Combine brown sugar, 1 tablespoon flour, and pecans in a small bowl. Stir in melted butter; set aside.

Combine 1 cup all-purpose flour, whole-wheat flour, and next 5 ingredients in a large bowl; make a well in center of mixture.

Stir together egg, buttermilk, and oil; add to dry ingredients, stirring just until moistened. Fold in blueberries.

Spoon about 1/3 cup batter into each of 12 lightly greased muffin cups. Sprinkle batter evenly with reserved pecan mixture.

Bake at 375° for 19 to 21 minutes or until lightly browned. Cool in pans on wire rack 5 minutes. Remove from pans, and cool slightly on wire rack. Serve warm.