Pedigreed Grape Vines

Many viticulturists, in common with orchardists, believe that their
plants should be propagated only from parents which have good
characters, that is, are vigorous, healthy, productive, and bear fruit
of large size, perfect form, good color and good quality. They
believe, in short, that varieties can be improved by bud selection.
There is, however, but little in either theory or fact to
substantiate the belief of those who say that varieties once
established can be improved; or, on the other hand, that they
degenerate. Present knowledge and experience indicate that heredity is
all but complete in varieties propagated from parts of plants. The
multitude of grapes in any variety, all from one seed, are
morphologically one individual. A few kinds of grapes go back to
Christ's time, and these seem to agree almost perfectly with the
descriptions of them made by Roman writers 2000 years ago. How, then,
can the differences between vines of a variety in every vineyard in
the land be explained?

Ample explanation is found in "nurture" to account for the variation
in vines without involving a change in "Nature." Soil, sunlight,
moisture, insects, disease, plant-food, and the stock in the case of
grafted vines, give every vine a distinct environment and hence a
distinct individuality of its own. Peculiarities in a vine appear and
disappear with the individual. A variety can be changed temporarily by
its environment, but remove the incidental forces and it snaps back
into its same old self.

Heredity is not quite complete in the grape, however; for, now and
then, sports or mutations appear which are permanent and, if
sufficiently different, become a strain of the parent variety or
possibly a new variety. There are several such sports of the Concord
under cultivation. The grape-grower can tell these sports from the
modifications brought about by environment only by propagation. If a
variation is transmitted unchanged through successive generations of
the grape, as occasionally happens, it may be looked on as a new form.
"Pedigreed" vines, then, should be subject to a test of several
generations in an experimental vineyard before the grape-grower pays
the price demanded for the supposed improvement.

TTTTLE STOCKS AND RESISTANT VINES

Phylloxera, a tiny root-louse, made its appearance in France in 1861

and began multiplying with a fury unparalleled in the insect world. By
1874, the pest had become so widespread in Europe that it threatened
the very existence of the great vineyard industry of that continent.
All attempts to bring the pest under control failed, although the
French government offered a reward of 300,000 francs for a
satisfactory remedy. Numerous methods of treating the soil to check
the ravages of the insect were tried, also, but none was efficacious.
Finally, it dawned on European vineyardists that phylloxera is not a
scourge in America, its habitat, and that European vineyards might be
saved by grafting Vinifera vines on the roots of immune American
grapes. At once the reconstruction of vineyards in Europe was begun by
grafting the grapes on phylloxera-resistant roots. Meanwhile,
consternation spread to California when it was discovered that
phylloxera was running riot in some of the vineyards of the Pacific
slope; however, with the knowledge derived from viticulturists in
Europe, they too began reconstructing vineyards on immune roots,
without the same success as the Europeans, it is true, but with such
measure of success that it soon became the approved method of growing
grapes in this great region.

Through the use of resistant stocks, phylloxera is now defied in
Vinifera regions. Millions of American stocks are annually struck at
home, in Europe and wherever Vinifera grapes are grown, to be
top-worked with varieties susceptible to phylloxera. Seldom has
mastery over a pest been so complete; but, to triumph over the tiny
insect, the industry has had to be revolutionized. Resistant stocks,
in their turn, brought innumerable new problems, many of which are
still unsolved. Investigations and experiences in rehabilitating
vineyards have been carried on for forty years, the results set forth
in books and bulletins and yet there are many problems to be solved.
The grape-grower in regions infested with phylloxera is always under
the necessity of taking advantage of the latest demonstration of
practices in the use of resistant stocks. These practices are best
studied in the experiments of state experiment stations and the United
States Department of Agriculture, and in the vineyards of leading
grape-growers, since even those most needing elucidation can be but
briefly discussed in the following paragraphs.

The wild vines of a species are always seedlings and are hence
exceedingly variable. The first vineyards of resistant stocks were
vines grafted on stocks of wild vines, and the results were very
unsatisfactory; for, naturally, there was divergence in many
characters and especially in the vigor of the vines. Also, there was
difficulty in grafting, since some wild vines are stout and others
slender; some bear grafts well, while others do not. It soon became
apparent that to succeed, varieties must be selected from the
different species for vineyard work. The great task of the
experimenter and grape-grower, therefore, has been to select varieties
of the several species sufficiently resistant, vigorous and otherwise
possessed of characters fitting them to become good stocks. Out of
vast numbers tested, a few are now generally recognized as best for
the several groups of Vinifera grapes and the several distinct regions
in which these grapes are grown.

Resistant species and varieties.

The reconstruction of phylloxera-ridden vineyards by the use of
resistant stocks is possible only because some species and varieties
are, as has been said, more resistant to the root-louse than others.
All degrees of resistance exist, as would be suspected, from immunity
to great susceptibility. It is obvious that the foundation of the art
of growing resistant vineyards is exact knowledge of the immunities
and susceptibilities of the many varieties and species of grapes. From
the first use of resistant vines, experimenters everywhere have set
themselves at work to determine not only what the most resistant vines
are, but what the causes and conditions of immunity. In spite of a
wealth of empirical discoveries as to what grapes can best resist the
root-louse, causes and most of the conditions of immunity are still
little understood. Definite, useful knowledge, so far, goes little
further than the establishment of lists of species and varieties, the
latter subject to change, that are most useful in setting resistant
vineyards.

