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THE APRICOT AND THE LOQUAT

AN OPPORTUNITY FOR THE EXPERIMENTER

"The only use I have for the apricot," said a visitor, "is to supply a flavor for soda water; but that use justifies the fruit's existence. No other flavor can match it." Doubtless my visitor spoke facetiously, but we may all agree with her that there is no other flavor quite to match the flavor of the apricot. Fortunately, however, there are uses to which the fruit may be put in addition to the one she suggested. Otherwise it would not be possible to find a market for the two hundred million pounds or so of apricots that California raises each year. In point of fact the uses of the apricot are quite as varied as those of most other fruits. It is an admirable table fruit in the fresh state for those who live near enough the orchards to secure it. It is in considerable demand by canners who find ready sale for the fruit when preserved in this way. But the chief demand, and the one that gives the apricot its real economic importance is based on the exceptional qualities of the fruit when dried. Something like three-quarters of the entire output of the California orchards is preserved in this way and shipped as dried fruit to all parts of the world, and brings about the highest price of any tree fruit under cultivation. A perhaps clearer estimate of the value of the industry may be gained if we recall that there are nearly three million apricot trees in California orchards. Indeed, this state has a practical monopoly of commercial apricot growing. Nowhere else in the world is the fruit of corresponding economic importance. The apricot has been cultivated from an early period of history, like the allied orchard fruits, and it has been grown more or less extensively in America for many years. But it is a fruit that is greatly restricted as to the regions in which it can advantageously be cultivated. The fact that there are very large areas of California where it thrives, sufficiently explains the virtual monopoly in the growth of this fruit that the Pacific Coast enjoys.

WHY APRICOT CULTURE IS DIFFICULT

The difficulty that the apricot grower encounters may be said to center on a single characteristic of the tree-the extreme sensitiveness of its blossoms to the slightest fall in temperature. The apricot tree itself under proper conditions is relatively hardy and extremely productive. It is long-lived, and it attains great size. Moreover, it sends out a very extensive root system; demanding plenty of room, and justifying the demand by its increased production when the trees are not crowded. It continues to grow for many years, constantly extending its root system; so that some orchardists recommend planting the trees originally twenty feet apart and then, after a number of years, as the trees increase in size, removing every other one, thus securing a forty foot space for the roots of each tree. In the matter of pests that attack it, the apricot is relatively favored. It is on the whole a very healthy and vigorous, as well as very beautiful tree. But the sensitiveness of its blossoms to the slightest chill has hitherto put a restriction upon the spread of the tree beyond the sub-tropical zones, except in such a territory as that of California, where, because of exceptional topographical conditions, a sub-tropical climate prevails even at relatively high latitudes. There are extensive areas of the middle and eastern states, well toward the north, where the apricot tree may be grown without difficulty, but where no fruit can be produced because the blossoms are invariably blasted by the frosts or near-frosts that are sure to come after they are put forth. It is obvious, then, that this fruit presents a very specific and unusual problem for the plant developer. In case of many other fruits, to be sure, it is desirable to increase hardiness; but with no other fruit that we have hitherto considered is it so preeminently desirable to focus on this single object. For in the case of no other is there so striking a disparity between the roots and the blossoms as regards the climate to which they are adapted.

MAKING THE APRICOT HARDY

The idea that naturally suggests itself to the plant developer is that of selective breeding, in which the individuals chosen are those that have shown themselves relatively able to withstand cold. These, of course, can readily be selected in any region along the outer limits of the apricot's present zone of productivity, by merely noting the exceptional individuals that produce fruit in the season when their fellows are rendered infertile by the frost. Seedlings grown from these relatively hardy plants would, on the average, tend to manifest exceptional hardiness; and by successive selection through many generations it would thus be possible, without question, to modify the sensitiveness of the apricot blossom in such a way as to adapt it for cultivation far beyond the limits of its present range. Of course such selective breeding would be subject to the usual difficulties and complications that attend the development of any new or exceptional quality in an orchard fruit. Here, as elsewhere, there are complications due to the fact that the fruit will not grow true to type from seed. In this regard, however, the case of the apricot is somewhat more favorable than that of most other orchard fruits, because this species has been less widely cultivated, and is therefore less complex as to its hereditary tendencies than most others. Moreover, it is fairly easy in the case of the apricot to predict the qualities of the fruit from observation of the very young seedlings. In general the buds and leaves and wood in the first season give one a fairly good idea as to what size and quality of fruit the future tree will bear. On the other hand, the apricot has a peculiar habit of sending out a young shoot, and then postponing further growth until the buds set and ripen, and this complication may make the choosing of the seedlings a more difficult matter than it is in the case of apples, pears and peaches. For when the growth is checked in this manner the buds may become turgid and the leaves of unusual size on some plants, suggesting great possibilities, whereas, in point of fact, these plants may have no greater intrinsic merit than others that have continued their growth and so will show at the moment smaller buds and leaves. These complications must be very carefully taken into account in choosing seedlings to save for the development of improved varieties. The general rule that large leaves, full buds, and large short-jointed stems indicate individuals that will bear large fruit of fine quality must be constantly regarded, but the complications introduced by the anomalous habit of growth just referred to must not be overlooked.

