The Crush September 2022 - 1

Volume 49 | Issue 9 | September 2022
Drought Tolerant Rootstocks
Article by Ted Rieger
Given current and expected future impacts of
climate change and prolonged drought periods
in California, winegrape growers will need more
drought tolerant and water-efficient grapevines
(rootstocks and cultivars) to avoid declines in berry
yield and quality under the hotter, drier conditions
expected for California wine regions.
Rootstock selection for planting is commonly
based on multiple factors related to site specific
conditions that can include: pest resistance-notably
for phylloxera and nematodes; soil
conditions--depth and composition, moisture
and water retention, fertility and salinity; climate-seasonal
temperatures and precipitation; ease
of propagation--rooting characteristics, vine
establishment and scion compatibility; and vine
vigor, yield and quality factors.
Research indicates that grapevines can respond
to drought in several ways: by reducing vapor
conductivity through their stomates to reduce
water loss; by developing extensive and deeper
root systems to find more water; by increasing the
water conductivity of the soil-stem pathway; by
increasing their ability to maintain osmotic water
pressure, which increases their water potentials;
and by increasing their water use efficiency (WUE)-the
amount of biomass produced per unit of water
Rootstocks available for California winegrape
growers that are considered to have high, or
medium to high, drought tolerance include:
99R, 110R, 140Ru, 1103P, Ramsey (Salt Creek),
Harmony, Freedom, UCD GRN3,
UCD GRN-4, and UCD GRN5.
St. George has high drought
tolerance in deep soils. 110R and
1103P are commonly planted in
Lodi Pinot Noir
Three main native American Vitis species--V.
rupestris, V. berlandieri and V. champinii--are
commonly part of the parentage of drought
tolerant rootstocks available today. Rootstocks
with both V. berlandieri and V. rupestris parentage
include 99R, 110R, 140Ru and 1103P and they
tend to have deeper roots and have higher vigor. V.
champinii is found in rootstocks such as Dog Ridge,
Ramsey, Freedom, Harmony and the UCD GRN
series that tend to have deeper roots, and drought
and salt tolerance. St. George is a V. rupestris
based rootstock.
UC Davis (UCD) Professor Emeritus and grape
breeder Andy Walker and his lab worked on
collecting, breeding and evaluating new rootstocks
new vineyards as they are higher vigor rootstocks
able to tolerate stress from drought and from
poorer soil and site conditions, they provide good
phylloxera resistance, and they are commonly
available from nurseries.

The Crush September 2022

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