GEORGE M. DARROW, Senior Pomologist, Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry
[ABSTRACT.] THE work of the Department of Agriculture in strawberry breeding gives an excellent idea of the amount of detail involved in the production of improved varieties of plants. In Maryland, the Department has fruited 86,000 strawberry seedlings, representing artificial crosses among 150 different varieties. Of these, 1,999 were selected for further testing, and only 7 have been finally considered worth naming and introducing. In North Carolina, 54,000 seedlings have been grown and 1,245 selections have been made for further testing. In Oregon, the number of seedlings grown was 97,000 and the number selected for further testing is 1,331. In these few projects, then, more than a quarter of a million seedlings were involved; fewer than two out of a hundred were found to be worth further testing; and perhaps a score or fewer of new varieties will finally result. But of the few varieties already introduced, one is Blakemore, now considered 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 strawberries 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.
The strawberry came from North America, and some people think it is delicious enough to be 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 varieties now grown have originated within the past 45 years. Seventy years ago the strawberry was produced almost entirely near a few of the large cities. Now it is produced commercially in every State in the United States, as well 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 strawberries 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 grown; 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 different conditions; (2) the ability of the strawberry 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, 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 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 Duch.) 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 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 hybrids are more vigorous and have wide adaptation.
Before Columbus landed at San Salvador, unknown Indians of Chile, South America, had selected, from among the wild strawberries that grew only along the beaches, plants that bore fruit of exceptional size, “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 determine the value of the Chilean wild berries in breeding.
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 strawberry 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 stamens in their flowers and bore fruit, that others had only pistils and bore no fruit unless they grew near varieties that had stamens, and that still 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 Knight, who originated the Downton and 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 Longworth, 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 sex types in the strawberry. Longworth rediscovered these differences some time before 1834. He and his associates 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 same plant. Longworth found that not over one-third of the flowers of the hermaphrodite varieties ever set fruit, while all, or usually all, of the flowers of pistillate varieties set fruit. Longworth’s work eliminated one great cause of failure in commercial berry production and made it possible to raise strawberries much more widely than before. Though the difference between pistillate and so-called perfect-flowered varieties has been common knowledge since the time of Longworth, much of his work on the degree of sterility of the perfect-flowered varieties was lost sight of until rather recently, when it was rediscovered by Valleau (60) of Minnesota.
The varieties originated in Europe were soon introduced into the United States, and many of them were grown extensively in: this country, especially in the years before 1850. Commercial strawberry growing near the largest cities had begun in the United States about 1800, with such old varieties as Large Early Scarlet, Early Hudson, Hudson’s Bay, Crimson Cone, Red Wood, and later the Hovey.
Since the time of Nicholas Longworth the outstanding development has been the introduction of a succession of new varieties with qualities that have made possible the extension-of the territory where strawberries could be grown (28). Among the most important of these have been the Wilson, originated in 1851; Crescent in 1870; Sharpless in 1872; Aroma in 1889; Dunlap and Marshall in 1890; Thompson in 1894; Klondike (10) about 1896; Missionary about 1900; Ettersburg 121 in 1907; Howard 17 in 1909; Progressive in 1908; Blakemore, Dorsett, and Fairfax in 1923; and Catskill in 1924 (18, 29).
In England, Myatt introduced the British Queen in 1840, and Bradley originated the Sir Joseph Paxton in 1862 and introduced the Dr. Hogg in 1866. The Jucunda originated with Salter before 1860.
A large number of the other important English varieties were originated by Thomas Laxton and by his sons, the firm of Laxton Bros. With the encouragement of Darwin, Thomas Laxton began his strawberry breeding about 1865. His first variety was the Noble, introduced in 1884 and still grown extensively, especially in Germany and the Netherlands. In 1888 the King of the Earlies was introduced, and in 1892 the Royal Sovereign, a cross of Noble and King of the Earlies. Though British Queen and Dr. Hogg are the finest in quality in England, Royal Sovereign has high quality and is probably the most widely grown variety in northern Europe. Latest of All was introduced by Laxton Bros. in 1894, and Givons Prolific, raised by William Peters of Givons Gardens, was introduced in 1901. Bedford Champion was introduced by Laxton Bros. in 1904 and The Duke in 1919.
In France (38, 46) Pelevain introduced Princess Royale in 1844, and it was said to have been the leading French variety for over 50 years. About 1856 the Vicomtesse H. de Thury, raised in 1845 by M. Jamin, was introduced; Marguerite was originated in 1859 by M. Lebreton; and in 1871 the Dr. Morere, raised by M. Berger, was introduced. Dr. Morere has been grown as widely in France as the Royal Sovereign in England.
In the Netherlands, Mme. Kooi was raised by G. Kooi before 1920 and introduced by R. Hendrikson, who also introduced the Mme. Lefébre.
In Germany, Late Leopold, raised by L. Lierke, was introduced in 1904. Deutsch Evern, a cross of Sieger X Noble, was raised in 1902.
STRAWBERRY VARIETIES OF THE WORLD3UNITED STATES
A GREAT many varieties have been grown in the United States, but at present only about 30 are important, 20 of them in about the order shown in table 1.
Besides the 20 listed, 11 other varieties make up about 4 percent of the total acreage (18). These varieties, with the same abbreviations for origin as in the table, are Catskill (Br), Clark (Br), Oelrich (Ulrich) (Ch), Ettersburg 121 (Br), Corvallis (Br), Glen Mary (Ch), Ridgely (Ch), Sample (Ch), Clermont (Br), Fairfax (Br), and Narcissa (Br). Though there are many other varieties in the trade, they are grown to a very limited extent.
Twenty-two of the thirty-one varieties were originated as the result of breeding, and they constitute over 75 percent of the acreage (18, 32). For the most part, each of the important varieties has made its way rather quickly into a prominent position. Growers generally are interested in testing new sorts and are ready to change to any promising new variety. For example, the Howard 17 was introduced under that name in 1918, and 10 years later it was the principal variety north of the Ohio and Potomac Rivers. The Dorsett, introduced in 1933, has already become well known on the larger markets of the Eastern States.
|Total acreage (Percent)||Origin*||Approximate date introduced (i) or originated (o)|
|2||Howard 17 (Premier)||16.0||Br-Pri||1918 (i)|
|16||Nick Ohmer||1.0||Br-Pri||1898 (i)|
|18||Belt (Wm. Belt)||0.5||Br-Pri||1888 (o)|
The varieties now used probably represent better adaptation to conditions in the regions where they are grown than former sorts. Varieties such as Missionary, Klondike, Dunlap, and Heflin are more like the wild meadow strawberry of eastern North America than like the beach strawberry. Through the hundred years of evolution in the cultivated strawberry the varieties have been tending toward the native eastern wild strawberry. This has occurred because (1) most varieties have originated in the East; (2) seedlings with more of the characteristics of native wild strawberry have naturally succeeded best and have been selected by breeders; and (3) many varieties, such as Missionary, were found in the wild as chance seedlings. The latter may have originated either from seed of cultivated varieties,or as the result of bees carrying pollen of cultivated sorts to the native strawberry. In some regions along the Atlantic coast most of the strawberries found growing wild are now in part derived from cultivated sorts. Natural crossing of cultivated with the beach and the Rocky Mountain strawberries has already started in the Western States, and many natural crosses have been found there.
Fairfax, of the eastern varieties, and Ettersburg 80 and 121, of the western varieties, are the nearest to an intermediate between the eastern meadow strawberry and the beach strawberry. Dorsett (fig. 5), Howard 17, Chesapeake, and Marshall are thinner leaved and thus somewhat closer to the Missionary, Klondike, and Dunlap group. The success of Etter (8) and Georgeson (30) whose work will be discussed later, in using selections of the beach strawberry has revived interest in this species. It is now being used extensively, particularly in the California and the United States Department of Agriculture breeding work, to increase vigor and to obtain resistance to root rots. Hybrids of cultivated varieties with Fragaria chiloensis, the beach strawberry, have much greater vigor than most variety crosses. It appears that through the scores of years since the strawberry came back from Europe some inbreeding has occurred that has lessened the vigor of the cultivated strawberry.
The strawberries of Canada are similar to those of the United States, the varieties being the same in most instances. In eastern Canada, Dunlap, Parsons, Howard 17, and Glen Mary are the chief sorts. In British Columbia, British Sovereign, Magoon, Marshall, and Sir Joseph Paxton are raised in the milder coast climate, and Dunlap, Glen Mary, and Parsons (Gibson) in the interior.
Because wild parental types of the cultivated strawberry are not
native to Europe, Asia, Africa, or Australasia, varieties of these countries are all, or nearly all, the result of breeding. The varieties so developed differ from one another more than do American sorts.
The principal varieties grown in each country are as follows:
England.—Royal Sovereign, Mme. Lefébre, Late Leopold, Oberschlesien, and Huxley (probably Ettersburg 80). The Duke, Sir Joseph Paxton, Bedford Champion, and Mme. Kooi are being grown somewhat, and Western Queen and Pillnitz are being tested.
Scotland.—Scarlet Queen, John Ruskin, Royal Sovereign, MacMahon, and The Duke.
Germany.—Deutsch Evern and Noble for early, Sieger, Oberschlesien, and Roter Elefant for midseason, and Jucunda and Leopold for late. Vierlanden is raised near Hamburg.
Netherlands.—Jucunda, Deutsch Evern, and Noble, with some Scarlet and Oberschlesien.
France.—Minerve, Souveraine, Moutot, V. H. de Thury, Dr. Morere, Paxton, Tomate, Marguerite, Leopold, and others.
Norway.—Deutsch Evern, Abundance, and Bedford Champion.
New Zealand.—Marguerite, Melba, Ettersburg (80 or 121?), Captain Cook, Noble, Helenslea, Surprise, and Royal Sovereign.
Victoria.—Melba and Wilson’s Pride.
Tasmania.—Ettersburg (80 or 121?), Royal Sovereign, Melba, and Abundance.
The varieties of cultivated strawberries of the United States do not come true from seed. If 1,000 seeds of Marshall or Klondike or Howard 17 are planted, no 2 seedlings will be exactly alike. Some plants will be weak, some strong; some will make few runners, some many; some will have large fruit, some small; some will be productive, some unproductive. Out of the thousand, few if any will be as good as the parent. Because they do not come true from seed, and because they are so easily propagated by runners that root at the tip to form a new plant, all American varieties are propagated in this way, never seed.
In Europe there are a few cultivated varieties called alpines or everbearing wood strawberries, some of which are often and others of which are always raised from seed. They produce much smaller fruit than do our cultivated varieties and are closely related to the wood strawberries of North America. Thus, the Bush White is an alpine variety that makes no runners, has small, white fruit, and, because it makes no runners, is always raised from seed. The Belle de Meaux is an alpine that produces runners, has red fruit, and may be raised from seed or propagated by runners. Such varieties have been selected, as have vegetables and other seed-propagated plants, until they come approximately true from seed. Seed varieties of alpines are relatively easy to establish as compared with seed varieties of the common cultivated strawberry. However, these alpine varieties are rarely grown in the United States.
Though it is extremely unlikely that any one of 1,000 seedlings of Marshall, Klondike, or Howard 17 will be better than its parent, breeders have learned that if Marshall is crossed with some other variety and 1,000 seedlings are raised, the progeny will be far more vigorous and productive than seedlings of Marshall that are not the result of crossing. Thus, from a cross between Marshall and Howard 17, Slate, at the New York (State) Agricultural Experiment Station, raised. 1,132 seedlings and saved over 150 as especially promising (55). From these he selected a seedling that he named Catskill, which combines many of the good qualities of both parents. It is now widely grown.
