Performance of Rootstocks in a Cabernet Sauvignon Vineyard with Xiphinema index Nematodes and Grapevine Fanleaf Virus
Rhonda Smith* and M. Andrew Walker
*University of California Cooperative Extension, 133 Aviation
Blvd., Suite 109, Santa Rosa, CA 95403 (rhsmith@ucanr.edu)
Grapevine fanleaf virus (GFLV) is the causal agent of fanleaf
degeneration, which significantly reduces yield due to poor fruit
set. Vine decline is progressive and fruit quality is reduced;
thus, diseased vineyards are replanted. Xiphinema index nematode
acquires GFLV by feeding on roots of infected vines and remnant
roots in replanted vineyards. Subsequent feeding transmits the
virus, causing disease in future plantings. We evaluated the
performance of grapevine rootstocks selected for broad resistance
to nematodes by establishing a field trial in a replanted
vineyard in 2012, one year after removal of vines which had
severe fanleaf degeneration. The UCD GRN series
of rootstocks and O39-16—all highly resistant to X. index—and
medium- to low-resistant rootstocks—RS-3, RS-9, Schwarzmann,
1616C and 1103P—were planted in a randomized complete block
design with eight replications of five-vine plots without pre-
plant fumigation. Nematode samples were collected by plot. There
was no difference in the number of X. index nematodes found in
O39-16 and GRN rootstock plots; however, more X. americanum were
found on GRN-1 and O39-16 than in the other GRN rootstocks.
Grapevine fanleaf virus status was determined by ELISA from shoot
tip samples. In 2019, 26 (65%) of the GRN plots and three (37%)
of the O39-16 plots tested GFLV-positive and pruning weights were
reduced in infected vines. In 2019, only one vine in each of
three GRN-1 plots was infected with GFLV; yet from 2015 to 2019,
GRN-1 consistently had lower pruning weights than the other GRN
rootstocks. In 2019, mean yields of the GRN rootstocks ranged
from 8.4 to 10.2 kg/vine and were not statistically different.
O39-16 yield averaged 11.8 Kg/vine. At this time, it is still
uncertain whether the GRN rootstocks induce tolerance to fanleaf
degeneration.
Funding Support: California Grape Rootstock Improvement Commission
