Rapid propagation of grape planting
by M. Andrew Walker, Deborah A. Golino
Department of Viticulture & Enology, Foundation Plant Materials Service
University of California, Davis, CA
A thriving international market for wine and grapes has resulted in an
explosion in vineyard plantings in many parts of the world. One of the
consequences in some countries has been a shortfall in desirable planting
stocks. This is especially true for countries with strict quarantine
regulations governing the importation of grapevines. In those countries, it is
necessary for the domestic nursery industry to respond to demand for scarce
varietal and clonal selections, or new rootstocks, with techniques that allow
the rapid expansion of propagating stock.
Cirami and Ewart (1995) were referring to clonal evaluation in the following
quote, but the statement is equally true for new varieties or rootstocks.6 "The identification of superior clones
without a mechanism of vine certification and multiplication can lead to
enormous frustration in the wine industry. The vine grower learns that improved
planting material is available, he is just unable to obtain it."
Both the slow movement of new introductions through quarantine and
certification programs and the relatively slow process of grape propagation via
dormant cuttings are responsible for this frustration. There is great interest
at this time in any technique that might speed up the process by which new
materials are made available to growers. This is particularly true in
California, where the current planting boom has prompted accellerated
acceptance of some of the rapid propagation techniques.
California planting boom
The demand for grape planting materials is at an all time high in
California. New vineyards are being planted in all areas of the state, and
thousands of acres of vineyards once planted to the phylloxera-susceptible
rootstock AXR1 continue to be replanted each year. Nurseries are struggling to
keep up with demand.
The California Department of Food & Agricultures Agricultural
Statistics Service tracks the grape acreage by variety and region. These
records provide us with some statistics about the extent of the current
planting boom, although records are reported for the previous year, and by some
accounts (California Association of Winegrape Growers 1998), they may
underestimate acreage of some varieties by as much as 40%.
According to these reports, four widely planted varieties have experienced
remarkable growth in California (Figure
1). In 1982, there were 22,050 acres of Chardonnay, 21,289 acres of
Zinfandel 16,640 acres of Cabernet Sauvignon, and 2,147 of Merlot. By 1991,
there were 56,609, 34,369, 34,176, and 8,188 acres of each, respectively. The
1997 acreage records list 88,517, 50,498, 45,307, and 38,522. These four
varieties now account for 54.7% of the 407,230 winegrape acres in California
recorded for 1997.2
In addition to the increase in acreage of these major varieties, some
varieties, which have previously been planted to a limited extent, are suddenly
becoming more popular. For example, there is increasing interest in Sangiovese
and Syrah. Prior to 1982, there were respectively 25 and 89 acres, of these
varieties in California. By 1991 there were 232 and 413, and the acreage
records for 1997 list 2,498 and 4,277. This represents a 50-fold increase in
Syrah and a 100-fold increase in Sangiovese.
addition to the demand for varietal grape materials from nurseries, the issue
of clonal selection has become increasingly important to California growers and
winemakers. It is not unknown in California for wineries to pay a premium for
particular clones and to contract with growers based on the clones planted in
selected vineyards. There is particular interest in clones from France and
Italy, which are new to the U.S. These clones have been arriving in the state
via legal and illegal channels and are now in great demand.
Although little data exist regarding how well these clones perform in
California, they are being utilized in replanted vineyards and newly developed
sites at an increasing rate. Several California nurseries are now collaborating
with French and Italian nurseries, as well as vine improvement centers, such as
ENTAV and Rauscedo, to provide California growers with better access to these
clones. These joint ventures will increase the rate of new introduction,
resulting in higher demand for these "new" products, and increased
pressure on nurseries for rapid propagation.
The California table grape industry is especially quick to change to new
varieties. The varietal loyalties of winemakers do not apply; successful new
releases by breeders can become popular and even dominate the market in a very
short period of time. Propagators need to respond to these table grape demands
with very quick production schedules.
Economics and global demand for wine and fruit are fueling huge new
plantings in California. But even when the demand levels off, there will still
be a strong need for planting materials beyond this current generation of
For example, a majority of Californias vineyard acreage is currently
planted without rootstock. These vineyards are on sandy soils in the Central
Valley and are rarely affected by phylloxera. However, nematodes, most notably
an array of root-knot species (Meloidogyne), build up to high levels on
these soils, and the establishment of second generation vineyards on such sites
will require use of nematode-resistant rootstocks.
Further, California is only in the early stages of regional evaluation of
varieties, clones, and rootstocks. As new materials are tested, it can be
anticipated that vineyards will need to be replaced to keep up with newly
defined regional markets. Finally, new generations of rootstocks are being
produced for California soils to resist specific pest complexes.19 The demand for these
rootstocks will increase as sites are replanted to second and third generation
Role of new propagating techniques
Traditional grape propagation techniques utilize mother vines, from which
dormant cuttings are taken for rooting, bench grafting, or field budding.
