Genetic diversity and phylogenic relations among Sahelian sorghum accessions

To establish the genetic relationship among Sahelian sorghum [Sorghum bicolor (L.) Moench S.L.] landraces from Burkina Faso were submitted to electrophoretic analysis for 10 enzymatic systems and 18 loci. Four enzymatic systems (ADH, LAP, MDH, PGD) and five loci revealed polymorphism both within and among landraces. Thirty-eight per cent of the landraces were monomorphic in all the 18 loci. The genotypic frequencies in most of the landraces deviated markedly from Hardy-Weinberg proportions due to a major heterozygote deficit, the landrace being homozygous or a mixture of homozygotes. Multivariate analysis yielded three main groups, containing native landraces and five minors, containing introduced cultivars, randomly distributed over the territory. The pattern of allelic occurrence was random and unrelated to external selection pressures. The major diversity among landraces appears to be from genetic shift caused by farmers' selection of their seeds. It could also be due to the low rates of outcrossing (19%) and migration (0.06) prevailing in the set.