Volume Number: 1  2  3  4  5  6  7  8  9  10  11  12 

 

THE RASPBERRY AND SOME ODD CROSSES

MUCH BETTERMENT-AND A FEW BAFFLING PROBLEMS

Let us take up the story of small fruit development where the preceding chapter left it. We are still concerned with the blackberry, but we now have to do also with the companion fruit, which is obviously a not very distant relative, yet which has certain typical peculiarities that mark it as belonging to an altogether different branch of the race of brambles. Most conspicuous of these is the fact that the ripe raspberry separates from the receptacle when picked, whereas the blackberry is permanently attached to the receptacle. The raspberry, unlike the blackberry, has been cultivated in Europe from an early period. The red raspberry, in particular, grows wild all over Europe, from Greece to Spain and northward to Norway and Sweden. It was originally christened Rubus Idaeus, after Mount Ida in Greece. Like other cultivated plants, it tends to vary, and it is said that more than twenty varieties were under cultivation in England a century ago. The American colonists introduced this favorite European berry at an early date, but it did not find a congenial environment in the new country. The long, cold winters of the northern states, and the dry heat of the southern summers were alike hostile to it; and its lack of hardiness denied it general recognition except as an occasional garden plant. But the new continent possessed many wild raspberries that were of course adapted to the environment, and in time these came under cultivation. Their introduction, however, was so gradual that it was quite unnoticed. The only raspberry cultivated extensively for the New York market early in the nineteenth century was known as the English Red. It is believed to have been an offspring of a native berry, known as Rubus neglectus (itself believed to be an accidental hybrid of our wild red and black raspberries), but this was not generally known, and the name given the fruit suggests that it was supposed to be of European origin. During the latter half of the nineteenth century many improved red and yellow raspberries were introduced, and various of these have been utilized in the course of my hybridizing experiments. But perhaps the chief favorite among American raspberries is the one introduced in the early forties by Nicholas Longworth, of Ohio, and known as the Wild Black or Black-cap Raspberry, Rubus occidentalis. This berry was a great addition to the list of cultivated fruits. It soon became a favorite everywhere it could be successfully grown. Mr. Longworth himself introduced it into England, but it did not thrive in the English climate and it never competed with the native European species.

INTERBREEDING THE RASPBERRIES

The familiar cultivated raspberries of the present time owe their origin to the species just named, and to two other allied species, one our wild red raspberry, Rubus strigosus, a close relative of the common European species, the other known as Rubus leucodermis, a western relative of the familiar black-cap. All the red raspberries now under cultivation have sprung from either the European or American red species. The Purple-cane type apparently sprang from the Rubus neglectus (very probably a hybrid between R. strigosus and R.occidentalis); such varieties as the Reliance, Shaffer, Philadelphia, and Gladstone are, at least in part, probably of this origin, as was the historical English red. The Purple-cane was a native of the northeastern part of the United States, being especially common in New York. The original American red raspberry, Rubus strigosus, first became known to the horticultural world in 1860, through the introduction of Allen's Antwerp and Allen's Red Prolific. For several years preceding 1880 I had been raising seedlings of blackberries, raspberries, gooseberries, Juneberries, strawberries, currants, and various other berries on my experiment farm, and many variations were developed in that way which aroused my enthusiasm. These experiments were largely instrumental in teaching me the then not known or not generally accepted value of cross-pollenizing as the means of introducing the tendency to vary among existing species or varieties. And my experiments with the different raspberries had a prominent share in the demonstration of this very important and hitherto unappreciated principle. In the course of these experiments it was first found that the black-cap would cross with the red raspberry, although with difficulty. Seedlings from this cross sometimes bore perfect berries abundantly, but much oftener they bore imperfect berries having perhaps only two or three seeds. Again, after blooming, there would be no development of fruit, only a core or stem remaining. Among some of these crosses I met with a difficulty not encountered in crossing any other of the members of the great Rubus tribe. The plants at first seemed sickly, having little or no vitality. When transplanted from greenhouse to open field they made little growth the first season and the second season at about the time for fruit bearing they all seemed to fail utterly. Every seedling among a lot of these hybrids would sometimes thus be suddenly destroyed. In continuing the experiment, I found that there was strong individuality among the different plants, so that some of the red or yellow raspberries crossed readily with the black-caps, while others failed to do so; there being all gradations. In some cases the resulting seedlings would show the prepotency of one parent or the other. But, generally, in the first generation, there would be a blending of the characteristics of the two.

