Chromosome number and ploidy level of some South American species of Schizachyrium (Poaceae, Andropogoneae)

Chromosome numbers are reported here for 53 accessions belonging to 13 taxa of the genus Schizachyrium. The chromosome counts for the following seven species are recorded here for the first time: S. bimucronatum (2n = 20), S. gracilipes (2n = 20), S. hatschbachii (2n = 20), S. lactiflorum (2n = 20), S. plumigerum (2n = 20), S. salzmannii (2n = 20; 2n = 40) and S. spicatum (2n = 20). Counts differing from those previously reported are given for two species: S. scabriflorum (2n = 20 and 80) and S. tenerum (2n = 40). Most of the analyzed species of this genus are diploids. The occurrence of polyploidy in S. glaziovii, S. lactiflorum, S. salzmanni, S. scabriflorum and S. tenerum is reported here for the first time. Data on chromosome numbers and ploidy levels are discussed in relation to the taxonomy and evolution of the genus.