Luther Burbank: His Methods and Discoveries (1914)
THE SUNBERRY—A PRODUCTION FROM THE WILD
A NEW FOOD PLANT FROM A POISONOUS FAMILY
SUPPOSE that you had been trying for twenty-five years to effect a certain purpose—say the cross-pollenizing of a particular pair of species of plant.
Suppose that year by year your efforts had met with total failure; but that finally, just as you were on the point of giving the matter up as hopeless, you were to attain success.
Doubtless under these circumstances you would be somewhat elated over your achievement.
Suppose, then, further, that the plant that grew from this hybridization, achieved with such infinite difficulty, proved a producer of valuable fruit. Suppose that the fruit met with almost immediate recognition, and that the plant was widely introduced and attained exceptional popularity.
And then, finally, suppose that some one should come along and decry the fruit, not because of its lack of merit, but because the parent plants from which the hybrids grew belonged to a family of poisonous plants.
Suppose the hue and cry thus raised should be given an element of plausibility by the fact that some unscrupulous person had sold to gardeners a plant of a different species from either of the parents of your hybrid, yet of an allied race, and had claimed that this plant, which bears a fruit of doubtful edibility, is identical with the one you had introduced.
Suppose all this, I say, and then try to imagine just what would be your attitude of mind toward the work you had accomplished on one hand, and the persons who—not always for the best motives or without prejudice—were its traducers.
THE SUNBERRY AND ITS CRITICS
In suggesting this I am only asking you to put yourself in my place and imagine what must be my natural attitude of mind toward one of the most celebrated, and without doubt the most berated, of all my plant productions—the fruit which I named the Sunberry, and which the dealer to whom I sold it rechristened—without my consent and much against my wishes—the "Wonderberry."
For the supposititious case that I have just outlined really summarizes the facts as to the production and introduction and traduction of that fruit.
The Sunberry, far from being merely a familiar form of Solanum introduced under a new name as some ignorant and misguided critics have alleged, is in reality the product of one of the longest and most persistent series of experimental hybridizations, culminating in the blending of two specific plant strains that had seemed to be antagonistic beyond the possibility of amalgamation.
The parent plants themselves, though they no doubt belonged to a poison-bearing family, were not in themselves poisonous. And the fruit of their hybrid progeny is not only palatable in high degree, but altogether wholesome, as hundreds who have eaten it habitually could testify.
Let me quote a paragraph from a letter recently received, by way of substantiation, and then let me turn from this controversial aspect of the subject to consider the story of the Sunberry itself:
"I have grown the Sunberry for the past three years," says a college professor who is an amateur gardener. "We have used the berries for sauce, cobbler, and pies—principally for pies. Some were eaten raw from the vines. For me the pie is the one great way to use the berry. Without exception I place a Sunberry pie at the head of the pie list, and I do this with a full appreciation of the excellence of cherry pie, apple pie, pumpkin pie, mince pie, berry pie, etc.
"I think it hardly does the Sunberry pie justice to compare it to blueberry pie. They have much in common, but the Sunberry is richer.
"I have never kept account of the yield, nor tried for a large yield. I have a small strip of ground, eight by sixty-five feet, which gave us pie each day from early in August until frost usually about November 1st, and left us a surplus of forty to fifty quarts to can for winter use."
So much for the fruit itself. Then touching on the other aspect of the subject, the writer continues:
"There has been much criticism here, some of it the most senseless stuff I ever heard outside of an asylum, and most of the extreme criticism by those who never grew the plant. One man, an attorney, planted some Sunberries and pulled them up because they looked like nightshade. I completely converted him by sending him a pie."
In conclusion, the writer goes to the heart of the matter when he says: "I think much of this criticism was originally due to some very unfair articles that got copied and were thus spread somewhat generally. As far as I can judge, the original article was written out of pure malice. I can account for it in no other way."
These quotations will perhaps serve sufficiently to suggest the quality of the Sunberry, and to suggest also the animus of the criticism that has been directed against it. It seemed necessary to advert to this aspect of the matter because a fair proportion of the people who have heard of the "Wonderberry" at all have heard only words of condemnation.
