Cassava (Manihot esculenta Crantz) is an important food security crop for many tropical and subtropical countries. It is also acquiring an increasing role in rural development as raw material for different industries. The most important industrial uses of cassava are as a source of energy in the feed industry and as a source of starch. To consolidate and expand the industrial uses of cassava, an increased emphasis in the search for value-added traits, while maintaining or enhancing its productivity, has recently been given by the cassava breeding project at CIAT. For the feed industry, the main objective is enhanced nutritional quality, particularly with regard to protein content. The high-protein trait is being introgressed from related Manihot species. In addition, several M. esculenta clones with more than double the normal protein content have been identified. For the starch industry, different approaches to produce cassava roots with novel starch types have been initiated. Inbreeding has been introduced to cassava genetic improvement because it offers many advantages, including a facilitated identification of useful recessive traits. Ongoing research for the production of doubled-haploid lines will reduce the time required to reach full homozygosity. Plants from irradiated seed in a mutation-breeding project have been evaluated in the field and many self-pollinations have been made to implement the TILLING system specifically targeting the waxy starch trait. Waxy starch will also be produced through gene silencing using genetic transformation. Conventional recurrent selection methods have also began for a divergent selection searching to increase or reduce amylose content in the starch from the roots. Novel starch types are also sought through crosses with related Manihot species. Finally, CIAT has set up a high capacity root-quality laboratory to routinely screen the roots of the thousands of new genotypes generated every year.
Acta Horticulturae (2006) 703: 63-70. II International Symposium on Sweetpotato and Cassava: Innovative Technologies for Commercialization