Mother vines are generally planted from dormant rootings or potted plants and
require about three years to produce generous amounts of cuttings.
When new clones or varieties are released from breeders or from quarantine
programs, there is very little wood available for distribution and a variety of
techniques have been employed to produce commercial amounts of planting stock
over a short period. Many of these techniques are labor and
technology-intensive, and their cost may not compete with that of traditional
methods of propagation when source materials are not limited. However, when
planting stock of new varieties, clones, or rootstocks is limited, rapid
propagation techniques can speed up release and offer large economic
The introduction of new planting materials through vine improvement
associations is a major limitation to grape industry utilization of new clones,
varieties, and rootstocks. Many of the rapid propagation techniques were
developed by these associations to speed up the release of material and to
avoid the spread or infection of certified material with pests and diseases.
Mist propagation of herbaceous cuttings
Rapid propagation techniques most often use herbaceous plant material
ranging from apical meristems to partially lignified, 25 cm shoot cuttings.
Propagation from herbaceous material must be done in very high humidities
utilizing mist propagation or tissue culture techniques.9
The simplest procedure for the multiplication of an actively growing plant
involves making multiple green cuttings and rooting them under mist
propagation. Mist propagation requires a very fine mist or fog of high quality
water, bottom heat, and a porous propagation media to provide the high
humidity, warmth, and oxygen needed for leafy cuttings to root. Cuttings are
taken from actively growing plants and work best with at least two nodes and
two lateral (prompt) buds.
A balance must be achieved in tissue maturity. Although the mother vines
should be actively growing, cuttings from the most succulent tissues often fail
to root. Conversely, once the cuttings become too greatly lignified, the
lateral buds have often abscised, and cuttings may fail while the dormant
(latent) bud goes through a required dormancy before growing.13
In the field (UC Davis, CA), suitable tissue can be collected from most
grape selections between early June and late August. Alternatively, mother
vines can be maintained in a greenhouse and will provide excellent cuttings for
propagation as long as there is sufficient light for active growth. We have had
excellent success propagating from seedlings and newly rooted plants as long as
these plants are kept growing actively with supplemental light and heat as
There are many appropriate media for mist propagation including vermiculite,
perlite, sand, rock wool, and cellulose sponges. These media must maintain
moisture and provide oxygen root development. By itself, vermiculite, a
micaceous mineral expanded with heat, can become too wet and compacted over
time, leading to low oxygen levels and poor rooting. Perlite, a gray-white
silicaceous material mined from lava flows, which is also expanded with heat,
holds less water and provides a less "soggy" environment, but
provides poor cation exchange leading to poor nutrient uptake of rooting
cuttings. We have used both one-to-one mixes of vermiculite and perlite and
pure perlite mixes with great success. Coarse sand can also be used, but the
light-weight, pest-free nature of vermiculite and perlite make them superior.
Some grape varieties and rootstocks will produce roots (under mist
propagation) but fail to establish after potting in greenhouse soil mixes or
upon transfer to the field. Such failure is often due to root damage upon
removal from the propagating substrate. In these cases, cellulose sponge or
rock wool are better media, because they maintain strong root attachment to the
cutting stem, resulting in greatly improved rooting. We have increased the
establishment of new plants from green cuttings of hard-to-root Vitis
species like V. cinerea and V. monticola by three to five fold
with cellulose sponge cores (Grow-Tech Techniculture, San Juan Bautista, CA).
Rooting hormones do not dramatically improve rooting success of green
cuttings from most V. vinifera varieties. However, they are very
beneficial for rooting other Vitis species and some rootstocks. The
auxins indolebutyric acid (IBA) and napthaleneacetic acid (NAA) are commonly
used as five- to 10-second dips at 1000 to 3000 ppm.
Warmth, humidity, and light are critical for success with mist propagation.
Temperatures in the 28º to 30ºC range are ideal. Humidities are kept
constant and high using either electronic timers that discharge about five to
10 seconds of mist every five to 10 minutes or moisture-sensing devices, such
as the "mist-a-matic" (Hummert Intl., Earth City, MO), that detect
moisture levels below a set point and discharge the mist to compensate.
Moisture sensing devices can be difficult to set up but more than compensate
for this effort by preventing moisture levels from getting too high during
cloudy weather or evenings. Excessive water logging can be a serious limiting
factor to success with mist propagation. As long as humidities are controlled,
high light levels produce optimum rooting. Normal greenhouse shading levels
with adjustments for climate are needed.
