QUICK POSSIBILITIES IN FRUIT IMPROVEMENT
SPECIFIC NEEDS, AND HOW TO ACCOMPLISH THEM
The old pear tree out there in the corner of your garden was perhaps planted by your father's father. The twig you cut from it today may take root and become a thrifty tree that will bear fruit to gladden the hearts of your grandchildren long years after you are dead. And that possibility puts the tree on a very different footing as the friend and companion of man from that occupied even by the best-prized members of the company of forage plants and garden vegetables. When you work with fruit trees you are making permanent records. You are building on a rock. You are reaching out your hands to future generations, and erecting a monument that will remain as a testimonial to your foresight and wisdom long after you are gone. And doubtless this fact of the permanence of the tree accounts in large measure for the interest with which almost anyone will take up the culture of fruits if given the opportunity. Not that we are always thinking of posterity; but one can develop an enthusiasm about the production of something having an element of permanency that does not attach to such transient things as annual or biennial plants. The fruit tree in the old orchard is like an old friend when we get back to it. The mere view of it brings up reminiscences of our youth, and the tree that we planted in childhood may remain as a stimulus to us in old age. There is no friendlier compact than that between man and the fruit tree. It is an age-long compact withal. Not so ancient as the compact of bees and flowers-for as compared with the archaic and honorable order of insects man is a parvenu-but far older than human civilization none the less. Indeed, it was probably the fruit tree, giving an example of fixity of habitat, that encouraged man to give up the life of a nomad and establish a fixed abode. Not unlikely it was the evidence presented by the fruit tree that first suggested to man the possibility of raising a supply of foods from the soil, and thus lured him away from the precarious pursuits of the hunter and fisher and put him on the road to future greatness. And all along the road of advancing civilization the friendship with the fruit tree has been kept up. Yet, it is only in comparatively recent times, probably, that rapid progress has been made in aiding our coadjutors of the pomological world to step forward and better themselves as man had long ago bettered himself with their assistance. To be sure, our forebears developed many forms of fruit that were not lacking in palatability; but the great advances in the improvement of orchard fruits are matters of the nineteenth century. Recent progress in this field has been almost as wonderful as progress in the fields of mechanics and electricity. The orchard fruits of today that find their way to the markets are so different in size and quality from the fruits with which our grandparents were satisfied-even though some of them are grown on cions grafted on the old trees-as to seem to belong almost to different orders, certainly to different species from the fruit stocks from which they have been developed. Yet what has been done is only the beginning. We speak of "perfected" fruits, and in a sense the word is justified, so conspicuous are the good qualities of the new fruits as contrasted with the old. But no fruit has really been perfected, in the sense of having reached the limits of improvement. There are numberless opportunities for betterment even in the case of the very finest varieties of fruits of every kind. The successive chapters of the present volume will be devoted to specific suggestions as to the betterment of each of the important classes of orchard fruits. In the present chapter, it is my purpose to take a general survey of the field, pointing out various lines of betterment not so much with reference to any particular fruit, although we shall constantly draw our illustrations from specific fields, as with reference to the entire class of orchard fruits. The suggestions here outlined are the result of lifelong association with trees of the orchard. Probably not less than half my experiments of every character have been conducted in connection with one form or another of fruit trees. And a very large proportion of my most important new products, considered from an economic standpoint, have been products of the orchard.
AS TO MERE SIZE
Almost the first thought that comes to one who goes into the average orchard and looks about with a really observant eye is that orchard trees in general are not well-adapted to man's needs in the matter of size. I have in mind certain orchards of New England and Long Island, for example, in which the apple trees seem to have done their very best to rival the elms and oaks in size. Their trunks and main central branches rise, barren of fruit-producing branches, to a height of twenty or even thirty feet. The strength of the tree has gone to producing wood instead of fruit-bearing twigs. Such fruit as does appear is suspended so high that long ladders are required to reach it when it has ripened. This is obviously all wrong. There is no reason why the apple tree should be permitted to grow high into the air even if it has the inherent propensity to do so. By proper trimming, the young tree can be made to assume a spreading form, so that it will bear most of its fruit within easy reach. Moreover, it is easily possible through selective breeding to develop an apple stock that will have no tendency to grow into tall, or otherwise ill-shaped trees, but will naturally take on the compact, low-growing habit that is to be desired in a fruit tree. What is true of the apple is equally true of its cousin the pear. This tree also has been permitted in the old-time orchards to develop the pernicious habit of too slender upright growth and undesirable tallness, too much like a wildling. These defects have been corrected with some of the newer varieties, to be sure, but these have not been introduced universally. The same criticism applies to the cherry. Everyone knows how often this tree is seen growing in the New England dooryard, with trunk like that of the sturdiest oak, and with its inviting clusters of red fruit suspended at such a height as to be quite beyond reach of everyone but the birds. A well-trained cherry should renounce this tantalizing habit and make its wares reasonably accessible to the wingless biped that has fostered it. The other notable members of the company of orchard trees, namely the plum, peach, quince and orange, have in the main developed a more commendable habit of growth. Their trees are for the most part not too large, and the best varieties have a spreading form that leaves little to be desired. But some of these, and in particular the peach and orange, have other faults that urgently call for correction. The peach in particular is a tender and short-lived tree, peculiarly subject to the attacks of insects and to fungoid pests. Seemingly the developers of this luscious fruit have been so concerned to foster the remarkable qualities of the fruit itself that they have neglected the tree on which the fruit grows. So the peach orchard, instead of outlasting a human generation as it should, is an ephemeral growth, the individual trees of which are in good bearing only for a few years, after which they must be replaced. The peach grower is always uprooting the dead trees in one part of his orchard and planting new ones in another.
