Manual of American Grape-Growing Part 25

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 cl.u.s.ter 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 cl.u.s.ter as possible, but success is not always certain; when there is doubt, the uncertain flower should be removed from the cl.u.s.ter.

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 cl.u.s.ter 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-cl.u.s.ter. 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 pa.s.sed which can be tied when the upper end of the bag is squeezed about the cl.u.s.ter.

_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 acc.u.mulated 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, a.s.sure 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.

[Ill.u.s.tration: PLATE XXI.--Jefferson (3/5).]

CHAPTER XVI

MISCELLANIES

There yet remain several phases of grape-culture essential to success, none of which quite deserves a chapter and none of which properly falls into any of the foregoing chapters. The subjects are not closely related, are by no means of equal importance, yet all are too important to be relegated to the limbo of an appendix and are, therefore, thrown into a chapter of miscellanies.

CROSS-POLLINATION

The blooming of the vine had little significance to the grape-grower, the blooming period being so late that grapes are seldom caught by frost, until the discovery was made that many varieties of grapes are unable to fertilize themselves, and that failure of crops of these varieties was often due to the self-sterility of the variety. Until this discovery, the uncertainty attending the setting of the grape in these varieties was one of the discouragements of grape-growing.

Following investigations of the self-sterility of the tree-fruits, an investigation of the grape showed that the vines of this fruit are often self-sterile. This knowledge has in some degree modified the planting of all home collections and has more or less affected the plantings of commercial sorts.

Varieties of American grapes show most remarkable differences in the degree of self-fertility. Many sorts fruit perfectly without cross-pollination. Others set no fruit whatsoever if cross-pollination is not provided for. Most varieties, however, are found in groups between the two extremes, neither self-fertile nor self-sterile.

Figure 51 shows staminate and perfect cl.u.s.ters on one vine. Some varieties show no variation in the degree of self-sterility or self-fertility; others behave differently in regard to these characters under different environment. Now and then the widest variations are to be found in a variety in respect to self-fertility.

[Ill.u.s.tration: FIG. 51. Staminate and perfect cl.u.s.ters on one vine; _right_, staminate; _left_, perfect.]

Following the lead of Beach at the New York Agricultural Experiment Station, several workers have made careful studies of the self-fertility of the grape, and now the cultivated varieties of native grapes are divided into four groups in accordance with the degree of self-fertility. Cla.s.s I includes self-fertile varieties having perfect or nearly perfect cl.u.s.ters; Cla.s.s II includes self-fertile varieties having cl.u.s.ters loose but marketable; Cla.s.s III includes varieties which are so imperfectly self-fertile that the cl.u.s.ters are generally too loose to be marketable; Cla.s.s IV includes self-sterile varieties. The following is a list of commonly cultivated grapes cla.s.sified according to the divisions just given:

CLa.s.sIFICATION OF GRAPES ACCORDING TO SELF-FERTILITY

CLa.s.s I. Cl.u.s.ters perfect or varying from perfect to somewhat loose.

Berckmans Bertha Cottage Croton Delaware Diana Etta Janesville Lady Washington Lutie Moore Early Poughkeepsie Pocklington Prentiss Rochester Senasqua Winch.e.l.l

CLa.s.s II. Cl.u.s.ters marketable; moderately compact or loose.

Agawam Brilliant Brown Catawba Champion Chautauqua Clinton Colerain Concord Dutchess Early Victor Elvira Empire State Fern Munson Hartford Iona Isabella Isabella Seedling Jefferson Jessica Lady Mills Missouri Riesling Perkins Rommel Triumph Ulster

CLa.s.s III. Cl.u.s.ters unmarketable.

Brighton Canada Dracut Amber Eumelan Geneva Hayes Lindley Noah Northern Muscadine Vergennes

CLa.s.s IV. Self-sterile. No fruit develops on covered cl.u.s.ters.

America Aminia Barry Black Eagle Clevener Creveling Eldorado Faith (?) Gaertner Grein Golden Hercules Jewel Ma.s.sasoit Maxatawney (?) Merrimac Montefiore Requa Salem Wyoming

In the main, the cause of infertility, as with other fruits, is the impotency of pollen on the pistils of the same variety. There are a few cases in which pollen does not seem to be formed abundantly, but these are very few. There are a few cases, also, in which the pistil does not become receptive until after the pollen has lost its vitality; these, however, are very few. In a greater number of cases the pollen is found defective. However, dismissing all of these as the exception, the rule is that self-sterility is due, as has been said, to the lack of affinity between pollen and pistils produced on the vines of some varieties.

