Harold Olmo

Brief Biography and Chronology of Scientific Activity

Harold P. Olmo (1910–2006) was an eminent American scientist, geneticist, breeder, and ampelographer, widely regarded as one of the world's foremost experts in the field of viticulture. Born in San Francisco in 1910, he developed a strong interest in horticulture during his youth. In 1931, he graduated from the University of California, Berkeley (UC Berkeley) with a B.S. degree in horticulture. In the same year, Olmo recorded his first controlled grapevine cross, mating Muscat of Alexandria with Black Corinth.

In the spring of 1933, he joined the staff of the Agricultural Experiment Station as an Associate. He earned his Ph.D. in genetics from UC Berkeley in 1934, and subsequently joined the Division of Viticulture at the University of California, Davis (UC Davis) as an assistant professor of viticulture in 1938. Professor Olmo officially retired in 1977, continuing his academic activities as Professor Emeritus. He passed away on June 30, 2006, due to medical complications following a hip fracture.

Breeding Operations and Grapevine Cultivar Development

During his career at UC Davis, the breeder developed and released 29 grape varieties and 2 rootstocks. Olmo's breeding program was broadly focused, encompassing the development of table, wine, raisin, and juice grape cultivars. His most commercially successful and widely cultivated releases include the table grapes Redglobe, Ruby Seedless, and Perlette, the wine grape Ruby Cabernet, and the juice grape Rubired. By 2005, these five varieties alone occupied over 38,000 acres in California.

Following his retirement from the university, the researcher continued his breeding efforts for Marko Zanninovich, Inc., securing patents for several new table grape varieties. He donated hundreds of thousands of dollars in patent royalties generated from these varieties back to the Department of Viticulture and Enology to establish an endowment for assisting new faculty and funding graduate students.

Contributions to Ampelography and Germplasm Preservation

As an expert in ampelography—the science of grapevine identification—Harold Olmo developed a methodology for the comparative analysis of grape seeds. This approach solved the problem of identifying cultivars from decayed vine samples sent by growers that degraded during transit. Throughout his extensive international travels, he collected hundreds of wild grape species and domesticated varieties. This extensive collection later became the core of the United States Department of Agriculture (USDA) National Grape Germplasm Repository located in Winters, California. Olmo also co-authored the foundational reference work, the Brooks and Olmo "Register of Fruit and Nut Varieties".

Clonal Selection and Interspecific Hybridization

The researcher was a pioneer in utilizing clonal selection to improve existing wine grape cultivars. By applying clonal selection techniques to Chardonnay vines (utilizing clones originally gathered by viticulturist Louis Martini), Olmo focused on enhancing fruit quality and productivity. Prior to this work, Chardonnay was an uncommon and unproductive variety in California; following his selection efforts, its cultivation expanded to nearly 100,000 acres in the United States.

In the field of genetics, Olmo investigated the introgression of the distantly related species Vitis rotundifolia into the cultivated genome of Vitis vinifera. Despite the differing chromosome numbers between these species and the resulting sterility of early hybrid generations, the breeder successfully developed a limited number of fertile hybrids, which remain in use in modern molecular and classical breeding programs worldwide. A key practical result of this research was the creation of the interspecific hybrid rootstock 039-16. This rootstock effectively resists the feeding of the dagger nematode vector (Xiphinema index) and induces tolerance in the fruiting scion to fanleaf degeneration disease, thereby preventing severe impacts on fruit set and overall yield.

Agrotechnics, Mechanization, and Clean Stock Programs

Harold Olmo experimented with novel vine training and trellising methods, and contributed to the development of early mechanical harvesting technologies. In the 1960s, he pioneered the "cane severance" technique to produce dry-on-vine raisins suitable for mechanical harvesting, a method that facilitated automated harvesting on continuous paper trays.

Among his most significant structural achievements was his leading role in formulating the grapevine clean stock program. This framework for establishing foundation collections, testing vines for viral pathogens, and distributing certified healthy planting stock to commercial nurseries served as a definitive model for clean stock programs globally.

International Missions and Recognition

For over twenty years, the researcher served as an international consultant to the Food and Agriculture Organization (FAO) of the United Nations. He advised on viticultural practices and directed vineyard establishment and redevelopment projects across India, Afghanistan, South America, Australia, as well as Eastern and Western Europe.

In recognition of his scientific achievements, Harold Olmo was honored with numerous prestigious awards, including:

• The Wilder Medal of the American Pomological Society (1958);
• The Laureate and Medal for Outstanding Contributions to World Viticulture by the Office International de la Vigne et du Vin (OIV, 1965);
• Charter and Honorary Life Membership in the American Society for Enology and Viticulture (ASEV, 1973);
• The Award of Merit by the American Pomological Society (1974);
• The Papal Medal, Benemerenti, by the Catholic Church (1979);
• The Rockefeller Spirit of Service Award, International, Executive Service Corps (1993).

He was also a Guggenheim Fellow and a Fulbright Scholar.