This is in some respects one of the most remarkable, and unquestionably the most maligned, of fruits. It resulted from a hybridization of two Solanums effected after years of unsuccessful efforts. It was named Sunberry by Mr. Burbank, but was subsequently re-christened the Wonderberry, quite against his will, by the dealer who purchased and introduced it. It has been fiercely assailed, largely because it was confounded with quite a different species of Solanum; notwithstanding which it has made its way in the fruit-garden, and is destined to be much more popular in the future than it has been hitherto.
Moreover a large proportion of the people think they have seen or grown this fruit have in reality never seen it.
Whoever supposes that the true "Wonderberry," or Sunberry as I still prefer to call it is identical with the ordinary nightshade is laboring under an illusion that might readily be dispelled by inspection of the respective plants themselves.
And whoever doubts that the true Sunberry is an appetizing fruit and a valuable addition to list of table berries might readily be convinced, had he some neighbor to make the demonstration suggested by our correspondent, through sending him a Sunberry pie.
But let us forget all controversial aspects the subject and make inquiry as to the origin the new fruit.
THE NIGHTSHADE FAMILY
I have elsewhere referred to my interest in the members of the nightshade family, or, as the botanist calls them, the Solanaceae.
The fact that the potato, with which my first experiments in plant development were made, belongs to this family would naturally give me an interest in the tribe. But I was particularly attracted also because of the diversity of characteristics among the members of the family.
Here, on one hand, are the potato, the tomato, and the eggplant, ranking among our highly important garden vegetables, and the strawberry-tomato or ground cherry among the minor vegetables that have a good share of popularity; and, on the other hand, closely related species are bearers of the most powerful narcotic poisons, including belladonna and hyoscyamus, drugs that have an accepted place in the pharmacopoeia.
Add that the tobacco plant is another member of the family, and it is clear that this is one of the most curiously versatile, and, from a human standpoint, one of the most important plant tribes.
My interest in the family extended beyond the familiar plants just named, and included several species of nightshade that are chiefly known as roadside weeds and bearers of berries some of which are eaten on occasion by country folk, but which in the main have a bad reputation, some of them being accounted highly poisonous.
The name "deadly nightshade," applied to one of the most familiar species, suggests the repute in which these weeds are commonly held.
Yet it is known to the residents of some country districts, particularly in the Mississippi Valley, that the little black berries of the nightshade, thoroughly ripe, may be made into pies and eaten with at least relative impunity. It is only in lieu of any fruit of more acceptable character that any one would be likely to make the experiment, however, as the distant relationship of the plant to the deadly nightshade, Atropa belladonna, and the henbane, Hyoscyamus niger, from which well-known poisonous drugs are obtained, is at least vaguely recognized, and the plants are very generally held under suspicion.
Nevertheless the potato, the tomato, and the eggplant may be cited as affording a convincing demonstration that there is merit in the family. even though one were to dispute that the tobacco could legitimately be put in evidence in the same connection. And, for me at any rate, there was interest in the knowledge that at least two species of Solanum were available for experimental purposes that were hardly under suspicion as to the production of poisonous fruit, however lacking in attractive qualities their products might be.
PROGENITORS OF THE SUNBERRY
One of the nightshades in question is a rather large plant known botanically as Solanum guinense which found its original home in Africa, but which has been known for a generation in this country, and is sometimes referred to as "garden huckleberry."
Sister of the Sunberry
These little seedlings are the result of a cross made between the Solanum Guinense and the Solanum nigrum. One of the parents, therefore, is a parent of the sunberry, the other being a related species. It is as yet too early to say just what possibilities of development this new hybrid holds.
The other is a smaller species, known as Solanum villosum, which was indigenous to Europe, but which is said to have been accidentally introduced in this country a good many years ago from seed mixed in the ballast of a ship. This chanced to be thrown out where it had opportunity to establish itself, near Philadelphia; from which region, after the manner of wandering weeds, it found its way across the country.
The African plant is a strong and heavily fruiting shrub, growing about two feet high on good soil, and spreading to be about three feet diameter.
It produces large black berries in clusters than stand upright, and that, in the case of some varieties, are nearly as large as cherries. The fruit is not unattractive in appearance, and, as already noted, attempts have been made to introduced it as the "garden huckleberry." But such attempts have met with small measure of success for the very excellent reason that the berry is practically inedible.
I have tested it often, and have always found that one berry is more than any person is willing to eat.
I have never known a person who could be induced the second time to attempt to eat this so-called "garden huckleberry," the taste being villainous.
