Genome Wide Association Analysis of Biomass Yield and Stem Composition in a Sorghum Backcross Nested Association Mapping Design

Recently, sorghum biomass production and its composition became specific targets of breeding programs in accordance with their importance for animal nutrition and energy / biomaterial applications. In this context, it is of key importance to understand well the accumulation and especially the composition of biomass in order to maximize genetic gains per unit of time. These growing traits and biochemical components are strongly regulated by major genes affecting maturity (Ma), dwarfism (dw), lignin composition (bmr) and juiciness of the stem (d). However, a deeper understanding of the genetic determinism of these traits and the additional genomic regions exhibiting smaller effects on the traits variability is required and are still unknown. A multi-parental BCNAM design involving 2 elite recurrent parents and 29 donor parents has been developed by the Malian breeding program. This design, which combined the advantages of biparental QTL detection and association mapping involves approximately 1600 BC1F4 families that have been phenotyped over 2 years for their cycle duration and it components and the stem biochemical composition (Van Soest and Aufrere parameters) at the grain physiological maturity. Genome-wide association study (GWAS) was performed using 51 000 SNP obtained by Genotyping by Sequencing (GBS). Genomic regions encompassing already detected major effect genes (Ma, Dw) and new candidate regions have been identified. Based on these results putative candidate genes have been identified. The benefits of this BCNAM design regarding genetic analyses and breeding applications for the soudano sahelian regions and more generally for the sorghum scientific community will be discussed.