Cultivated strawberries produce two general types of flowers— pistillate, and perfect or hermaphrodite (11, 18). Pistillate flowers contain pistils, the female parts, but no stamens, while perfect or hermaphrodite flowers contain both pistils and stamens, the male parts. The other two types of plants, staminate and that with both pistillate and perfect flowers on the same plants, are rare. Pollen is carried by bees and other insects, but it is also thrown out of the stamens as the anthers crack open (fig. 6), or it is jarred out and blown by the wind and falls on the pistils. A variety having perfect or hermaphrodite flowers can produce fruit when planted by itself, but one with pistillate flowers cannot set fruit unless perfect-flowered plants are nearby to furnish pollen through the agency-of bees or other insects. Because of this, varieties having pistillate flowers are not generally so desirable as those having perfect flowers, and few of them are grown now. However, some of these pistillate varieties are very productive. Pistillate varieties are also injured less by the strawberry bud weevil than perfect sorts, since this insect feeds on pollen; and in regions where it is serious, pistillate sorts are still grown. When the plants are in flower it is very easy to tell a pistillate from a perfect- flowered variety, as illustrated in figure 7.
Though the flowers of pistillate varieties nearly always set fruit when pollinated, those of perfect-flowered varieties rarely all set fruit. The flower may appear to be normal, but the pistils may be sterile. Under some conditions not 1 in 50 of the flowers of certain varieties sets fruit. Studies by Valleau (60) have shown that only the pistillate plants of the wild meadow, beach, and mountain strawberries set fruit. Perfect-flowered plants in the wild are in reality males, even though the pistils usually appear normal. Occasionally the first flower to open on a wild perfect-flowered plant may set a berry, and very, very rarely most of the perfect flowers on a plant of the wild meadow strawberry may set fruit.
The first flowers to open on a cluster of a perfect-flowered variety are more likely to set fruit than the later ones, and the last ones to open are most often sterile. On the average about one-third of the blossoms of cultivated perfect-flowered varieties are sterile. The clusters produced by the main crown of a plant have fewer sterile flowers than the later-formed clusters of branch crowns. Through scores of years, by breeding and selection, perfect-flowered varieties have now been obtained that set nearly all their flowers. In fact, under favorable conditions all the flowers of the Rockhill everbearing seem to set.
At its base the pistil contains a minute egg cell ready for fertilization when the flower opens. After pollen is placed on the end of the pistil, one or many of the pollen grains start to grow a tube down the center of the pistil. The pollen absorbs food from the tissues of the pistil, and finally one pollen tube reaches the egg cell. The sperm nucleus, a minute globular mass in the pollen grain, passes down the pollen tube, enters the egg cell, and unites with the egg nucleus. When the nuclei of the pollen and egg unite they form a single cell that is the germ of a new plant. By successive divisions of this original cell, the embryo plant, contained in the seed that we see on the outside of the strawberry, is finally formed. Within a few hours after the pollen and egg nuclei unite, the ends of the pistils dry up. If no pollen reaches the ends of the pistils they will not dry up nearly so quickly. After the embryo has started to grow, the tissue around the seed starts to develop into what we call the strawberry. If any pistil is not pollinated, then the tissue around the base of that pistil does not develop. When the pistils on one side or part of a flower have not been pollinated or have been damaged by frost, the result is a misshapen berry.
Crossing of strawberries may be done in the field under cages of wire screen or cloth or under sun traps (fig. 8, A). Making large numbers of crosses in the field is very laborious and must be done within a short time. Flowers may be killed by unseasonable late frosts, so that the work has to be repeated and time is lost. For these reasons, if facilities are available the crossing should be done in greenhouses, either heated or unheated (fig. 8, B).
The other advantages of using an unheated greenhouse are that
In emasculating, the thumbnail is generally used to cut away the stamens, corolla, and calyx at one operation (fig. 9, A). If this is done with ordinary care, no injury to the pistils follows. Often the calyx and corolla are removed to identify crossed flowers even though emasculation is not necessary. The primary and secondary flowers, the first and second to open, contain far more pistils than the flowers opening later in a cluster. Berries developing from the primary and secondary flowers can set far more seed than the later berries, hence every effort is made to pollinate the earliest flowers on each cluster.
In crossing, the flowers having unopened pollen-bearing stamens are picked and allowed to wilt until the anthers crack open to let the pollen out. The flowers are used directly on those to be crossed, being held so that the stamens touch the pistils. The flower is then twirled by its stem so as to cover all the ends of the pistils with pollen (fig. 9,B).& flower with abundant pollen may be used to pollinate four to six flowers or even more. Some breeders collect pollen and then use small brushes to apply it.
After being pollinated, the flower, flower cluster, or plant is marked to indicate the cross (fig. 10) and then bagged or protected in some way from insects if necessary (fig. 8, A). The berries are picked as soon as they are fully mature. The fresh berries may be mashed in dry sand to separate the seed, and the mixture of seed, pulp, and sand is sowed in flats and pots at once. They are then covered with about one-eighth of an inch of sand, and at no time is the seed allowed to become dry. With temperatures from 60° to 80° F., the seed germinates in a few days. With very high temperature the seed may become dormant and stay dormant until after a period of cold weather. Soil to which commercial fertilizer has been added should not be used, for it may prevent germination.
When they reach a size convenient for handling (fig. 11), the seedlings are pricked either into flats 2 inches apart or into thumb pots. As soon as they are large enough (2 to 4 weeks) they are set in the field. If set in the field in Maryland by July 1 they should produce a good crop the next spring. The plants may be set 4 to 5 feet apart and allowed to make a small mat of runner plants, or 12 to 18 inches apart in the row and all runners kept off.
At the beginning of the ripening season, all plants that would not be desirable commercially, including dwarfs and those subject to leaf or root diseases, may be cut out. Further selection when fruit characters are judged will then be easier. The number of selections made for future testing varies greatly but is rarely over 10 percent and is usually less than 2 percent of the plants fruited (fig. 12). The selections are then propagated and a second test on a larger scale, either a 25- or a 50-foot row, is made in comparison with standard varieties. After the second test some selections may be tested further for some special quality such as suitability for preserving, canning, or shipping, or for behavior in different regions of the country.
THE FINE dessert quality and the extensive cultivation of the strawberry today are a tribute to the ability and industry of breeders of the past century and a half. Further improvement may consist largely in obtaining varieties with (1) greater resistance to leaf, crown, and root diseases, to the virus diseases, and possibly to insects and nemas (eelworms); (2) greater resistance to high and low temperatures and to drought; (3) better adaptation to long and short days (17); (4) better dessert quality under adverse weather conditions; (5) increased firmness and toughness of skin; and (6) better adaptation to specific uses such as deep red, firm, tart varieties for canning; varieties holding their shape, texture, flavor, and color after freezing; light red but red to the center, tart, firm ones for preserving (14); varieties with aroma suitable for flavoring, etc. Such improvements would lessen the risks now faced in growing strawberries. Varieties most desirable for freezing for the small-package trade have been found too subject to diseases or not productive enough to become commercial sorts. Southern varieties have been highly acid and without much aroma in cold and unfavorable weather, yet there are varieties that have high flavor under such conditions.
The use of selfing to obtain relatively pure lines has not been satisfactorily explored, though some selfing has been done by several breeders. When selfing has proceeded for two or three generations, the plants are not vigorous and may be easily lost. Only under very favorable conditions can they be kept alive. For this reason, little information on this method is yet available. Yet immunity from or high resistance to leaf spot or other diseases may be due to recessive genes and appear only after inbreeding. Yellow leaf seems to be a recessive character that might be eliminated by selfing and by selecting selfed lines that do not carry it.
Of the private breeders who produced varieties previously listed, the following are still living: A. F. Etter, Ettersburg, Calif., originator of Ettersburg 121 and other varieties; E. C. Howard, Belchertown, Mass., who was associated with his father in the origination of Howard 17 and Howard Supreme varieties; Harlow Rockhill, Conrad, Iowa, originator of Rockhill and Progressive, everbearing varieties; and Jeff Beaver & Son, Eau Claire, Wis., originators of Beaver. Other private breeders are Horace Wray, White Salmon, Wash., originator of Wray Red; and W. Kosuga, Sandy, Utah, originator of Berri Supreme.These breeders made crosses and selected the seedlings that seemed to come nearest their ideal. Some of them have kept detailed records of their work, as the following parentage of Howard 17 shows:
The Howards tried to recombine in one variety the desirable qualities in several. Slate (55) has stated that Howard 17 is the outstanding parent used at the New York station. It has also been an exceptional parent in the breeding work of the United States Department of Agriculture.
A. F. Etter (fig. 13) has collected and used selected wild strawberries in his breeding work, which began about 1885 (8). His most valuable contribution has been this use of selections from the wild. Most of the 50 or more varieties introduced by him are derived from selections of the beach strawberry, Fragaria chiloensis, crossed with cultivated varieties. Qualities that he has bred into strawberry varieties through use of selections of the beach strawberry are being extensively used by other breeders. Thus, Redheart is a cross of Portia X Euresko, the latter being one of Etter’s varieties. Southland resulted from a cross of Howard 17 X Ettersburg 80, while Corvallis is a cross of Marshall X Ettersburg 121. Many selections at experiment stations resulting from breeding work and under test at present have as one parent one of the Etter varieties or a variety or selection derived in part from his varieties.
Harlow Rockhill began his work with the everbearing strawberries in 1895 and has used both American and European sorts in his breeding. Progressive was his first production to be widely grown. His later variety, Rockhill (Wayzata), is resistant to cold and to leaf diseases and is one of the highest in dessert quality in the United States (fig 14).
The Federal strawberry-breeding work (19, 20) has been carried on in Maryland since 1920. The work was extended in 1928 to include cooperative work at the North Carolina Coastal Plain Branch Station at Willard and the Oregon Agricultural Experiment Station at Corvallis.
Over 86,000 seedlings, representing hundreds of crosses, have been fruited at Glenn Dale, Md., and at United States Horticultural Station, National Agricultural Research Center, Beltsville, Md. In all, over 150 varieties and 20 selections of species have been used in this breeding work. Selections to the number of 1,999 have been made, 7 varieties have been named and introduced, while 342 selections are still unnamed and are being held for further testing or for breeding.
The first work at Willard consisted of tests of selections from the Glenn Dale station. Beginning in 1929, small seedlings raised in Maryland were taken to Willard and fruited there. Since the beginning about 54,000 seedlings have been grown at Willard and 1,245 selections have been made. No selections have been named, though several are being extensively tested and propagated. The crosses have been made especially to obtain firmer, higher flavored shipping varieties for the South.
At the Oregon station the first work also consisted of tests of selections made in Maryland. However, crossing was immediately begun, and to date some 97,000 seedlings have been fruited and 1,331 selections made. No selections have yet been named, though many are being extensively tested. The crosses made have been largely to obtain better preserving, freezing, canning, and shipping berries.
At the United States Horticultural Field Station, Cheyenne, WY, the first selections of the wild Rocky Mountain strawberry, Fragaria cuneifolia Nutt., were made in 1935. Though small fruited, they proved much hardier than cultivated varieties, and in 1936 over 30,000 plants were collected, chiefly from the States of Wyoming, Colorado, Utah, Montana, and South Dakota. Selections of these are to be used by Powers and Hildreth in crossing to produce varieties more resistant to cold, dry winters.