The plant is indeed somewhat closely related to the black nightshade, Solanum nigrum, the American species that is common everywhere, one form of which, known as the stubble-berry, is said to be poisonous, especially if eaten by children, in large quantities when not fully ripe, although fairly palatable when cooked.
The stubble-berry in one or another of its varieties has been used for cooking, in all countries where it grows, when fruit is scarce, chiefly to make pies, as well as for canning. But it is necessary to have the fruit fully ripen; which is often accomplished in cold climates by spreading the berries thinly on shelves and allowing them to mature slowly.
In some regions, as in the Dakotas, the bushes are pulled and hung in the cellar, the fruit being used from time to time as it ripens.
In France the young shoots of this plant are used as a green vegetable, and the plant is even advertised in French catalogs.
The "garden huckleberry," however, differs considerably from the ordinary French stubble-berry, the fruit being much larger in size but far inferior in flavor. It is, however, more nearly free from poisonous qualities, notwithstanding its vile taste.
The differences between the plants themselves are marked, the Solanum guinense being, as already noted, a rather heavy shrub, while Solanum nigrum, though varying considerably, is usually a low spreading and slender plant. It may be said, however, that both of these species, like most other members of the family, show a strong propensity to vary. The black nightshade in particular takes a great variety of forms according to soil and other conditions; each locality having its own variety differing in minor respects from plants of other regions.
I have gone somewhat into detail in this matter, because I wished to establish clearly the standing of the Solanum guinense that was used in my hybridizing experiments, and which thus became one of the parents of the Sunberry; and in particular I wished to make clear that this is a species differing considerably from the better known black nightshade, Solanum nigrum, with which it has been confounded.
The other parent of the Sunberry, already named as Solanum villosum, is a plant differing conspicuously from either of those just described. It is low, and tends to a spreading growth a few inches above the ground, never growing upright. The foliage of the plant is pubescent or downy, accounting for its scientific name. In this regard also it is quite different from Solanum nigrum and Solanum guinense.
This picture shows the method of cultivating the sunberry. It thrives in almost any soil, and, curiously enough it seems to do the better where it Is somewhat neglected than where too highly cultivated; perhaps a reminiscence of the characteristics of the sunberry's half-wild parents.
The fruit grows in clusters of five berries that droop characteristically and always remain greenish in color even when ripe, whereas the fruit of most other Solanums turns black on maturing.
The berries are borne abundantly, and like the tissues of the plant itself they are free from poisonous qualities. The wholesome nature of the plant is attested by the fact that it is eaten freely by herbivorous animals wherever it grows. Rabbits, cattle, and pigs eat it with avidity.
PRODUCING THE SUNBERRY
I have already referred to the long series of fertilizing experiments through which I endeavored to cross the various Solanums.
I may add that Professor Hansen, of North Dakota, has also been interested in crossing the two fruiting Solanums of which we are speaking, and from which the Sunberry was ultimately produced. But his efforts at hybridizing these species were unsuccessful.
These details are mentioned to emphasize the fact that the production of the Sunberry—although, as will appear in a moment, it came about ultimately as the result of a single successful experiment—was by no means a task to be accomplished offhand by the first person who chose to place pollen of one flower on the pistil of the other. I did this season after season, seemingly with no effect whatever.
At last, however, in the season of 1905, after I had more than once half decided to relinquish the effort to hybridize these plants, my perseverance was rewarded.
I had cross-pollenized the great African stubble-berry, Solanum guinense, and the little downy nightshade, Solanum villosum, as I had done many times before, with no change or added detail of method, and for the moment I had no reason to suppose that the efforts had been more successful than before.
But when the seeds were sprouted in the greenhouse, a certain number of plants were discovered that differed from any I had seen before.
These plants were of a new type, and as they developed it became increasingly clear that they represented almost an exact compromise between two parent species.
There could be no question that they were the hybrids I was seeking.
But the appearance of these hybrids was such as to corroborate the belief, founded on my long series of unsuccessful hybridizing experiments, that the two Solanums I had finally mated were so widely different in constitution as to stand the very limits of affinity within which crossbreeding is possible.
We have discussed a number of instances which similar crosses have been made between species widely separated. Such, for example, was the cross between the California dewberry and the Siberian raspberry, which produced the Primus berry; also that between the dewberry and the Cuthbert raspberry, which produced the Phenomenal berry; and that between the plum and the apricot, which produced the Plumcot.
