Molecular Diversity among Sorghum (Sorghum bicolor (L.) Moench) Landraces in Uganda

The variability in sorghum germplasm is an invaluable input for sustaining and improving sorghum productivity. A wide range of variability in phenotypic traits exists among landraces in Uganda. However, the diversity of the germplasm at the molecular level is not described and therefore not known which hinders its use in modern plant improvement programs. This study was therefore undertaken to classify 241 sorghum accessions collected from different agro-ecological regions based on genetic distances estimated using 21 Simple Sequence Repeat (SSR) markers. The SSR primers were highly polymorphic with average Polymorphic Information Content (PIC) of 0.65 ranging from 0.09-0.89. A total of 205 alleles (9.8 alleles per locus) as well as a number of rare alleles were observed across all the accessions and this provides an opportunity for generation of a comprehensive fingerprint database. Gene diversity ranged from 0.09-0.90 with an average of 0.68. The average heterozygosity detected was 0.18 ranging from 0.00-92%. Analysis of molecular variation showed that variation was higher within races and agro-ecologies than among races and agro-ecological zones, respectively and this indicated the significance of gene flow. Cluster analysis delineated the accessions into two distinct clusters each with seven sub-clusters mainly according to agro-ecological zone. Clusters IA and IB had the most distinct accessions and these could be utilized in pre-breeding programmes aimed at overcoming yield barriers. The results confirm the ability of SSR markers to discern variability and also serve as guide for germplasm collection and conservation strategies.