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

profess onal 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.