A Tetraploid Cytotype of Paspalum Durifolium: Cytology, Reproductive Behavior and Its Relationship to Diploid P. Intermedium

Abstract

Paspalum durifolium is a South American bunchgrass that was previously reported to be an apomictic allohexaploid species. Ten accessions from recently acquired germplasm were investigated for ploidy level. Eight were tetraploid (2n = 4x = 40) and two were hexaploid (2n = 6x = 60). This is the first report of tetraploid plants in P. durifolium. The 4x accession Q‐3947 was chosen for cytological and embryological studies. It showed regular meiosis with primarily bivalent chromosome pairing. Embryological surveys demonstrated that this tetraploid reproduces sexually. Studies on pollen germination and pollen tube growth, after self and after open pollination, suggest that the tetraploid cytotype has a genetic system to prevent self‐fertilization. A controlled interspecific hybrid (2n = 3x = 30) was obtained among diploid P. intermedium (genome formula II) and tetraploid P. durifolium. The mean meiotic chromosome association for the hybrid was 8.7 I, 7.5 II, and 2.1 III with a range per cell of 5–14 I, 4–10 II, and 0–5 III. These results indicate that the parents of the hybrid have one homologous genome. However, some chromosomes of the P. intermedium genome may have some residual homology with chromosomes of the second genome of P. durifolium. Copyright © 1994, Wiley Blackwell. All rights reserved