January 2019 Issue of Wines & Vines

Growing Corot Noir Grapevines in Missouri

A study on the effects of training systems and pruning severity on performance

by R. Keith Striegler, Eli Bergmeier and Mark Pederson

Corot Noir is one of three varieties, along with Noiret and Valvin Muscat, that were introduced in 2006 by Bruce Reisch, professor of horticulture, plant breeding and genetics in the School of Integrative Plant Science at Cornell University.5 All three have developed a following with growers east of the Rockies, and Corot Noir, a red wine grape, is now planted in vineyards from New York and Pennsylvania to Illinois, South Dakota, Missouri and Colorado.

A mid- to late-season red wine grape, Corot Noir is the result of a cross made in 1970 between Seyve Villard 18-307 and Steuben. The vines are moderately winter-hardy and moderately resistant to fungal diseases. The wine has a deep red color, cherry and berry fruit aromas, and a soft, full tannin structure.

Choosing an appropriate cultivar for a specific site and market conditions is a critical component of successful viti¬culture and can be the difference between a vineyard or winery making a profit or loss with those grapes. Data collected in other Midwestern grape production regions indicate that Corot Noir has the potential to produce a varietal wine or be used as a component in red blends in the region and specifically in Missouri. Consequently, we set out to evaluate the performance of Corot Noir under conditions in Missouri.

Selection of an appropriate training system and pruning severity are fundamental components of a successful management strategy for any grape cultivar. The training system defines the architecture of the vine’s perennial structure and impacts canopy distribution and density, sunlight capture, and photosynthetic capacity and efficiency. Training systems can also significantly impact fruit zone microclimate, thereby influencing fruitfulness, source-sink relationships within the plant and fruit composition.

Simultaneously, pruning severity can influence vegetative and reproductive balance within the vine, canopy distribution and uniformity, and the rate at which the vine establishes a photosynthetically productive leaf canopy during the growing season.

The response of any given cultivar to these influences is dependent upon numerous genetically determined factors such as propensity for growth, adaptation to various climatic factors, productivity and growth habit in addition to site-specific management practices. Accordingly, training and pruning methods should be selected based upon a given cultivar’s traits and conditions under which it is being grown.

In the current study, own-rooted Corot Noir vines grown in a central Missouri commercial vineyard were trained to two systems: high bilateral cordon (HBC) and vertically shoot-positioned (VSP) or low cordon. In addition, vines were pruned to three levels of severity (10, 15 and 20 nodes retained per pound of dormant pruning weight).

Analysis of multiple-year mean data collected during the 2007, 2008 and 2009 seasons indicate that while fruit com¬position wasn’t strongly impacted by choice of either training system or pruning severity, both factors had some influence on yield, yield components and pruning weight (see Table 1).

Yield of vines trained to high cordons was greater than vines trained to low cordons (see Table 2). This appears to be caused by higher cane numbers observed on high-cordon vines (data not shown). Total yield was statistically higher for vines pruned to retain 15 or 20 nodes as compared to vines pruned more severely (10 nodes retained).
As has been reported for other cultivars by previous au¬thors, vine size was impacted by training system, with low-cordon vines producing greater pruning weight. Ravaz Index values (yield in pounds to dormant pruning weight in pounds) were somewhat low for vines trained to low cordons, near optimal for vines trained to high cordons, and generally improved with lower pruning severities (data not shown).

Few interactions between training system and pruning severity were observed, suggesting these influences acted independently upon Corot Noir under the conditions of this study. Retaining adequate node numbers on conservatively pruned, low-cordon-trained vines proved problematic due to cane maturation problems.

Vines in this study had lower vine size than vines in a previous study conducted in New York. Implemen¬tation of shoot- and cluster-thinning may have improved canopy microclimate and vine bal¬ance in this study.

Viticulturally, all treatment combinations tested produced commercially acceptable re¬sults under the conditions of this study, al¬though some treatments appear to provide significant advantages for Corot Noir producers in the Midwest. The higher yield of high-cordon vines observed in this short-term study, combined with the lower trellis cost and labor demands of this training system, suggests it may be economically preferable, rather than using low-cordon training.

Furthermore, the higher yields produced by retaining 15 or 20 nodes per pound dormant pruning weight rather than 10 nodes, without a meaningful penalty in fruit composition or vine balance, suggest either of the two former pruning severities may be appropriate and preferred by producers.

The results from this study indicate that performance of Corot Noir grapevines in Missouri would be optimal when vines are trained to a high-cordon system and pruned to retain 15 or 20 nodes per pound of dormant pruning weight. Future trials should incorporate production and analysis of research wines to fully evaluate treatment effects.

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