Genomic relationship between diploíd cytotypes of Paspalum simplex and P. procurrens (Poaceae, Paniceae)

Abstract

Interspecific crossing was conducted between diploid cytotypes of two Paspalum species of the subgenus Anachyris in order lo investigate their genomic relationshíp and to evaluate the possibilities of gene exchange between these species as a tool ror their genetic improvement. Paspalum simplex was the female parent. The F₁ hybrids showed stoloniferous growth habit which is characteristic or the male parent, P. procurrens. Regular meiotic behavior in the F₁ hybrids demonstrated that both species have significant homology in their genomes. Embryological studies and seed production analysis under selfand cross-poIlinated conditions demonstrated that the hybrids, like their parents, are sexual and selfsterile bllt cross-compatible. Both, the high level of crossabitity or the parents and the degree of fertility observed in F₁ hybrids and in backcross progenies. indicated the feasibility of gene exchange between these species. Morphologically, P. simplex and P. procurrens are easily recognized as different species. Notwithstanding. the high crossability and the high level offertility observed in hybrids and backcrossed progenies contrast with the lack of intermediate forms observed in herbaria and during field trips. Diploid cytotypes of both species seem lo be restricted to western areas of the phytogeographic Chaco province, from Bolivia to Argentina. However, divergent evolution likely occurred in correlation with latitude and specific soil requirements. Diploid P. simplex was found in the southwestern Chaco province on clayey soil while P. procurrens was collected in the northwest of the province, growing on sandy soil.