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Strawberry Improvement' STRAWBERRY IMPROVEMENT' GEORGE M. DARROW, Senior Pomolo- gist. Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry JL HE strawberry ctinae from North Amoricíi, and some people think it is delicious enough to bo a fair exchange for many of the fruits America has received from other parts of the world. Much of the work of developing the cultivated varieties has also been done in the United States; but so universal is the appeal of the strawberry that it is receiving the devoted attention of plant breeders in such remote lands as England, the Union of Soviet Socialist Republics (47) ^, and Japan (33,34,35,36). The cultivated strawberry is definitely a product of plant breeding and is relatively young. The commercial development of this fruit has come principally since the Civil War, and most strawberry varie- ties now grown have originated within the past 45 years. Seventy years ago the straw^berry w'as produced almost entirely near a few of the large cities. Now it is produced commercially in every State in the United States, as w^ell as in the interior of Alaska. The introduction of improved varieties has been responsible for the steadily widening commercial production. When the first productive firm-fruited variety, Wilson, was introduced about 75 years ago, it became possible to grow the strawberry as far south as Florida and^ Louisiana. The hardy Dunlap, introduced about 35 years ago, made it reasonably safe to grow straw^berries in northern Michigan, northern Maine, and parts of Canada. Later the origination of suitable high-quality varieties in Alaska made it possible to raise strawberries commercially even in that northern region. During the past century hundreds of thousands of seedlings have been tested, over 2,000 have been named, and a few^ score are widely grow^n; but these few score varieties combine the many qualities necessary for modern commercial production in every part of the United States and in every foreign country having a temperate climate. The world-wide distribution of the strawberry may be attributed to three things: (1) The origination of firm varieties like the Wilson, adapted to widely difl^erent conditions; (2) the ability of the straw- berry to grow from sea level up to elevations as high as 12,000 feet, in humid and dry regions, in the greenhouses of northern Europe, 1 This report has been made possible by the cooperation of George F. Waldo, of the TJ. S. Department of Agriculture, at Corvallis, Oreg., and reports for their stations by JT. n. Clark, of New Jersey; G. W. Gasser, of Alaska; A. N. Wilcox, of Minnesota; George L. Slate, of New York; S, M. Zeller, of Oregon; and H. E. Thomas, of California. W. J. Strong, of Vineland, Ontario, Canada; M. B. Davis, of Ottawa, Canada; W. S. Rogers, of East Mailing, Kent, England; Laxton Bros., of Bedford, England; P. Stedje, of Njos, Norway; C. G. Dahl, of Alnarp, Sweden; and many others have contributed information that has helped in the preparation of this report. 2 Italic numbers in parentheses refer to Literature Cited, p. 482. 445 446 YEARBOOK, 1937 where the winter day is only 6 or 7 hours long, in Florida and southern California, where the winter day is 9 or 10 hours long, and in central Alaska, where the summer day may be 24 hours long (17); and (3) the high dessert quality and usefulness of the fruit, which matures in early summer when few fruits are available. THE STRAWBERRY IS A TRAVELER THE STRAWBERRY was born in North America, traveled to Europe, and finally returned home. But the strawberry that returned was very different from the one that went to Europe. The cultivated strawberry of today is derived from two American species—the wild meadow strawberry (Fragaria virginiana Dnch.) of eastern North America (figs. 1 and 2), and the beach strawberry (F. chiloensis (L.) Duch.), found along the Pacific coast from Alaska to California and along the coast of Chile (figs. 3 and 4). The beach strawberry is also found on the mountains of the Hawaiian Islands. The meadow strawberry has thin leaves and bright-red aromatic berries with deep-set seeds, and it grows freely in many soils and many THE work of the Department of Agriculture in strawberry breeding gives an excellent idea of the amount of detail involved in the produc- tion of improved varieties of plants. In Maryland^ the Department has fruited 86ß00 strawberry seedlings^ representing artificial crosses among 150 different varieties. Of these^ 1^999 were selected for further testings and only 7 have been finally considered worth naming and introducing. In North Carolina^ 54ß00 seedlings have been grown and 1^245 selections have been made for further testing. In Oregon^ the number of seedlings grown was 97ß00 and the num- ber selected for further testing is 1^331. In these few projects^ then^ more than a quarter of a million seedlings were involved; feiver than two out of a hundred ivere found to be worth further testing; and