Studies about cytology, reproductive system and pollen-pistil compatibility in Panicum dichotomiflorum and Paspalum fasciculatum (Gramineae, Paniceae).

Abstract

Chromosome counts and meiotic chromosome behavior confirmed previous results for both species. One accession of Panicum dichotomiflorum Michaux, from Corrientes, Argentina, had 2n=4x=36 chromosomes with regular meiotic behavior. Three accessions of Paspalum fasciculatum Willd. ex Fluegge, two from Mato Grosso state, Brazil, and one from Chaco province, Argentina, had 2n=2x=20 chromosomes. This is the first report of the method of reproduction for both species. Embryological studies and observations on flowering habits and seed production indicated that Panicum dichotomiflorum, which is an annual species, reproduced sexually. lts floral arrangement, the flowering habit, and the lack of a genetic barrier to prevent self-fertilization suggested that the species reproduced mainly by autogamy. The three accessions of the perennial species Paspalum fasciculatum were sexual and self-incompatible. Since most diploid sexual self-incompatible species of the genus Paspalum usually have an apomictic tetraploid co-specific counterpart, it is possible that apomictic tetraploid races of Paspalum fasciculatum may also exist.