David Robert MacKenzie, 61, a plant pathologist who headed a regional agricultural research association based at the University of Maryland, died of cancer Oct. 23 at Inova Alexandria Hospital.

Dr. MacKenzie was executive director of the Northeastern Regional Association of State Agricultural Experiment Station Directors, one of four regional associations to further agricultural science research. He served as a liaison between the group's members, mainly agricultural colleges at land-grant universities and government agencies and laboratories.

He also served as vice chairman of the Homeland Agro-Security Task Force, which developed a plan aimed at protecting U.S. agriculture and food systems from a terrorist attack, and helped form the National Institute for Agricultural Security.

He wrote "Principles of Agricultural Research Management," and through other writings, he became an influential leader in shaping policy and focusing agricultural research on such issues as new products, climate change, natural resource conservation and food safety.

Before joining the regional association group in 1995, Dr. MacKenzie managed biotechnology research programs as national program leader for the Agricultural Department's Cooperative State Research, Education and Extension Service in Washington. He worked for the USDA for five years beginning in 1988.

Dr. MacKenzie, an Alexandria resident, was born in Hamilton, Mass. He graduated from the University of New Hampshire and received a master's degree and doctorate in plant pathology from Pennsylvania State University.

In the 1970s, he worked with Nobel laureate Norman E. Borlaug at the International Center for Maize and Wheat Improvement in Mexico City under a research program co-sponsored by the Rockefeller Foundation. Dr. MacKenzie later became a research scientist at the International Rice Research Institute in the Philippines, head of the department of plant breeding at the Asian Vegetable Research and Development Center in Taiwan and professor of plant pathology at Penn State.

He also was chairman of the board of trustees of the International Potato Center in Lima, Peru, and a longtime agricultural and natural resources management consultant to the World Bank.

His other interests included fly-fishing, hunting, golfing and producing videos.

Survivors include his wife of 39 years, Doris MacKenzie of Alexandria; three children, Wendy Pease of Sudbury, Mass., Scott MacKenzie of Atlanta and Todd MacKenzie of Concord, Mass.; his mother, Eleanor MacKenzie of Danvers, Mass.; two sisters, Susan MacKenzie of Fredericksburg and Jane Jenkins of Gloucester, Mass.; a brother, William MacKenzie of Hamilton, Mass.; and a grandson.