GRAPE-BREEDING
Chance, pure and simple, has been the greatest factor in the
production of varieties of American grapes. From the millions of wild
plants, an occasional grape of pre-eminent merit has caught the eye of
the cultivator and has been brought into the vineyard to be the
progenitor of a new variety. Or in the vineyards, more often in
near-by waste lands, from the prodigious number of seedlings that
spring up, pure or cross-bred, a plant of merit becomes the foundation
of a new variety. An interesting fact in the domestication of the four
chief species of American grapes is that none came under cultivation
until forms of them, striking in value, had been found. Catawba,
representing the Labrusca grapes; the Scuppernong, the Rotundifolias;
Norton, from _Vitis aestivalis_; Delaware and Herbemont from the
Bourquiniana grapes; and Clinton from _Vitis vulpina_, are, after a
century, scarcely excelled, although in each species there are now
many new varieties.
That our best grapes have come from chance is not because of a lack of
human effort to produce superior varieties. Of all fruits, the grape
has received most attention in America from the generation of
plant-breeders just passing. Grape-breeders have produced 2000 or more
varieties, a medley of the heterogeneous characters of a dozen
species. That so many of this vast number are worthless is due more to
a lack of knowledge of plant-breeding than to a lack of effort, for
the order and system in plant-breeding that now prevail, disclosed by
recent brilliant discoveries, were unknown to grape-breeders of the
last century.
GRAPE HYBRIDS
As early as 1822, Nuttall, a noted botanist, then at Harvard,
recommended "hybrids betwixt the European vine and those of the United
States which would better answer the variable climates of North
America." In 1830, William Robert Prince, Fig. 48, fourth proprietor
of the then famous Linnean Botanic Nursery at Flushing, Long Island,
grew 10,000 seedling grapes "from admixture under every variety of
circumstance." This was probably the first attempt on a large scale to
improve the native grapes by hybridizing, although little seems to
have come of it. Later, a Dr. Valk, also of Flushing, grew hybrids
from which he obtained Ada, the first named hybrid, the introduction
of which started hybridizers to work in all parts of the country where
grapes were grown.
[Illustration: FIG. 48. William Robert Prince.]
Soon after Valk's hybrid was sent out, E. S. Rogers, Fig. 49, Salem,
Massachusetts, and J. H. Ricketts, Newburgh, New York, began to give
viticulturists hybrids of the European Vinifera and the American
species which were so promising that enthusiasm and speculation in
grape-growing ran riot. Never before nor since has grape-growing
received the attention in America as given during the introduction of
Rogers' hybrids. It was the expectation of all that we were to grow in
America, in these hybrids, grapes but little inferior, if at all, to
those of Europe.
A statement of the difference between European and American grapes
shows why American viticulturists have been so eager to grow either
pure-breds from the foreign grape or hybrids with it.
[Illustration: FIG. 49. E. S. Rogers.]
European grapes have a higher sugar-and-solid content than the
American species; they, therefore, make better wines and keep much
longer after harvesting and can be made into raisins. Also, they have
a greater variety of flavors, which are more delicate, yet richer,
with a pleasanter aroma, seldom so acid, and are always lacking the
disagreeable, rancid odor and taste, the "foxiness," of many American
varieties. There is, however, an unpleasant astringency in some of the
foreign grapes, and many varieties are without character of flavor.
American table-grapes, on the other hand, are more refreshing, the
unfermented juice makes a pleasanter drink, and lacking sweetness and
richness, they do not cloy the appetite so quickly. The bunches and
berries of the European grapes are larger, more attractive and are
borne in greater quantities. The pulp, seeds and skins are somewhat
objectionable in all of the native species and scarcely so at all in
the Old World sorts. The berries of the native grapes shell from the
stem so quickly that the bunches do not ship well. The vines of the
Old World grapes are more compact in habit and require less pruning
and training than do those of the native grapes; and, as a species,
probably through long cultivation, they are adapted to more kinds of
soil, to greater differences in environment and are more easily
propagated than the American species.
Because of these points of superiority in the Old World grape, since
Valk, Allen and Rogers showed the way, American grape-breeders have
sought to unite by hybridization the good characters of the Old World
grape with those of the American. Nearly half of the 2000 grapes
cultivated in eastern America have more or less European blood in
them. Yet, despite the efforts of the breeders, few of these hybrids
have commercial value. Whether because they are naturally better
fixed, or long cultivation has more firmly established them, the vine
characters of _Vitis vinifera_ more often appear in varieties arising
as primary hybrids between that and the native species, and the
weaknesses of the foreign grape, which prevent their cultivation in
America, crop out. Hybrids in which the vinifera blood is more
attenuated, as secondary or tertiary crosses, give better results.
Several secondary hybrids now rank among the best of the cultivated
grapes. Examples are Brighton and Diamond. The first is a cross
between Diana-Hamburg, a hybrid of a Vinifera and a Labrusca, crossed
in its turn with Concord, a Labrusca; the second is a cross between
Iona, also a hybrid between a Vinifera and a Labrusca, crossed with
Concord. Both were grown from seed planted by Jacob Moore, Brighton,
New York, in 1870. Brighton was the first secondary hybrid to attract
the attention of grape-breeders, and its advent marked an important
step in breeding grapes.
