IN 1938 E. F. Farlow, like many of his neighbors in eastern Maryland, had to give up growing strawberries. Each spring his plants died soon after growth started. By harvesttime only plants on the higher ground were alive. Growers clear across the Northern States were having the same trouble, and the losses were serious.

Research workers who tackled the problem found first that a fungus was the cause. It rotted off the roots of the strawberries. It spread rapidly in cool, wet weather, but not in well-drained soil or in summer.  Next, by testing many varieties, men at the Illinois Agricultural Experiment Station discovered that the Aberdeen strawberry was highly resistant to the devastating disease, which was called red stele disease. Never was a crop failure of Aberdeen due to the red stele disease—but the fruit of Aberdeen was too soft to sell in any but local markets, and it usually lacked flavor. The Department and the Maryland Agricultural Experiment Station joined forces. The Aberdeen was crossed with the Fairfax, a firm, high-flavored kind, and with other varieties. We raised thousands of seedlings on red stele-infested soil, retested those that were least affected, and tested the best of the survivors a third time.

On Mr. Farlow’s place one selection proved to be productive; it had high flavor and it shipped well. It was named the Temple in 1943.  Three years later it had become an important early variety in eastern Maryland, Virginia, and Delaware. Farlow and research workers want still better varieties. So now Farlow is growing several acres of Temple, an acre of seedlings, and about 100 other selections for the Department and the Maryland station for further testing. He and his neighbors have again become strawberry growers. The project is indeed a cooperative one:  Research workers in Scotland, where the red stele disease is also serious, others in Illinois, and a research group in Oregon have exchanged both breeding material and ideas with those working in Maryland, all with the same objective, to originate varieties resistant to the red stele disease and adapted to each section of the country.

Another example also will illustrate the aims and methods of plant breeders. For 40-odd years, up to 1940, Klondike, because of its adaptation to the South, was almost the only strawberry grown in Louisiana.  But during that time the leaf spot disease had become more and more injurious, until the plants had to be sprayed several times a year. Then research workers at the Louisiana Agricultural Experiment Station crossed Klondike with Blakemore, and got thousands of offspring, which they raised. These seedlings the scientists sprayed with leaf spot spores.  All seedlings that developed much leaf spot were thrown away.  Only those not injured were retested. But to be a good variety in southern Louisiana, a plant must throw out many runners. Therefore, in the second test, only good producers of runners were saved. They were fruited, and one, later named Klonmore, was found to produce large crops of firm, bright berries of good flavor. Only 4 years after its introduction, more than half of the crop in Louisiana was Klonmore. No spraying was necessary, for leaf spot has left Klonmore alone up to now.

Thus, when the cause of low yields has been determined or when growers need a variety better suited to preserving, shipping, freezing, or another use, or require one with better flavor, we survey the problem and determine which is the best method of breeding to obtain the desired end.

In California, for instance, virus diseases have been especially serious, and varieties healthier than the Marshall have been bred, named, and introduced by the California Agricultural Experiment Station workers.

In the Great Plains none of the older varieties is fully hardy, but the wild native strawberries are. So, crosses were made at the United States Horticultural Field Station at Cheyenne, Wyo., between the hardy wild kinds and the best cultivated varieties. The seedlings were planted in the field, and only those that survived the severe winters without protection were saved. Three selections far hardier than older kinds have been introduced for home gardens in that region—the Early Cheyenne 1, which is early; Cheyenne 2, midseason; and Cheyenne 3, a late kind.

For long-distance shipments from the South, much firmer berries than the Missionary were needed. The losses between the field and consumer were sometimes as high as 75 percent. Now, as the result of breeding, the Blakemore and Massey are grown, and losses have dropped considerably. In Tennessee, the Tennessee Shipper, still firmer than Blakemore, was obtained as a cross of Missionary and Blakemore and has been introduced. Berries as firm as the Tennessee Shipper—ones that will not bruise easily and are not so subject to decay as present varieties—are needed for each section of the country. Breeders have set out to get them.

Twenty years ago we had several kinds that were far above run-of-mine strawberries in flavor, but they could be grown only in a few localities.  The aim of breeders since then has been to obtain high-flavored varieties that could be raised in all sections. We have been fairly successful.  Among the flavorful new kinds are Fairmore, Dorsett, Fairfax, Narcissa, Redheart, Massey, Midland, Fairpeake, and Suwannee.

