Abstract

ZAPATA, ANDRES; NEME, RAFIK; SANABRIA, CAROLINA  and  CAMILO, LÓPEZ. Analysis of Cassava (Manihot esculenta) ESTs: A Tool for the Discovery of Genes. Acta biol.Colomb. [online]. 2011, vol.16, n.1, pp.95-108. ISSN 0120-548X.

Cassava (Manihot esculenta) is the main source of calories for more than 1,000 millions of people around the world and has been consolidated as the fourth most important crop after rice, corn and wheat. Cassava is considered tolerant to abiotic and biotic stress conditions; nevertheless these characteristics are mainly present in non-commercial varieties. Genetic breeding strategies represent an alternative to introduce the desirable characteristics into commercial varieties. A fundamental step for accelerating the genetic breeding process in cassava requires the identification of genes associated to these characteristics. One rapid strategy for the identification of genes is the possibility to have a large collection of ESTs (Expressed Sequence Tag). In this study, a complete analysis of cassava ESTs was done. The cassava ESTs represent 80,459 sequences which were assembled in a set of 29,231 unique genes (unigen), comprising 10,945 contigs and 18,286 singletones. These 29,231 unique genes represent about 80% of the genes of the cassava’s genome. Between 5% and 10% of the unigenes of cassava not show similarity to any sequences present in the NCBI database and could be consider as cassava specific genes. A functional category was assigned to a group of sequences of the unigen set (29%) following the Gene Ontology vocabulary. The molecular function component was the best represented with 43% of the sequences, followed by the biological process component (38%) and finally the cellular component with 19%. In the cassava ESTs collection, 3,709 microsatellites were identified and they could be use as molecular markers. This study represents an important contribution to the knowledge of the functional genomic structure of cassava and constitutes an important tool for the identification of genes associated to agricultural characteristics of interest that could be employed in cassava breeding programs.

Keywords : cassava; ESTs; functional genomics; annotation; molecular breeding.

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