Assessment of genetic diversity within and among germplasm accessions in cultivated sorghum using microsatellite markers

Microsatellite markers are increasingly being used in crop plants to discri minate among genotypes and as tools in marker-assisted selection. Here we e valuated the use of microsatellite markers to quantify the genetic diversit y within as well as among accessions sampled from the world germplasm colle ction of sorghum. Considerable variation was found at the five microsatelli te loci analysed, with an average number of alleles per locus equal to 2.4 within accessions and 19.2 in the overall sample of 25 accessions. The coll ection of sorghum appeared highly structured genetically with about 70% of the total genetic diversity occurring among accessions. However, differenti ation among morphologically defined races of sorghum, or among geographic o rigins, accounted for less than 15% of the total genetic diversity. Our res ults are in global agreement with those obtained previously with allozyme m arkers. We were also able to show that microsatellite data are useful in id entifying individual accessions with a high relative contribution to the ov erall allelic diversity of the collection.