In each of these cases, it will be recalled, the hybrid showing intermediate characteristics between its parents, constituting virtually a new species, and proving its individuality by breeding true to type from the seed.
It was rather to be expected, then, that the hybrid Solanum would similarly prove its individuality, and the expectation was fully realized.
As the plants came to maturity, one bloomed but failed to produce fruit. The others, however, fruited quite abundantly, some of them profusely.
The fruit was intermediate in size between the fruits of the parent plants. Its quality was entirely different from that of either parent. It had something of the flavor of the blueberry or huckleberry of the East, and was especially delicious when cooked.
It differed as widely as possible from the vile-tasting fruit of one parent and from the insipid, tasteless fruit of the other.
It should be explained that there were only about twenty of these hybrid plants in a large colony of seedlings. The remaining members of the company were precisely similar to the mother plant on which they grew—this being the small, downy species, Solanum villosum—thus showing that they were not hybrids. It is probable that there was only a single fruit that had been hybridized, although the foreign pollen had been applied to many pistils.
The entire company of new hybrid Solanums were probably produced from the seeds of a single berry, the other berries having been quite unaffected by the attempt at cross-pollenizing.
But it sufficed to have produced a score or so of hybrids; I should have been delighted with a single one, after all these years of waiting.
Naturally I selected the best two or three individuals among the twenty hybrids—the ones excelling as to profusion, size, and flavor of berries.
The seeds of these plants were carefully saved, and next season there grew from them a crop of plants precisely like the parents. The progeny the hybrids followed their parents more closely than the unhybridized offspring of either of the Solanums used in the original cross usually do.
As already noted, all species of wild Solanums tend to vary, but the new species reproduced itself exactly, except that a very slight difference in the flavor of the berries was barely perceptible.
As two crops of these plants could be raised in a season, they were multiplied rapidly, and there was astonishingly little variation in the size, quality, or growth of the bushes. Without exception plants resembled the original hybrid, and differed radically from either parent of that hybrid.
It was obvious, therefore, that a new and fixed species of Solanum had been evolved through the hybridizing experiment. As the reader already knows, the new plant was christened the Sunberry.
The unwarranted change of the name from Sunberry, the only name I ever authorized or approved for the plant, to "Wonderberry", and mis-statements that have gained currency regarding the origin of the plant and the characteristics of its fruit have been sufficiently referred to.
The true qualities of the fruit itself have also been revealed through a quotation from one of the many amateur gardeners who have grown it I successive seasons and found it a valuable addition to the list of garden fruits.
It may be added, however, that the Sunberry makes particular appeal because it ripens late in the season, after most other berries have ceased to bear. It is well to note, also, that the plant shows the hardiness and thrift and vitality usual with hybrids, and will often grow to better advantage on a poor soil and without much cultivation than when especial attention is given it. In most regions, to water it is a mistake, and to fertilize the soil for it an even greater one—making the blossoms drop.
In a word, it is a plant that resents too much petting. It retains something of the character of its wild ancestors.
As to inherent constitution, the Sunberry is a perennial, but it may best be grown annually from seed, quite as its relative the tomato is grown, although that plant also can live from year to year in the proper climate.
As already stated, it grows true from seed year after year, proving thus its specific individuality. and differing not alone from hybrids in general but from the greater number of our cultivated fruits.
Branch of Sunberries
The Sunberry has unexpectedly been found adapted to cold northern climates. In the Alberta country, in the latitude of northern Alaska, the Sunberry is highly appreciated, especially as it is about the only berry that can be raised where the thermometer often goes to 40 or even to 60 degrees below zero.
VARYING TRAITS OF HYBRIDS
From the standpoint of the gardener, the Sunberry has importance as a notable addition to the list of small fruits.
From the standpoint of the plant developer it may be said to have perhaps greater importance as illustrating the possibilities of the development of new species by hybridization—species markedly different from, and in many ways superior to, those from which they spring.
It is true that other experiments have been detailed that illustrate the production of new forms of plant life through hybridizing already existing ones. A few paragraphs back several of these were named—the Primus berry, the Phenomenal berry, and the Plumcot. But in the case of these fruits, it will be recalled, the parent forms were one or both bearers of valuable fruits. The hybrid plants improved upon their parents, but did not show entire departure from the traditions of the races from which they sprang.
