Walnut Scion & Rootstock Improvement
Walnut Scion & Rootstock Improvement
Walnut Scion & Rootstock Improvement
University of California
Walnut Scion & Rootstock Improvement

Program History 1948 - 1979

1948 - 1978

The Walnut Germplasm Collection is contained is a reserve block of walnut trees, called the Stuke Block, located at the Wolfskill Experimental  Station in Winters, California. The source of much of this material was the variety Block of Gene Serr and Harold Forde, early UC Davis walnut breeders. This collection of old California walnut cultivars, selected parental stock and rootstock species is a source of material for future walnut breeding at UC Davis.

Harold Ford, 1914- 2001
Harold Ford, 1914- 2001
Gene Serr, 1898-1968
Gene Serr, 1898-1968
Early farmers and nursery workers imported walnuts into the state from various foreign sources and these growers obtained their cultivars through the by selecting seedling that occurred by chance. In contrast, the walnut breeding program, initiated at in 1948 UC Davis by Serr and Forde, used a methodology based on controlled crosses. In their systematic breeding program, emphasis was placed on characters affecting yield such as number and location of pistillate flowers and pollen abundance, shell  and nut qualities, tree vigor, timing of maturity and disease resistance. Constant attention to these critieria, detailed evaluation of progeny and keen field observations characterized their work. Their general procedure of isolating pistillate flowers in bags in the spring, injecting pollen form selected male flowers into the bag, harvesting and planting seeds in the fall, is reflected in current breeding practice.

Walnut cultivars released by UC from Serr & Forde's program.
Walnut cultivars released by UC from Serr & Forde's program.
Serr and Forde’s initial baseline included the standard cultivars of their day, such as Payne, Harley, and Fanquette. As their program developed over the next three decades, they acquired more cultivars, including foreign collections. They evaluated close to 6000 progeny. After his retirement in 1965, Serr recommended and named ten cultivars which were released by the University: Lompoc, Gustine, Vina, Amigo, Pioneer, Tahama, Pedro, Midland, and Chico. The tenth was named after him: Serr. Subsequently, Forde continued the program, releasing in 1979: Howard, Sunland and Chandler, which is now the dominant cultivar grown in the state. Their program provided a strong basis for continuing work in the University and a model that is recognized around the world.

Source: Walt Tulke and Gale McGranahan. 1994. The Walnut Germplasm Collection of UC Davis. Report 13. Genetic Resources Conservation Program. DANR, UC Davis. 48p.

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