DNA POLYMORPHISMS IN GRAIN-SORGHUM (SORGHUM-BICOLOR (L) MOENCH)

Molecular markers [random amplified polymorphic DNA (RAPD) and restric tion fragment length polymorphism (RFLP)] were used to determine the f requency of DNA polymorphism in grain sorghum (Sorghum bicolor (L.) Mo ench). Twenty-nine oligonucleotide primers were employed for RAPDs, ge nerating a total of 262 DNA fragments, of which 145 were polymorphic i n at least one pairwise comparison between 36 genotypes. Individual pr imers differed significantly in their ability to detect genetic polymo rphism in the species. The overall frequency of polymorphisms was low with a mean frequency of 0.117 polymorphisms per RAPD band being obtai ned from all pairwise comparisons between genotypes, with maximum and minimum values of 0.212 and 0.039, respectively. Results from phenetic analysis of bandsharing data were consistent with current sub-specifi c groupings of the species, with clusters of Durra, Zerazera, Caud-Nig , Caud-Kaura and Caffrorum being discernible. The results also indicat ed that individuals of a similar taxonomic grouping but different geog raphic origin may be genetically less identical than previously consid ered. Similar frequencies of polymorphism to that obtained with RAPDs were obtained with RFLPs. Results from these experiments indicated tha t a high level of genetic uniformity exists within S. bicolor.