CAN THE MICROSCOPIST HELP?

In carrying out a series of selections with the idea of developing a race of apricots with blossoms resistant to low temperature, there is unfortunately little to be expected from crossing different varieties of this species, because all existing varieties have been cultivated under more or less the same climatic conditions. Indeed, the outlying forms to which one would naturally appeal are chiefly natives of Asia Minor, Palestine, and Persia, and while they might serve a useful purpose, if hybridized with races now growing in America, in giving a tendency to variability and perhaps also an added virility, it is hardly to be expected that they bear hereditary factors that would greatly aid in the particular matter under consideration, because of the warm climate to which they and their ancestors have been habituated. Nevertheless, the experiment is well worth making for we know that there are latent qualities in the germ plasm of almost every race of plants that are revealed only through hybridization, and the presence of which would otherwise be quite unsuspected. In any event there are differences to be observed between individual apricot trees as to the relative hardiness of their blossoms. So material is at hand, with or without hybridization, from which to begin the work of selection. Doubtless this work might be carried forward much more rapidly if we had a clearer knowledge as to what the precise anatomical conditions are that are associated with extreme sensitiveness of the blossoms. We know that some blossoms (those of certain Japanese plums, for example) may retain their fertility even when subjected to freezing temperature; being able to live even through snow storms, in contrast to the apricot blossoms which wither under influence of the lightest frost. But no elaborate studies have been made to determine whether this difference is associated with anatomical differences of structure, the knowledge of which might guide the plant developer. That such differences really exist is suggested by the observed fact that the leaves of very hardy varieties of apples, for example those grown in Siberia, have exceptionally deep layers of epidermal cells to give protection to the less hardy cells that make up the bulk of the leaf. Possibly some similar modification of the cells may account for the resistant quality of blossoms that are observed to be able to withstand frost.

THE MICROSCOPE MAY HELP

If such is really the case, the microscopist might come to the aid of the practical fruit grower, pointing out to him the particular trees in his orchard that tend to produce flowers having their structure thus favorably modified. This method of selection would have obvious advantages over the method of planting trees at random in the colder regions, and waiting the selective influence of frost. If the fruit grower could gain such information as this in advance, thus planting only the hardier individuals and subsequently making selection of the best among these, he might obviously hope to advance with greater rapidity. And as the task at best is a tedious one, the plant developer should welcome any aid that may be offered, from whatever source. As yet, however, we have no assurance that definite assistance can be given us by the microscopists. It may be that the physical conditions that determine hardiness or sensitiveness in the flower are dependent on molecular arrangements that lie far beyond the limits of microscopic vision. In that case, we shall be obliged to depend upon the old method of selection, picking out plants that have proved somewhat hardier than their fellows, and being on the alert at all stages to discover the correlations as to color or form of stem or leaf that are associated with hardiness of blossom, that these may aid us in making early selection among our seedlings.

