On March 27, 2024, a study published in the journal Nature announced that the sugarcane genome had at last been cracked. This was a remarkable achievement because of the complexity of the sugarcane’s genome. That of rice, the first crop genome to be sequenced, more than 20 years ago, was „simple“: 12 chromosomes, two identical copies of each, for a total of 400 million base pairs (Mb) (nitrogen base pairs located on two complementary DNA strands).
a study published in the journal Nature announced that the sugarcane genome had at last been cracked. This was a remarkable achievement because of the complexity of the sugarcane’s genome. That of rice, the first crop genome to be sequenced, more than 20 years ago, was „simple“: 12 chromosomes, two identical copies of each, for a total of 400 million base pairs (Mb) (nitrogen base pairs located on two complementary DNA strands).
Sugarcane is much more complex: the plant, a polyploid, contains more copies of each chromosome than conventional plants. It has 10 times more chromosomes to sequence than rice, each of them longer, for a genome that is 20 times the size. To crack the code, the CIRAD research team came up with the idea of using sorghum as a model, as it is a close cousin from the same family (Graminaceae or grasses) with far less redundancy in its genome.
But why bother studying the genome of crops and their different varieties? The diversity they contain in fact reveals the way in which they have evolved as farmers have selected them in different environments and for various purposes. For instance, rice has evolved through mutations and natural crosses between different forms that appeared around the Himalayas, which were selected each year during its domestication, which began as much as 10,000 years ago. This has resulted in a sufficient number of varieties to guarantee production in a vast range of environments.
Sugarcane, for its part, comes from the islands of Southeast Asia: it is the result of broader genetic mixing, incorporating several related species. This has enabled it to combine resistance to various diseases and incomparable vegetative vigor, making it the plant that is most efficient at producing biomass. It is so tolerant of genetic mixing that all sorts of hybrids can be produced, even intergeneric ones, combining different botanical species.
Understanding how plants have adapted in the past serves to plan and speed up future crop adaptations.
This is what prompted CIRAD to set up a tropical species genome analysis laboratory as long ago as 1986. The laboratory later became the Grand plateau technique régional de génotypage (regional genotyping platform). Its teams produced the first genetic maps and then, thanks to the national genotyping structure, notably the Génoscope, and to various international collaborations, they made the news in the 2010s by placing several tropical plants among the leading biological models, for instance cocoa, banana and citrus.