Phylloxera does little damage to species of Vitis native to the same
general region in which the pest has its habitat, but nevertheless
there are some differences in resistance in American grapes. Munson,
one of the best American authorities on the resistance of species to
phylloxera, says:[7] "Rotundifolia is entirely immune, then Rupestris,
Vulpina, Cinerea, Berlandieri, Champini, Candicans, Doaniana,
AEstivalis and Lincecumii are so high in resistance as to be
practically uninjured, though they may be attacked, while Labrusca is
low in resistance and is much weakened in clay soils, if infested, and
Vinifera is entirely non-resistant." Some of these species are hard to
propagate and difficult to suit in soil and climate so that but two of
them are much used for resistant stocks. The two most used are
Rupestris and Vulpina (Riparia), of both of which there are varieties
which give satisfaction. Bioletti, a leading authority on resistant
stocks in California, says:[8]

"Varieties of resistant stocks which will in all probability be used
in California are Rupestris St. George (du Lot), Riparia x Rupestris
3306, Riparia x Rupestris 3309, Riparia Solonis 1616, Mourvedre x
Rupestris 1202, Aramon x Rupestris 2, Riparia gloire, and Riparia
grande glabre. These are all varieties which have given excellent
varieties for years in Europe, and have all been tested successfully
in California. Among them are varieties suitable for nearly all the
vineyard soils of California, with perhaps the exception of some of
the heavier clays.

"The only one of these varieties which has been planted extensively in
California is the Rupestris St. George. There can be little doubt,
however, that it will fail to give satisfaction in many soils, and
though we may not find something better for all our soils it is
probable that we will repeat the experience of Southern France and
find that in most soils there is some other variety that gives better
results. Without attempting to describe these varieties, but to give
some idea of their merits and defects and of the soils most suited to
each, the following indications are given, based principally on the
opinions of L. Ravaz and Prosper Gervais, and on a still limited
experience in California:

"The Rupestris St. George is remarkably vigorous and grows very large,
supporting the graft well even without stakes. It roots easily and
makes excellent unions with most vinifera varieties. It is well suited
to deep soils where its roots can penetrate. Its defects are that it
is very subject to root-rot, especially in moist soils; it suckers
badly and it suffers from drought in shallow soils. Its great vigor
produces coulure with some varieties and often necessitates long
pruning.

"In moist or wet soils 1616 or 3306 had given better results in France
and gives indications of doing equally well here. In drier soils 3309
will probably be found preferable.

"Aramon Rupestris No. 2 is suited to the same soils as Rupestris St.
George, and does particularly well in extremely gravelly soils. It
has some of the defects of the St. George and is moreover more
difficult to graft, and its only advantage in California is that it is
rather less susceptible to root-rot.

"There are no better resistant stocks than Riparia gloire and Riparia
grande glabre, wherever they are put in soils that suit them. They do
well, however, only in deep, rich, alluvial soils which are neither
too wet nor too dry. Their grafts are the most productive of all, and
ripen their grapes from one to two weeks earlier than the grafts on
St. George. Their principal defect is that they are very particular as
to the soil, and they never grow quite as large as the cion. The
gloire is the most vigorous, and the difference of diameter is less
with this variety than with any other Riparia.

"The Mourvedre x Rupestris 1202 is extremely vigorous, roots and
grafts easily, and is well adapted to rich, sandy and moist soils. In
drier and poorer soils its resistance is perhaps not sufficient.

"The most promising varieties for general use at present seem to be
the two hybrids of Riparia and Rupestris, 3306 and 3309. They have
great resistance to the phylloxera, root and graft almost as easily as
St. George, and are quite sufficiently vigorous to support any variety
of vinifera. The former is more suited to the moister soils and
wherever there is danger of root-rot, and the latter to the drier
soils. In general, they are suited to a larger variety of soils and
condition than perhaps any other varieties.

"Riparia gloire should be planted only on rich, deep alluvial soil
containing an abundance of plant food and humus, what would be called
good garden land, such as river bank soil not liable to overflow.

"In most other soils Riparia x Rupestris 3306 is to be recommended,
except those that are rather dry, where 3309 is to be preferred, or
those which are very wet, where Solonis x Riparia 1616 is surer to
give good results."

The value of a species or variety for a resistant stock may be judged
somewhat by the visible effect of the phylloxera on the roots of the
vines. On susceptible species, the punctures of the insects rapidly
produce swellings which vary in size and number in accordance with
resistance of the species. Technically, the first swelling on the
young tender rootlets of the vine is called a nodosity. The presence
of a few nodosities on the root system does not indicate that a vine
is not a valuable resistant stock. When the nodosity begins to decay
and becomes of a cancerous nature, it is called a tuberosity. These
tuberosities decay more or less rapidly and deeply, and when they rot
deeply cause enfeeblement or death to the vine. Thus, on Vinifera
varieties the tuberosities are several times larger and decay sets in
much more quickly than on American species which show these
tuberosities. Ratings as to resistance of species are usually made
from the size and number of the tuberosities, though when these are
found producing a scab-like wound which scales off, there may be high
resisting power.

In order to convey with some degree of definiteness the power of
resistance to phylloxera, an arbitrary scale has been agreed on by
viticulturists. In this scale, maximum resistance is indicated by 20
and minimum by 0. Thus, the resisting power of a good Vulpina is put
as 19.5 and that of a poor Vinifera variety as 0.

Next: Adaptations Of Resistant Stocks To Soils And Climates
Previous: Grafting

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