The influence of ecosystems on cassava (Manihot escutentaCrantz) cultivars and the possible reasons for this are discussed, as well as the effect of distinct negative production factors, i.e., edaphic and climatic constraints, and disease and pest stresses, on regional and introduced varieties. Decentralised improvement programmes in different ecosystems based on 10 years research are suggested, and are selected according to socioagro-economic studies related to actual and/or potential production of cassava.