Most of the world's poorest smallholders depend on tropical roots and tubers crops as their principal source of food and nutrition. These species provide large quantities of dietary energy and produce stable yields under difficult environmental conditions. The most important crops are cassava, sweet potato, yam and the aroids, sharing important common traits such as bulkiness, post-harvest perishability and vegetative propagation. This book compiles the most up to date information on the origin, genetics, physiology, agronomy, pests and diseases and post harvest processing of these crops, while attempting to provide ideas for further research and development. Main contents: I: Cassava: 1. Origin and history. 2. Taxonomy and botany. 3. Breeding and genetics. 4. Developmental physiology. 5. Agronomy. 6. Pests and diseases. 7. Post harvest quality and marketing. 8. List of references cited. II: Sweet potato: 1. Origin and history. 2. Taxonomy and botany. 3. Breeding and genetics. 4. Developmental physiology. 5. Agronomy. 6. Pests and diseases. 7. Post harvest quality and marketing. 8. List of references cited. III: Yams: 1.Origin and history. 2. Taxonomy and botany. 3. Breeding and genetics. 4. Developmental physiology. 5. Agronomy. 6. Pests and diseases. 7. Post harvest quality and marketing. 8. List of references cited. IV: Aroids: 1. Origin and history. 2. Taxonomy and botany. 3. Breeding and genetics. 4. Developmental physiology. 5. Agronomy. 6. Pests and diseases. 7. Post harvest quality and marketing. 8. List of references cited