Beta vulgaris subsp. vulgaris Genome sequencing and assembly. Beta vulgaris subsp. vulgaris

Sugar beet (Beta vulgaris ssp. vulgaris) is an important crop of temperate climates which provides nearly 30% of the world's annual sugar production and is a source for bioethanol and animal feed. Sugar beet genome has an important size (758 Mbp) and includes at least 63% repetitive DNA. When we started our study, sugar beet genome was not available in public database. In order to isolate new coding sequences and to complete sugar beet sequences database (about 30 000 ESTs), a Cot filtration followed by 454 sequencing was realized. Indeed, Cot filtration leads to the separation of single copy sequences (potential coding sequences) and repeat sequences, allowing further experiments on these two distinct fractions. Cot fractionation analysis indicated that the single/low copy fraction could be estimated at 38 Mbp (5% of the genome). 466 386 reads were obtained and assembled into 6 231 contigs, including 2 211 large contigs (over 500 bases, 832 bases average size, 14 860 bases largest size), and covered 2 953 454 bases.