UC Davis has introduced five new pest-resistant grape rootstocks developed by geneticist Andy Walker of the Department of Viticulture and Enology. At a media event March 31 at Foundation Plant Services, Connie Lopez delivers one of the new rootstocks to Jim Pratt, owner of Cornerstone Certified Vineyard and research committee chair of the California Grape Rootstock Improvement Commission. Walker experimented for 15 years to develop the rootstocks.