SEEKING AID FROM THE PLUM

I have said that the plant experimenter who attempts to give us a race of apricots with blossoms resistant to cold can perhaps expect little aid from crossing the existing varieties of apricot. Fortunately, however, there are possibilities of wider hybridizations that give far greater promise. There are varieties of Japanese plums that will stand hard freezing every morning from the time the buds start until the fruit is of good size. With ordinary plums such freezing absolutely prohibits the development of fruit, and the apricot, of course, cannot withstand even a single light frost. The resistant quality of the Japanese plum, then, marks it as a plant having in pre-eminent measure the precise quality that the apricot most conspicuously lacks. So the question at once arises as to whether it may not be possible to hybridize the apricot and the Japanese plum and by so doing breed into the apricot strain the quality of hardiness, just as we have seen specific qualities bred into other plants by similar hybridization. Fortunately it is possible to make such a cross. Reference has already been made to the new fruit called the Plumcot that I produced a good many years ago by making use of this particular combination. A full account of the methods involved and the difficulties overcome in producing this very unusual hybrid will be given in a subsequent chapter. It will then appear that the plumcot is to all intents and purposes a new species of fruit. It combines the qualities of the plum and the apricot, but in itself it is neither plum nor apricot. So while the plumcot has exceptional qualities of its own, it does not solve the particular problem with which we are at the moment concerned. We are seeking, not a new fruit, but an apricot having a particular quality that the present apricot lacks. And the question of the moment is whether there is a probability that after blending the strains of the Japanese plum with its hardy blossoms and the apricot with its peculiar qualities of fruit, it may be possible in subsequent generations to reassemble the qualities in such a way that we would have an apricot retaining the fruit qualities of its apricot ancestor, but combining with them the hardiness of blossom of its plum ancestor. Were the plum and the apricot a little less distantly related the question would admit of a ready answer. It would then be almost certain that we could, by a series of selective breedings, produce the desired combination from union of the materials at hand. But the plum and the apricot, as the qualities of the hybrid plumcot show, lie so far apart that their progeny tends to reveal a blending of characters rather than a segregation of unit characters. So it is somewhat less certain than it otherwise would be that the unit characters of the two fruits may be segregated and re-assembled in the way desired. Nevertheless I am disposed to think that this result may prove attainable. There are considerable variations between the different plumeots. Some of them tend to vary in the direction of the apricot, and others in the direction of the plum. By breeding with reference to a particular set of qualities-in this case the restoration of the apricot qualities and the retention of the hardy quality of bloom-it would probably prove possible to segregate and reassemble the qualities now blended in the plumcot in such a way as to give us a true apricot. Enough has already been done to convince me that this is possible. Such being the case I see no reason to doubt that by careful attention to the question of hardiness of bloom at all stages of the experiment our redeveloped apricot might be induced to retain this quality, a heritage from its Japanese plum ancestor, while retaining also the peculiar qualities of flesh and texture and flavor that are the hall-marks of the apricot. We shall have occasion, perhaps, to revert to this aspect of the subject more in detail in discussing the plumcot with regard to its various possibilities of improvement. Here it is enough to call attention to the fact that the hybridization of the apricot with the plum offers at least a possible solution of the vitally important problem of the development of a cosmopolitan apricot. Perhaps there is no single problem of orchard fruit development that offers possibilities of greater economic importance.

MATING WITH ORIENTAL COUSINS

As to other hybridizations, we may add that there is a quite different species of apricot growing in Japan, known as Prunus mume, which may possibly be of value in the development of new races of apricots, either with reference to the essential quality of hardiness or to the development of other qualities. This Japanese apricot bears a small fruit of very poor and acid quality, of use only for cooking. Moreover, it is not an abundant bearer, and it has few qualities that tend to commend it. It crosses readily with the cultivated apricot, however, and although the fruit is very inferior, there is always a possibility that later generations of such a progeny may develop unexpected qualities. Even better results might possibly be attained by crossing our best apricots with the hardy Russian apricots, which will bear fruit in much colder climates, but the fruit of which is but little superior to that of the Japanese apricot, Prunus mume, just described. The Mananites have brought many varieties of this species to America, and some of them are classed in the eastern states as good. The best of them, however, could never be compared in size or quality with our improved Persian varieties. There is also a fruit known as the black apricot, classified by some botanists as Prunus dasycarpa, which is allied to the apricot and which crosses readily with it, although it may more properly be regarded as a plum; being in fact a variety of Prunus ceresafera, as has been abundantly proved by numerous seedlings and hybrids produced on my own grounds. Hybrids of this fruit with the apricot and with the Japanese apricot and Japanese plum have been made in various combinations. Here, again, I shall have occasion to go more into detail in another chapter. I mention these various hybrids here to illustrate further the possibilities of development of new races of apricots, or of altogether new fruits, through various hybridizations in which the apricot is one parent. To mention only one other quality of the present apricot that is in great need of improvement, we may note that the fruit usually grows lopsided and has a tendency to ripen on one side while the other is partly green. There is great call among apricot growers, and especially from canning establishments, for a large, globular, sweet, free-stone apricot with a small pit. No apricot now known fully fills the bill. There is also opportunity to improve greatly the drying qualities of the apricot. All these matters will, of course, receive attention from the plant experimenter who endeavors to improve this fruit at the same time that he is considering the question of hardiness of blossom, although the latter quality deserves pre-eminent attention.