The signal success achieved by hybridizers of the European grape with
native species quickly led to similar amalgamations among American
species. Jacob Rommel, of Morrison, Missouri, beginning work about
1860, hybridized Labrusca and Vulpina grapes so successfully that a
dozen or more of his varieties are still cultivated. All are
characterized by great vigor and productiveness; and, although they
lack the qualities which make good table-grapes, they are among the
best for wine-making. Rommel has had many followers in hybridizing
native species, chief of whom was the late T. V. Munson, Fig. 50,
Denison, Texas, who literally made every combination of grapes
possible, grew thousands of seedlings and produced many valuable
varieties.
[Illustration: FIG. 50. T. V. Munson.]
_Improvement by selection._
Selection, continued through successive generations, so important in
the improvement of field and garden plants, has played but small part
in the domestication of the grape. The period between planting and
fruiting is so long that progress would be slow indeed were this
method relied on. Moreover, selection, as a method in breeding, is
possible only when plants are bred pure, and it is the experience of
grape-breeders that in pure breeding this fruit loses in vigor and
productiveness and that the variations are exceedingly slight and
unstable. Many pure-bred grapes have been raised on the grounds of the
New York Agricultural Experiment Station under the eyes of the writer,
of which very few have surpassed the parent or have shown promise for
the practice of selection.
_New varieties from sports._
Bud-sports or mutations now and then arise in grapes. But not more
than two or three of the 2000 varieties now under cultivation are
suspected of having arisen in this way. It is true that mutations
seem to occur rather often in grapes, but they are easily confused
with variations due to environment and are usually too vague to lay
hands on. Until the causes of these mutations are known and until they
can be produced and controlled, but little can be hoped for in the
amelioration of grapes through mutations.
HYBRIDIZING THE GRAPE
Hybridization has been the chief means of improving the grape. At
present, from what is being accomplished by many workers, it looks as
if it will long continue to be the best means of improving this fruit.
Since the grape-grower must depend on new varieties for progress, as
old varieties cannot be changed, it should be the ambition of growers
to produce varieties better than those we now have. Many amateur and
professional grape-growers in the past have found breeding grapes a
pleasing and profitable hobby, so that much knowledge has accumulated
in regard to manipulating the plants in hybridization, and the results
that follow in the offspring of hybridization.
_How to hybridize._
It is assumed that the reader is familiar with the botany of flowers
and the essential principles in crossing plants. If he is not, he must
carefully study the structure of flowers, especially those of the
grape, so as to be able to distinguish the different organs and to
discover when the pollen and stigma are ready for the work of
pollination. He should, also, read any one of several current books on
plant-breeding.
The first task in crossing grapes is to remove the anthers before the
flower opens, a process known as emasculation. This is necessary to
prevent self-pollination. This first operation having been performed,
the cluster of grape-flowers must be tied securely in a bag to protect
it from foreign pollen which otherwise would surely be carried to the
stigma by insects. As soon as the stigma is ready to receive the
pollen, the bag is removed and pollen from the male parent is applied,
after which the bag is again put on the flower to remain until the
grapes are well set. By examining the stigmas in the flowers of
uncovered grapes, the operator can tell approximately whether the
covered stigma is ready to receive pollen. The time required after
covering depends, of course, on the age of the bud when emasculation
takes place. It is, by the way, best to delay emasculation until just
before the flowers open, but one must be certain that the anthers have
not discharged their pollen before the flower has been emasculated.
Emasculation is a simple operation. The essential organs of the
grape-flower are covered by a small cap; this in some grapes must be
removed before the anthers can be reached. In many native grapes,
however, the cap and the anthers may be removed at one stroke by the
operator. The best tool for this is a small pair of forceps. Each of
the blades of the forceps in working with native grapes should have a
sharp cutting surface, but with Vinifera sorts, where the cap must be
removed before the anthers can be reached, forcep blades with a flat
surface are best. There is, of course, some danger when the buds are
well developed that the pollen may be squeezed out and so reach the
stigma or adhere to the instrument and thus contaminate future
crosses. The first danger must be avoided carefully by the skill of
the operator, while the second is easily overcome by sterilizing the
forceps in alcohol. An effort should be made to fertilize as many of
the flowers in the cluster as possible, but success is not always
certain; when there is doubt, the uncertain flower should be removed
from the cluster.
The flower from which the pollen is to be taken must be protected from
wind and insects; otherwise pollen from another flower may be left on
it. Protection should be given by tying the flowers in a bag while
still in bud. There are various ways of obtaining pollen from ripe
anthers and applying it to the stigma of the flowers to be crossed.
The simplest is to crush the anthers, thus squeezing out the pollen,
after which, with a brush, scalpel or other instrument, it may be
placed upon the stigma. A brush is very wasteful of pollen and often
becomes a source of contamination to future crosses, so that the
scalpel is the better implement of the two. When pollen is plentiful,
as will usually be the case when a man is working with vines in his
own vineyard, by far the best method is to take the cluster from the
male vine and apply the pollen directly to the stigma of the flower to
be crossed, thereby making certain of fresh pollen and an abundance of
it. The stigma, if pollen suffice, should be covered with pollen.