UNDERLYING PRINCIPLES

At that time no plant developer fully realized that all the best variations and recombinations in a hybrid stock appear in the second and a few succeeding generations. A recognition of this principle constituted my first very important step toward the development of new forms of plant life. I discovered, in connection with the raspberry hybrids, that in the second and a few succeeding generations different combinations were brought out in the most wonderful variety; and that from these certain individuals could be selected having almost any qualities of either parent combined in almost all possible proportions, and often greatly intensified. This was, as we now know, substantially the discovery that Mendel had made almost twenty years before. But no one heard of his discovery till long afterward (about 1900), and at about the time when I was independently learning the same lesson Mendel himself died, quite unknown to fame, without having been able to bring his discovery to the attention of the scientific world. Meantime, without formulating the principle in precise terms as Mendel had done, and without following up results with numerical exactness, I came to full recognition of the principle of blending of characters in the first filial generation and their reassortment and segregation in the second and succeeding generations. All my experimental work was carried forward with a clear recognition of that principle. As to the work with the raspberries, my first aim was to accumulate as much available material as possible. This has been my custom throughout. The chances of obtaining results from a large number of experiments are proportionately greater as the number increases, and I find, within limits of time, that it is just as simple to conduct a thousand or ten thousand experiments, or even a hundred thousand experiments, as to conduct a few. So I worked on a comprehensive scale with the raspberries from the outset; and it was not long before I developed several varieties of value; varieties, in fact, superior in size, quality, and productiveness, to any raspberries hitherto known.

FIRST FRUITS OF THE EXPERIMENTS

The first of my new raspberries offered to the public was named the Eureka. This raspberry, introduced in 1893, was described as "larger than any raspberry in cultivation; bright red, firm, very productive, and similar to Shaffer's Colossal in its piquant acid flavor. It is nearly twice as large as Shaffer's Colossal, its great-grandparent, and a better color and quality, firmer, handsomer, and in all respects an improvement on that well-known variety. The bushes are more compact in growth, almost free from prickles, and of a sturdy appearance." Particular attention should be called to the fact, just stated, that the new raspberry was almost thornless. This was true of a number of my raspberries, as by selective breeding I was able to give these vines smooth stems at a time when my similar attempts to remove the thorns from the blackberry had not been successful. The difference was due, perhaps, to the fact that the raspberry, having been long under cultivation, had partly lost its thorns through more or less unconscious selection on the part of many generations of fruit growers. The thorns had been reduced in many varieties to prickles, and occasionally individual specimens appeared that lacked even these. By selective breeding from such specimens I was able to produce varieties that had practically smooth vines. A selected seedling of the Eureka was remarkable for its habit of bearing in October as well as for the enormous size of the berries, which were frequently almost four inches in circumference. The berries were of a beautiful bright red, but were rather too soft except for home use. Another of my crossbred raspberries, originated at the same time with the Eureka, was called the Dictator. This also is a mammoth bright red berry. It combines the flavors of the Gregg and Shaffer's Colossal from which it originated. The combination is one of the happiest, as the acidity of one is modified by the sweetness and aroma of the other. The berries were more than three times as large as those of the Gregg, and almost twice as large as those of Shaffer's Colossal, which until the production of these new hybrids bore the largest raspberries known. Another cross of the Gregg, this time with the Souhegan, produced a seedling that had astonishing crops of fine, medium-sized, red berries, that ripened during October. The Souhegan was also crossed with the Shaffer, and this union produced in the second generation a new variety that was known as the Sugar. From the seeds of other members of this same generation two or three other promising berries were produced. One of these bore large, firm berries, conical shaped, and a dark rich purple color.