THE QUESTION OF STAMINA
Unfortunately the peach is so specialized that it will not thrive on any roots except its own. It should be possible, however-at least the project is one that invites the experimenter-to develop a more vigorous and longer-lived race of peaches. Something could doubtless be done by mere selection, taking cions for grafting or raising seedlings from the hardiest and most vigorous trees of the orchard. It has been shown that it is possible to hybridize the peach with its hardier relative the almond. Probably in successive generations there might be developed a hybrid stock of trees that would retain all the good qualities of the peach and yet would be as long-lived and vigorous as the almond, and hardier and more resistant than either. It is true that no very striking results have yet been produced by crossing almond and peach, though many unusually vigorous and rapid-growing trees have been produced which will far outgrow the most vigorous individuals of either species. But hybridizing, followed by rigid and persistent selection, is a practical method that is still in its infancy. It is not so very long since orchardists in general, supported by technical botanists, denied the possibility of hybridizing different species. My long series of varied experiments were perhaps more directly instrumental than any other influence in showing the fallacy of this belief. The reader will recall that I have in many instances interbred species belonging to different genera; and that the interbreeding of different species in my orchards and gardens is a commonplace. Yet it is still true that there are many cases in which there are seeming barriers erected between plants that obviously are closely related, which prevent the advantageous hybridizing and grafting of one species with another. And the peach is a case in point. It accepts the pollen of its nearest relations (except the almond) unwillingly, and as yet no useful product has come of such union. Yet the peach is not more isolated in this regard than its relative, the apricot, seemed to be until I was able, after many futile efforts, to break through the barriers and hybridize that fruit with the plum. The hybrid that resulted, named the plumcot, is virtually a new species. It combines the good qualities of both parents and is a very valuable addition to the list of orchard fruits. It seems not unlikely that some future experimenter will be able to effect a correspondingly useful hybridization of the peach; then the way will be open for the development of a race of peaches that will combine with the existing qualities of fruit production the qualities of hardiness and resistance to disease that the present peach tree so notably lacks.
BIG FRUIT AND FREE BEARING
Size of fruit and prolific bearing are characteristics of such obvious desirability that they cannot be overlooked even by the tyro. Yet the average amateur, who has a group of fruit trees in his garden or even a fair-sized orchard on his country place, is content to buy large, handsome, and well-seasoned fruits in the market, taking it for granted that his own trees cannot be expected to supply similar products. But in point of fact it is well within the possibilities to produce good orchard fruits wherever the trees exist that produce any fruit at all. Conditions of soil and climate cannot, of course, be ignored. One cannot grow oranges in Canada or grapefruit in New England-as yet. But if you have apple trees or pears or plums or cherries that bear fruit, it is a matter of your own choice whether they shall bear good fruit or bad. All that is necessary is that you should send to some reputable nurseryman or orchardist and secure cions of good variety for grafting on your trees. All apple trees are closely related, the cultivated varieties being without exception of mixed strains. The same is true of pears and plums and cherries. In each case you may graft on your native stock cions of any variety of the same species, or a dozen or a score of different varieties, and, if the work is done properly and at the right season, the new twigs will soon become a part of the old tree as regards vitality and capacity for growth and fruiting; but-as we have learned in earlier chapters-they will retain their inherent hereditary tendencies as to quality of fruit. Growing side by side, on the same tree, you may have summer apples and winter apples, sweet apples and sour, green varieties and red varieties. And all this without any necessity for experimentation on your part. You need have no knowledge of plant breeding except an understanding of the simple technique of grafting. The professional experimenters have supplied the material; you have but to avail yourself of the results of their work. Of course, if you wish to go a step farther there are inviting fields that you may enter. With the materials furnished by a single old apple tree you may become a plant developer. You may plant the seed of any choice apple purchased in the market and from the seedlings you will develop an interesting variety of fruits, some of which may seem to you better than any existing varieties. We have already caught glimpses, in the outlines of my work already given, of the possibilities of the development of various orchard fruits as to size and flavor and other desirable qualities. If you desire to try your hand at similar improvement either of the fruit now growing on your ungrafted trees, or of that growing on cions of improved varieties, it will require only reasonable attention to the principles already outlined in earlier chapters of this work, together with a fair degree of patience and persistency, to insure some measure of success. There is one additional hint that it might not be amiss to emphasize. In selecting seed for planting, it is desirable, of course, to select the largest and best specimens. But it should be recalled that the real test of quality in a tree is not the production of exceptional individual fruits, but the size of the average fruit that it bears. Exceptional conditions of nutrition may cause a single apple to grow very large on a limb that as a rule produces only fruit of meager proportions. Seedlings from this exceptional fruit do not inherit the exceptional quality of their parent. It is the germ plasm of the tree itself that counts. Seed from a very small apple of a good variety will produce better offspring than the seed of a very much larger individual specimen of a poor variety; so it is far better to select the poorest fruit of a good variety rather than the best of an ordinary variety. This principle should be borne in mind in undertaking plant development of any kind, not merely with reference to orchard fruits. It is the inherent properties of the plant organism as a whole that will determine the average character of the fruit.
