GIEMSA C-BANDED KARYOTYPES OF 2 CYTOTYPES (2X, 4X) OF PSATHYROSTACHYS-LANUGINOSA (POACEAE, TRITICEAE)

The karyotypes of the diploid (2n = 2x = 14) and tetraploid (2n = 4x = 28) cytotypes of the outbreeding P. lanuginosa collected from one pop ulation in China were investigated by Giemsa C- and N-banding and AgNO 3 staining. The complement of the diploid consisted of 14 large chromo somes: 8 metacentrics and 6 SAT-chromosomes, one metacentric and 2 sub metacentric pairs, with small to minute, polymorphic, completely heter ochromatic satellites. Except that only eight SAT-chromosomes were obs erved, the complement of the tetraploid matched a doubling of that of the diploid and indicated an autoploid origin. The existence of 12 chr omosomes with nucleolus organizers was established through AgNO3 stain ing demonstrating nucleoli. C-banding patterns comprised from zero to three (2x), or four (4x) small bands per chromosome giving a low conte nt of constitutive heterochromatin ( < 3 %). The level of banding patt ern polymorphism was low. N-banding produced no bands. Variation in th e size of nucleoli demonstrated a differential nucleolus forming capac ity of nucleolus organizers among SAT-chromosomes. The basic karyotype was similar to those of P. fragilis, P. juncea and P. stoloniformis, indicating a close relationship and the presence of genome N. Meiotic analysis suggested the presence of a chromosomal rearrangement in the diploid. The frequency of interstitial chiasmata was high. Differences in pollen diameters differentiated the two cytotypes.