Sorghum [Sorghum bicolor (L.) Moench], a cereal crop of family Poaceae, is believed to be originated in Ethiopia and Sudan. It is an important food security crop mainly in semi-arid and tropical parts of the African countries. Although many morphological and molecular diversity studies reveal the existence of genetic variations with sorghum populations, their distribution within basic races were not considered. Hence, the present study aimed to analyze the extent and distribution of genetic variation within basic Ethiopian sorghum landraces using SSR markers. A total of 107 landraces obtained from Ethiopian Biodiversity Institute (EBI) representing 12 ecological zones grouped according to their race types based on inflorescence and spiklet on field at their maturity time. Twelve SSR markers revealed a total of 110 alleles with average polymorphic content of 0.76 and the allele frequencies shows 42 of them were rare (less than 0.05), 22 ranged from 0.05 to 0.1, while 46 of them were higher than 0.1. Expected and observed heterozygosity were 0.78 and 0.2 respectively. The genetic differentiation between populations were also moderate (FST=0.07 for races and 0.13 for E/zones) indicating continuous exchange of genes among them. Partitioning the total genetic variation also, indicated 61.38% and 55.17% of the variations were among individuals within racial and zonal populations respectively. Neighbor-Joining cluster analysis also indicated four major grouping of the landraces according to their racial groups where majority of race caudatum and durra form separate groups while intermediate durra-bicolor form two separate sub-clusters. Overall locus, the intra-racial population diversity showed the greatest genetic diversity (He=0.77 and 0.75) among race dura-bicolor and caudatum respectively. Information with sorghum races along their important agronomic traits could be used for conservation and future breeding programs of sorghum.

Keywords: Sorghum bicolor, races, Genetic diversity, SSR