916.441.2031 debbie@agamsi.com


Your Assessment Dollars at Work

Assessments on purchases of grape rootstocks fund important research to help protect vineyards from pests, disease and environmental factors. This work takes years of financial support to achieve results, and it would not be possible without the investment you make through the California Grape Rootstock Commission.

The Commission has funded several rootstock breeding programs including Dr. Andrew Walker’s work at the University of California, Davis. In addition to the Walker GRN series rootstocks now available, new rootstocks to address key grape farming issues are on the horizon.  Below is a summary of the most important developments achieved by the California Grape Rootstock Commission.


Researchers are screening hundreds of potential rootstocks each year for their resistance to different kinds of nematodes through a painstaking and time-consuming process. To date, five rootstocks in the ‘GRN’ series have been released with outstanding and broad nematode resistance.  These five GRN rootstocks are now being adopted by nurseries, so they are more readily available to growers. Work continues to create more options to help growers manage these pests.


Researchers continue their work to thoroughly understand phylloxera in California grapevines – which is the first step in managing this pest and the resulting fungal diseases that eventually cut nutrients and water to the vine. To date, the only successful means of controlling phylloxera is through resistant rootstocks. The Commission is focused on creating new, improved options for growers. In recent years, researchers have identified several new strains of phylloxera and study of their potential impact is under way. This work includes the evaluation of DNA from 500 phylloxera collections from across the U.S. to understand and fingerprint their genetic diversity.  Researchers are also looking at the role phenolics play in phylloxera susceptibility and are exploring the association between grape berry color and infestation level.


California grape growers continue to deal with the spread of Red Leaf Viruses. Researchers are evaluating the impacts of these viruses, but there is still a need for improved control beyond what is currently available. Researchers are using tissue culture-based screening to rapidly select for rootstock seedlings with tolerance to Red Leaf viruses.


Work to help grape farmers deal with climate change, drought and salty soils is ongoing. California Grape Rootstock Commission researchers have collected about 1,000 southwestern grape species, many of which have high salt and drought tolerance. They have also developed a rapid greenhouse assay for salt tolerance and have been able to create rootstocks capable of growing in a solution with 12 percent sea water. These promising new rootstock selections are now ready for field trials.