Combine crabmeat, lemon juice and salt in a medium bowl and refrigerate while preparing sauce. Melt butter or margarine in a medium saucepan. Add flour, stir and cook for about 1 minute. Add milk slowly, stirring constantly, and cook until sauce thickens. Add seasonings, cheese and wine (optional).
Stir until cheese is melted and sauce is smooth. Drain crabmeat, add to sauce and heat until bubbly. Layer cooked wild rice in bottom of a lightly oiled 2 quart casserole dish.
Pour crabmeat and sauce over rice. Top with mushroom slices and bake at 350~ for about 30 minutes or until lightly browned. Serve with a crisp green salad and crunchy rolls.