VARIATION AND GEOGRAPHICAL-DISTRIBUTION OF PLOIDY LEVELS IN PENNISETUM SECTION BREVIVALVULA (POACEAE) IN BURKINA-FASO, BENIN AND SOUTHERN NIGER

Pennisetum sect. Brevivalvula is a species complex characterized by po lyploidy and apomixis. Ploidy level was assessed by DAPI-flow cytometr y for 304 plants of the section, originating from Burkina Faso, Benin and southern Niger. The results were confirmed for 54 plants based on chromosome counts. The samples show four euploidy levels (with x = 9) distributed among five species: P. hordeoides (2n = 36, 54), P. pedice llatum (2n = 36, 45, 54), P. polystachion (2n = 18, 36, 45, 54), P. se tosum (2n = 54), and P. subangustum (2n = 18, 36, 54). The geographica l distribution of these ploidy levels seems related to major vegetatio n zones present in Africa. Diploid populations of P. polystachion and P. subangustum were found in the Banfora area, in Burkina Faso.