A step towards association studies for amylose and protein contents in sorghum

Sorghum is a crucial food crop in Africa and Asia and has a significant role as feed in the Americas and Europe. Grain quality determined by amylose and protein contents is an important trait for varietal acceptance by consumers. The genetic traits have been previously explored using QTL approaches. To validate candidate genes, we started association studies in a sorghum core collection of 210 accessions whose structure is already well understood. Using cereal sequences of the Waxy and Opaque-2 genes involved in amylose and protein content respectively, we designed primers and sequenced the amplification products to detect single nucleotide polymorphism (SNPs). Using a set of 22 accessions representative of the core collection diversity, we sequenced 53 and 47% of the Waxy and Opaque-2 genes, respectively. We found 21 SNPs in the Waxy gene, 5 being non-synonymous, which allowed grouping the 22 accessions into 7 haplotypes. For Opaque-2, we found 9 SNPs, one being non-synonymous, defining 3 haplotypes. These SNPs will be genotyped in the whole core collection. We phenotyped the core collection for amylose and protein contents using near infra-red spectrometry (NIRS). From the results of a first NIRS run, a sample of 110 accessions was selected to be analyzed chemically and was used for the establishment of calibration equations. The phenotypes of the remaining accessions were predicted by NIRS. Prolamine profiles were established by HPLC. All accessions were phenotyped for vitreousness and hardness index. Association tests will be carried out. (Texte integral)