Extensive tests of many of the selections at Willard, N. C., have been made in Maryland and at Corvallis, Oreg., to find some especially adapted to freezing in small packages with sugar or sirup. Similar tests have been made of the preserving and canning qualities of many varieties. As a result of this work, the Blakemore was selected early in the breeding work for its superior qualities for the making of preserves (15). It is considered the best of all varieties for this purpose in the United States. The Redheart was selected for its canning qualities and is now raised more extensively than any other canning variety. Breeding for firmness and adaptation to short day length requirements at the Willard station have been other objectives. Some of the crosses that have some of these desirable qualities are listed in the appendix under Sources of Superior Qualities in Strawberries.
Studies on the sterility of flowers (12), types of flower clusters (13), number and length of runners, stomata of the leaves (14), transpiration from the leaves, fruit-bud development (6), spacing of plants, and leaf area in the late fall have shown just what plant characteristics are most desirable and why. Thus, the fertility of all the flowers of Rockhill, the low-branching fruit clusters and early fruit-bud initiation of Howard 17, the long, large runner and natural spacing of plants of Fairfax, the type of stomata of Blakemore (14), and the extensive leaf area of Dorsett when spaced—these have been found to be desirable characteristics under some conditions and useful in breeding. In fact, an intimate and extensive knowledge of such characteristics in varieties is of great importance in selecting varieties for breeding and in making selections from seedling fields.
Extensive strawberry breeding is a part of the work at many State experiment stations. A list of the workers at these stations and the locations of their work is given in the appendix.
A relatively small part of the total strawberry acreage of the country—about 10 percent—consists of varieties originated by public agencies. However, the acreage of Catskill, Dorsett, Fairfax, and other new introductions is increasing rapidly, and these varieties are becoming important commercial sorts. Strawberry breeding has been started only recently at many experiment stations as the need for better varieties has become apparent. Results from much of this work are not yet, of course, in the trade.
Strawberry breeding was begun in Alaska (30) in 1905, the first crosses being made between cultivated varieties and selections of the beach strawberry, Fragaria chiloensis. Later, selections of the hardy interior wild strawberry, F. cuneifolia(F. platypetala Rydb.), as well as numbered seedlings, were also used in crossing. Named varieties from the States do not succeed in the climate of Alaska, and crosses were made to obtain varieties with the size and productiveness of the cultivated varieties and the hardiness of the native wild strawberries. Some of the resulting hybrids were found to be hardy at Fairbanks, in the interior of Alaska, where extremely low temperatures occur in winter and where there is continuous daylight for about 2 months in summer. Up to 1922 some 11,600 seedlings had been raised. As a result of this breeding work strawberries are now commonly grown in Alaska. Since about 1922, varieties originating at the experiment station at Sitka have supplied the markets both on the coast and in the interior, even above the Arctic Circle.
Strawberry breeding in Minnesota was begun in 1908 and has continued to the present. The earlier work consisted of crosses between commercial varieties to obtain hardier sorts. Between 75,000 and 100,000 seedlings were raised from 1909 to 1924. Seven varieties were named and introduced as the result of this work—Duluth and Deephaven as everbearing sorts, and Minnesota, Minnehaha, Chaska, Easypicker, and Nokomis as early summer sorts. The principal varieties used as parents were Abington, Autumn, Beder Wood, Brandywine, Clyde, Crescent(?), Duluth, Dunlap, Easypicker, Enhance, Golden Gate, Jessie, Margaret, Pan American, Prolific, and Sheppard. Similar work on a smaller scale has been continued since 1927.
Selection within self-fertilized lines was begun in 1922 and is being continued. Varieties selected for desirable characters are self-pollinated, about 5 percent of the better seedlings propagated, compared, and the superior lines again selfed. Lines that have been selfed for one, two, and three generations are now being grown. The principal varieties used in this work are Belt, Chaska, Dunlap, Howard 17, Marshall, and Minnehaha, and to some extent Beaver, Duluth, Early Bird, Mastodon, Minnesota, and Progressive.
The breeding work in South Dakota (31) has consisted of an attempt to introduce into the cultivated strawberry the hardiness of the native strawberry of the Dakotas. Dakota No. 1 and Dakota No. 2 were introduced, and the former, now known as Dakota, is perhaps the hardiest variety known in the United States.
The breeding work in California was begun by W. T. Horne and A. G. Plakidas in 1925-26 to obtain varieties resistant to the yellows or xanthosis virus disease. In recent years the work has been carried on by E. V. Goldsmith and H. E. Thomas, and resistance to phytophthora root rot has been made a second major objective. es and selections obtained from A. F. Etter and the United States Department of Agriculture, as well as many commercial varieties, have been extensively used. Among the desirable characters for California conditions not necessarily considered elsewhere are longevity of plant, open crowns, long inflorescences, small seeds, and heavy production in spring, summer, and fall. The work has centered at San Jose until recently, when part of it was transferred to Davis. Though very large numbers of seedlings have been raised and many selections made, no varieties have yet been named and introduced.
Breeding work at the New Jersey Agricultural Experiment Station (7) was begun in 1928 and has continued to the present. All available varieties having promise for New Jersey conditions, as well as many unnamed selections from other institutions carrying on strawberry breeding, have been tested. The principal varieties used include Aberdeen, Berri Supreme, Bliss, Bouquet, Chesapeake, Dorsett, Fairfax, Gandy, Howard 17, Lupton, Mastodon, Parcell, Pearl, Redheart, Teddy Roosevelt, Wyona, and U. S. D. A. 854 and 875. Besides published data on inheritance of earliness and lateness, data have been obtained on sex ratios, shape, color, flavor, and firmness of berry, and on inheritance of the everbearing characteristic. One variety, N. J. 35, was introduced in 1936. Lupton transmitted its size and attractiveness but also its poor quality to its seedlings. Chesapeake transmitted its good flavor and its unproductiveness. Many of the best very late ripening seedlings have had Pearl as one parent. Fairfax seedlings have had high flavor and were exceptionally firm.
Strawberry breeding at the New York station at Geneva was begun in 1889 by C. J. Hunn and has been continued at intervals ever since (1, 2, 54). At least 68 named varieties, as well as many selections from crosses, have been used in the breeding work. Over 13,000 seedlings have been raised and 21 varieties have been introduced. Several of the more recent introductions are grown to a slight extent, chiefly in New York State. Clermont is grown to a considerable extent in Erie and Oswego Counties. Catskill, however, is rapidly becoming an important commercial variety from Maryland to Missouri and northward. Most of the introduced varieties have had Marshall or Howard 17 or both as a parent, Marshall contributing high flavor and large size of berry, and Howard 17 productiveness and disease resistance. In a summary of the best parents in the breeding work, the importance of Howard 17 as a parent is emphasized. A large percentage of its seedlings produce very smooth, uniform- shaped, glossy berries that hold up well to the end of the season. A few selections of species have been used in crosses.
At the Connecticut station, Howard 17, Chesapeake, and Glen Mary were inbred for three generations and then the F3 (third-generation) progeny were crossed. The strawberry was reported to respond to inbreeding and crossing in much the same way as corn. The F3 plants were dwarfed, but crossing seemed to bring back the vigor that the varieties originally possessed. From about 9,000 seedlings that resulted from crossing the F3, promising selections have been made and are being given field trials in different sections.
At the Maine station, breeding work was begun in 1934 to obtain better late varieties. At the Massachusetts station, breeding work was also begun in 1934 to obtain late varieties of better dessert quality and also better pistillate sorts.
In Illinois, breeding work to obtain varieties resistant to brown stele root rot was started in 1935. Mastodon, Aberdeen, and Redheart, which appear resistant, have been used in crossing.
In Wisconsin, breeding was begun in 1933 to obtain productive early and late commercial sorts. Howard 17, Beaver, Corvallis, and Vanguard have been used as parents.
In Missouri, though some crossing was done at the Mountain Grove station in 1902 and 1919, no varieties were introduced. In 1936 selections of the meadow strawberry, (Fragaria virginiana), were crossed with Aroma, Blakemore, Fairfax, Dorsett, Chesapeake, Howard 17, and Joe, to obtain varieties with the resistance to cold, drought, and disease, and the high flavor of the wild strawberry.
In North Dakota, small-fruit breeding began in 1920 and has continued to the present. The Dry Weather variety, resistant to drought, was introduced in 1928. Resistance to winter cold, summer heat, and drought is being emphasized.
In Tennessee, strawberry breeding began in 1923 and has continued to the present. Both selfing and crossing have been carried on to obtain productive varieties hardy in summer, resistant to leaf and root-rot diseases, and with attractive, firm, high-flavored berries suitable for processing and shipping. Some selfed seedlings of Aroma were found to be notably vigorous and productive.
At the Louisiana station breeding work has recently started with the objective of producing varieties resistant to leaf spot and scorch, of good shipping qualities, and sweeter than Klondike.
In Texas breeding work began in 1933 to obtain varieties resistant to heat, drought, and leaf spot, and that would produce sufficient runners under the climatic conditions of southern Texas.
In Washington State, at Puyallup, strawberry breeding was begun in 1929 and has been continued to the present. The objectives have been firm- and soft-fruited, high- and low-yielding, and red- and light-fleshed varieties.
In Oregon, at Corvallis, breeding work has been carried on in cooperation with the Federal work since 1928. Previously, however, the Corvallis variety was originated by C. E. Schuster from a cross between Marshall and Ettersburg 121. Schuster noted that Ettersburg 121 transmitted its vegetative characteristics with remarkable uniformity.
The Central Experimental Farm of the Dominion of Canada at Ottawa and several of the provincial experiment stations, notably the Ontario Horticultural Experiment Station at Vineland, have. carried on strawberry breeding more or less continuously for many years. Several recent selections made at Ottawa are being extensively tested (21). At Vineland some 30,000 seedlings of 300 crosses and 60 open and self pollinations were raised, 340 selections were made, and several named (59). Two, Vanguard and Vanduke, were grown to some extent at one time.
Among private breeders in England, the firm of Laxton Bros., at Bedford, has been prominent for its berry breeding for over 50 years, and the varieties of strawberries originated by the firm have long been important in Great Britain as well as on the continent of Europe, in Australasia, and in other parts of the world. Among these, Noble, Royal Sovereign, Scarlet Queen, Leader, Fillbasket, The Laxton, Latest, Bedford Champion, and The Duke have been particularly important varieties. Royal Sovereign is one of the parents of Dorsett and Narcissa and possibly of Fairfax (16) also.
Strawberry breeding by public agencies in England is being carried on at the Long Ashton Research Station, University of Bristol, at the Horticultural Research Station at East Malling, Kent, and at the John Innes Horticultural Institution, Merton. The earliest work was that by C. W. Richardson from 1910 to 1922, on inheritance of characteristics in the species having seven pairs of chromosomes and to some extent in cultivated varieties. Spinks carried on rather extensive breeding work at the Long Ashton station. By 1923 some 5,000 seedlings had been raised and 145 selections made. He noted that Leopold transmitted its resistance to aphids, that seedlings of Leopold X Royal Sovereign and President X British Queen were susceptible to mildew, but that seedlings of Leopold x Stirling Castle were resistant to both aphids and mildew. All seedlings of V. H. de Thury X The Earl and L. Gautier X White Perpetual were resistant to mildew, and only 1 in 60 seedlings of V. H. de Thury X King George was susceptible. The seedlings of Bedford Champion X King George, Leader X St. Antoine, and Fillbasket X Bedford Champion were the best flavored.
