Identification of the somatic chromosomes of Psathyrostachys fragilis (Poaceae)

The karyotype of the outbreeding P. fragilis (2n = 2x = 14) was investigated by Feulgen staining and by C-, N-, and Ag-banding techniques. The complement consisted of 14 large chromosomes, 8 metacentrics and 6 satellite (SAT) chromosomes, probably among the longest within the Poaceae. Two SAT-chromosome pairs carried small, and one pair carried minute, polymorphic, completely heterochromatic satellites. Each chromosome could be referred to one of the seven chromosome pairs by its C-banding pattern. The patterns comprised from zero to three conspicuous, but not large bands per chromosome resulting in an overall low content of constitutive heterochromatin (<4%). The C-banded karyotype of P. fragilis differed from any previously reported in the Triticeae. Six of seven chromosome pairs were polymorphic either for C-banding patterns or satellite size (or for both). N-banding gave no differential staining of chromosomes. Silver nitrate staining established that the nucleolar organizers had different nucleolus-forming capacities. The presence of the small and minute satellites was more consistently demonstrated after C- and N-banding than after Feulgen staining.Key words: Triticeae, Poaceae, karyotype, C-, N-, and Ag-banding.