Although the potato is usually thought of as a temperate-zone crop, potato growing in the tropics and subtropics is spreading rapidly. In terms of the dollar value of the crop, this edible root now ranks fourth in the developing world after rice, wheat, and maize. Nevertheless, policymakers often underrate the importance of the potato as a source of employment, income, and food or they underestimate the potential benefits from expanding potato production and use. The payoff from applied research on potato cultivation in the tropics and subtropics is high due to the large body of scientific...