A NEW SPECIES-THE PRIMUS BERRY

All the raspberries commonly known to the cultivator, and many new ones that I imported from Asia and the Southern hemisphere, were growing on my grounds from 1890 to 1900, and were intercrossed very extensively. Numbers of highly interesting hybrids were thus produced, and at least one of these was of so distinctive a character as to merit the title of a new species. This was the fruit that was introduced as the Primus berry. This highly interesting fruit, one of the first plants of any kind that could properly be termed a new species to be developed under the direct guidance of the hand of the experimenter, was the progeny of a hardy little berry indigenous to Siberia and Russia, called the Siberian raspberry (Ruibuts crataegifolius), and the California dewberry. The little hardy Northern raspberry bore fruit about the size of a pea, of a dark mulberry color, with rather large seeds, and a flavor not such as particularly to commend it. It is, however, remarkable for its large palmate leaves, and the sturdy growth of its stems. The California dewberry, Rubus bitifolius, is a trailing vine which is extremely variable in foliage, habit of growth, size, and quality of fruit. It is found wild everywhere in the foothills and lower elevations throughout the Pacific slope of the United States, but seems to be at its best in Northern California and Oregon. The berries of this wild species are often produced abundantly. They are black, usually of good size, and of superior quality. They are often gathered in large quantities for market and home use. The fact that the dewberry bears so-called dioecious flowers-that is, flowers of opposite sexes-on separate plants-has discouraged a very general cultivation of the plant. It is necessary to grow both male and female plants to ensure fertilization, and fruit growers do not relish the idea of having half their vines unfruitful. Nevertheless there was one variety of the California dewberry, called the Aughinbaugh, which had been under cultivation for several years. This was the one selected for most of my experiments in hybridizing the dewberry; and this plant had a share in the production not only of the Primus berry, but of the even more remarkable Phenomenal berry to which reference will be made in a moment. The cross between the Siberian berry and the California dewberry, from which the Primus sprang, was made without particular difficulty. I had learned by this time that blackberries and raspberries and dewberries could be hybridized almost indiscriminately; and the fact that one of the parents in the present combination had grown originally in Siberia and the other in California offered no barrier to the union. With the first lot of seedlings, five hundred or more, from this union of the California dewberry and the Siberian raspberry, some strange specimens were revealed. Nearly all were worthless plants, some of which seemed hardly to have vitality enough to live, much less to produce fruit. Others bore small, unattractive berries, insignificant in every respect. Three or four individuals, however, grew with unusual vigor. They differed so widely from the others that I was at first inclined to suspect that they were dewberries unhybridized. As to this, however, I was in error. One of these exceptional vines was particularly notable. It neither trailed nor stood upright, but took an intermediate position. The leaves were not palmate like those of the raspberry, nor were they like the foliage of the dewberry. They were a compromise between the two. The fruit, which was larger than that of either parent, resembled the blackberry most in form, but was of a dark mulberry color. When the fruit was just ripe it parted from the stem like the blackberry; but when fully mature the core came out as it does in the raspberry. Thus the combination of all these important characteristics was almost absolutely complete. The hybrid was a perfect blend. It was this plant that was christened the Primus berry. Seedlings by the thousand were raised from this selected hybrid and all of them came as true as the seeds of any wild species of the family. The offspring closely resembled the Primus, but none of them quite equaled it in fruiting qualities. If found growing wild, the original Primus plant and its progeny would be pronounced by any botanist a distinct species. The explanation of the summary production of a hybrid differing in this remarkable manner from either parent and being so fixed in type as to breed true to the new form thus suddenly developed would seem to be that the two parent species were separated almost to the limits of affinity. The fact that most of the hybrids of the same generation with the Primus were feeble and degenerate creatures is corroborative. It appeared, however, that there were elements in the two types of germ plasm that if combined in just the right way would produce a virile offspring. By chance the right combination was effected, and the Primus berry was the result. The berry itself has not proved a great commercial success, but that is a matter of small importance. The real importance of the experiment was in what it proved as to the possibility of the production of new species through hybridization. This was, in short, one of the first instances to come under my observation of the production of a hybrid that blends the characteristics of the parents, producing a new type and breeding true to that type. To my mind-and I think the facts are convincing to any unprejudiced mind-this and many similar experiments that have been successfully accomplished demonstrates beyond dispute that hybridization is one of nature's methods of creating new species. I have dwelt at length on this subject in earlier chapters. I revert to it here because of the importance of the subject itself, and also because the Primus berry furnishes us a new and striking illustration of the truth of the principle. Of course the Primus berry was produced by artificial pollenizing of the plants that were so located geographically that they would have had no chance to hybridize unless brought together by man. But my observations show that natural hybrids are not at all unusual among wild members of this family. I have met with them often where two or three closely related species were growing side by side. Near Lake Sycamour, for example, at Alberta, Canada, I have observed two common raspberries, Rubus leucodermus, a red raspberry, and Rubus strigosus, a black-cap, growing in close proximity around the hillsides and along the streams. In every case where I found these two species growing together there were numerous natural hybrids in evidence. None of these hybrids were as productive as the parents, but the vines were usually stronger growers than either, and appeared to be hard pressing both parent species, with the prospect that they would in time supplant them in this region. I gathered large quantities of seeds from the best of these hybrids and brought them home for planting. Many seedlings were thus raised which obviously carried the combined characters of both their wild parents. These representatives of a new species developed by hybridization under natural conditions have obvious scientific interest even though they failed to develop sufficient productivity to be of commercial value. Let me repeat that natural hybrids are much more numerous than is generally supposed. I have found them among other wild plants. Especially are they to be observed among strawberries, blueberries, huckleberries and California lilacs (Ceanothus). I have elsewhere cited instances of the hybridization of the tar-weeds and the mints. There can be no doubt that some of our well-known species of today were produced by Nature in this way within recent times. I have elsewhere observed, and I emphatically repeat, that any theory of the origin of species that does not recognize this among the methods employed by Nature for the production of new species is altogether inadequate.