Herbaceous grafting under greenhouse and in vitro conditions has been
practiced with cucurbits and solanaceous plants for many years.14, 9
This process involves placing a shoot tip or meristem on the
freshly cut surface of a seedling epicotyl, where it is held in place while it
heals under high humidity conditions. Green-grafting has also been done in the
field by grafting green scions or buds onto green shoots. This technique has
worked with grape, but has not been widely utilized.5
Grapevines have been green grafted under greenhouse and in vitro
conditions. Green-grafting has the advantage of being easy, having high success
rates, and is capable of overcoming the graft incompatibility sometimes
experienced between distantly related Vitis species.1,18 This
technique has been used to screen for virus resistance and more recently as a
means of evaluating virus presence in certification programs.17,20
Green-grafting has also been promoted as a method to rapidly produce grafted
plants. In this process, greenhouse-grown mother vines of rootstocks and scions
can supply the needed cuttings for year-round grafting. Plants can also be
produced without being exposed to the field, greatly reducing the chance of
virus and pest infection. Several California nurseries are producing plants
with this process.
Success with green grafting is very dependent upon high-quality cuttings. We
have obtained the best success with partially lignified cuttings from
field-grown mother vines. It is possible to have good success with cuttings
from greenhouse-grown mother vines, but only when conditions are optimized with
high light, moderate humidity, proper fertilization and nutrient balance, and
fungal and insect pest control. It is extremely difficult to produce
high-quality cuttings during the winter months even with supplemental light and
heat. In addition, greenhouse mother blocks are most successful when they are
regularly repropagated into fresh support media.
The scion cuttings should have a full-sized leaf, which is trimmed by about
half, and an active lateral (prompt) bud. The rootstock cuttings need to be at
least 25 cm long, so that adequate spacing between the roots and graft union
can be achieved for field planting, and should also have a trimmed leaf and an
active lateral bud.
Most often the rootstock and scion cuttings are fitted together with a cleft
graft which makes a slit down the center of either the rootstock or scion,
while a long tapered wedge cut is made on the opposing piece. Razor blades or
scalpels are ideal for making this graft, and the process has also been
mechanized (La Haltogel Greffenvert, Mumm & Perrier-Jouët, Vignoble et
Recherches, Épernay, France). Parafilm, perforated plastic bandage tape,
or small clips can be used to hold the rootstock and scion in place while the
Once the graft has been made, the union must be healed under conditions of
moderate light, high humidity, and good air circulation. The grafted plants can
be placed in perlite, rock wool, or cellulose sponge. One technique recommends
that the union be healed by placing the grafted plants into a small closed
plastic tent with moderate temperatures and low light. Over several weeks, more
light is provided and humidities are decreased. Fungal diseases thrive in this
environment, and they must be controlled with fungicides. Alternatively, the
grafted plants can be healed and rooted under the mist propagation conditions
described above. In cases where rootstocks or species are more difficult to
root, it is advisable to pre-root these cuttings under mist propagation prior
Over a two- to four-week period, the union heals, the rootstock roots, and
the plant is ready to establish for a month or more under greenhouse
conditions. Following a "hardening-off" period, the green-grafted
plants can be planted in the vineyard or continue growing in the greenhouse to
become dormant before planting the following year.
Green-grafting produces an excellent graft union which appears more seamless
than traditional bench-graft unions made with omega or dado saw cuts. However,
after several years no apparent differences can be detected in health or nature
of the graft union when compared with traditionally grafted plants. At the time
of field planting, green-grafted plants normally have limited carbohydrate
reserves and relatively weak root systems; they require careful care and
watering for successful establishment.
Tissue culture propagation
Grapevines can be propagated fairly easily in tissue culture. Meristem or
shoot tip tissue culture has been used to eliminate grape viruses in
certification programs. Grapes have also been grafted under tissue-culture
conditions to detect and evaluate resistance to viruses.18 Tissue culture has
also been suggested as a means for rapidly propagating scarce or
hard-to-propagate planting stock of clones or varieties.11,10,8 The techniques are straight forward,12 but they are practiced skills
requiring substantial amounts of time and labor.
For routine elimination of viruses, shoot tips can be taken from actively
growing plants in the greenhouse or field. As in the case of mist propagation,
the high-quality of the plant material from which the tips are cut is essential
to the success of the work.
Under sterile conditions, fresh cut tips are gently sterilized in a mild
bleach solution with a few drops of detergent, rinsed, and then excised under a
The tips are placed on an initial media for six weeks, followed by rooting
media. After about a month on rooting media, most shoot tips will be ready for
transplanting. The roots are trimmed, and the young plants are transferred to
sterile soil mix in a closed container. Air circulation is gradually increased
after new growth occurs. After about one month, the plant is ready to be moved
from the growth chamber to a greenhouse.
