Publication Date


Date of Final Oral Examination (Defense)


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

Marcelo D. Serpe, Ph.D.


James F. Smith, Ph.D.


Krista C. Shellie, Ph.D.


Markus Keller, Ph.D.


This two part study was carried out in the Snake River Valley American viticulture area (SRV AVA) in Idaho. This area is a northern latitude, high elevation plateau where growing season is delimited by cold temperature. For the first part of the study, the performance of red and white-skinned winegrape cultivars (Vitis vinifera, L.) were compared to that of the widely grown cultivars Merlot and Cabernet Sauvignon. Phenology, juice composition, yield, cold injury, and cold hardiness were observed during the 2011 and 2012 growing seasons. Phenological events occurred later in the cooler 2011 season than the warmer 2012 season. At harvest, the sugar to acid ratios in both seasons were higher for Grüner Veltliner, Trousseau, Merlot, and Sauvignon Gris and lower for Aglianico and Aleatico, indicating overripe and unripe fruit, respectively. Touriga Brasileira had high yields, low pruning weights, and a high Ravaz index while Carmenère had lower yields, higher pruning weights, and a low Ravaz index. These results indicated that these vines were out of balance with too much growth directed to either vegetative or reproductive organs. Montepulciano and Tinto Cão had the highest percentage of cold injury, which excluded them from performance evaluations. Maximum cold hardiness occurred during December and January for all tested cultivars, with some month to month differences amongst cultivars. The second part of the study characterized cold hardiness in two widely grown cultivars, Chardonnay and Cabernet Sauvignon, throughout their dormancy cycle. The aims were to identify differences in cold hardiness between the two cultivars, to characterize the relationship between cold hardiness and stages of dormancy, and to analyze the buds ability to deacclimate and reacclimate during ecodormancy. Data were collected over two seasons (2011-12 and 2012-13) on vines grown in an experimental vineyard in Parma, ID. The stage and depth of bud dormancy was assessed using a forcing bioassay to evaluate percent budbreak and the cold hardiness of buds was evaluated by determining the temperature that caused 50% bud death (LTE50) using a differential thermal analysis (DTA) system. The cold hardiness data was also used to evaluate the accuracy of the Ferguson dynamic thermal time model on predicting bud LTE50 values of Chardonnay and Cabernet Sauvignon. Chardonnay acclimated earlier and more rapidly than Cabernet Sauvignon during autumn. The buds of Chardonnay transitioned to ecodormancy earlier than those of Cabernet Sauvignon and in both cultivars maximum bud cold hardiness was acquired during ecodormancy. Acquisition of maximum bud cold hardiness after release from endormancy suggests that some metabolic factors associated with cold acclimation are independent of endodormancy. The dynamic thermal model accurately predicted cold hardiness in both cultivars, though it was more accurate for Cabernet Sauvignon than Chardonnay. Results indicate that Chardonnay is better adapted to areas with colder falls and winters than Cabernet Sauvignon. Furthermore, Chardonnay is better suited than Cabernet Sauvignon for sites that experience early autumn cold events. Cabernet Sauvignon was more resistant to deacclimation and more capable of reacclimation than Chardonnay. These results suggest that Cabernet Sauvignon is better suited than Chardonnay for sites that experience fluctuating mid-winter temperature events and late spring frosts.