Rootstock Effects on Mature Pinot Noir Growth and Productivity Under Cool Climate, Dry-farmed Conditions
Vine growth, yield, and fruit composition of Pinot noir grafted to 19 rootstocks and own-rooted vines were quantified during 2021. The vineyard was 24-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, there were some key differences noted. Dormant pruning weights in early 2021 indicate that 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 high vigor vines. These differences carried into spring with differences in shoot growth from early may through bloom, with 3309C and Riparia Gloire having the least amount of shoot growth leading up to bloom, and 1616, 5BB, 140R, 5BB, 5CTE, and 420A having the most growth. There were some differences in fruitfulness, with SO4 having the greatest fruitfulness of 1.7 inflorescences/shoot while Riparia Gloire and own-rooted had only 1.4 inflorescences/shoot. There were yield differences by harvest, with 420A having higher yields than Riparia Gloire, 1616, and own-rooted. The impact on yield is mostly explained by differences in cluster weight. Pinot noir grafted to 1616, had the smallest clusters that were sparse due to poor set. This could be a result of high vigor of these vines early in the season. Berry ripeness did not differ for most rootstocks. However, Schwarzmann and Böerner had higher total soluble solids than 125AA. Schwarzmann also had the highest pH and lowest TA. The remaining rootstocks were all within commercially acceptable ripeness (TSS = 23.6, pH 3.2, and TA=8.6 g/L). We anticipated that variations in canopy size created by rootstock vigor may impact berry phenolics through vine stress and/or differences in canopy microclimate. However, there were no rootstock differences in total anthocyanin, phenolic, or tannin content. Similarly, there were no differences in berry phenolic concentrations in 2020. This second 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 phenology advancement, fruit ripeness, or berry phenolic concentration at harvest.