Nature is helpful to the grape-grower in giving a guide to self-fertility. The length of stamens is a fairly safe indication of self-fertility. All grapes which are self-fertile bear flowers with long stamens, although the latter are not a sure sign of self-fertility, as a few varieties with long stamens are self-sterile.

On the other hand, short or recurved stamens are always a.s.sociated with complete or nearly complete self-sterility.

The remedy for self-sterility is inter-planting. Only the varieties named in Cla.s.ses I and II in the foregoing cla.s.sification should be planted alone. The sorts named in Cla.s.ses III and IV must be planted near other sorts which bloom at the same time in order that their flowers may be cross-pollinated.

It is evident that the grape-grower must have some knowledge of the relative time that grapes bloom, if he is to plant intelligently to secure cross-pollination. The following table, taken from Bulletin 407 of the New York Agricultural Experiment Station, shows the blooming time of grapes at that Station. Variations due to location and season must be expected, but within the bounds of the regions in which these grapes are grown variations will be slight. When this table is used for other regions than New York, it must be borne in mind that the farther south, the longer the blooming season; the farther north, the shorter the season.

_Blooming dates of grapes._

From three years' records, the average length of blooming season for grapes was twenty days, nineteen days in 1912 and 1914 and twenty-two days in 1913. The first date in the average year of 1912 was June 14, while for 1914, it was June 7:

TABLE IV.--SHOWING BLOOMING TIME OF GRAPES

===================================================================== VERY MID- VERY EARLY EARLY SEASON LATE LATE -------------------+---------+---------+---------+---------+--------- Agawam * America * August Giant * Bacchus * Barry * Beacon * Bell * Berckmans * Black Eagle * Brighton * Brilliant * Brown * Campbell Early * Canada * Canandaigua * Carman *

Catawba * Champion * Chautauqua * Clevener * Clinton * Colerain * Columbian Imperial * Concord * Cottage * Creveling * Croton * Delago * Delaware * Diamond * Diana * Downing * Dracut Amber * Dutchess * Early Victor * Eaton * Eclipse * Eldorado * Elvira * Empire State * Etta * Eumedel * Eumelan * Faith * Fern Munson * Gaertner * Geneva * Goethe * Gold Coin * Grein Golden * Hartford * Headlight * Helen Keller * Herbert * Hercules * Hicks * Hidalgo * Hosford * Iona * Isabella * Janesville * Jefferson *

Jessica * Jewel * Kensington * King * Lady Washington * Lindley * Lucile * Lutie * McPike * Manito * Martha * Ma.s.sasoit * Maxatawney * Merrimac * Mills * Missouri Riesling * Montefiore * Moore Early * Moyer * Nectar * Niagara * Noah * Northern Muscadine * Norton *

Oporto * Ozark * Peabody * Perfection * Perkins * Pierce * Pocklington * Poughkeepsie * Prentiss * Rebecca * Regal * Requa * Rochester * Rommel * Salem * Secretary * Senasqua *

Stark-Star *

Triumph *

Ulster * Vergennes * Winch.e.l.l * Worden * Wyoming * =====================================================================

RINGING GRAPE VINES

The ringing of woody plants is a well-known horticultural practice.

Three objects may be attained by ringing: unproductive plants may be brought into bearing by ringing; the size of the fruits may be increased and thereby the plants be made more productive; and the maturity of the fruit may be hastened. In European countries, ringing has long been practiced with all tree-fruits and the grape, but in America the operation is recommended only for the apple and the grape and with neither fruit is ringing widely practiced. Experiments carried on at the New York Agricultural Experiment Station by Paddock, as reported in Bulletin 151 from this Station, show that ringing may well be practiced by grape-growers under some conditions. Since Paddock's experiments, and possibly to some extent before, the grape has been ringed to produce exhibition fruits or a fancy product for the market.

Ringing consists in taking from the vine a layer of bark around the vine through the cortex and bast of the plant. The width of the wound varies from that of a simple cut made with a knife to a band of bark an inch in diameter. The operation is performed during that period of growth in which the bark peels most readily from the vine, the period of greatest cambial activity. The term "ringing" is preferred to "girdling," a word sometimes used, since the latter properly designates a wound which extends into and usually kills the plant.