WASHINGTON (Reuters) - Kathleen Merrigan, who made promoting farmers markets and local food a top priority, has resigned as deputy agriculture secretary, a job that put her in charge of day-to-day operations of the mammoth federal department from 2009.

There was no immediate word on Friday on a successor on Friday. The post requires Senate confirmation.

Merrigan, 53 announced her decision on Thursday evening with no word of her future plans or her departure date.

In 2010, Merrigan, who has a doctorate in environmental planning from the Massachusetts Institute of Technology, was listed among Time magazine's "100 Most Influential People in the World."

Merrigan spearheaded the "Know Your Farmer, Know Your Food" initiative at the U.S. Department of Agriculture to encourage local food production and marketing. Earlier, she had a leading role in developing national organic food-labeling rules.

Mainline farm groups have said the USDA's promotion of small farms and local food production, and Merrigan's prominent role in it, was a sign of hostility to the so-called production agriculture that produces most U.S. food.

Merrigan was director of a food and environment program at Tufts University before she was appointed deputy secretary. She headed the USDA's Agricultural Marketing Service from 1999-2001 and as a Senate Agriculture Committee staff worker worked on the organic-food labeling law.

(Reporting by Charles Abbott; Editing by Lisa Von Ahn)