The University of California, Davis, and Global Plant Genetics, a European company that manages intellectual property for various crops, have entered into an agreement to commercialize and distribute two UC Davis-patented grape rootstocks in Europe. Both rootstocks, GRN1 and GRN3, are resistant to a number of nematodes, including root-knot, which are microscopic, unsegmented roundworms that feed on, and harm, the roots of grapevines.
Nematodes cause damage to plants by stunting root elongation, changing root growth patterns and removing nutrients. And since many countries around the world prohibit the use of soil sterilants to control them, the economic impact of damage from nematodes is growing. Efforts to find nematode-resistant grape rootstocks began at UC Davis in 1993, when 75 crosses were made, producing 5,000 individual seedlings for assessment. Evaluation of the results of these crosses began in 1996, with 1,000 seedlings identified — from which the best 100 were advanced to test for nematode resistance. This work was undertaken by Andy Walker, grape breeder and professor in the Department of Viticulture and Enology, and Howard Ferris, professor in the Department of Entomology and Nematology, both from UC Davis.
Walker and Ferris continued their testing and laboratory analysis, using soils with high known and quantifiable nematode infestations as well as plants in pots infected with nematodes. Tests were also undertaken, against a control variety, at temperatures of 30 degrees and higher, where root-knot nematode resistance often breaks down.
Having narrowed down the group of seedlings to five selections, two were identified by UC Davis for commercialization in Europe — GRN1 and GRN3.
GRN1 was found to be the most nematode resistant of all the rootstocks tested. It offers resistance to root-knot, dagger, citrus, lesion and ring nematodes as well as phylloxera, a tiny aphidlike insect. This rootstock may be particularly beneficial to wine producers in areas where soil sterilization is no longer an option. GRN1 has a relatively deep rooting profile with moderate vigor and will likely suit warmer climates. It is potentially adaptable to all grape cultivars and has proven easy to graft assuming well matured cuttings are selected.
GRN3 has moderate to high vigor and is more likely to do well in lime-based soils. GRN3 is easy to graft and more adaptable to colder climates. It offers resistance to root-knot, dagger, citrus, lesion and phylloxera, but not ring nematodes.
“We are pleased to be working with Global Plant Genetics as our licensee in the EU to commercialize these rootstock varieties,” said Dushyant Pathak, associate vice chancellor of research and executive director of Venture Catalyst at UC Davis. “The novel properties of the rootstocks developed by professors Walker and Ferris are expected to support the environmentally and economically sustainable production of grapes within the European context.”