BREEDING FOR QUALITY
As to the special qualities of fruit that call for improvement, details, of course, differ with different species. We have seen that sugar content is an all-important item in the case of the prune; and that sweetness and flavor and color are matters of importance in the case of the cherry. We have also seen with what relative ease varieties may be developed that surpass their parent forms in these regards. An interesting illustration of the possibility of breeding new qualities into a fruit or accentuating old ones, to which reference has not hitherto been made, is manifested by one of my new cherries, which, through selective breeding, became so sweet that its sugar content acts as a preservative, quite as in the case of the sugar prune. These cherries, instead of decaying rapidly after ripening, dry on the tree in a state of perfect preservation. This particular feature is of no present commercial value, but the case illustrates the possibility of altering the inherent qualities of a fruit, and of doing this in the course of a few generations through systematic selection. The same thing is illustrated by another of my cherries which, by careful attention to a combination of qualities that would ordinarily be quite overlooked, had its stem so strongly anchored to the stone that when the fruit is picked the flesh tears away leaving stem and stone on the tree. Now it will be recalled that, in the case of the prune, it is a serious defect to have the fruit so firmly attached to the stem that it clings to the tree after ripening. A prune must drop of its own accord when ripe or the prune dealer will have none of it. But the quality that would make a prune commercially worthless, when accentuated in the cherry, becomes a mark of possible exceptional value. The cherry that leaves its stone on the tree might conceivably fill a special purpose. So this variation in the inherent properties of the cherry might produce a new race of commercial value to meet an exceptional need. It requires but little ingenuity to suggest possible developments that would similarly give added value to the fruits of various species. For example, there is the matter of color in the pear. Unlike most other fruits, this one, as everyone knows, is for the most part lacking in the brilliant color that purchasers of fruit in the market usually find so attractive. But there is no reason why pears of various brilliant and attractive colors should not be developed just as colored apples have been developed. Our native crab apple is dull greenish brown or dull red, and unattractive in color even when ripe. Of course this is not the direct progenitor of the cultivated apple, but it obviously belongs to a closely related strain, and it shows us the apple in a state of nature and gives us a clue as to what qualities of fruit are advantageous to the apple itself, and what ones have been bred into the stock to meet the demands of the fruit developer. So the fact that the wild crab apple is dull in color suggests that the variously pigmented coat of the cultivated apple is an artificial product, not primarily beneficial to the plant itself, that man has developed through selection. It is not unlikely that the relatively thin skin of the cultivated apple, coincidentally developed, makes pigmentation desirable, to protect the tissues of the fruit from too much sunlight. The fact that many apples redden, where exposed to the sun, and remain green where protected by the shadow of a branch or leaf, suggests that such is the case. Be that as it may, the point I wish to emphasize at the moment is that the pigmented coat of the apple has been produced mostly by unconscious artificial selection. There can be no doubt that the pear could be similarly given a brightly colored skin should anyone care to take the trouble to make the experiment in selective breeding. Indeed, a few varieties of partly red pears have been developed, and have proved a valuable novelty in the market. Other and better varieties, variously tinted, should follow. It has been suggested that a globular or apple-shaped pear with a short stem would be acceptable to the packers because it would crate more compactly and carry better than the ordinary pear. But this would rob the fruit of one of its distinctive characters, so on the whole the change would probably not be an improvement. In the matter of size, also, it would appear that the pear, in its best varieties, has attained a maximum development. To make it much larger would be detrimental, as it would probably be torn from the tree by the wind. Even now some varieties are so large that they break away from the tree before ripening, and so these varieties are avoided. The Beurre Clairgeau, one of the best of pears, is little grown for this very reason. But in matter of flavor there is still opportunity for indefinite variation. Some European cultivators have recently produced remarkably pleasing and varied flavors in this fruit. An illustration of how the flavor of a fruit may be radically modified is furnished by my Apple Plum, which, while retaining the characteristic attributes of its race, curiously simulates the apple in the matter of form and even in taste and texture. Another instance is my Bartlett plum, which out-Bartletts the Bartlett pear in its own peculiar quality and flavor. Yet others are the Pineapple quince, which has the flavor of the pineapple itself, and the Sunberry, which has the exact flavor of the blueberry intensified. Corresponding modifications of the pear as well as of all other fruits lie within reach of the patient experimenter.
