Mejoramiento de la yuca para adaptacion en condiciones de estres : desarrollo de una metodologia

Several physical and biological factors that limit cassava productivity are described: temp. and photoperiod, soil water availability, RH, soil characteristics (fertility and pH), and pests and diseases. Six edapho--climatic zones (ECZ) for cassava production are defined on the basis of temp.: lowland tropics, ECZ 1 (low to moderate rainfall and long dry season; high annual temp.), ECZ 2 (moderate to high rainfall on acid, infertile soils), and ECZ 3 (no marked dry season, high rainfall, high constant rh); intermediate alt. tropics, ECZ 4; highland tropics, ECZ 5; and subtropics, ECZ 6. A unique combination of potential pest and disease problems can be identified for each ECZ. In Colombia, conditions for 5 of the 6 ECZ (ECZ 1-5) have been identified. CIAT`s improvement strategy consists of: (1) germplasm collection in different Colombian ECZs; (2) selection of parents and formation of gene-pools for each ECZ; (3) evaluation and selection of hybrids within and between the zones; and (4) recommendations to national programs on the testing of selected clones and/or specific progenies. Results obtained using this methodology prove the highpotential existing for improving cassava productivity under stress conditions through var. improvement methods and simple cultural practices. (CIAT