In Germany three stations are carrying on breeding work with strawberries. At the University Institute for Fruit Culture, in Berlin, quick- and early-ripening varieties with not too many flowers are being bred for forcing houses. At the Kaiser Wilhelm Institute in Müncheberg the breeding of large, productive, high-flavored everbearers has been started, and studies are being made on methods used in making selections, on inheritance and correlations of different qualities, on sex ratios, and on the periodicity of the growth phases. At the Horticultural Station at Pillnitz, under the direction of Professor Schindler, productive, high-flavored varieties that hold their color, that are resistant to unfavorable weather conditions, and that ship well are the objectives. Six varieties have been named and introduced from this station.
At the Hawkesbury Agricultural College, New South Wales, breeding for resistance to diseases such as root rot and leaf scorch is a primary objective. Seedlings of Fragaria chiloensis X British Sovereign, Fendalcino X British Sovereign, and Southland X British Sovereign have shown the most promise.
In THE STRAWBERRY, as in other plants and in animals, superior germplasm refers to one or more inheritable qualities that may be desirable or useful to the grower or consumer. Thus, a variety or a species with fine flavor, or resistance to disease or to extremes of high or low temperature, would be counted as having superior germplasm in that respect. Certain characters would be considered undesirable; for example, the one-flowered cluster of Fragaria daltoniana J. Gay. Both of the species from which the common cultivated varieties are derived, F. virginiana and F. chiloensis, as well as F. cuneifolia, are extremely variable in the wild. Cultivated varieties, therefore, have various combinations of characters, desirable as well as undesirable. In general, the scarlet color, high aroma, tart flavor, and wide adaptation to climatic and soil conditions in cultivated varieties are derived from F. virginiana. The history of the strawberry and the success of Etter and Georgeson, who have used new selections of F. chiloensis, indicate that there may be many desirable characters in the wild forms of this species that have not yet been used. Tests of selections of F. cuneifolia and of hybrids with it indicate cold and drought resistance, everbearingness, and quickness of response to warm spring temperatures in this species (figs. 15 and 16). These desirable qualities might extend both the range of cultivation and the fruiting season of strawberries. As yet the collections and tests of F. cuneifolia are too limited to fully evaluate these and other qualities that it may have. However, hybrids of F. cuneifolia with cultivated varieties have made strawberry production possible even at Fairbanks, Alaska (30). Because native species often are rather difficult to keep alive, crosses showing hybrid vigor may be useful in holding their superior germplasm in breeding stock. Fragaria chiloensis is susceptible to cold injury in Maryland. Its hybrids with Fairfax and Blakemore are vigorous and are used as a source of the characters of F. chiloensis in the Federal breeding work. Because F. cuneifolia becomes everbearing at low elevations, it makes few runner plants, and for this reason, too, hybrids serve as a source of its characters. Some of these hybrids and other selections having superior germplasm are listed in the appendix.
Studies indicate that a variety or species showing any characteristic actually will transmit the character to a large proportion of its seed- lings. Crosses of varieties and. species, as well as genetic research, support the supposition that in the strawberry most qualities of importance in breeding are quantitatively inherited, that is, that there are genes for such qualities as flavor, color, size, firmness, etc., in each, or in many at least, of the eight homologous chromosomes (one pair in each four sets), and they have a cumulative effect. For example, it is as if the dark Redheart contained a gene for color in seven of the eight chromosomes, the less dark but still deep-red Dunlap in six of the eight, the medium-red Dorsett in five of the eight, the light-red Blakemore in four of the eight, and the White Sugar in about two of the eight. If Redheart is crossed with a dark- fruited variety, the seedlings are mostly dark-fruited; if it is crossed with a light-fruited variety, the seedlings are mostly intermediate. In making crosses, therefore, breeders have learned that if a variety shows any desirable quality, in general that quality can be transferred to any other variety if a large enough number of seedlings (crosses between the two) are raised. Sometimes the seedlings nearest the ideal are backcrossed with one or the other parent before the desired character is obtained. The results published by Spinks (57, 58) and by Richardson (50, 51) in England indicate that it is easier to obtain many qualities in certain crosses than in others. Thus, Bedford Champion X King George V gave 80 productive seedlings out of 235, while Royal Sovereign King George V gave only 8 out of 114. Richardson obtained seedlings with the highest flavor from a cross of Filbert Pine X King of the Earlies. Until the genetic constitution of varieties is worked out, the location of superior germplasm must be assumed to lie only in varieties that show it.
Because of the apparent quantitative inheritance of characters in the strawberry, a scoring system is used in the Federal breeding work to evaluate the qualities. A similar system was used by Keffer in Missouri in 1893. For flavor, color, firmness, resistance to leaf spot, resistance to leaf scorch, and vigor, seedlings are scored on a scale of 1 to 10, 1 representing best and 10 worst. Thus, at Beltsville, Md., Missionary might score 3 in resistance to leaf spot, Fairfax 1.5, Howard 17 also 1.5, Marshall about 8, and Beaver 8. For flavor, Dorsett would score 1, Howard 17 about 3, and Lupton 5. Richardson in England used such a scoring system for strawberries, although he used 1 as poor and 8 as finest in flavor. Since the vegetative cells of garden strawberries contain eight sets of chromosomes (seven to a set, 8 X 7 = 56 chromosomes), Richardson’s scoring corresponds to the number of sets.Figure 16.—Crosses of the Rocky Mountain strawberry, Fragaria cuneifolia, with the Marshall variety.
Though in years past it may not have seemed possible to have most of the desirable qualities of the strawberry in any one variety, it now seems practicable to get most qualities in breeding stocks and then cross these to obtain combinations of the qualities desirable for certain conditions. The history of the strawberry bears out this conclusion. Thus, the origination of the Wilson is considered, to have made it possible to obtain varieties both firm-fruited and productive for different regions. The Howard 17 has added high resistance. to diseases in Northern States to the superior germplasm. Possibly within the next few years breeding stocks may have, in addition to the fairly firm fruit, the productivity, and the disease resistance already obtained, (1) the cold-hardiness of the Progressive and of Fragaria cuneifolia; (2) the heat resistance of Missionary; (3) the drought resistance of F. cuneifolia and of U.S. D. A. 1791; (4) the smoothness of flesh of Corvallis; (5) the dessert quality of Rockhill in Minnesota and of Dorsett in Maryland; (6) the size of Marshall in the Pacific Northwest; and (7) the tough skin of Redheart. Later breeding may then add qualities for specific regions or uses, as the bright color of Blakemore for a preserving and shipping sort; the deep color of Redheart for a canning sort; the peculiar flavors—like grapes, apricots and red and black raspberries—of crosses of USDA 652 for novelties; the short-day adaptation of the Missionary for Florida; the longer day adaptation of Howard 17 for other regions; and the everbearingness and runner production of Mastodon.
In Europe the source of superior germplasm may also be indicated by the qualities for which outstanding varieties are known. Thus, British Queen and Dr. Hogg are considered to have the finest flavor, while Royal Sovereign and Paxton have the best flavor of the widely raised sorts; The Duke, an early, and Waterloo, a late variety, are often considered drought-resistant; Noble retains its color especially well in cooking and is one of the finest flavored and most widely adapted sorts; H. Vicomtesse de Thury (Stirling Castle), Deutsch Evern, and Little Scarlet are considered the best for jam and are very rich-flavored; Laxton's Latest, Late Leopold, Waterloo, and Givon’s Prolific are very late sorts; Deutsch Evern and Royal Sovereign are superior forcing varieties; Mme. Kooi is very large and one of the most productive but is soft and of poor quality; Laxton's Latest is of the largest size; and Royal Sovereign, Sir Joseph Paxton, and Dr. Morere are widely grown, productive main-crop sorts, the Sir Joseph Paxton being frost-resistant. Late Leopold also escapes spring frosts. The Laxton grows where most other sorts do not succeed. Deutsch Evern is one of the best for preserving.
Tues has been little satisfactory interpretation of the inheritance of characters in the strawberry, although there has been considerable study of the matter (3,4,5,6). This is because most of the characters such as color, size, shape, and structure of berry are quantitative and determined by several genes. Three pairs of contrasting characters, however, are available for study.
Femaleness versus various degrees of hermaphroditeness has been extensively studied. In most cases when a hermaphrodite variety is selfed only hermaphrodite seedlings are obtained (2, 9,37). Femaleness X hermaphroditeness gives in most cases at least a 1 to 1 ratio, apparently indicating a single pair of allelomorphs located in a single pair of chromosomes. However, hermaphroditic varieties and seedlings represent an unbroken series from complete fertility to complete sterility of the pistils, and a satisfactory genetic explanation is yet to be made. If the chromosome sets of the cultivated strawberry are not now identical, and if pairing takes place between chromosomes in different sets of seven, then more or less sterility would be expected.
The unbroken series from complete sterility to complete fertility indicates that random pairing between all the chromosomes of all four sets actually occurs.
A second pair of contrasting characters is June-bearing versus everbearing. Everbearing varieties X everbearing varieties gave at Ottawa, Canada, 85 everbearing to 66 June-bearing, while everbearing x June-bearing and June-bearing X everbearing gave 257 everbearing to 788 June-bearing. The everbearing varieties are evidently heterozygous and the June-bearing homozygous. Assuming that everbearingness is due to two dominant complementary genes, A and B, then the everbearing would have the composition AaBb and, selfed, would give a 9 to 7 ratio, which was found, 85 everbearing to 66 June-bearing, When June-bearing are crossed with everbearing, a 1 to 3 ratio would be expected, or 261 everbearing to 783 June-bearing, which is very close to the 257 everbearing and 788 June-bearing actually found.
In England, Richardson selfed both the everbearer St. Antoine de Padoue, getting 108 everbearing to 22 June-bearing, and the everbearer Laxton Perpetual, getting 69 everbearing to 11 June-bearing. When he crossed a June-bearing Bedford Champion with an everbearing Laxton Perpetual he got 24 everbearing to 53 June-bearing. One of these June-bearing F1 plants, when selfed, gave 8 June-bearing to 6 everbearing. These numbers indicate (1) that his everbearers did not have the same genetic constitution as those at Ottawa, Canada, and (2) that more than two and probably four complementary genes were involved, or that, if there were only two genes for everbearingness, they were linked. However, too few numbers have been raised for definite conclusions.
A third set of contrasting characters may possibly be useful in studies on inheritance, namely, normal versus variegated or chlorotic leaves. Richardson and Clark have made some studies on their inheritance. However, enough records have not yet been secured to indicate the genetic composition of a variegated plant.
Although about 150 species names have been applied to the strawberry, the most recent monograph (42) described but 45, a number that
is undoubtedly much too large. This monograph lists 4 species for
Europe, 26 for North America, 1 for South America, and 15 for Asia.
However, many of these can hardly be separated from one another
and a total of about eight includes all the distinctive species. These
eight belong to three groups as follows:
Fragaria vesca (wood strawberry) group, 7 pairs of chromosomes:
1. F. daltoniana J. Gay, southern Asia.
2. F. nilgerrensis Schlecht., southern Asia.
3. F. vesca L., circumpolar.
Variety semperflorens Duch., Alps.
