• C3 photosynthesis;
  • C4 photosynthesis;
  • chromosome number;
  • dodecaploid;
  • hexaploid;
  • octoploid;
  • Paniceae;
  • Panicoideae

A cytotaxonomic investigation was undertaken to assess the taxonomic status of the grasses Alloteropsis semialata subsp. eckloniana and A. semialata subsp. semialata, distinguished because of a C3 photosynthetic pathway in subsp. eckloniana and a C4 pathway in subsp. semialata. Of the 30 analysed specimens of population A, 14 (46.7%) were diploid, 14 (46.7%) hexaploid, one octoploid (3.3%) and one dodecaploid (3.3%). Of the 21 specimens of population B, 14 (66.7%) were diploid, three (14.3%) hexaploid and four (19.0%) octoploid. All the diploids belonged to subsp. eckloniana, while all the polyploids belonged to subsp. semialata. Meiosis of the diploids appeared normal, with nine bivalents and a mean metaphase I chiasma frequency of 12.7 per cell. The hexaploids displayed a large range of chromosome pairing associations, although a high percentage of bivalents was recorded (89.9%). Three of the hexaploids showed 100% bivalent pairing, but the largest multivalent found in other hexaploids was a hexavalent pairing. The three octoploids analysed had 93.5% bivalent pairing. B chromosomes were found in five diploids, two hexaploids and one octoploid. Slow-moving bivalents, two in the diploids and up to four in the polyploids segregated late at anaphase I in most specimens.