Resumen
- The performance of 15 cassava (Manihot esculenta Crantz) clones in 14 environments in Colombia was analyzed to determine the possibility of improving stability of root-yield in cassava in association with minimum acceptable yields. The specific objectives were to study the relationship among agronomic traits, to evaluate genotypic sensitivity to changes in the environment, and to characterize and determine the representativeness of the evaluation environments. Correlations found between root yield and related physiological or quality traits were in a favorable direction for breeding purposes. This indicates that when selecting for a complex set of traits, indices might be established with major emphasis on traits with high heritability and/or stability. For some traits (number of commercial roots and length of stem with attached leaves) the range of genetic variability was broader in favorable environments. Variation among evaluation sites was greater than variation across years. The results indicate that intermediate to low genotypic sensitivity in terms of cassava root yield andry matter content can be combined with improved potential for dry matter production per unit area. In order to improve the performance and stability of cassava gene-pools, representative sites should be selected within the priority agro-ecosystem, to evaluate the genetic base for at least two years before selection is made. Association between the mean and the sensitivity coefficient for different traits was either nonsignificant or positive for breeding purposes. Improvement in the mean of traits can be made independently from, or in relation to, genotypic ability to react to environmental changes.