When plant material is severely limited or in high demand, additional
meristems could be taken from these plants at this time. However, it would be
more economical, in terms of time and money, to begin mist propagating
herbaceous cuttings at this point. In most cases, it is more practical to begin
mass propagation after disease testing has insured that virus has been
ELISA and PCR testing can be used as the plants become established in the
greenhouse. Woody indexing, still the definitive virus disease tests for the
California registration and certification program, can begin during the first
dormant season following tissue culture; normally the new tissue culture
explants (TCEs) are at least six months old before they are woody indexed. We
have found that initial screening of plants with laboratory tests allows us to
eliminate some of the TCEs from the secondary testing process.
Green-grafting for virus indexing has proven useful to many labs for virus
disease testing.20 It has
not proved practical in our hands. Although some tests can be run more quickly
with green-grafting, the technique requires extremely high quality, year-round
greenhouse space and is very labor-intensive.
Further, the green-grafting technique is not accepted by the California
Department of Food & Agriculture or the U.S. Quarantine officials as a
substitute for woody indexing, thus there are regulatory barriers to its use.
It is probably most valuable in climates where the woody field index cannot be
accomplished routinely. In Davis, the woody field index produces reliable
results in two years, and winter cold is not a factor in completing the test.
We expect the most rapid progress in shoot tip culture is the elimination of
viruses to come from developments in PCR detection of grapevine viruses, which
should result in early, accurate screening of TCEs for disease. Ultimately,
these PCR tests are likely to eliminate the need for either woody or
In vitro-grafting as a tool for propagation can be done in a similar manner
to the green-grafting described above for virus.4 For difficult to root Vitis species
and hybrids, it is possible to optimize rooting and cultivation treatments
in vitro to an extent that is impossible on a mist bench. Some countries
(Chile and South Africa, for example) that have established strict
phytosanitary rules for grapevine importation have made it relatively easy for
in vitro plants to pass through quarantine. By establishing a new selection in
tissue culture, an importer might save months or even years of time that would
be lost before traditional materials cleared quarantine.
Outlook for rapid propagation methods
Rapid propagation methods are very important when plant materials are
limited due to the scarcity of a clone or variety or due to dramatic expansion
in acreage. Much of the grape-growing world is currently experiencing both of
these circumstances. New clones and varieties are in high demand, and there
seems to be boundless demand for the fruit from new wine and table grape
The most important aspect of the rapid propagation methods discussed above
is their ability to quickly provide relatively large amounts of planting stock
to grapegrowers. However, these techniques are rarely competitive with
traditional bench-grafting methods. The production of green-growing
bench-grafts from dormant cuttings requires about eight to 10 weeks from
grafting to field planting. It is rapid, provides high- quality planting stock,
and can be relatively inexpensive. However, this technique depends on adequate
numbers of mature mother vines of the needed rootstocks and scions, and these
require three to four years to reach maturity in terms of their wood
Rapid propagation methods allow growers to get new planting materials two
years earlier than they would be available via traditional propagation methods.
However, there are potential problems with these techniques. First, there are
great differences in rapid propagation practices compared with traditional
techniques, and therefore knowledge gaps could lead to uneven plant quality.
The second problem relates to growers and their ability to alter
establishment practices to deal with a planting stock with lower carbohydrate
reserves and with much less tolerance for uneven irrigation or rainfall. It is
also important to time plantings of these rapid propagation materials so that
there is sufficient time for roots to develop and lignify and for basal dormant
(latent) buds to complete maturation, so winter cold damage is prevented.
There are other problems coincident with rapid expansion of vineyards.
Limited planting stock and high demand have led to errors in labeling and
distribution. The quality of planting stock can often be uneven, as demands on
nurseries outstrip the normal limits to their production capacity. Growers are
also less inclined to check materials and may be less likely to demand high
quality when they are desperate to plant.
Rapid expansion in vineyard acreage also brings many new growers into the
grape business, often without the knowledge or background to handle planting
stock properly. Instructions from nurseries and viticulturists regarding
storage and handling before planting, soils, proper hole size, irrigation
schedules, fertilization, protection from vertebrate and insect pests, and
training may not be understood or followed. Rapid vineyard expansion also
brings great increases in diseases such as young vine decline, a complex of
wood-rotting fungi (Phaeoacremonium spp.), that, when associated with
weakened planting stock or poor vineyard establishment, can damage vines.15,16
Whether purchasing traditionally or rapidly propagated planting stock, the
grower is well advised to make contact with highly regarded and trusted
nurseries. Close associations with nurseries will result in better monitoring
of planting stock and/or avoiding improper grower practices that result in poor
It is doubtful that rapid propagation techniques will supplant traditional
grafting and propagation methods; however, these techniques can provide scarce
materials in a more timely fashion and will greatly advance vine improvement
and certification programs. Rapid propagation will always be more common during
periods of burgeoning vineyard expansion. These materials can meet
growers needs, but care must be exercised to meet the requirements of
such planting stock.
Edited from presentation to the Tenth Australian Wine Industry Technical
Conference, Sydney, Australia, 1998.
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