ANOTHER NEW SPECIES-THE PHENOMENAL BERRY

The result of thus mating the dewberry with the little raspberry from an almost Arctic climate having proved so remarkable, almost numberless tests were made in which the dewberry was crossed with a great variety of other raspberries and blackberries. And among the hybrids thus produced there was at least one that might be considered more remarkable even than the Primus berry. This was the fruit which afterward became famous as the Phenomenal berry. This extraordinary berry was the outcome of a series of experiments in which the red and yellow raspberries were variously combined with the dewberry. In the first generation of these hybrids, numerous red berries and black berries were produced, but no yellow ones. A large proportion of the red varieties followed the raspberry in general characteristics except in form, but some of them acquired the high flavor of the dewberry combined with the aroma of the raspberry. Most of the seedlings of this first generation resemble the wild dewberry in habit of trailing along the ground. Yet there were some that favored the raspberry, standing upright. In flavor many were a good combination of the two parents, but the variation was pronounced in this respect. Some were highly flavored while others were quite insipid, and between the two were all gradations. Variations in size and shape were equally marked. Most of these seedlings were quite productive, but no one plant was sufficiently valuable to warrant its introduction as a new variety worthy of cultivation. Berries were gathered, however, from the most promising of the dewberry-raspberry hybrids. Among the second-generation seedlings thus produced was one that was of different caliber from all the rest as shown by the character of its fruit. No such berries were perhaps ever seen before as those that grew on this second-generation offspring of the Cuthbert raspberry and the California dewberry. Some of the berries were an inch and a half long and an inch in diameter. They were a dark rich crimson color, slightly downy, and glossy. In flavor they combined the qualities of raspberry and blackberry, both flavors seeming to be intensified. In a word the fruit was a blend between the fruits of the parent races. It was a new variety so markedly distinct from either parent as to justify the designation of a new species. The new berry was originally called the Humboldt, but was subsequently rechristened the Phenomenal by the purchaser. The new fruit was not altogether unlike the Loganberry, which was an accidental hybrid discovered by Judge J. H. Logan on his place near Santa Cruz, which was believed to be a hybrid between the red raspberry and the California dewberry. But the Phenomenal is far superior in size, quality, color, and productivity, and it is gradually displacing the Loganberry. Unfortunately the two are sometimes confounded, and unscrupulous dealers have been known to sell the Loganberry under the name Phenomenal. The new fruit, like most other plant developments-the Burbank plum, the Wickson plum, and the Pineapple quince, for example-was not fully appreciated for about ten years. But it is now a standard berry on the Pacific Coast, and as far as possible it is being introduced in other regions wherever it will thrive. As already noted, it is probably the largest of all known berries. As a fruit for drying and canning it is of the first importance. From the standpoint of the plant developer the Phenomenal is of additional interest because of its almost exact combination or blend of the qualities of its parents. I have raised numerous seedlings from the Phenomenal, but up to the present have found none that quite equals it in all its excellent qualities, though, like the Primus, it is a fixed new species, the seedlings not reverting to either parent form. The new berry has also been used as seed parent in a number of crosses with other blackberries and raspberries. Some thousands of seedlings thus produced are now under observation. Among these hybrids great variations will of course, occur, and while nearly all will undoubtedly be of inferior quality, I have confidently expected to find at least one that surpasses even the Phenomenal; and now this expectation has been fully realized in a new sweet variety which will later be introduced.