F. californica? Cham. and Schlecht., North America.
4. F. viridis Duch. (F. collina Ebrh.), central Europe.
Fragaria moschata (open wood strawberry) group, 21 pairs of chromosomes:
5. F. moschata Duch. (F. elatior Ebrh.), central Europe.
Fragaria virginiana (cultivated strawberry) group, 28 pairs of chromosomes:
6. F. chiloensis(L.) Duch., coast of Alaska to central California, southern Chile, mountains of Hawaii.
7. F. cuneifolia Nutt. (F. platypetala Rydb.), Rocky Mountains.
8. F. virginiana Duch., eastern North America.
Though these eight may include all the wild species, a final classification must await extended field studies of Asiatic forms. Six of the species are illustrated in figures 17 and 18.
The first four species have seven pairs of chromosomes (40, 62, 64) and are in general smaller plants with thinner leaves and smaller fruit than American cultivated varieties. Fragaria daltoniana, F. collina, and F. nilgerrensis belong to the F. vesca group and so far have not appeared to have qualities of value for breeding. F. daltoniana is unproductive, since it has one-flowered flower clusters. The fruit of F. collina is very small, and the plants have not survived in Maryland. The berries of F. nilgerrensis are many-seeded and rather tasteless. The plant, however, is vigorous. A number of varieties of the everbearing F. vesca var. semperflorens are grown to some extent in Europe. Though the fruit is smaller than that of American cultivated sorts, it is aromatic and borne freely throughout the summer in the climatic conditions of northern Europe, but it has not been successful in the United States. The fruit of F. vesca and F. californica is small—too small to be worth while.
Varieties of Fragaria moschata, the open wood strawberry of Europe, which has 21 pairs of chromosomes, are cultivated to some extent in European gardens for their very aromatic vinous-flavored fruit. Though the fruit is small, it is larger than that of the alpines. Varieties like Royal Hautbois and Black Hautbois grow fairly well in the northern United States if protected in the winter, but they have never succeeded commercially. La Constante, a French variety supposedly derived from F. chiloensis X F. virginiana, is reported to have much of the vinous flavor of F. moschata and may possibly be a source of this flavor for breeders.
Species with 14 pairs of chromosomes have not been known in the wild until recently, when Fedorova (27) reported that Petroff found a form with 14 pairs of chromosomes, which he referred to as Fragaria orientalis A. Los. Los., an eastern Asiatic species formerly classified with botanical varieties of F. vesca. Longley has suggested that the ancestral strawberry from which the others descended was close to F. vesca. This has the basic number of 7 chromosomes in the germ cells (diploid number 14). Lilienfeld (39, 40) recently has apparently proved that F. moschata (F. elatior), which has 21 chromosomes in the germ cells (diploid number 42), actually was derived in ages past from species with 7 pairs of chromosomes. He reached this conclusion because, in crossing a species having 7 pairs of chromosomes with one having 21 pairs of chromosomes, 14 chromosomes of F. moschata paired with 14 from the vesca type, and 2 sets of 7 from F. moschata paired with 2 other sets just as though they were a 14-chromosome species. The resulting seedlings were fertile and constitute a new species with 14 pairs of chromosomes named by Lilienfeld F. elnipponica Lil. (derived from F. elatior, a synonym of F. moschata, and F. nipponica Mak., which is a Japanese form of F. vesca). Yarnell also raised 14-chromosome seedlings from F. bracteata X vesca var. rosea, and Fedorova (27) 14-chromosome seedlings from F. vesca X moschata.
In a similar manner East (26) was able to get pairing of one set of chromosomes from F. vesca (n=7) with a set from (F. virginiana) (n=28). Though the resulting diploid seedlings were not as fertile as seedlings of F. vesca, the chromosomes were actually related closely enough to pair. Apparently through the ages since the 28-chromosome species originated, some changes have occurred in the chromosomes, but not enough to prevent pairing.
The only known species with 21 pairs of chromosomes is Fragaria moschata, which has been discussed above.
(Fragaria virginiana), F. cuneifolia, and F. chiloensis, the group from which the cultivated strawberry has descended, each has 28 pairs of chromosomes. F. cuneifolia is the Rocky Mountain wild strawberry, native from Arizona to Alaska and Colorado to Oregon. It has been used. very little in breeding. However, its resistance to low winter temperatures and drought and its everbearing character at low elevations indicate its potential value.
Many attempts have been made to cross Fragaria vesca and moschata with the cultivated strawberry. Such crosses have actually been made, but in carefully controlled tests the seedlings have been entirely or nearly sterile. However, evidence indicates that all four sets of chromosomes of the cultivated strawberry and of the species with 28 pairs of chromosomes had a common origin and are probably homologs of those of F. vesca. It seems entirely possible that in some cases where cultivated varieties have been crossed with varieties of F. vesca, true hybrid seedlings may have originated by a substitution of 7 chromosomes of F. vesca for a set of 7 of the mother plant, and, by a subsequent doubling of the 28, a seedling with the full 28 pairs developed. If the sets are homologs, as suggested by Longley (41) and East (25) and if those of F. vesca should pair with those of the cultivated strawberry, the differences in seedlings might be so slight as to be unnoticed. The everbearing crosses (Chesapeake X F. vesca and Early Jersey Giant X F. vesca) reported by Van Fleet may have had such an origin, for neither Chesapeake nor Karly Giant seedlings would be expected to be everbearing.
Figure 17.―Native American strawberry species: A,B, (Fragaria virginiana), of eastern North America: C, D, F. cuneifolia, of western North America; E, F, F. chiloensis, of the beaches from Alaska to California and of Chile. These are the three 56-chromosome species, from two of which the cultivated strawberry has descended.
Figure 18.―European and Asiatic strawberry species: A, B, Fragaria nilgerrensis, a 14-Chromosome strawberry of southern Asia: C, D, F. vesca, the 14-Chromosome wood strawberry of Europe; E, F, F. moschata, the 42-chromosome open wood strawberry of Europe. F. nilgerrensis is a rather tasteless strawberry but may possibly be of use for breeding. From an everbearing form of F. vesca have originated the small alpine strawberries grown in the gardens of Europe. From F. moschata have come the high-flavored, rather small Hautbois varieties of Europe.
Yarnell (63) studied the chromosomes of strawberries in an attempt to find constant differences among them and concluded that the only constant difference was in length.. He found that their small size, their shape, and their position made even an estimate of length difficult. He found the chromosomes of different species very similar. The length averaged 1.7, 1.5, 1.4, 1.3, 1.2, 1.0, and 0.9 microns. The two shorter and the longest were usually easy to distinguish, but the others were not.
Longley (41), Yarnell, and Lilienfeld (40) all suggest that the chromosome sets in the species with 21 pairs and 28 pairs of chromosomes are homologs. Longley notes also that variability is associated with polyploidy and that the species with 7 pairs of chromosomes are much less variable than the species with 21 or 28 pairs of chromosomes. The diploid Fragaria are perfect-flowered, and sex differentiation occurs only in polyploid forms. So far as the wild forms are known, the species with 21 pairs and those with 28 pairs of chromosomes are far more variable than the forms with 7 pairs of chromosomes, and it is evident that variability has come in with polyploidy.
Millardet (45) in France, Richardson (48, 49, 50, 51) in England, Solms-Laubach (46) in Austria, and Schiemann (54) in Germany have made crosses between species of the different chromosome groups. However, the crosses made at the Bussey Institute by East and by two of his students, Mangelsdorf (43, 44) and Yarnell (62, 63, 64, 65), and reported by these investigators and by Ichijima (33, 34), cover most of the species crossed. An outline of the crosses reported by them follows:Hybrids within the groups having 7 and 28 pairs of chromosomes8
Species with 7 pairs of chromosomes:
Fragaria californica Cham. and Schlecht. X bracteata Heller (= californica), F1 fully fertile.
F. californica Cham. and Schlecht. X vesca rosea Rostr., F1 fully fertile.
F. collina Ehrh. (= viridis) X maxima (?), F1 flowered.
F. collina Ehrh. X nilgerrensis Schlecht., F1 vigorous.
F. mexicana Schlecht. (= vesca) X americana alba Clute (= vesca alba or vesca americana alba), F1 fully fertile.
F. americana alba Clute X mexicana Schlecht., F1 fully fertile.
F. vesca rosea Rostr. X americana alba Porter, F1 fully fertile.
F. vesca rosea Rostr. X mexicana Schlecht., F1 fully fertile.
F. vesca rosea Rostr. X collina Ehrh., F1 partially fertile.
F. vesca L. X vesca rosea Rostr., F1 fully fertile.
F. vesca L. X nilgerrensis Schlecht., F1 dwarfs, no flowers.
F. vesca L. X americana alba Porter, F1 fully fertile.
F. vesca L. X maxima (2?) (= vesca or vesca maxima), F1 partially fertile.
F. vesca L. (Tiflis, Union of Soviet Socialist Republics) X vesca rosea Rostr., F1 fully fertile.
F. bracteata Heller X vesca rosea Rostr., F1 flowered.
F. bracteata Heller X americana alba Porter, F1 fully fertile.
F. bracteata Heller X collina Ehrh., F1 partially fertile.
F. bracteata Heller X maxima (?), F1 partially fertile.
F. bracteata Heller X nilgerrensis Schlecht., F1 dwarfs, no flowers.
Species with 28 pairs of chromosomes:
F. chiloensisDuch. X virginiana Duch., F1 fully fertile.
F. virginiana Duch. X chiloensis Duch., F1 fully fertile.
F. virginiana Duch. X glauca Rydb. (= cuneifolia), F1 fully fertile.
F. chiloensis Duch. X platypetala Rydb. (= cuneifolia), F1 fully fertile.
Mangelsdorf and East reported on hybrids between different chromosome groups—14 x 42, 14 x 56, 56 X 42—and on generic crosses. Fragaria vesca (2n=14) X elatior (= moschata) (2n=42) resulted in no F1 plant that fruited out of 600 seeds. F. vesca (2n=14) X chiloensis (2n=56) resulted in 6 nonblooming seedlings out of over 1,200 seeds. F. americana alba (=F. vesca alba or F. vesca americana alba) (2n=14) X glauca (= F. cuneifolia) (2n=56) gave only 1 plant from 66 seeds, and it did not bloom. F. vesca (2n=14) X glauca (2n=56) gave 5 nonfruiting plants out of 250 seeds. F. vesca rosea (2n=14) X glauca (2n=56) gave 7 nonfruiting plants from 76 seeds. F. vesca (2n=14) X virginiana (2n=56) gave 21 F1 plants from 500 seeds, none of which was fertile. F. bracteata (=F. californica) (2n=14) X virginiana (2n=56) resulted in 10 nonfruiting plants from 24 seeds and 2 pistillate plants that crossed with F. vesca rosea.
(F. virginiana) (2n=56) X elatior (2n=42) resulted in 90 plants from 100 seeds, many of the plants being vigorous; all those considered hybrids were sterile.
Yarnell crossed chromosome groups as follows: 14 X 28, 14 X 42, 14 X 56, 42 X 28, 56 X 28, and 56 X 42. The 14 X 28, 14 X 42, and 42 X 28 proved to be nearly or completely sterile. The 56 X 28 cross gave flowering plants, but none produced pink flowers as would be expected with pink dominant. This is explained by assuming that the crosses were hexaploid (28 X 14)/2 and that there were four recessive factors for color (pppp) and only two dominant factors (PP). In a seedling having the composition PPpppp, the two dominant genes would be unable to function.
