In retailing, it’s a given that a long-term, severe recession will cut through the ranks of food, drug and general merchandise retailers like a scythe through wheat, pushing weaker players out of the market as consumer spending dries up and Darwinian realities winnow the field. But it’s also true that the strongest merchants can emerge not only intact, but also with even brighter prospects if they innovate, invest and retain the loyalty of their customers.