LEAVING OUT THE CORE
But perhaps the most inviting field of all, in connection with the possible development of orchard fruits, is that having to do not with the form or texture or flavor of the pulp but with the seed of the fruit. Of course it must not be overlooked that, from the standpoint of the fruit itself, or rather from the standpoint of the tree on which it grows, the seed is the only really essential part of the fruit. All of the embellishment of juicy pulp and highly pigmented skin is but the lure put forth by the plant on behalf of the seed, in the interests of self-preservation. The really essential part of the entire structure is but an infinitesimal cell lodged at the heart of each kernel of the seed. Indeed, we may go even one step further, with the aid of the microscope, and say that the nucleus of a single cell, born of the union of the nuclei of two germ cells, is the really important part not merely of the fruit but of the tree on which it grows. For within the infinitesimal structure of the nucleus, by the most mystifying of all Nature's feats of jugglery, are lodged those hereditary factors or determiners that will ultimately transmit the traits of the ancestral tree to the tree of the future. In the widest sense it is true that the sole purpose of the entire plant is to produce a certain number of these germinal nuclei, each representing the union of a pollen grain with an ovule; each carefully encased in the structure that we call a seed; and each capable of reproducing, with sundry modifications, the characteristics of the parent plant, or, in a profounder view, the blended characteristics of the entire ancestral race which the plant represents. When we consider the seed in this way it does not seem strange that all the resources of Nature should concentrate on the development of the fruit structure in which the all-important seed or cluster of seeds finds lodgment. And by the same token it is comprehensible that Nature will hold to the seed with the most unwavering persistency. And so it is not strange that the plant experimenter should be able to alter the size and texture and quality of the fruit pulp far more readily than he can modify the core or stone that lies at its center. Yet from man's standpoint this inevitable central structure, forming the heart of every orchard fruit, is a conspicuous detriment. And it is altogether desirable that fruits should be developed in which the stony or fibrous covering of the seed is eliminated, or in which the substance of the seed itself has been substituted by juicy tissues. Everyone knows that this much desired modification has been effected, or all but effected, in the case of the so-called navel orange. An accidentally discovered mutant, doubtless a pathological specimen, was seized on by some keen-eyed observer, and a race of seedless oranges was developed by selection, and widely disseminated by grafting. Also there are seedless grapes. The reader will recall the long series of experiments through which I was enabled, by taking advantage of a similar malformation in a wild European plum, to develop by hybridization and selective breeding a race of stoneless plums. Everyone knows, also, that there comes to us from the tropics a familiar fruit, the banana, that is seedless; although perhaps it is not so well known that this fruit has lost its seed through being propagated for long generations by division. The precise steps through which this development has taken place in the case of the banana are not matters of record. But its condition is similar to that of the sugar cane and of the familiar horseradish in our gardens, both of which have been so long propagated by division that they have abandoned the habit of seed formation. The banana in its wild state was practically filled from end to end with large, hard, bullet-like seeds or stones, with just enough pulp surrounding them to make the fruit attractive to birds and wild animals that could not destroy the seeds. In this state it was practically worthless to man. Had not a pathological form appeared without seeds, which must be cultivated solely by division, the banana would be a practically useless fruit to-day. And, for that matter, the potato furnishes us with an even more familiar illustration of the renunciation of the most primitive and important of all plant functions, that of seed bearing, which has developed under cultivation within the past half century. But among orchard fruits of temperate zones the orange and the stoneless plum, as just instanced, are the only examples of plants that have been thus profoundly modified-although a seedless (but not coreless) apple and pear, in the experimental stage of development, have been announced. These examples, however, are stimulative. They show that the possibility of cooperating with Nature is almost limitless; and it is hardly to be doubted that the plant experimenter of the not distant future will carry out the process of making all our orchard fruits seedless and coreless. As I said before, this is doubtless the most important opening that presents itself for the fruit developer. It is a field in which there is room for all and the allurements of which should prove inviting to a vast number of workers.
-When you work with fruit trees you are making permanent records-reaching out your hands to future generations-erecting a monument that will remain long after you are gone.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 4 Chapter 1