Richardson (48) in England obtained normal hybrid segregation in the species Fragaria vesca, with seven pairs of chromosomes. He crossed a trifoliate with a monofoliate plant. The F1 plants were all trifoliate. When these were selfed he got 177 trifoliate to 73 monofoliate instead of the expected 187.5 to 62.5. He also crossed a white- with a red-fruited variety. The F1 plants were red-fruited but when selfed gave 70 red-fruited to 20 white, which is close to the theoretical 67.5 to 22.5. In crosses between single- and double- flowered forms the F1 was single but gave 155 single to 62 double in the F2 instead of 163 single to 54 double. A cross between runnerless and runner-producing gave runner-producing in the F1, but 342 runner- producing to 97 runnerless in the F2 instead of the expected 329 runnered to 110 runnerless. Though the above four characters showed inheritance not far different from the expected 3 to 1 ratio, Richardson had difficulty in classifying his F2 in a cross between pink- and white- flowered plants. Mangelsdorf and East, however, obtained 128 pink and 46 white in a similar cross, which is very close to the expected 3 to 1 ratio. They also crossed red- with white-fruited plants and obtained 102 red-fruited to 56 white-fruited plants instead of 118.5 red to 39.5 white.
Fragaria vesca (n=7) X Duchesnea indica (L.) Focke (n=42) resulted in 30 plants from 500 seeds, 26 being hybrids, all small and weak. F. vesca (n=7) X Potentilla nepalensis Hook. (n unknown) resulted in 2 seedlings from 141 seeds, but both died before flowering. Crosses between the strawberry and the raspberry have been reported, but the proof of such crosses has not been fully established. The so-called strawberry-raspberry is not a hybrid but a low-growing raspberry from China; and the so-called tree strawberry is simply a species of tree, Arbutus unedo L., bearing fruit with a slight resemblance to a strawberry.
Paternal inheritance.—Millardet (23, 24, 45) reported four cases in which the seedlings resembled the male parent. These crosses were Fragaria vesca X Globe, F. vesca X Ananas, F. vesca X chiloensis (n=7 X n=28 crosses), and F. moschata (elatior) X Globe (n=21 & n=28). Though the first two crosses gave sterile seedlings and the last two gave seedlings with reduced fertility, they may have been physiological males or imperfect hermaphrodites. Ichijima (33), working at East’s laboratory, counted chromosomes of several patroclinous hybrids and found them equal to the sum of the haploid numbers of the parents. In a cross of F. vesca (rosea X alba) X virginiana, however, Ichijima found one plant with a somatic number of 56 chromosomes that was close to (F. virginiana) in appearance. Yarnell has also reported two octoploid seedlings from crosses of n=7 X n=28 plants. Longley also reported a cross of F. vesca alba X Aroma where the seedling resembled the male parent and had the same chromosome number. Rygg and Darrow (63) found a considerable percentage (1.2 percent) of such plants out of 3,519 crosses of cultivated varieties X F. cuneifolia, both with parents with 28 pairs of chromosomes. Waldo has also found 5 plants of the maternal, 22 of the paternal, and 6 of the hybrid types in a cross of F. chiloensis X cuneifolia. The full explanation of this appearance of seedlings identical with or very like the male is not yet apparent. However, an observation of Ichijima that the pollen mother cells have two nuclei, and observations by Rudloff (42) that two complete embryo sacs were often seen side by side in (F. virginiana) and F. vesca and that they may fuse, may have some bearing on this.
Pairing of chromosomes in an artificial polyploid—When fertile tetraploids originated as the result of a cross of Fragaria bracteata (= F. vesca californica) X vesca rosea, Yarnell (64) concluded that the four homologous chromosomes paired at random. That is, the sets of seven chromosomes in each species were sufficiently alike so that the long chromosomes from F. bracteata might pair with the long ones from F. vesca rosea, and the short with short. However, a critical review of the vesca group indicates that bracteata might better be classed as a botanical variety, F. vesca californica, coordinate with rosea. If this classification be made, the chromosomes of this hybrid may be considered homologs of these botanical varieties of vesca.
Again in a cross of Fragaria vesca alba (n =7) X virginiana (n= 28), East obtained a diploid hybrid. Nine of the F2 were fertile, three seedlings did not flower for the 3 years they were observed, and seven were sterile. It is noteworthy that a set of seven chromosomes of (F. virginiana) paired with a set of F. vesca alba well enough to form some fertile seedlings. Yarnell also reported diploid hybrids of F. vesca rosea (n = 7) X glauca (= F. cuneifolia) (n = 28) and of F. vesca alba (n = 7) X chiloensis (n = 28).
Pairing of nonhomologous chromosomes.—Yarnell (64) reported that tetraploid plants resulting from crosses of F. bracteata X vesca rosea were crossed with three species having seven chromosomes. The seedlings were triploids with 21 somatic chromosomes. Examination showed that the nonhomologous chromosomes paired. Later he reported other similar instances. Conditions were present—possibly high temperatures—that made possible the pairing of chromosomes that were not homologs, even though pairing of homologous chromosomes only is supposed to be essential to the Mendelian conception of heredity.
Production of homozygotes through induced parthenogenesis.—A single-factor pair, Pp, was found by East (24) and his students to be responsible for pink and white color of flower, and another pair, Rr, for red and white fruit color in the diploid species. In crossing F. bracteata X vesca rosea, a heterozygous red-fruited, pink-flowered plant was obtained. Among the diploid plants produced by crossing (F. bracteata X vesca rosea) X virginiana and X chiloensis there were 12 with red fruit and pink flowers, 3 with white fruit and pink flowers, 7 with red fruit and white flowers, and 2 with white fruit and white flowers. Some, or more probably all, of these diploids were considered to have arisen through induced parthenogenesis, that is, the embryo must have developed without fertilization. At the beginning of development, then, the organism was a haploid, but because the seedlings all proved to be diploids, the haploid chromosomes must have divided. Thus, the seedlings were homozygotes. East (25) points out that if a means can be found for inducing parthogenesis from which homozygous diploids develop, it might eliminate the uncertain and costly methods now employed to obtain plants that are homozygous.
Bud selection in the strawberry has never been a method of obtaining improved varieties or strains, as in apples, oranges, etc. Only a few kinds of bud sports have been observed. Only the probable production of an everbearing sport in the case of the Pan-American and of a noneverbearing sport in the case of the June Rockhill have had economic value. Another kind of sport—variegated foliage—is a serious limitation to the value of such varieties as the Blakemore, Howard 17, and many others.9 Bud sports of many plants result in the appearance in somatic tissue of recessive characters. Thus, in the strawberry, selfed seedlings of varieties that sport to variegated plants show a proportion of yellow seedlings. If, as the evidence given above indicates is probable, most characteristics are quantitative, then a change in a single gene in one of the eight chromosomes is not likely to make enough of a change in the external appearance of the plant to be noted or measured.
|Glenn Dale and Beltsville, Md||W. Van Fleet, George F. Waldo||George M. Darrow|
|Corvallis, Oreg.||R. H. Roberts, V. R. Gardner, C. E. Schuster, B. S. Pickett, G. L. Rygg, George M. Darrow||George F. Waldo|
|LeRoy Powers, A. V. Hildreth|
|Alaska, Sitka||C. C. Georgeson||[blank]|
|California, San Jose and Davis||William T. Horne, A. G. Plakidas||V. Goldsmith, H. E. Thomas|
|Connecticut, New Haven|
|D.F. Jones, W. R. Singleton|
|Florida, Plant City||A.N. Brooks||[blank]|
|Georgia, Experiment||J. G. Woodruff||H.P. Stuckey, H. L. Cochran, J.E. Bailey|
|Illinois, Urbana||J.E. Vaile||A.S. Colby|
|Iowa, Ames||J.L. Budd, G.A. Ivins||[blank]|
|Louisiana, Baton Rouge|
|J.C. Miller, W. D. Kimbrough, G. Plakidas|
|Maine, Orono||R.M. Bailey|
|Massachusetts, Amherst||A.P. French|
|Minnesota, Excelsior||Charles Haralson, M.J. Dorsey, W. D. Valleau||A.N. Wilcox, W. H. Alderman, E Angelo, W. G. Brierley, F. E. Haralson|
|Columbia||J.W. Clark, C.A. Keffer||[blank]|
|Paul H. Shepard, Guy Rook|
|Nebraska, Lincoln||H.F. Howard, C.C. Wiggins||[blank]|
|New Hampshire, Durham||W.F. Massey|
|New Jersey, New Brunswick|
|J. H. Clark|
|New York, Geneva||C. J. Hunn, S.A. Beach, W. Paddock, R. D. Anthony, O. M. Taylor||George L. Slate, R. Wellington|
|North Carolina, Raleigh||W. F. Massey||[blank]|
|North Dakota, Fargo|
|A. F. Yeager, D. H. Scott|
|Ohio, Wooster||Paul Thayer||[blank]|
|Rhode Island, Kingston||F. W. Card, G.E. Adams|
|South Dakota, Brookings||Charles Haralson||N. E. Hansen|
|Tennessee, Knoxville||J.A. McClintock, E. M. Henry||B.S. Drain, C. D. Sherbakoff|
|Texas, Winter Haven|
|E. Mortensen, S. H. Yarnell|
|Vermont, Burlington||M.B. Cummings, E.W. Jenkins||[blank]|
|Washington, Puyallup||M. B. Hardy||C. D. Schwartze|
|R. H. Roberts|
|Dominion Experimental Farm, Ottawa||W.T. Macoun, A.J. Logsdail||M. B. Davis|
|Nova Scotia, Kentville|
|Alberta, Lacombe||F.H. Reed|
|British Columbia, Sidney||F.E. Buck||E.M. Straight|
|W. R. Leslie|
|Vineland||F.S. Reeves||W. S.Strong, E. F. Palmer|
|Guelph||D. A. Kimball||[blank]|
|Long Ashton, Bristol||C. W. Richardson||J. G. Maynard, G. T. Spinks|
|East Malling, Kent|
|W. S. Rogers|
|John Innes Horticultural Institution, Merton||[blank]|