Grape pollen does not keep well and an effort should be made to have
it as fresh as possible. The work of pollination is best performed in
bright, sunny weather when the pollen is very dry. As may be seen from
the foregoing statements, tools and methods are of less importance
than care in doing the work. The only tool absolutely necessary is a
pair of forceps, although a hand-lens is often helpful. Bags for
covering the flowers should be just large enough and no larger. A bag
to cover the pollen-producing flower may well be an ordinary manilla
bag sufficiently large to amply cover the flower-cluster. It is
helpful, however, to have a light transparent oiled bag through which
one can see the condition of the anthers. It is desirable that the bag
for the female flower be permitted to remain until the fruits ripen as
a protection against birds and fungi. It must, therefore, be of larger
size. While the bags are still flat, a hole is made near the opening
through which a string is passed which can be tied when the upper end
of the bag is squeezed about the cluster.
_Choosing the parents._
Very much depends on the immediate parentage in hybridizing grapes.
Some varieties when crossed produce much higher averages of worthy
offspring than others. There is so much difference in varieties in
this respect that to discover parents so endowed should be the first
task of the grape-breeder. Fortunately, considerable work has been
done by several experiment stations in breeding grapes, and their
accumulated knowledge, together with that from such workers as Rogers,
Ricketts, Campbell and Munson, furnishes beginners with good starting
points. There is no way possible of discovering what the best
progenitors are except by records of performance. Very often varieties
of high cultural value are worthless in breeding because their
characters seem not to be transmitted to their progeny and, to the
contrary, a good-for-nothing variety in the vineyard is often valuable
in breeding.
From present knowledge it does not appear that new characters are
introduced in plants by hybridizing. A new variety originating from
hybridization is but a recombination of the characters of the parents;
the combination is new but the characters are not. Thus, one parent of
a hybridized grape may contribute color, size, flavor and practically
all the characters of the fruit, while the other parent may contribute
vigor, hardiness, resistance to disease and the characters of the
vine. Or these and other characters in the make-up of a new grape may
be intermingled in any mathematical way possible. The grape-breeder
must make certain that one or the other of the parents possesses the
particular characters he desires in his new grape.
It is now known that the characters of the grape, in common with those
of other plants, are inherited in accordance with certain laws
discovered by Mendel. The early workers in grape-breeding did not know
of these laws and could not take aim in the work they were doing.
Consequently, hybridization was a maze in which these breeders often
lost themselves. Mendel's discoveries, however, assure a regularity of
averages and give a definiteness and constancy of action which enable
the grape-breeder to attain with fair certainty what he wants if he
keeps patiently at his task. The grape-breeder should inform himself
as to what Mendel's laws are, and on the work that has been done on
the inheritance of characters of the grape. A technical bulletin
published by the State Experiment Station at Geneva, New York, and
another from the North Carolina Station at Raleigh give much
information on the inheritance of characters in certain grapes, and
further information can be secured by applying to the United States
Department of Agriculture at Washington for literature on the subject.
The grape-breeder can hope to progress only by making many
combinations between different varieties and growing large numbers of
seedlings. He should extend his work to all varieties which show
promise in the breeding of grapes for the particular purpose he has in
mind. The seed may be saved and planted as directed in the chapter on
propagation. Unless he desires to make scientific interpretations of
his results, weak seedlings should be discarded the first year, and a
second discard may be made before the young plants go in the vineyard.
The breeder will soon discover that he can tell fairly well from the
character of the seedlings whether they are of sufficient promise to
keep. Thus, if the number of leaves is small or if the leaves
themselves are small, the vine is of doubtful value; if the internodes
are exceedingly long, the prospect is poor; slenderness of cane, if
accentuated, does not promise well; on the other hand, great stoutness
and very short internodes are not desirable indications. Through these
and other signs, the breeder will come quickly to know which vines
should eventually go to the vineyard.
RESULTS OF GRAPE-BREEDING
There are now 2000 or more varieties of grapes of American origin, all
produced within approximately a century. It is doubtful whether any
other cultivated plant at any time in the history of the world has
attained such importance in so short a time from the wild state as
American grapes. It would seem that almost every possible combination
between species worth considering has been made. Through
hybridization, species and varieties have become so mixed that the
grape-breeder cannot now work intelligently with these gross forms and
must work with characters rather than with species and varieties which
are but combinations of characters. Great progress, it is true, has
been made in the past in breeding grapes in America, but the work has
been wholly empirical and extremely wasteful. Many varieties have been
called, but few have been chosen. With the new knowledge of breeding
and with the experience of past workers, progress should be made with
greater certainty. From what has been done and from work now under
way, it is not too much to say that we shall soon be growing grapes
everywhere in America, and kinds so diverse that they will meet not
only all purposes to which grapes are now put, but also the demand for
better grapes made by more critical consumers.
[Illustration: PLATE XXI.--Jefferson (x3/5).]