G.M. Darrow, The Strawberry: History, Breeding and Physiology
* By George Darrow and John Meader
JAMES MERRICK, whose important work, The Strawberry and Its Culture, is reviewed in Chapter 5, described a phenomenon he observed in 1870 which is no less noteworthy today; that of the evident pleasure which accompanies the breeding of strawberries. Merrick writes, "The fascination that attends the raising of seedling fruits is well marked in the case of the strawberry. The abundance of seeds, the ease with which they germinate, the early age at which the new plants bear fruit, and the tolerable certainty of getting a very good variety from a hundred or two seedlings, all conspire to lead on the amateur, and induce him annually to increase the size of his seed-beds." Merrick goes on to say, "The careful hybridizer can plan in his mind what kind of a strawberry he will have, and by a skillful selection of parent plants he can realize his ideal."
During the past one hundred and fifty years many thousands of people from various backgrounds and positions of life have yielded to this fascination, and thereby found a source of interest and pleasure in growing strawberries from seed. These thousands have helped develop the wild strawberry into the magnificent fruit that we now enjoy, whether this help was the actual origination of new and better varieties, or whether it took the form of support and enthusiasm, providing the climate conducive to a springing up of interest, and the initiation of intensive work. For many, the reward of such interest has been an increase in knowledge, coming as a pleasurable familiarity with how plants are grown from seed, how the seed gerininates and how tiny plants develop size enough to set in the garden, where, encouraged by care yet almost mysteriously, they blossom, are visited by bees and set fruit. Then, following this, comes a more tangible reward for the "careful hybridizer": the sampling of ripe berries and a noting of the attributes of each -the mixing of acid, sugar, and astringency which when balanced go to make a good berry; the quality of flesh, whose smoothness determines a very good fruit; and the aroma, where a certain perfume adds the final cachet necessary to the delicate composition of what is presently termed the excellent berry. And through the months, from seed planting to ripe berry, a deeper understanding is gained of all living things.
Though it is possible to obtain good berries simply by growing seedlings, a good gardener soon learns many other things, along the lines of botany, as well as those of technique. For example, facts of sex in the strawberry were first learned in 1760 by Duchesne when he was thirteen. They were again discovered about 1808 by Keens, an English market gardener, whose variety Keens Seedling became the first great strawberry variety and an ancestor of most cultivated ones. In the United States these facts were again discovered by a market gardener of Philadelphia, named Abergust, and probably independently discovered and then forgotten by many others.
And one thing overlooked by many breeders even today is the importance of the source of the seed which they plant. If seed is taken from berries in the market, by far the most of them will not produce vigorous plants, for such berries come from large fields of one variety, and the seeds develop from self-pollinated flowers. If seed were obtained of the very large Fukuba of Japan, or of Madame Moutot, the large strawberry of Europe, or of the fine-flavored Royal Sovereign of England, most or all seedlings would be weak and give an entirely erroneous idea of the mother variety. This one point alone has discouraged many a promising hybridizer. Vigorous seedlings result only when actual crosses occur between two varieties or two different seedlings; a weak seedling of Fukuba, or Madame Moutot, or Royal Sovereign when crossed with another variety will give vigorous plants and may, in fact, give the very qualities of such varieties that are sought for.
It is also interesting to read about inbreeding and such things as hybrid corn, and then to attempt applying this method of breeding to the strawberry. Altogether too little is known about the results of inbreeding strawberries, and those who point their endeavours in this direction embarck on a venture as interesting as a trip to the moon, for possibilities are unlimited. In the case of inbreeding, however, it must be remembered that most seedlings of inbred strawberries are very dwarf and weak and more difficult to keep alive than hybrids, and only outcrossing or recrossing of inbred lines can recover the needed vigor.
Besides absobing matters of botany, there are numerous other sources of interest and stimulus, for the strawberry breeder soon comes to know other breeders and thus can see how others do their work. There are breeders' conferences, such as the one held at Rutgers University in January 1963, where breeders, in this case from all over the United States and Canada, meet to study mutual problems. There are numerous articles available for study and for the developing of a better understanding of what has been done, and what might be done. And the problems that need to be tackled are legion! Some may be an after-office reason for having an intensely interesting small garden. Some problems for study can be combined with a search for the best strawberries for the table, and still others may lead to a part-time summer job, or one that lasts for a lifetime!
Here are some of the problems concerned with the Virginian and the western American wild strawberries: How common is mid-summer flowering in wild Virginian strawberries on the Blue Ridge of Virginia, or near your home, or in the meadows and pastures of all North America? Why do a large part of the wild strawberries of western America become summer- and fallfruiting in Maryland and other parts of the East? How many generations of crossing and backcrossing wild strawberries with cultivated varieties will it take to recover full size, firmness, and yellow seeds on the berry surface? What crosses will do the job in one generation and what crosses will need two or more generations, and why? Can we ever get from summer-flowering wild plants the type of strawberries which will be two-crop varieties in the hot summers, like the two-crop raspberries that are fine garden plants in much of the United States? Interestingly, breeders are producing these fall-fruiting raspberries from selections having fall-fruiting wild plants as one parent.