|Norway, Njos, Hermansverk||P. Stedje|
|Sweden, Alnarp||C. G. Dahl|
|Berlin, Institute for Tree Fruits of the University|
|Muncheberg, Kaiser Wilhelm Institute for Genetics||Dr. Rudorf|
|Pillnitz, Research Station for Garden Plants||Prof. Schindler|
|Switzerland, Geneva||F. Chodat|
|Union of Soviet Socialist Republics:|
|N. Ia. Federova|
|Mitchurin Institute||A. Petrov, V. G. Lithovitzer|
|Japan||H. Kihara, K. Ichijima||F. A. Lilienfeld|
|Australia: New South Wales, Sydney|
|Location||Variety||Year introduced||Parentage||Superior qualities||Estimated acreage|
|Federal station: Beltsville, Md.||Blakemore||1929||Missionary X Howard 17||Firm, light red, preserving, southern||16,000|
|Bellmar||1931||Missionary X Howard 17||Attractive, good flavor, large||200|
|Southland||Ettersburg 80 X Howard 17||Attractive, high flavor in South, disease resistant||50|
|Redheart||Portia X Euresko||Very firm, canning, resistant to crinkle||700|
|Dorsett||1932||Howard 17 X Royal Sovereign||Vigor, high flavor, disease-resistant||4000|
|Oxheart||1933||Firm, deep red, high flavor||None|
|Alaska, Sitka||President Harding||-----||Hollis X Fragaria chiloensis||Productive in Alaska; firm, high flavor||[blank]|
|Minnesota, Excelsior||Duluth||1920||Pan American X Dunlap||Productive, everbearer, hardy.||Small|
|Minnesota||Dunlap X Pocomoke||Productive, attractive, high flavor.|
|Minnehaha||Minnesota X Abington||Vigorous, hardy, large, firm, late.|
|Chaska||1922||(Dunlap X Pocomoke) X Brandywine||Attractive, high quality.|
|Easypicker||Dunlap X unknown|
|Nokomis||Dunlap X Abington||Productive, large.|
|New Jersey, New Brunswick||N.J. 35||1936||-----------------------------------||Attractive, productive.||20|
|New York, Geneva||Hunn||1895||Johnson Late X Sharpless||Late, attractive.||None|
|Prolific||1908||Sample X Marshall||Very productive, attractive.|
|Magnus||1910||Hunn X Marshall||High flavor, large.|
|Quality||Hunn X Atlantic||High flavor, late.|
|Addison||1918||President X Marshall||Productive, mild, large|
|Alden||Productive, glossy, large|
|Arcade||Productive, firm, large.|
|Argyle||Productive, glossy, large|
|Athens||Productive, bright red, large|
|Aurora||Seedling of Prolific||Vigorous, firm, large|
|Beacon||1923||President X Marshall||Early, large, attractive.||Small|
|Bliss||Chesapeake X Atkins||Late, high flavor, attractive.|
|Bouquet||Chesapeake X Pan American||Firm, productive.||Few acres|
|Caledonia||1929||Marshall X Howard 17||Preserving||Small|
|Camden||1931||Mild, productive, vigorous.|
|Cato||1929||Vigor, high flavor||10|
|Catskill||1933||Very large, attractive, productive.||500|
|Clermont||1929||Attractive, holds up in size.||100|
|North Dakota, Fargo||Dry Weather||1925||Americus X Howard 17||Sweet, drought-resistant, everbearer||2|
|Oregon, Corvallis||Corvallis||1930||Ettersburg 121 X Marshall||High flavor, fine texture, canner, freezing||150|
|South Dakota, Brookings (31)||Dakota No. 1||1907||Jessie X Manitoba Wild||Possibly hardiest variety||Small|
|Dakota No. 2||Glen Mary X Cavalier Wild||Hardy||None|
|Tennessee, Knoxville||McClintock||1932||Aroma selfed||Large, productive||Small|
|Dominion Experimental Farm, Ottawa||Bianca||1913||-----------------------------------||-----------------------------------||None|
|Cassandra||Seedling of Bubach||Large, glossy, late, attractive||Some|
|Cordelia||Seedling of Bubach||Deep salmon color, productive|
|Desdemona||Dark red, good flavor|
|Hermia||Seedling of Wm. Belt||Firm, attractive|
|Julia||Seedling of Bubach||-----------------------------------|
|Luc[r?]etta||Seedling of Bubach||Firm, attractive|
|Ophelia||Seedling of Wm. Belt||Large, bright scarlet.|
|Portia||Firm, excellent canner.||Some|
|Virgilia||Deep red, large|
|Alberta, Lacombe||Lacombe||1928||Late Stevens X Dunlap||Hardy, good preserver||[blank]|
|British Columbia, Sidney||New Victoria||1930||Royal Sovereign X Magoon||Large, firm, drought-resistant.|
|Guelph||O.A.C.||1925||Parsons X Howard 17||Large, glossy, red||[blank]|
|Vineland||Valentine||1919||Williams X Brandywine||Excellent flavor||None|
|Valet||Large, similar to Joe|
|Valiant||Brandywine X Williams||Oval, smooth.|
|Valid||Dunlap X Ozark||Large, dark, productive.|
|Valonic||Light, bright color|
|Van Dyke||Early, productive.||Some|
|Vanessa||Dunlap X Brandywine||Large, home use.||None|
|Vanguard||Pocomoke X Ozark||-----------------------------------|
|Vanilla||Dunlap X Williams||Large, attractive|
|Vanquish||Dunlap X Pocomoke||Late|
|Vantage||Williams X Ozark||Large, firm, dark|
|Vaquero||Williams X Dunlap||Large|
|Vassal||Ozark X Williams||Early|
|Vast||Ozark X Michel|
|Vaunt||Brandywine X Michel|
|Vavasor||Pocomoke X Ozark||Large|
|Veda||Sample X Dunlap||Very large|
|Vena||Parsons X Michel||White flesh|
|Vendance||Nettie X Williams||Very late, large|
|Vendor||Dunlap X Ozark||Large, very dark|
|Vendue||Williams X Ozark||High flavor, early|
|Venus||Joe X St. Louis||Large, very late|
|Manitoba, Morden||Rosthern||1929||-----------------------------------||Hardy, large, light color|
|Czechoslovakia, Pruhonice||Prof. Jelinek||-----||M. Moutot X Deutsch Evern||Early, hardy||[blank]|
|Bonmir Landovsky||Kentish Favorite X Deutsch Evern||Early, firm, large.|
|England: Merton, John Innes Horticultural Institution||Richardsons Seedling|
|Germany, Pillnitz||Oberschlesien*||1924||Large, deep red, vigorous, productive|
|Frau M. Schindler|
|Sweden, Alnarp||Inga||1933||Frau Direktor Echtenmeyer X V.H. de Thury||Early, excellent flavor|
|Luna||1934||Late Leopold x V.H. de Thury||Early, excellent flavor, productive|
|Name and address||Variety||Year introduced||Parentage||Superior qualities||Estimated acreage|
|C. H. Beaver, Eau Claire, Wis.||Beaver||1925||Howard 17 X Burrill||Hardy, productive, good shipper||2,000|
|E. C. Howard, and father, A.B. Howard, Belchertown, Mass||Dighton||1908|
|Howard 17||1909||Crescent X Howard No. 1||Early, productive, large, attractive, frost and disease resistant.||32,000|
|Howard Supreme||1929||Howard 103 X Howard 17||Productive, high flavor, excellent for freezing||75|
|J. E. Kuhns, Cliffwood, N. J.||Aberdeen||1923|
|Productive, resistant to brown stele disease||2,000|
|George Voer, Peru, Ind.||Mastodon||1924||Kellog Prize X Superb||Productive, everbearing, produces runners freely||1,000|
|Keith Bros., Sawyer, Mich||Kanner King||1932|
|Dark red, firm, canner.||Small|
|Joan||1933||Ananas de Guemene X Mastodon||Large, everbearing||[blank]|
|Uncle Cap||Mastodon seedling||Large, sweet, everbearing.|
|H. Rockhill, Conrad, Iowa||Francis||1910||Louis Gautier X Pan American||Very good flavor, everbearing, early.||None|
|Americus||1911||Excellent flavor, everbearing|
|Iowa||Dunlap X Pan American||Everbearing|
|Progressive||Pan American X Dunlap||Everbearing, vigorous, very hardy, excellent flavor, early, healthy.||200|
|Rockhill (Wazata)||1922||Progressive X Early Jersey Giant||Everbearing, large, one of best flavored berries in the United States, large, disease-resistant, very hardy.|
|June Rockhill||1932||Rockhill sport||Noneverbearing, but like Rockhill otherwise||Small|
|Gardner Nurseries, Osage, Iowa||Red Gold||1925||Howard 17 X Everbearer||Sweet, large.||[blank]|
|Everbearing, propagates freely.|
|Gardner 999||1925||Everbearing, high flavor.|
|W. Kosuga, Sandy, Utah||Berri Supreme||1929||Everbearing||20|
|Twentieth Century||1936||Berri Supreme X Rockhill||[blank]|
|A. F. Etter, Ettersburg, Calif||Rose Ettersburg||1903||(Sharpless X Parry) F3 X Fragaria chiloensis, Peru||Vigorous, productive, fragrant, drought-resistant||None|
|Ettersburg 121||1907||Derived from (F. chiloensis)X ?||Vigorous, many crowns, hardy foliage, best canner in United States, solid, high flavor, very late.||250|
|Ettersburg 80||1912||In part at least from Rose Ettersburg and a selection of F. chiloensis||Vigorous, large, healthy foliage, solid flesh, large||Little in the United States, but some in Australasia.|
|Nor-J||1913||Fendall X Ettersburg 121||Productive, firm||None|
|Ettersburg 76||(Michel* X Rose Ettersburg) x F. chiloensis|
|Ettersburg 84||Sister to Ettersburg 80||Vigorous|
|Ettersburg 89||1913||Dornan and F. chiloensis||Vigorous, few runners|
|Ettersburg 111||Sister to Ettersburg 80||Productive, drought-resistant|
|Ettersburg 112||Large, glossy|
|Ettersburg 91||1914||Deep red, high flavor, drought-resistant|
|Cap or calyx stays on plant, light pink.|
|Ettersburg 75||(Michel* X Rose Ettersburg) x F. chiloensis||Red to center, firm.|
|Ettersburg 79||Deep red, high flavor.|
|Ettersburg 88||Wm. Belt cross||Deep red, canning variety|
|Ettersburg 93||Sister to Ettersburg 80||Deep, glossy red|
|Ettersburg 94||Rose Ettersburg X F. chiloensis||Very attractive, acid|
|Ettersburg 108||Vigorous, pink, evergreen|
|Ettersburg 114||Rose Ettersburg X Michel* X ?||Similar to Ettersburg 94|
|Ettersburg 116||Sister of Ettersburg 94|
|Ettersburg 200||Dunlap X F. chiloensis, Peru||Pink, productive, deep-set seeds|
|Ettersburg 24 (Michel X Rose Ettersburg) cross|
|Excellent flavor, large, firm, attractive.|
|Sweet, very firm.|
|Euresko (Eurisko)||1916||Chesapeake X Ettersburg 20 (Rose Ettersburg X F. chiloensis)||Deep red to center, firm.|
|Beaderarena||F. chiloensis X Bederwood||Very hardy foliage, attractive|
|Califour||1918||Ettersburg 88 X 2||Deep red, black-raspberry flavor.|
|Juicy, high flavor, late.|
|Fendalemo||Deep red, vigorous|
|Seedling of Beaderarena||High flavor, sweet|
|Fantastic||1918||Fendall X Ettersburg 121||Vigorous, large|
|Ossie||Seedling of Ettersburg 84||Meaty flesh, early, showy|
|Cream||1920||Ettersburg 330 Trebla||Yellow cream color, productive, late|
|Fendalcino||Fendall X Ettersburg 121||Large, resistant to heat, productive.|
|Kalicene||Ettersburg 216 X Trebla or Ettersburg 121 X Trebla||Early, solid flesh, very productive, red center, vigorous.|
|Lnge||Unknown||Canning, solid, brilliant red, firm|
|Red Cross||Ettersburg 216 X Trebla||Very glossy, sweet, attractive, uniform shape|
