Performance of 'Chambourcin' Winegrape on Nematode-resistant Rootstocks in Missouri.

One of the most popular winegrapes (Vitis sp.) for red wine production in the midwestern United States is 'Chambourcin', a French-American hybrid. It is typically produced on own-rooted vines in the region, but the potential benefits of grafting it to improved rootstocks are becoming better-known. Nematodes present occasional serious winegrape production challenges in the midwestern United States, and are capable of transmitting pathogenic viruses. New rootstocks developed by University of California, Davis (UCD GRN series) are resistant to several species and races of nematodes, but have not been evaluated under midwestern U.S. production conditions. A study with 'Chambourcin' grafted to four of these new nematode-resistant rootstocks ('UCD GRN-2', 'UCD GRN-3', 'UCD GRN-4', and 'UCD GRN-5') and 'Couderc 3309', along with own-rooted vines was established in 2010 in southwest Missouri, and fruited in 2013-15. Three of the nematode-resistant rootstocks (GRN-2, 3, 4) performed as well as the standard 'Couderc 3309' and own-rooted vines, with yields among all rootstocks ranging from 10 to 13 kg/vine. The rootstock 'UCD GRN-5' generally performed poorly, however, manifested by low pruning weights and a high Ravaz index value (25) in 2013 that necessitated defruiting the vines in 2014. Fruit yields on 'UCD GRN-5' rootstocks were satisfactory in 2013 and 2015, but the vines eventually deteriorated, with 99% shootless nodes by 2017. Although more evaluations of these new rootstocks are needed in the midwestern United States, we conclude that 'UCD GRN-2', 'UCD GRN-3', and 'UCD GRN-4' show promise, whereas 'UCD GRN- 5' does not appear suitable for growing conditions in southern Missouri. [ABSTRACT FROM AUTHOR]