Strawberries. James F Hancock
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and many European cultivars, and it was particularly noted for its resistance to leaf diseases and viruses, formation of many crowns, frost-hardy flowers and high productivity. ‘Aberdeen’ was grown in the 1930s in New Jersey and the east but may have found its greatest importance as a breeding source for red stele resistance in both European and North American cultivars.
The most active breeder around the turn of the century was probably Albert Etter of California who developed dozens of varieties utilizing native F. chiloensis clones (Wilhelm and Sagen, 1974; Fishman, 1987). His most successful variety was ‘Ettersburg 80’ (1910), which was widely grown in California, Europe, New Zealand and Australia. Renamed as ‘Huxley’, it was still popular in England as late as 1953. ‘Ettersburg 80’ was extremely drought resistant, of outstanding dessert and jam quality due to its solid bright red colour and was unusually hardy for a California type. Other outstanding Etter varieties were ‘Ettersburg 121’, ‘Fendalcino’ and ‘Rose Ettersburg’. Although his releases were very successful as cultivars, they may have had their greatest impact as breeding parents. Almost all California cultivars (and many others) have an Ettersburg variety in their background (Darrow, 1937, 1966; Sjulin and Dale, 1987).
In the 1930s and early 1940s, several new cultivars became important across the USA including the great US Department of Agriculture (USDA) breeder G. Darrow’s ‘Blakemore’ (USDA-MD, 1929) and ‘Fairfax’ (USDA-MD/NC, 1933), G. Slate’s ‘Catskill’ (New York, 1933), K. Keplinger’s ‘Gem’ (Michigan, 1933), J. Haley’s ‘Robinson’ (Michigan, 1940) and E. Henry’s ‘Tennessee Beauty’ (Tennessee, 1943). ‘Blakemore’ became the major southern variety in the mid-1930s until the early 1960s because of its earliness, firm, bright-red berries, suitability for freezing and preserving, and disease resistance. ‘Blakemore’ was used extensively in breeding, finding its way into the ancestry of a diverse array of cultivars grown in all parts of the USA. ‘Tennessee Beauty’ became dominant in the upper south from 1940 to the 1960s due to its high productivity, tolerance to virus and good freezing quality. ‘Gem’ (also called ‘Superperfection’ and ‘Brilliant’) was the most important everbearer from 1940 to the modern period. ‘Fairfax’ was widely planted in the middle of the century from southern New England to Maryland and westward to Kansas. It was particularly noted for its outstanding flavour but may have been more important as a breeding parent, finding its way into the pedigree of numerous European, USA, Canadian and even Japanese cultivars.
In the late 1940s and early 1950s, several more cultivars achieved importance including J. Clarke’s ‘Sparkle’ or ‘Paymaster’ (New Jersey, 1943), E. Morrow’s ‘Albritton’ (North Carolina, 1945), H. Thomas and E. Goldsmith’s ‘Lassen’ and ‘Shasta’ (California, 1945), D. Scott and G. Darrow’s ‘Pocahontas’ (Maryland, 1946) and C. Schwartze’s ‘Northwest’ (Washington, 1949). ‘Sparkle’ dominated in the north-east and mid-west in the 1950s and 1960s, due to its high flavour, attractive appearance and resistance to red stele. ‘Northwest’ was the most planted variety in the USA in the 1960s, even though all of the acreage was in Oregon and Washington (Darrow, 1966). It was particularly noted for its lateness and tolerance to virus diseases. ‘Shasta’ was widely grown in the central coast of California in the 1950s and 1960s because of its large size, firmness and long season. ‘Lassen’, grown extensively in southern California about the same period, was prized for its short rest period and high productivity. ‘Pocahontas’ was widely grown in the lower mid-west and south in the 1960s and 1970s, and even became important in Italy in the late 1970s. It was known for its productivity, large, attractive, firm berries and good freezing quality.
The middle decades of the 20th century saw the release of D. Scott’s ‘Surecrop’ (Maryland, 1950) and ‘Midway’ (Maryland, 1960), R. Bringhurst and V. Voth’s ‘Tioga’ (California, 1955), P. Hawthorne’s ‘Headliner’ (Louisiana, 1957) and ‘Dabreak’ (Louisiana, 1961), L. Spangelo’s ‘Redcoat’ (Ontario, 1957), H. Thomas and E. Goldsmith’s ‘Goldsmith’ (California, 1958) and A. Brook’s ‘Florida 90’ (Florida, 1952). ‘Surecrop’, which was important in the upper south and lower mid-west during the 1960s and 1970s, was noted for its high disease tolerance both to leaf and soil pests. ‘Midway’ replaced ‘Robinson’ in the 1960s in the mid-western USA, primarily because of its firmer berries and resistance to red stele. ‘Redcoat’ dominated eastern Canada in the 1960s and 1970s. It was known for its high yield, appearance, earliness and shipping qualities. ‘Headliner’ and subsequently ‘Daybreak’ became important in the south in the 1960s and 1970s, replacing the earlier varieties, due to their larger size, higher productivity and an earlier season. ‘Tioga’ replaced ‘Lassen’ in California in the late 1960s because of its greater size, attractiveness, firmness and productivity. ‘Florida 90’ became popular in Florida in the late 1950s due to its very long, large, early berries and high flavour (Darrow, 1966). ‘Goldsmith’ was the first important private variety in California, noted for its productivity and shipping quality.
DIVERGENCE OF NORTH AMERICAN BREEDING PROGRAMMES
As previously described, strawberry breeding began in North America by hybridizing F. × ananassa cultivars derived from Europe with native genotypes of the founding species of F. chiloensis and F. virginiana that came from diverse geographic and subspecies origins (Darrow, 1966). Breeding programmes subsequently cropped up all across the continent in a broad range of climates ranging from the cold temperate climates of the eastern seaboard to the mild Mediterranean ones of coastal California. Over time, considerable genetic differentiation occurred among the various breeding programmes through hybridization and selection. The wild progenitor ecotypes would have provided an almost unlimited source of genes to generate unique regional group structures (Hancock and Luby, 1993).
Over 50 years ago, Darrow (1966) identified a series of 18 traits that separated F. chiloensis from F. virginiana and then rated five eastern varieties for the proportion of their phenotype that appeared to be based on F. chiloensis. According to his rating system, ‘Fairfax’ expressed 57% of the characteristics of F. chiloensis; ‘Earlidawn’, 28%; ‘Blackmore’, 31%; ‘Howard 17’, 31%; and ‘Missionary’, 27%. From these values he suggested that his eastern breeding programme had been selecting for more F. virginiana characteristics than F. chiloensis characteristics. He further asserted that ‘Fairfax’ with the most F. chiloensis characteristics would be more broadly adapted than the others and that ‘greater use of F. chiloensis in breeding for superior varieties seems indicated’ (Darrow, 1966).
Much more recently, Hardigan et al. (2018) analysed genome-wide DNA profiles of 1300 octoploid individuals, including wild species, historic varieties (1814–present) and the University of California germplasm collection. They evaluated 16,492 polymorphic and subgenome-specific markers. They found that the cultivars bred for California were substantially differentiated from the temperate-climate cultivars developed in eastern North America and they did indeed carry a much higher proportion of genes from F. chiloensis. Selection over the last 20–30 years in California had restructured genetic diversity similar to the restructuring that occurred during the first 200 years of breeding, and coastal F. × ananassa has diverged further from the temperate F. × ananassa than the latter from their wild progenitors (Fig. 2.8).