The seed systems of RTB (root, tuber, and banana) crops are unique because they are propagated from vegetative parts of the plant, not from true seed. RTB seed is thus bulkier, more perishable, and more subject to the attacks of pests and diseases than is true seed. Because of this, there is often a gap between potential and real crop yields, which seed interventions seek to narrow. Seed systems are formal or informal networks of people and organizations that produce, plant, and distribute seed. Informal systems may deliver low quality seed, but not always. This book describes 13 RTB seed system interventions, using a framework based on the concepts of seed availability, access, and quality. The 13 case studies included (1) a potato-growers’ association in Ecuador, (2) a hydroponic seed potato in Peru, (3) a yam seed technology in Nigeria, (4) a banana and plantain project in Ghana, (5) a sweetpotato seed project in Tanzania and (6) one in Rwanda, (7) a seed potato system in Kenya, (8) cassava in Nicaragua, (9) seed potato in Malawi, (10) disease-resistant cassava varieties in seven African countries, (11) a tissue culture banana project, (12) an emergency plantain and banana project in East Africa, and (13) a large cassava seed project in six African countries.