – 11:00 am	Assessing Fresh-Market Potential of Vitis x Muscadinia Wide Hybrids through Consumer Sensory Renee Threlfall, University of Arkansas, Fayetteville
11:00 am – 11:20 am	Evaluating ABA Analogues to Improve Dormancy Maintenance and Cold Hardiness in Multiple Grapevine Cultivars James Willwerth, Brock University, Canada
11:20 am – 11:40 am	Genetic Analysis of Bud Break and Cold Hardiness in an Interspecific Grapevine F₁ Population Using rhAmpSeq Markers Hava Delavar, North Dakota State University, Fargo

Viticulture – Breeding & Cultivar Evaluation Session

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