FITTING THE APRICOT TO NEW CLIMATES

The apricot, both as a canned and as a dried product, is becoming better known and more highly appreciated year by year. If a variety could be produced that would grow in wider territories, unimpaired by the vicissitudes of temperature of our north central states, this fruit would probably become as important as the apple and as extensively grown. And enough has already been accomplished to justify us in asserting that the prospect of extending the culture of this fruit into territories that are now prohibited is extremely good. Already there is a variety of medium size called the Royal that grows in many regions where other apricots refuse to produce fruit, and there are a few other varieties that somewhat approach it. These offer special material for further selection, and by combining such selection with skilful hybridizing the plant experimenter should be able to produce an apricot that will stand quite unrivaled among the stone fruits.

WHAT THE LOQUAT OFFERS

There is another fruit to which reference may be made here perhaps as well as elsewhere. This is the loquat, a plant classified by the botanists as Eriobotyra. There are several species sometimes classed as loquats, but the common Japanese loquat is the only one which the botanist places in the genus just named. It is a small, broad-leaved, woolly-branched evergreen, useful not only for ornamental purposes, but for its fruit which ripens from February to June, growing from blossoms that usually appear in December and January. The wild loquat of Japan bears a small fruit about the size of a very large cherry or small plum, nearly all skin and seeds, and outwardly somewhat resembling a small apple or large hawthorne fruit, except that it is yellowish in color and rusty woolly. But there are several improved varieties of fruit, due to selective cultivation. These oftenest bear pear-shaped fruit that is sometimes two and one-half inches in length and two inches in diameter. The increased size is due to the pulp, the seeds not being changed in size. Indeed there is a tendency in the direction of smaller seeds, and some of the improved loquats are almost seedless. I know of one tree that generally bears fruit that is altogether seedless. This would be a very valuable tree were it not that the particular variety is extremely unproductive. The fruit is usually of a pale yellow or deeper golden color, sometimes shaded with crimson on the sunny side. The flavor suggests that of some early apples, but is generally considered superior. The fruit grows in clusters of three to ten or more, and the improved varieties bear very abundantly. In some cases two crops may be produced in the same year. The tree grows in the Gulf States and along the Pacific Coast, and it is considerably hardier than the orange, but not quite as hardy as the fig. It is quite commonly grown in California and similar climates for the decoration of parks and home grounds, but most varieties grown for this purpose bear little or no fruit. It grows readily from seed, which germinates at any time of the year. But it is a very difficult seedling to transplant, so the seeds should be planted in pots and the entire contents turned out when the plant is a few inches high, after the method used with geraniums and various other garden plants. The better varieties of loquat can be grafted during January and February. Grafting may be done by the "cleft" method or any other of the usual methods already described. It is well to remove most of the leaves from the cion, leaving a cluster of the tip bud leaves. Wax should be applied freely, and a paper sack tied tightly over the graft and stock to protect it from drying winds. Later the sack may be partially opened, and at last removed. The large number of seedling loquats in my orchard were grown from one tree, bearing giant fruit, imported from Japan. The seedlings vary decidedly in growth and in foliage. As these come into bearing they may be expected to produce new varieties of loquats, some of which will combine size, quality, rapid growth, and productiveness. My first seedlings fruited at about the age of three years from seed, some not until the fourth year. The better varieties of the loquat are quite often grafted or budded on common quince stock, on which the trees thrive as well apparently, as if on their own roots. This would indicate the possibility (but not necessarily the probability) of crossing the loquat and the quince. So far as my experience indicates, the loquat is perfectly self-fertile. It is readily crossed and yields rather promptly to efforts at its improvement. There is every probability that it will become a much more important fruit in the near future. And among our minor orchard fruits there are few, if any, that offer better opportunities for the amateur plant experimenter.

-There is no single problem of orchard fruit development that offers possibilities of greater importance than the development of a cosmopolitan apricot.

This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 4 Chapter 8