In its 2020-21 fiscal year, the Oregon Wine Board of Directors granted $350,000 to researchers for eight projects with the potential to advance quality grape growing and winemaking in Oregon. The update below is part of a series to let industry members know about the status of these projects.

Dr. Patty Skinkis is a professor and viticulture extension specialist in the Department of Horticulture at Oregon State University and a member of the Oregon Wine Research Institute. She has prepared the update below.

Additional support for this project was provided by Erath Family Foundation for purchase of equipment to allow more streamlined plant water stress data collection starting in 2021.

Rootstock effects on mature Pinot noir growth and productivity under cool climate, dry-farmed conditions

Project objectives:

  1. To determine phenological advancement, vine health, and fruit productivity of Pinot noir grafted to different rootstocks; and
  2. To determine differences in fruit composition of Pinot noir grafted to different rootstocks.

Importance to the Oregon wine community:
The wine industry has continued interest in rootstock performance with new vineyard development and seasonal climate change in the region. However, Oregon growers have little experience with rootstocks outside of what is currently being grown, and there are no data available from regional field studies to indicate the best-performing rootstocks for vineyards long-term under the Willamette Valley’s cool climate and mostly dry-farmed vineyards. With recent changes in vineyard production, such as increased target yields (i.e., less crop thinning) and the movement toward no-till practices and/or no herbicide use, it is unclear how different rootstocks will perform under these conditions. This study is evaluating a mature rootstock trial to help provide the industry with information on best-suited rootstocks.

Progress so far:
Vine growth, yield, and fruit composition of Pinot noir grafted to 19 rootstocks and own-rooted vines were quantified during 2020. The vineyard was 23 years old, and we hypothesized cumulative impacts of the rootstock on vine growth would be distinguished by rootstock. Specifically, we hypothesized that Riparia Gloire and other vigor-reducing rootstocks, such as 101-14, 3309C, and 420A, would have reduced canopy growth compared to other rootstocks not commonly planted in Oregon due to high vigor potential, such as 110R, 140R, 1103P, and 161-49.

Results show that the majority of rootstocks performed similarly for vine canopy growth and fruit production. However, Riparia Gloire, 44-53, and 3309C had the lowest pruning weights, indicating low vigor vines, and 161-49 and 1616 had the highest pruning weights, indicating vigorous vines. Despite vigor differences, there were no differences in growth stage advancement at bud break, bloom, or fruit set. By the start of véraison Riparia Gloire and SO4 had the most advanced color development, while 101-14, 3309C, and own-rooted were the least advanced. However, within six days, the rootstocks became less different in percent of berries colored, and 3309C had the highest rate of color change.

There were no differences in rootstock yield except for Riparia Gloire and SO4, which had the lowest and highest yields, respectively. Berry ripeness did not differ for most rootstocks. However, Schawarzmann had higher Brix than 420A, 5BB, 125AA, own-rooted, 5CTE, and 99R. There were few differences in pH and variable differences in titratable acidity.

We anticipated that rootstock may impact berry phenolics through vine stress and/or differences in canopy microclimate. However, there were no rootstock differences in total anthocyanin or phenolic content, and only minor differences in total tannins. We also anticipated that vine vigor conferred by rootstock may affect berry nitrogen, but there were few differences in juice primary amino N except for 1616 and 5BB, which had more than double the primary amino N than 44-53 and own-rooted vines.

This first year of data analysis suggests that rootstock has the greatest impact on vegetative growth and yield, thereby causing some differences in vine balance. There is less impact on Pinot noir phenological advancement, fruit ripeness, berry N, or phenolics at harvest.

Next steps:
The research will continue in 2021 and 2022 to evaluate seasonal effects on the vine performance. More detailed phenological data and plant water stress measures will be taken in these two growing seasons to discern impacts of rootstocks that may confer drought tolerance.