Genetic structure and gene flow in Ethiopian sorghum [Sorghum bicolor (L.) Moench] landraces

Understanding the genetic structure of sorghum is a baseline for developing effective variety selection, conservation and management strategies. Here, we addressed the genetic diversity and population structure of sorghum [Sorghum bicolor (L.) Moench] landraces using simple sequence repeat (SSR) markers. Seventy-seven sorghum accessions representing five regions and ten populations were analyzed using eleven SSR markers. Genetic diversity indices and diversity parameters were determined using GenAlEx, PowerMarker and Arlequin. Structure software was used to determine population genetic structure of sorghum. A total of 49 alleles with an average of 4.5 alleles per locus were identified. The average Shannon's diversity index and expected heterozygosity were 0.61 and 0.36, respectively. The polymorphic information content (PIC) ranged from 0.23 to 0.67 with an overall mean of 0.48. The study revealed high gene diversity within the populations ranging from 0.25 to 0.72 with an overall mean of 0.53. AMOVA revealed 82.21% and 79.22% of total variation within regions and populations respectively, leaving only 17.79% and 20.78% variations for among regions and populations. The unweighted neighbour-joining based clustering, PCoA, and population structure analysis failed to group accessions according to their collection region and population. It indicates the presence of high gene flow between regions (Nm = 1.16) and populations (Nm = 0.95). Similarly, structure analysis confirmed two sub-groups with a greater degree of genetic admixture for both regions and populations. Therefore, the present study has generated useful information on the genetic diversity and structure of Ethiopian sorghum landraces which could be used for its improvement and conservation.