Genetic diversity and relationships among sweet grain sorghum genotypes across agroclimatic zones revealed by SNP markers

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Résumé

Sweet grain sorghum is exploited in Burkina Faso through the consumption of fresh grains early at the doughy stage. To identify, valorise and conserve the genetic diversity of this agricultural resource, SNPs markers are essential tools. The aim of the present study is to assess the genetic diversity of sweet grain sorghum expressed in a linear DNA sequence, and to identify SNPs. To this effect, 50 sweet grain sorghum genotypes were sequenced using DArTseq genotyping platform. The results identified 4610 polymorphic loci with a major allele frequency ≤ 95%. The SNPs identified are made up of 55.23% transitions and 44.77% transversions with an average polymorphism information content of 0.26. The expected heterozygosity value He of 0.18 shows moderate genetic diversity in sweet sorghum in Burkina Faso. The results of the PCoA and AMOVA analyses revealed that genetic diversity is more closely linked to botanical race than to the area of origin of the genotypes. In addition, analysis of the population structure identified two homogeneous subpopulations and one admixture subpopulation. Subpopulation 1 contains 13 genotypes of the Caudatum-Guinea race, sub-population 2 contains 32 genotypes of the Caudatum race and the admixture sub-population contains 5 genotypes that could belong to the Guinea-Bicolor race. Genetic differentiation index was higher between subpopulation 2 and the admixture subpopulation (Fst = 0.26) and lower (Fst = 0.13) between subpopulations 1 and 2. The results of this study revealed the first SNP linkage map that can be used to identify QTLs for a marker-assisted breeding program in sweet grain sorghum.

Mots-clés

Burkina Faso; DarTseq; factors; Sorghum bicolor; population structure