Henry A. Jones, 91, a retired geneticist whose pioneering research on onion hybridization made production of hybrid onions commerically practicable, died of cancer Feb. 24 at his home in Cave Creek, Ariz.

In 1925, while conducting research on plant crossbreeding at the University of California at Davis, Dr. Jones found a distinctive type of male sterility in onions that could be easily propagated and cross-bred. His discovery led to development of the approximately 2,000 lines of breeding onions being produced today, as well as development of hybridization techniques for other crops, such as sorghums, sugar beets, corn and spinach.

Dr. Jones joined the Department of Agriculture in 1936 as principal horticulturist in the Bureau of Plant Industry. According to USDA records, the first onion hybrid based on his research was released in 1944, subsequently leading to the release of many other hybrids. He also directed the development of new and better spinach varieties that could be harvested mechanically.

He was the coauthor of a standard text on onions. He also was the author or coauthor of several other books and more than 100 articles on horticultural subjects.

Dr. Jones was born in a log cabin in Deer Park, Ill., and grew up on a farm. He started high school at age 20 and earned a bachelor's degree in botany and plant pathology from the University of Nebraska in 1916. In 1918, he earned a doctorate in plant physiology from the University of Chicago.

After retiring from the Agriculture Department in 1957, he became director of research at the Dessert Seed Co. in El Centro, Calif., one of the country's largest onion-seed growers. He retired a second time in 1979 and moved to Cave Creek, Ariz.

Dr. Jones, who had lived in University Park, was a president of the American Society for Horticulture and received numerous professional awards for his contributions to the hybrid production of vegetables around the world.

His wife, the former Louise Francis White, died in 1963.

Survivors include two daughters, Mary Goodman Espy of McLean, and Joy White of Adelphi; two sons, Myron, of University Park, and Dr. Henry A. Jr., of Santa Monica, Calif.; a sister, Ruth Stoltenberg of Woodward, Okla.; a brother, Col. Erwin Jones of Virginia Beach, Va., 13 grandchildren and nine great-grandchildren.