And there are other problems: Hansen in South Dakota, Powers in Wyoming, and Georgeson in Alaska all succeeded in getting large-fruited strawberries hardy, to -401 and -50' F. without snow covering or mulch. But in the humid regions of the eastern United States all strawberries still have to be covered to protect them from the cold of winter. Our strawberry varieties still have non-hardy genes tracing back to their Chilean ancestry. Native wild strawberries, on the other hand, are hardy under the conditions of eastern United States. Mulching material is harder to obtain now and adds to the expense of strawberry growing. New varieties are needed that require no mulch.
While of less practical value for the present, a source of great enjoyment lies in trying to grow seedlings of strawberry crosses selected to give a great range of flavors, from apple, pineapple, apricot, raspberry, cherry and grape, to vinous and musky flavors. Merrick, a hundred years ago, called attention to such ranges of flavor in varieties of his time:
There is really a much wider difference in the flavor of different strawberries than many inexperienced people will at first admit. Some have a distinct and delicate pineapple flavor, as Lenning's White-the White Pineapple and White Albion of some foreign lists-and River's Eliza. The Lucas, a fine seedling from La Constante, has a marked flavor of raspberries, while the Duc de Malakoff has a strong apricot, or, as some say, mulberry taste. The Hautbois strawberries are musky. A French berry, the Exposition de Chalons, has a marked taste of currants. Some foreign kinds have a decided cherry flavor. Our native wild strawberries have a delicious aroma, which is wholly absent in many of the largest kinds.
Such a range of flavors is still available in certain crosses, especially those which involve varieties not far removed from the Chilean. Selections with such flavors have not become major varieties in the past, but they are nonetheless delightful. Suwannee has the finest pure strawberry flavor (whatever that may mean) under most climatic conditions, but this flavor can be modified to involve less acidity, more sugar, less astringency, and any combination of the esters that make up the perfume of strawberries. Florida Ninety grown under some weather conditions can have a delightful perfume, even on arrival at a distant market. Perhaps new varieties can be bred to hold such a delightful flavor under a wider range of conditions.
Before the Wilson variety, the strawberry was chiefly a north temperate variety. Then it moved south to Louisiana and Florida, and with the Neunan and Hoffman, later the Klondike, and now the Florida Ninety, it is staying there. But the strawberry is extremely heterozygous; it has great numbers of genes that can be combined in an infinite variety of ways. It is possible that varieties can be produced which adapt to climates even closer to being tropical.
For that matter, why should we always stoop to pick strawberries from the ground? Why not pick them from a bush, or from plants not as low as our present ones? Staudt (1959) has what is called a bush strawberry where the flower stems are 18 inches long. Perhaps a variety can be bred where applications of gibberellic acid will extend the stems still higher.
Can plants be bred to such vigor that they can compete with weeds and need no protection against them, or with strong, thick root systems resistant to red-stele and capable of supporting plant beds for many fruiting seasons? Perhaps an everbearing variety can be bred whose energy for runner-production is channeled into root development, so that plants seldom need replacement and runner-production is unimportant. The variety might be seedpropagated. Can a variety be bred from the Chilean with thick leaves as protection against drought and cold, and perhaps against aphids? If a woody layer was extended over the roots, would they be less susceptible to root nematode damage? Can varieties be bred with fruit capable of ripening after harvest, as in the case of bananas, so the fruit could be harvested before full maturity, while less liable to damage? Machine harvesting might be facilitated if long, stiff flower stems held the fruit upright, and all berries ripened at once. Some of the wild chiloensis selected on the Pacific Coast display resistance to many-diseases, including red-stele, Verticillium wilt, virus and mildew. How can these desirable characters be bred into the modern strawberry? Can these, or similar, characters be found in other wild strawberries? Do some possess immunity to leaf spot and leaf scorch?
While the questions are numerous and certainly could be multiplied, the possibilities of advance are far greater than any number of questions could ever imply. This, however, is not meant to intimidate the breeders of strawberries. On the contrary, such questions, problems, and suggestions should encourage breeding, for they show that the field is not a closed one, nor is the strawberry a finished fruit. There is room for further work with ample opportunity for amateurs, as well as for professionals, to make meaningful contributions. The strawberry is, after all, a plant, whose green foliage shelters shiny red fruit that is fragrant, sweet and juicy. The invitation is to enjoyment, both of work and its results.