Abstract

S6-22

Advantages of the New Cassava Breeding Scheme at CIAT

Pérez J.C., N. Morante, J. López, J.I. Lenis, G. Jaramillo, H. Ceballos and F. Calle

In 1999, a new breeding scheme was implemented at CIAT.  The main changes were in the initial stages where selection that was based on single-plant observations has been replaced with a more representative sample of six plants.  Also, data from all segregating progeny are recorded.  This new scheme shortens the breeding cycle, improves the heritability of the traits to be selected for and allows estimation of general combining ability from the genotypes that are also used as parents.  Preliminary results allowed the identification of important traits for cassava breeding.  Leaf retention at five months of age on 130 of 1350 segregating clones resulted in an average increase of productivity of about 2 t/ha of dry matter.  A group of genotypes showed the capacity to maintain high dry matter content (> 35 %), even after the end of the rains.  Two segregating families that were made up of several clones, revealed variation in their capacity to accumulate starches in the roots.  These three traits have important impact on dry matter yield and are likely to be controlled by one or few major genes.  Initial work has begun for the molecular identification of either the locus or loci that control these traits.