How the genome diversity of major crops tells the story of their evolution

The Cavendish variety of banana (below) is common in supermarkets, yet it has a complex genomic make-up. Angélique D’Hont, Fourni par l'auteur

On March 27, 2024, a study published in the scientific 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.