Spicy Baja Beef Tortillas

Ingredients:1/4 cup light sour cream1 tablespoon adobo sauce from canned chipotle chiles in adobo sauce (reserve chiles for another use)4 (6-inch) low-fat whole wheat tortillas5 cups gourmet salad greens6 ounces thinly sliced low-sodium deli roast beef (such as Boar’s Head)1 cup refrigerated prechopped tomato1/3 cup mild pickled banana pepper rings1 ripe peeled avocado, coarsely chopped