OTHER PERFECTLY BALANCED HYBRIDS

Hybridizing experiments of almost equal interest, even if not quite so striking in results, have been made between the various raspberries and the Lawton blackberry. The Lawton is a very prepotent parent in these crosses, and its characteristics will almost invariably be found to predominate. Even the pollen of the Lawton when applied to the raspberry more often produces the Lawton type of berry than any other type. But in exceptional instances I have produced Lawton hybrids in which the prepotency was not so strongly manifested. Such was the case, for example, with a cross between a yellow raspberry known as the Golden Queen and the Lawton. This produced a hybrid so well-balanced that no one who saw it could tell whether it was a raspberry or a blackberry. Numerous seedlings of this hybrid strain were raised, and in the second generation the qualities of the hybrid were reproduced, as in the case of the Primus berry and the Phenomenal. No variation occurred such as is usual in the second generation of most hybrid blackberries and raspberries. The bushes had prickles that were short and stout instead of long and slender as in the raspberry. The leaves also had the rough, ribbed appearance of the blackberry. The berries would cling to the receptacle (a blackberry trait), or part from it (a raspberry trait), according to ripeness. As to color, there were both red and yellow varieties among the hybrid plants. The flavor of the berries was not exceptional, but in some other similar crosses made at a later period the fruit was in some cases greatly superior in quality to that of either of the parents. Still greater interest attaches, perhaps, to a hybridizing experiment in which the parents were Shaffer's Colossal raspberry and the Crystal White blackberry. Some of the plants from this cross were of the most tree-like proportions. Most of them, however, were barren, though they bloomed freely. But there were exceptional ones that fruited, and selected seedlings were grown from these through a series of generations. In the fourth generation a plant appeared which was of such extraordinary characteristics that it was given the name of Paradox. This plant was in all respects a most perfect combination of the two ancestral forms from which it sprang. The wood, bark, leaves, blossoms, prickles, roots, and seeds could not by any test be proved to be like one or the other. The fruit, produced in abundance, was an oval, light red berry of good size, larger than that of either progenitor, and of fair quality. Many of the first generation descendants of the Paradox were partially barren, though blooming freely. Sterility as to fruit was often associated with gigantic growth. But some of the seedlings were fertile, and they manifested almost every possible combination of qualities of the raspberry and blackberry. Some were similar to the Paradox, except that they had white berries instead of red. By saving seeds from the white and the red varieties separately, I found that they bred true, each constituting practically a fixed species. As to the vines themselves, there is very little variation, the canes and foliage presenting an exact balance between the raspberry and the blackberry. The berries are not of great commercial value, as the fruit though large is soft. I hope, however, to harden the berry by selective breeding, and introduce a better flavor. Although this hybrid progeny of raspberry and white blackberry may ultimately have commercial importance, it is chiefly prized for the scientific significance of its revelations. Descended as it is from a cross between the raspberry and the blackberry, it constitutes a fixed species differing radically from every other Rubus known. So in this regard the Paradox takes its place besides the Primus and the Phenomenal berries as offering an impressive object lesson in the production of new species by hybridization. Let it be recalled, however, that the Primus was a first generation hybrid, whereas the Phenomenal appeared in the second generation, and the Paradox in the fourth. There has been occasion in an earlier chapter to tell of hybridizing experiments in some respects even more curious, in which the raspberry was fertilized with pollen of the strawberry. These experiments will be further examined in a later chapter, with reference to the interpretation of the observed phenomena of hybridization of the various brambles. But perhaps no comment could greatly add to the impressiveness of the simple recital of facts as to the production of new forms that, according to all botanical standards, should rank as distinct fixed species, through the purposeful blending, under the hand of the plant developer, of the germinal strains of the various blackberries and raspberries.

-The chances of obtaining results in plant improvement are directly proportionate to the number of experiments tried; and a hundred thousand experiments may be conducted as simply as a few.

This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 6 Chapter 2