The international effort to sequence the 17Gb wheat genome: Yes, Wheat can

Genome sequencing is a widely accepted mechanism to understand the molecular basis of phenotypic variation, accelerate gene cloning and marker assisted selection, as well as improve the exploitation of genetic diversity for efficient crop improvement. While rice and maize improvement is profiting already from information derived from their genome sequences, wheat has been lagging behind for the past decade. Bread wheat is grown on over 95% of the wheat growing area and has been chosen by the International Wheat Genome Sequencing Consortium (IWGSC, www.wheatgenome.org) as a target for genome sequencing. However, with a genome size 40 times that of rice, it represents a challenge for molecular studies. To meet this challenge and overcome the difficulties related to the size (17 Gb), and complexity (hexaploidy) of the bread wheat genome, the IWGSC decided to develop a strategy based on (1) the isolation individual chromosomes by laser flow cytometry and the construction of BAC libraries for each of the 21 wheat chromosomes, (2) the construction of physical maps anchored to genetic maps using these BAC libraries and (3) the sequencing of each chromosomes. As a proof of concept we constructed and sequenced using NGS technologies, the physical map of the largest hexaploid wheat chromosome (3B; 1Gb). The physical map of the other 20 chromosomes is well underway and various sequencing efforts have been launched to produce survey sequences for each of the chromosomes while waiting for the MTP based reference sequences. An overview of the strategies and results will be presented.