Rootstock is a term that dates back to Roman times and originated due to the accidental importation of phylloxera to Europe, which devastated grapevines. Great efforts were made to advance the concept of grafting grapevines to American rootstocks as a solution to combat phylloxera infestation.
This blog post discusses why we need to continue to trial and develop rootstocks based on episode 31 of the Vineyard Underground podcast where we interviewed Dr. Gill Giese, who performed the trials. Below is a short recap of the results.
Why We Need to Continue to Trial & Develop Rootstock
- It allows growers to find rootstock varieties that are suitable for their specific site and region, enabling them to compare and choose the best option.
- Rootstock development focuses on adaptation to soil chemistry, extremes in hot and cold weather, and the ability to adapt to drought or poor water quality. Additionally, by investing in rootstock research, we can stay ahead of climate change and adapt to shifting environmental conditions.
- Studying different rootstocks in various climates and soils allows us to anticipate their behavior and choose the most effective options for each unique situation.
The Results of the Rootstock Trials
Highest & Lowest Mortality Rates
When examining the mortality rates of different rootstocks in the New Mexico trials, some stood out with the highest risks. Notably, 5bb and 1103 Paulsen have been shown to have the highest mortality rates among the rootstocks studied. These rootstocks are known for their high vegetative vigor, which may contribute to their increased mortality if they do not harden off properly for winter conditions.
On the other hand, there were rootstocks that demonstrated lower mortality rates. For instance, SO4 and 775 Paulsen exhibited better survival rates compared to others. These rootstocks seemed to be more resilient and have a reduced risk of mortality. However, it is important to consider that the scion may also influence mortality rates. Looking at the scion data alone, Gewürztraminer had a 33% mortality rate, while Refosco had a higher mortality rate of 50%. This indicates that Refosco may be less adaptive to the winter conditions compared to Gewürztraminer.
Yield Differences
During the experiment, all nine rootstocks were grafted onto two grape varieties: Gewürztraminer and Refosco. The results indicated a yield difference between the rootstocks. For Refosco, the 110 Richter rootstock produced the highest yields. However, when it came to Gewürztraminer, there was minimal yield variation observed, with no significant statistical differences recorded over the five-year period from 2017 to 2022. Among all the rootstocks used, Gewürztraminer displayed similar yield characteristics in general.
Ravaz Index
The Ravaz index serves as an indicator of vine balance. In the case of Refosco, the Ravaz Index was much higher, suggesting an imbalance in the vine due to excessive pruning. This indicates that the vine may have been pruned too severely, potentially impacting its overall health and productivity. On the other hand, the rootstock SO4 displayed the highest production, indicating that it performed well in terms of yield and vine balance.
If you want to learn more about rootstocks, check out https://www.vineyardundergroundpodcast.com/vu031.
