Cassava Genome from Ancestor to Cultivar

Cassava (Manihot esculenta Ctantz) , a perennial cultivar domesticated from a jungle ancestor of Eurphorbiaceae,  currently is the sixth world  food crop for more than 600 million people in tropical and sub-tropical Africa, Asia and Latin America, also a potential sources for bio-fuel. Less knowledge on cassavas genome and genes for main agronomic traits have been uncovered up to now. We sequenced a wild ancestor W14 and two cultivars, KU50 and a sugary variety with high coverage of short Illumina reads and longer 454 reads, the draft genomes were assembled with assistance of  BAC-pooled Illumina reads to facilitate longer contig assembling.  The assembled genomes reached 460Mb for W14 and 380Mb for KU50, respectively, with the coverage of transcribed region for over 95%. Comparative genomic analysis among the wild and the two cultivars are done in aspects of repeat sequences, transposons, SNPs and indels, non-coding RNA and miRNA, starch biosynthesis pathways, carotene synthesis pathways and cyanide biosynthesis pathways.  A series of chart and variation revealed changes of genome from low-yield wild ancestor to high-yield cultivar in evolution. The large amount of gene resources and molecular markers generated from this project should inevitably boost cassava research ether of biological mechanisms or breeding.

Key words: cassava; genome sequence; evolution