Dorothy Houston Jacobson, 77, an assistant secretary of agriculture for international affairs in the Johnson administration who also worked with private groups on food and population problems, died of respiratory failure July 13 at Fairview Hospital in Minneapolis.

Mrs. Jacobson was chairman of the Minnesota Democratic Farmer Labor Party from 1950 to 1954. In 1955, she went to work as an assistant to Orville Freeman, then the governor of Minnesota. She accompanied him to Washington in 1961 when he became secretary of agriculture in the Kennedy administration.

President Johnson nominated her to be assistant secretary for international affairs in 1964 and she held that post until 1969. Among her duties was representing the United States at meetings of the Food and Agriculture Organization in Rome and at other international forums.

After leaving the government, Mrs. Jacobson was executive director of the Population Crisis Committee, a Washington-based group that is concerned with world hunger and population control. She also was director of the Washington office of the Freedom from Hunger Foundation and a director of the Greenbelt Cooperative.

Mrs. Jacobson was born in Herman, Minn. She graduated from St. Cloud State Teachers College and earned bachelor's and master's degrees in political science at the University of Minnesota. In the 1930s and 1940s, she was a teacher and held a number of posts in the Minnesota Department of Education.

In 1945, she joined the faculty of Macalester College in St. Paul and taught political science. Among other faculty members was Hubert H. Humphrey and the students included Walter Mondale.

With Humphrey and others, Mrs. Jacobson was credited with creating the Democratic Farmer Labor Party in Minnesota. She accompanied Humphrey to the 1948 Democratic National Convention at which he made a famous speech in behalf of civil rights. She taught at Macalester until joining Freeman's staff.

Mrs. Jacobson and her husband, George, lived in Washington until moving to Richfield, Minn., in 1982.

In addition to her husband, of Richfield, survivors include a brother, Howard Houston of Burnsville, Minn.