But the Sunberry, as we have seen, sprang from parent forms neither of which produced edible fruit.
This was a union of two racial forms that were separated almost to the point of permanent segregation. The combination of hereditary factors of two distinct species from two hemispheres developed a hybrid that differed very widely from either parent. As it chanced, this hybrid had qualities of fruit that gave it a new appeal and a standing, from the viewpoint of man, quite different from that accorded either of its parents.
The case, then, of the Sunberry emphasizes anew the principle that new species may be produced through hybridization, and that, provided the parents are genetically separated just widely enough, their offspring may show such a blending of characters as to constitute a new form, and to be able to transmit these characters to its progeny in such a way as to meet the test by which species are everywhere recognized.
We have seen that there is possibility of hybridization between forms that are a shade more widely separated, in which case the hybrid offspring have the appearance of new species, but lack fertility. Such instances were presented in the hybrid colony of offspring of the dewberry fertilized by pollen from the apple and pear and mountain-ash and rose; also by the hybrid between strawberry and raspberry.
These strange hybrids would clearly enough have been entitled to recognition as new species had they been able to reproduce themselves. But their sterility reduced them to the rank of mules—to make comparison with the most familiar instance of an infertile hybrid in the animal world.
From these sterile hybrids the Sunberry differs fundamentally in that it is if anything more prolific than either of its parents.
Meantime the Sunberry differs from the hybrids of another and more familiar type that arise from the union of parents that are so closely related that cross-pollenizing is easily effected between them. Such hybrids, of which we have seen many examples—crosses between the different daisies, between black and white blackberries, thorny and thornless briers, stone-seed and stoneless plums, and sundry others—follow, as we know, a characteristic line of development. The hybrids of the first generation resemble one parent more than the other. The hybrids of the second generation show wide variation, some of them reverting to one ancestral strain and some to the other, the characteristics of each strain being variously segregated and recombined.
Nothing like the direct and complete reproduction of the characteristics of the hybrid in its offspring, as shown by the Sunberry, is manifested in the ease of these familiar hybrid forms that spring from the union of closely related species or varieties.
WHAT THE SUNBERRY TEACHES
All this should be borne in mind by anyone who is prone to reduce the principles of heredity to formulae of undue simplicity.
The new formulae of the Mendelians, for example, which have such admirable application to many cases of the crossing of related forms—where particular unit characters are segregated and recombined—have no application, or to be applied must be distorted from their original implications, in dealing with such a case as that of the Sunberry.
Here there is no clear balancing of dominant and recessive factors, with the overwhelming presentation of the dominant factor in the first generation and the reappearance of the recessive factor, beautifully segregated, in the second.
Instances of inheritance of that order we have had presented again and again. We shall hear of more of them before we are through.
But, in the meantime, let us not forget the lesson taught by the Sunberry—let us recognize that there are conditions of hybridization under which characters appear to be permanently blended when first brought together; not momentarily linked in an unequal union to be segregated in the next generation, but fixed in a new and lasting combination that strikes a balance between the combinations presented by the parent forms.
It is possible, to be sure, to interpret this aspect of heredity in Mendelian terms. Nor should we deny altogether the validity of such application, for we may well believe that there are gradations all along the line, could we search them out, between the case of the sterile hybrid, born of widely diverged parents, and the case of offspring of members of the same species that differ only as to some varietal character.
Of course the same laws, could we fathom them in their broader aspect, apply to each and every case.
But, on the other hand, it is at least open to question whether it would not be better to reserve the application of the Mendelian terms to such types of inheritance as Mendel himself studied, in which there was interplay of dominant and recessive factors, and the varied segregation of the different factors in new combination in the second filial generation.
Thus restricted, the Mendelian formula has individuality and specific meaning.
There is danger that it may lose such individuality and such specific meaning, and with these a large measure of its real value and importance, if the propensity of some present day enthusiasts to make the words Mendelism and Heredity synonymous is generally followed.
Be all that as it may, at least we hazard nothing in saying that the case of the hybrid Sunberry, sprung at a bound into existence as a full-fledged species, is of compelling interest to the student of heredity, from whatever aspect he may view the subject.
—Whatever else may be said of the Sunberry, for or against, the fact remains that it was a successful union of two racial forms that were separated almost to the point of permanent segregation.
More on the Sunberry