The highly complex sugarcane genome has finally been sequenced

Sugarcane was the last major cultivated plant to have its genome sequenced. This was because of its huge complexity: The genome comprises between 10 and 12 copies of each chromosome, while the human genome has just two. 

It was an international team coordinated by CIRAD that achieved this milestone, as reported in Nature Communications on July 6. It will now be possible to modernize the methods used to breed sugarcane varieties. This will be a real boon to the sugar and biomass industry.

Sequencing the sugarcane genome was so complex that conventional sequencing techniques proved useless. This meant that sugarcane was the last major cultivated plant to have its genome sequenced.

The team took up the gauntlet using a new approach based on a discovery made at CIRAD some 20 years previously: The genome structures of sugarcane and sorghum are very similar. The term for this is "collinearity," which means that there is a degree of parallelism, with numerous genes occurring in the same order. Olivier Garsmeur, a CIRAD researcher and lead author of the study, was thus able to use the sorghum genome as a template to assemble and select the sugarcane chromosome fragments to sequence. "Thanks to this novel method, the reference sequence obtained for a cultivar from Réunion, R570, is very good quality," says Angélique D'Hont, a CIRAD geneticist who coordinated the study.

That reference sequence is a vital step toward fully sequencing the sugarcane genome and analysing the variations between the various sugarcane varieties more effectively. Angélique D'Hont had the same experience with the banana genome in 2012. She says, "having a reference sequence for a species radically changes all the genomic and more broadly genetic approaches for that species."