Hi Ms. Judy,
Rice is a staple that lends itself to easy growth and distribution in developing countries. Another thing to think about is that potato production in tropical agriculture does not yield very high returns because of a pest called "Nematodes".
These very tiny creatures thrive in the warm soil and propagate profusely. We who live in the northern hemisphere experience the antidote to these pests, which is when winter sets in and the frost penetrates the soil and kills the nematodes. Remember that different regions have different types of agriculture.
Southeast Asian countries, Sub-Saharan countries, and Tropical African countries have their own indigenous agriculture. If you introduce a "foreign" species of agriculture you will cause more problems than you solve. The trick is to identify which vegetables, plants, shrubs, and trees that are endemic to the region and then have a system by which one introduces those very same species in quantites so that people in developing countries will benefit from their own endemic agricultural system.
Cheers,
CD