Evaluating Rootstocks for Cool-Climate White Wine Grape Production

Goals / Objectives
Objective 1: Determine phenology, vine health, water status, and fruit productivity of Chardonnay and Pinot gris grafted to different rootstocks. Objective 2: Determine differences in fruit composition of Chardonnay and Pinot gris grafted to different rootstocks.

Project Methods
Grapevine phenology will be documented on individual nodes within treatment plants starting at woolly bud stage and continuing through bloom, fruit set, and veraison using the method described by Coombe (1995). This will determine if rootstocks advance or delay key growth stages compared to the regionâ¿¿s standard rootstocks (3309C, 101-14 and Riparia Gloire). Early spring shoot growth will be measured starting at ~6â¿ of shoot growth and continuing weekly until bloom, or until the canopy is hedged. Shoot growth rate will help us understand if there are growth rate differences in response to variable carbohydrate reserves in early spring. Vine leaf area index will be measured at bloom and veraison using a ceptometer (LP-80, Decagon Devices). Vine nutrient status will be measured at bloom at veraison each year. Tissues (leaf blades and petioles) will be submitted to Fruit Growersâ¿¿ Lab, and donation of analytical services will be sought. Vine water status will be monitored every 7 to 10 days from post-bloom (early July) through veraison and ripening stages (early September) using a leaf porometer (LiCOR 600) to measure stomatal conductance and a pressure chamber (PMS Instruments) to measure stem water potential. Measures will be made during the peak heat of the day as directed by Tian and Schreiner (2021). Vine productivity (yield) will be measured in spring with fruitfulness counts once inflorescences are visible and shoots have been thinned to standard shoot density. Yield will be measured at harvest by counting all of the clusters per plot and weighing all fruit weight. Yield metrics will be determined from the field data (cluster weight) and from a sub-set of five clusters selected randomly per plot at harvest. These clusters will be measured for cluster weight, berry count, berry weight, and rachis length. After each crop year, dormant pruning weights will be measured at pruning. If vines are of very low vigor, balance pruning methods will be employed to reduce bud number per plant. Because rootstock may have an impact on yield performance, canopy size, and nutrient uptake, it is hypothesized that there may be differences in basic ripeness and yeast assimilable nitrogen (YAN). To quantify these differences, the sub-sample of fruit used for cluster morphology and yield metrics in Objective 1 will be pressed to juice. The juice will be measured for total soluble solids (TSS, Brix), pH, and titratable acidity (TA). Several aliquots of juice from each experimental unit will be saved and stored at -20 Â°C until analysis for ammonia nitrogen (r-Biopharm) and alpha-amino acid nitrogen (Dukes and Butzke 1998). No wine production is proposed herein due to the small plot size (only 25 vines total for each cultivar x rootstock combination).