Luther Burbank: His Methods and Discoveries (1914)
The White Blackberry
HOW A COLOR TRANSFORMATION WAS BROUGHT ABOUT
Luther Burbank (1914)
TO SPEAK of white blackbirds or of white blackberries is to employ an obvious contradiction of terms. Yet we all know that now and again a blackbird does appear that is pure white. And visitors to my experiment gardens during the past twenty years can testify that the white blackberry is something more than an occasional product-that it is, in short, a fully established and highly productive variety of fruit.
I doubt, however, whether there is record of anyone having ever seen a truly white blackberry until this anomalous fruit was produced.
Nevertheless it should be explained at the outset that the berry with the aid of which I developed the new fruit was called a white blackberry. It was a berry found growing wild in New Jersey, and introduced as a garden novelty, with no pretense to value as a table fruit, by Mr. T. J. Lovett.
He called the berry "Crystal White," but this was very obviously a misnomer as the fruit itself was never white, but of a dull brownish yellow. It had as little pretension to beauty as to size or excellence of flavor, and was introduced simply as a curiosity.
When a white blackbird appears in a flock, it is usually a pure albino of milky whiteness. It may be regarded as a pathological specimen, in which, for some unknown reason, the pigment that normally colors the feathers of birds is altogether lacking.
It is not unlikely that the original so-called white blackberry was also an albino of this pathological type. But if so, hybridization had produced a mongrel race before the plant was discovered by man, or at least before any record was made of its discovery; for, as just noted, the berry introduced by Mr. Lovett could be termed white only by courtesy.
Nevertheless the berry differed very markedly from the normal blackberry, which, as everyone knows, is of a glossy blackness when ripe. So my interest in the anomalous fruit was at once aroused, and I sent for some specimens for experimental purposes soon after its introduction, believing that it might offer possibilities of improvement.
Making use of the principles I have found successful with other plants, my first thought was to hybridize the brownish white berry with some allied species in order to bring out the tendency to variation and thus afford material for selective breeding.
CREATING A REALLY WHITE BLACKBERRY
The first cross effected was with the Lawton blackberry, using pollen from the Lawton berry. The Lawton is known to be very prepotent; it is of a very fixed race and will reproduce itself, from seed almost exactly, which is not true of most cultivated fruits. Its seedlings often seem uninfluenced when grown from seed pollenated by other varieties.
It was to be expected, therefore, that the cross between the Lawton and the "white" berry would result in producing all black stock closely resembling the Lawton; and such was indeed the result.
But the Lawton also imparts its good qualities to hybrids when its pollen is used to fertilize the flowers of other varieties. As a general rule it is my experience that it makes no difference which way a cross is effected between two species of plants. The pollen conveys the hereditary tendencies actively, and so-called reciprocal crosses usually produce seedlings of the same character.
That is to say, it usually seems to make no practical difference whether you take pollen from flower A to fertilize flower B, or pollen from flower B to fertilize flower A.
This observation, which was first made by the early hybridizers of plants more than a century ago,—notably by Kölreuter and by Von Gartner,— fully confirmed by my observations on many hundreds of species. Nevertheless it occasionally happens that the plant experimenter gains some advantage by using one cross rather than the other. In the present case it seemed that by using the Lawton as the pollenizing flower, and growing berries on the brownish white species, a race was produced with a more pronounced tendency to vary.
Still the plants that grew from seed thus produced bore only black berries in the first generation, just as when the cross was made the other way. It thus appeared that the prepotency of the Lawton manifested itself with full force and certainty whether it was used as the staminate or as the pistillate flower.
When the flowers of this first filial generation were interbred, however, the seed thus produced proved its mixed heritage by growing into some very strange forms of vine. One of these was a blackberry that bloomed and fruited all the year. This individual bush, instead of dying down like others, kept growing at the top like a vine or tree, and when it was two or three years old it was so tall that a step-ladder was required to reach the fruit. Its berries, however, were rather small, soft, and jet black in color.
This plant, then, was an interesting anomaly, but it gave no aid in the quest of a white blackberry.
But there were other vines of this second filial generation—grandchildren of the Lawton and the original "Crystal White"—that showed a tendency to vary in the color of their fruit, this being in some cases yellowish white. Of course these bushes were selected for further experiment. Some were cross-fertilized and the seed preserved.
The vines that grew from this seed in the next season gave early indications of possessing varied qualities. It is often to be observed that a vine which will ultimately produce berries of a light color lacks pigment in its stem, and is greenish or amber in color, whereas the stem of a vine that is to produce black berries is dark brown or purple. A few of the blackberry vines of the third generation showed this light color; and in due course, when they came to the fruiting age, they put forth heavy crops of clear white berries of such transparency that the seeds, though unusually small, could readily be seen through the translucent pulp.
These were doubtless the first truly white blackberries of which there is any record. But there were only four or five bushes bearing these white berries in an entire generation comprising several hundred individual bushes, all having precisely the same ancestry.
From among the four or five bushes, the one showing a combination of the best qualities was selected and multiplied, until its descendants constituted a race of white blackberries that breeds absolutely true as regards the white fruit.
NOW BREEDS TRUE FROM SEED
The descendants of this particular bush were widely scattered and passed out of my control. But subsequently from the same stock, I developed other races, and finally perfected, merely by selection and interbreeding from this same stock, a race of white blackberries that breeds true from the seed, showing no tendency whatever to revert to the black grand-parental type.
This is, in short, a fruit which if found in the state of nature would unhesitatingly be pronounced a distinct species. Its fruit is not only snowy white in color, but large and luscious, comparable in the latter respect to the Lawton berry which was one of its ancestors.
"Was there ever in nature a berry just like this?" a visitor asked me.
Probably not; but there was a small white berry and a large luscious black one, and I have brought the best qualities of each together in a new combination.
The original Crystal White blackberry (1871)
Henderson: Crystal White (1898)
Needham's White Blackberry (1852)
The Garden: White Blackberry Iceberg (1895)
Card: Crystal White and other light colored blackberries (1898)
Nettleton "Creamy White" blackberry patent
Burbank's 'Snowbank' (bred from 'Iceberg') from NCGR-Corvallis