perhaps a score or fewer of neiv varieties will finally result. But of the few varieties already introduced^ one is Blakemore^ now con- sidered to be the best preserving strawberry in the United States; another is Redheart^ now more extensively grown than any other canning variety; and two others are Dorsett and Fairfax^ which are superior in dessert quality to other varieties previously grown. In addition to this breeding work, 30,000 wild Rocky Mountain straw- berries were collected in 1936 to be grown at Cheyenne, Wyo., with the idea of incorporating their superior resistance to cold, dry winters into cultivated varieties. STRAWBERRIES 447 locations. In contrast, the beach strawberry has thick leaves and dull-red berries with less aroma, and the seeds are usually raised above the surface. It is native only along the beaches. But hj^brids are more vigorous and have wide adaptation. FIRST IMPROVEMENT WAS MADE BY AMERICAN NATIVES Before Columbus landed at San Salvador; unknown Indians of Chile, South America, had selected, from among the wikl strawberries that grew only along the beaches, plants that bore fruit of exceptional size, Figure 1.—'I'lie IIR-UIIOW strawberry of (lie eastern United States, Fragaria virginiana. The aroma, the beautiful color, and the wide adaptation of cultivated varieties come largely from this species. "commonly as large as a walnut and sometimes the size of a hen's egg" {48). The fruit was pale red, with firm, meaty, almost white flesh and a delicate aroma (figs. 3 and 4). More important, however, the selected plants, or at least one of them, had perfect flowers, while all the true wild beach strawberries and most of the wild meadow strawberries of North America have the sexes borne on separate plants {61). Just where the Indians found such a perfect-flowered wild plant, or how it came into cultivation, we do not know. An extensive search by the writer and others on the beaches of California, Oregon, and Washington has failed to locate a single perfect-flowered plant. One of the present needs in strawberry breeding is a survey of the coast of Chile, and particularly of Robinson Crusoe's island, Juan Fernandez, to locate plants having perfect flowers and to deter- mine the value of the Chilean wild berries in breeding. 448 YEARBOOK, 1937 This early Chilean variety was taken to Peru in 1557, and it is still grown in Chile, Peru, Ecuador, and other South American countries. The second important character in the story of the modern straw- berry was a French officer, M. Frezier, who returned to Europe from Chile in 1714. He arrived at Marseilles, after a 6-month voyage, with five live plants of the Chilean variety (48). Plants of the meadow strawberry of eastern North America had already been taken to Europe, and from crosses of these two forms the modern strawberry was developed in Europe. A third great character in the story was also a Frenchman, named Duchesne. In 1760, when only 19 years of age, he published a book of over 400 pages on the strawberry (22). He described the wild species, noted that some varieties had both pistils and sta- mens in their flowers and bore fruit, that others had only pistils and bore no fruit un- less they grew near varieties that had sta- mens, and that stUl others had stamens and pistils but were sterile. Duchesne was probably the first to make actual crosses of strawberries. A fourth character was an Englishman, Thomas Andrew Figure 2.—A pistillate-flowered feedling of a cross of the Knight, who originat- meadow strawberry (Fragaria virginiana) X'Dunlap. ed the Downton and Note the deep-set seeds. later, about 1820, the Elton Pine, which is still grown in Europe (29). He made many crosses and proved that systematic breeding would result in improved varieties. He was really the world's first systematic fruit breeder. Best of all, he was a scientist who combined his scientific studies with practical breeding to secure better varieties. He has been followed by many strawberry breeders in England and on the Continent. A fifth great character in strawberry history was Nicholas Long- worth, a prominent horticulturist of Cincinnati, Ohio, and great- grandfather of Nicholas Longworth, the late Speaker of the United States House of Representatives {11, 12). In spite of the work of Duchesne and a few others, few people in the United States knew there were different se.x types in the strawberry. Longworth redis- covered these differences some time before 1834. He and his asso- ciates are said to have examined millions of strawberry flowers and classified plants into four groups—(1) pistillate, (2) hermaphrodite or perfect, (3) two rather rare classes having staminate flowers, and (4) a class having both pistillate and hermaphrodite flowers on the STRAWBERRIES 449 Figure 3.—The Chilean strawberry (Fragaria cliiloensis) as grown at Ambato, Ecuador, at an elevation of about 10,000 feet, where the rainfall is probably not over 15 inches a yeeir.
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