Flavor, even in the best varieties, is affected greatly by weather conditions. Sunny days and cool nights are necessary for berries of the best flavor. Some varieties occasionally have high flavor; in Maryland, for example, Aberdeen, under the most favorable conditions, has high flavor, but it has favorable conditions for high flavor perhaps only once in a hundred times. Missionary has high flavor oftener than Aberdeen, although generally it is too acid to be a good dessert berry. Of the newer varieties, Fairfax, Dorsett, Midland, Fairpeake, Fairmore, Narcissa, Redheart, and Massey are usuallly high-flavored, although in cloudy weather with hot nights, their flavor is not always what we would like.  The Suwannee, introduced in 1945-46 as a home-garden variety by the Department and the Mississippi Agricultural Experiment Station, has very high flavor oftener than any other sort. It has good flavor even when the days are cloudy and the nights warm, and can be widely grown from Maryland to Georgia, and west to Texas and Kansas. It is too soft to be a good shipping variety, but it is usually well adapted to the home garden, and it may be the forerunner of commercial varieties of just as high quality.

Among the important differences in the three varieties in different locations are: The firmer, better flavored berries of Howard 17 grown in Massachusetts, as compared with the same variety grown in Maryland; the greater firmness of Missionary ripening under short days in midwinter in Florida, as compared with the way it ripens in North Carolina in the longer spring days; and the greater productiveness, flavor, and freedom from leaf spot in Oregon of Marshall, as compared with Marshall grown in Maryland.

In this comparison, the Tennessee Shipper is shown to have too small a berry to be a good commercial variety, while Midland has the largest berry and the most productive plant. Suwannee is too soft to be a commercial variety, while Tennessee Shipper is the firmest variety. Tennessee Shipper is too tart to be a dessert strawberry, but Suwannee has the highest flavor oftener than the others. Thus, the breeder’s ideal is to combine the size, productivity, and leaf spot resistance of Midland with the firmness of Tennessee Shipper, the flavor of Suwannee, and the appearance of Blakemore, plus whatever seasonal factors the grower desires. The special qualities of each of these varieties have all been bred into them by previous crossings. In the same way, further crossing may result in still finer varieties—a Midland, for example, that keeps its good size and productivity, and inherits Tennessee Shipper’s firmness, Suwannee’s flavor, Blakemore’s appearance, and Redstar’s late maturity or Maytime’s early maturity.

But, furthermore, other characteristics must be sought for special conditions. In much of California, aphid- or virus-resistant varieties are necessary. In Oregon, resistance to mildew is important. In Florida, varieties must be able to grow and fruit during the short days of winter.  In eastern North Carolina, resistance to leaf scorch is an important character. In all areas of the United States, drought resistance, abundant pollen in the flowers, bright color, and smoothness of fruit are needed. How can we get them? Extensive tests and an intimate knowledge of scores of varieties and scores of characteristics of each variety and of the inheritance of characters are essential for intelligent and effective breeding.

A small part of this seed was sent to others for growing. The seed for red stele resistance was sowed on sifted sphagnum in July and about 50,000 seedlings transplanted during the fall to greenhouse benches filled with red stele-infested soil for a resistance test. The rest of the seed was held for later sowing.

These seedlings were set in early summer. Runners were kept off most of them, and the plants grew large enough for the first selections to be made in May and June 1947.

In the following summary, I list varieties that are notably superior for certain qualities, although in some instances they are definitely inferior in other ways.  [Table reworked into what I think is a clearer format. -ASC]

THE AUTHOR
Much credit for many of the better berry varieties we have today is due to George M. Darrow, principal pomologist, Bureau of Plant Industry, Soils, and Agricultural Engineering. Except for time out during the First World War, he has been with the Department since 1911. Among the strawberry varieties he has originated in that time are Blakemore, Fairfax, Dorsett, Redheart, Redstar, Fairpeake, Midland, Massey, Maytime, and others; also to his credit are Sunrise red and Potomac purple raspberries, and rabbiteye blueberries. Through Dr. Darrow’s work on strawberries we know more about the factors that govern their yields and varieties that are adapted to different regions of the United States. He made studies on polyploidy and the botany of blackberries, blueberries, and strawberries.

FOR FURTHER READING
Darrow, George M., and Waldo, George F.:  Strawberry Varieties in the United States, U. S. D. A. Farmers’ Bulletin 1043, 1946.
Demaree, J. B.:  Diseases of Strawberries, U. S. D. A. Farmers’ Bulletin 1891, 1941.
Fisher, D. F., and Lutz, J. M.:  Handling and Shipping Strawberries Without Refrigeration, U. S. D. A. Circular 515, 1939.