Genetic Diversity of Sorghum (Sorghum bicolor (L.) Moench) Germplasm from Major Growing Areas of Ethiopia Using Simple Sequence Repeat (SSR) Markers

Abstract

Ethiopia is the center of origin of sorghum having wide variation of the crop. Evaluations and understanding of the genetic diversity of the species is fundamental to design appropriate conservation and management strategies. Therefore, the present study was designed to assess the genetic diversity and population structure of sorghum germplasm collected from major growing regions of Ethiopia. Eighty sorghum germplasm representing five populations were analyzed with 11 Simple Sequence Repeat (SSR) markers. A wide range of diversity indices including polymorphic information content (PIC), number of alleles, effective number of alleles, number of private alleles, Shannon's diversity index, expected heterozygosity and percentage of polymorphic loci (PPL) were computed to determine genetic variation within populations. Analysis of molecular variance (AMOVA) was executed to see genetic variation within and among populations. The unweighted Neighbour-joining-based cluster analysis, Principal components of analysis (PCoA) and structure analysis were done to elucidate clustering of populations based on their coefficient of similarity. All the microsatellite markers used in the present study were polymorphic and highly informative. The computed polymorphic information contents (PIC) ranges from 0.50 to 0.86 with a mean value of 0.75. A high within-populations genetic diversity was confirmed with gene diversity values ranging from 0.51 to 0.77 with an overall mean of 0.67. Moreover, AMOVA revealed that 93.26% of the total genetic variation was accounted for within populations, leaving only 6.74% for among populations. The unweighted Neighbour-joining-based cluster, PCoA and structure analysis failed to reveal a clear grouping of germplasm according to their geographical origins, confirming the high gene flow (Nm=6.65) among populations. In conclusion, the SSR markers used in the present study were highly informative and revealed the genetic structures of sorghum populations in Ethiopia. Among the studied populations, those from Oromia and Amhara displayed gene diversity greater than the grand mean value of 0.67 suggesting that these locations should be targeted to generate baseline information for breeding and conservation of Sorghum. The result of this study suggested that future germplasm collection and utilization strategies should take into consideration the magnitude and pattern of genetic diversity established at the genotypic level.