|Rena||Probably F. chiloensis X Ettersburg 84||Light pink, similar to F. chiloensis, late|
|Trebla||1916||Ettersburg 114 X Ettersburg 84||Firm, solid, productive, frost-resistant.||Small|
|White Sugar||1920||Unknown||White to pink, sweet, firm, large, late||None|
|Cross of Ettersburg 80|
|Late Cross||Seedling of Red Cross||Late, resembles Ettersburg 80.|
|Redfour||Ettersburg 121 X Trebla||Large, canner, early.|
|Von Humboldt||1930||(Rose Ettersburg X F. chiloensis) X cross of similar parentage||Evergreen, heavy foliage, vigorous.|
|Red Sugar X Kalicene||Meaty|
|Wickson||1930||(Red Sugar X Ettersburg 121) x F. cuneifolia||Evergreen, heavy foliage, firm.|
|Red Sugar X Kalicene||Firm, high flavor, firm|
|Deep red, firm, canning|
|New Deal||1935||Probably Red Sugar X Ettersburg 121 or Trebla|
|Gracilis||F. chiloensis hybrid|
|Thomas Laxton, Bedford, England||Traveller||1872||La Constante X Napier||Deep scarlet|
|Noble||1884||Seedling of Sharpless||Large, attractive, productive, wide adaptation.|
|Captain||Crown Prince X Foreman Excelsior||Most attractive of all, early|
|A.F. Barron||1885||Sir J. Paxton X Sir C. Napier||Glossy, scarlet|
|King of the Earlies||1888||Vicomtesse X Black Prince||Very early, high flavor|
|Commander||1889||British Queen X President||High flavor|
|Competitor||1890||Kerr Prolific X Foreman Excelsior|
|Scarlet Queen||1891||King of the Earlies X Noble||Early, attractive, high flavor.|
|White Knight||Light scarlet X white|
|Royal Sovereign||1892||Noble X King of the Earlies||Large, bright, scarlet, firm, high flavor|
|Latest of All||1894||British Queen X Helena Gloede||Late, very large, crimson, productive.|
|Monarch||1895||Latest of All X Captain||Large, attractive|
|Leader||Latest of All X Noble||Large, deep crimson, sweet.|
|Laxton No. 1|
|Noble X May Queen||Earliest|
|Bedford Champion||1895||Seedling (Scarlet Queen X John Ruskin) X seedling (Noble X Sir J. Paxton||Very large, scarlet, sweet.|
|Mentmore||1897||Noble X British Queen||Crimson|
|Fillbasket||Royal Sovereign X Latest of All||Scarlet, productive|
|Reward||1898||Royal Sovereign X British Queen||Large, high flavor, attractive|
|Trafalgar||1900||Latest of All X ?||Late, large, attractive.|
|Climax||1901||Latest of All X Waterloo||High flavor, large, firm.|
|The Laxton||Royal Sovereign X Sir J. Paxton||Large, firm, vigorous|
|Dr. Hogg X Napier||High flavor, scarlet.|
|Latest||1904||Latest of All X seedling||Very large, week later than Waterloo.|
|Progress||1906||British Queen X Latest of All||Late, bright scarlet, large.|
|Cropper||1907||Seedling X Fillbasket||Productive, large, crimson|
|Reliance||Vv. H. de Thury X seedling of St. Joseph||Productive, scarlet|
|Perpetual||Monarch X St. Joseph||Large, sweet|
|Profit||1908||Sir J. Paxton X Countess||Firm, productive, deep scarlet.|
|Rival||1909||Givons Late X Royal Sovereign||High flavor, late, deep scarlet.|
|Utility||Seedling 500 X Waterloo||Firm, high flavor.|
|Connoisseur||Scarlet Queen X Fillbasket||Excellent flavor, bright scarlet|
|Epicure||British Queen X Fillbasket||Excellent flavor|
|Excellent flavor, bright scarlet|
|Maincrop||1910||Bedford Champion X The Laxton||High flavor, large.|
|The Earl||1911||Waterloo X Royal Sovereign||Preserving|
|The Admiral||1914||Seedling X Bedford Champion||High flavor, productive, large.|
|White Perpetual||1916||Louis Gauthier X St. Antoine||Nearly white, everbearing.|
|International||Latest of All X Seedling||Bright scarlet, firm, high flavor|
|King George V||Royal Sovereign X Louis Gauthier||Bright scarlet, forcing, early.|
|The Duke||Seedling X Bedford Champion||Early, high flavor, scarlet, forcing|
|The Bit||1918||Reliance X Bedford Champion||High flavor, scarlet|
|Victory||1919||Seedling X British Queen||Crimson, sweet.|
|Sir Douglas Haig||Seedling X Dr. Hogg||Scarlet, yellow seeds, sweet|
|Marshal Foch||1920||The Bedford X Sir Joseph Paxton||Firm, dark.|
|Lord Beatty||Seedling X Bedford Champion||Light red.|
|Laxtonian||(?)1921||Seeding X seedling||High flavor, glossy, crimson, firm, large.|
|Bountiful||1921||D X D||Scarlet, large|
|Abundance||1922||Fillbasket X The Earl||High flavor, large, sweet|
|Omega||1923||Seedling X Bedford Champion||Latest, sweet, scarlet, firm.|
|Majestic||1924||Seedling X International||Bright, crimson, sweet, firm.|
|Rearguard||1925||Latest X Omega||Late, sweet, productive.|
|Robust||Bedford Champion X Bedford||Crimson, sweet.|
|Empress||Seeding X seedling||Firm, preserving.|
|Prolific||1926||Scarlet, sweet, resists mildew.|
|Duchess of York||1927||Laxtonian X Duke||Bright scarlet, drought-resistant|
|Primate||1928||Seedling X seedling||Firm, sweet, bright crimson.|
|The Queen||Waterloo X Queen of Denmark||High flavor, pale scarlet|
Note.—Though the following varieties and species are notable for superior qualities, it may be that they will not prove to be equally good transmitters of these qualities.
Hardy against cold: (Fragaria cuneifolia)selections and crosses (Beltsville, Md., Corvallis, Oreg., Fairbanks, Alaska, and Cheyenne, Wyo.); (F. virginiana) selections (Fargo, N. Dak), Dakota, Dry Weather, Dunlap, Rockhill, Progressive, Parsons (Gibson), Beaver, Camden, Culver, Minnehaha.
Resistant to frost: Howard 17 and Chesapeake in United States, Sir Joseph Paxton in England.Resistant to verticillium wilt: Chilean (F. chiloensis).
Resistant to brown stele (Phytophthora): Aberdeen, Mastodon, and Redheart in Illinois; Leopold and Oberschlesien in Scotland.
Resistant to leaf scorch: Southland, Fairfax, Howard 17, Dorsett. U.S. D. A. 1142 (652 X Ettersburg 450), 1572 (Howard 17 X Dorsett), 2124 (Chesapeake X Fairfax).
Resistant to leaf spot: Southland, Fairfax, Howard 17, Rockhill, USDA 1142 (652 X Ettersburg 450), U. S. D. A. 2120 (Chesapeake X Fairfax), U. S.D. A. 2124 (Chesapeake X Fairfax).
Resistant to mildew: Marshall and Rockhill in the United States; V. H. de Thury (Stirling Castle), McMahon, and Aberdeen Favorite in England.
Resistant to aphid: Late Leopold, Bedford Champion, Aberdeen Standard, John Ruskin, Marshal Foch, and Sturton Cross in England.
Resistant to mite: Marshall in California; Mme. Kooi, Laxtonian, and Oberschlesien in England.
Resistant to crinkle: Redheart, Rockhill, and some (F. chiloensis)hybrids in Oregon.
Resistant to yellows (xanthosis): Nick Ohmer, Bellmar, and probably some F. chiloensis hybrids in California.
Resistant to heat: Missionary, Klondike, Blakemore, Southland, USDA 1142 (652 X Ettersburg 450).
Resistant to drought: F. cuneifolia, USDA 1791 (Ettersburg 904 X Howard 17), Marshall, Gold Dollar; The Duke and Waterloo in England.
Greenhouse forcing: Marshall in the United States; Royal Sovereign in Europe; Deutsch Evern in frames in the Netherlands; Noble in low houses in Germany.
Adapted to short days: Missionary, Klondike, Blakemore in the United States; Chilean in Ecuador.
Early ripening: USDA 2267 (Missionary X Fairfax), USDA 1631
(Howard 17 X Dorsett), Michel, Blakemore, Dorsett, Howard 17, Ozark, Progressive, Rockhill, Beaver, Early Bird, Minn. 1200; Deutsch Evern, Avant Tout, Laxton No. 1, and The Duke in England; Sir John Ruskin in Scotland.
Late ripening: USDA 2263 (Ettersburg 904 X Fairfax), U. S. D. A. 2124 (Chesapeake X Fairfax), (F. chiloensis)and its crosses (Corvallis, Oreg., and New Brunswick, N. J.), Ettersburg 121, Wyona, Pearl, and Gandy. Omega, Latest, Utility, Jucunda, Rearguard, Givons, Waterloo, and Leopold in England.
Firm: USDA 2166 (Joe X Redheart), USDA 2120 (Chesapeake X Fairfax), Redheart, Fairfax, Blakemore, Minnehaha, USDA 2161 (Joe X Redheart). Many Chesapeake X Fairfax and Blakemore X Fairfax selections have firm fruit.
Large: U.S. D. A. 2182 (652 X Fairfax), N. C. 337 (Bellmar X Fairfax), Catskill, Dorsett, Marshall, Minnehaha, Minn. 1201 (Marshall selfed). Latest and Laxtonian in Europe.
Yellow seeds: Blakemore, Chesapeake, USDA 2061 (652 X Ettersburg 450), U.S.D. A. 1591 (Howard 17 X Dorsett), U.S. D. A. 2126 (Chesapeake X Fairfax).
Light scarlet color: Blakemore in United States; Royal Sovereign, Fillbasket, The Duke, The Queen, King George V in England.
Superior qualities for freezing: Fruitland, Joe, Big Late, Klondike in eastern United States; Howard Supreme in Massachusetts; Corvallis, Redheart (sliced), Marshall in Oregon and Washington. Also, selections from Blakemore X Ettersburg 450, Southland X Blakemore, Blakemore X Marshall, Blakemore X Klondike, Redheart X Ettersburg 121, Blakemore x Ettersburg 121, Ettersburg 121 X Clark, Clark X Narcissa, and Howard 17 X Marshall in Oregon.
Superior qualities for preserving: Blakemore in United States; V. H. de Thury and Deutsch Evern in Europe. Reported good in some localities: Culver and Dorsett in United States; Lacombe in Canada. Marshall and Missionary are extensively used for preserving, though they are not equal to Blakemore. Crosses of Blakemore with other varieties have proved superior for preserving.
Superior qualities for canning: Redheart, Corvallis, Ettersburg 121 in the West; Portia in the East. Reported good in some localities: Culver, Redfour, Lnge, Trebla. Probably Noble, Scarlet Queen, and Paxton in parts of northern Europe. Crosses of Narcissa X Ettersburg 121, Redheart X Ettersburg 121, and Oregon 14 (Ettersburg 121 X Marshall) X Narcissa have produced good canning selections in Oregon.
Excellent flavor: Dorsett, Fairfax, Rockhill, Southland, Marshall, Corvallis, U.S. D. A. 1008 (F. chiloensis X Progressive), U.S.D. A. 1128 (Howard 17 X Ettersburg 450), U. S. D. A. 2183 (Missionary X Howard 17). British Queen, Dr. Hogg, Scarlet Queen, Connoisseur, Epicure, Pineapple, The Duke, Aberdeen Standard, and Royal Sovereign in Europe.
Unusual flavors: U.S. D. A. 1021 (Kalicene X Howard 17), grape flavor; U.S.D. A. 1026 and 1028 (Howard 17 X Ettersburg 450), apricot flavor; U.S. D. A. 1145 (652 X Ettersburg 450), raspberry flavor; Califour, black-raspberry flavor.