New Nematode-resistant Grape Rootstocks are Nearing Release

– 8 – In 1993 and 1994, many crosses were made with the goal of developing rootstocks with broad and durable nematode resistance, while improving horticultural characters such as rooting ability and shoot length. The parents of these crosses included a number of grape species known to be highly resistant to both root-knot and dagger nematodes. They included several forms of Vitis arizonica, V. candicans, V. champinii, V. cinerea, V. rufotomentosa, and Muscadinia rotundifolia. Vitis riparia and V. rupestris were used in the crosses to improve rooting. About 75 crosses were made, leading to the establishment of over 5,000 seedlings in the vineyard. In 1996 these plants were evaluated for shoot growth, internode length, and the presence of laterals. One thousand selections were chosen, and that winter they were tested for their ability to root from dormant two-node cuttings. The best 100 were advanced to nematode testing.