Microsatellite markers are increasingly being used in crop plants to discriminate
among genotypes and as tools in marker-assisted selection. In this study microsatellite
markers were used to quantify the genetic diversity within as well as among 200
accessions sampled from sorghum germplasm collection at Tanzania National gene
bank germplasm collection of sorghum. Although all methods did not provide similar
description of relationships between accessions, there existed some consistency in
discriminating accessions which are closely related and the ones which were distantly
related. But, considerable variation was found at the 39 microsatellite markers
analysed, with an average number of alleles per locus equal to 9.49 within accessions,
the lowest was 2.0 from Xtxp114, Xcup61 and the highest number of allele was 25 as
for Xgap206 marker. The collection of sorghum appeared moderately structured
genetically with about 59% of the average gene diversity occurring among accessions.
The SSR markers were moderately polymorphic, with diversity
indices ranging from 0.07 to 0.91 with mean of 0.55.The UPGMA
dendrogram based on SSR marker data clearly discriminated among
clusters, even though some consistency in classification was
observed among clusters. However, differentiation among morphologically
accessions of sorghum, or among geographic origins, accounted for less than 35% of
the total genetic diversity. Data in this study demonstrated that accessions of Tanzania
sorghum contain a great deal of genetic diversity as indicated by the observed number
of alleles. These results are in global agreement with those obtained previously with
allozyme markers. It was also possible to show that microsatellite data are useful iniii
identifying individual accessions with a high relative contribution to the overall allelic
diversity of the collection. Therefore, from the result outcome the inventory was
compiled that will be used in future to characterize the rest of the sorghum germplasm
and make use of the identified potential parental genotypes for mapping populations
and marker assisted selection programs.
ICRISAT/BecA