Development and identification of cassava clones with special starch characteristics

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 for the starch and ethanol industries. 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. Different strategies have been implemented simultaneously. Since most traits offering qualitative changes in starch properties are recessive in nature, these strategies rely heavily in the self-pollination of a wide range of cassava genotypes to expose 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. Several novel starch types have been identified. A waxy starch mutation has been fully characterized. In addition, several other mutations have been identified and are currently being characterized. Among them a small-granule type which showed (in a preliminary evaluation) higher-than-normal levels of amylose. Another abnormal starch with granules that looked hollow through optical microscopy was also identified. There were several other abnormal types that need further analyses because the preliminary evaluations were made on single plants derived from botanical seed. All these off-types have been cloned and will be harvested again by the end of 2007. (Résumé d'auteur)