  We obtain a supergravity solution arising when D6-branes are wrapped on
coassociative four-cycles of constant curvature in seven manifolds of G_2
holonomy. The solutions preserve two supercharges and thus represent
supergravity duals of three dimensional Yang-Mills with N=1 supersymmetry. When
uplifted to eleven dimensions our solution describes M-theory on the background
of an eight manifold with Spin(7) holonomy.
