Interspecific Hybrids between Five Paspalum Species

Abstract

Interspecific crosses were made among Paspalum intermedium Munro, P. haumanii Parodi, P. brunneum Mez, P quadrifarium Lam., and P. rufum Nees, species with both sexual diploid (2n = 20) and apomictic tetraploid cytotypes. Eight different interspecific hybrid progenies involving diploid species were recovered from crosses using P. intermedium or P. haumanii as the female parent. When P. rufum was the female parent in crosses with the other four species, only the hybrid with P. intermedium as pollen donor was recovered. Paspalum brunneum as female parent gave hybrid progenies only with P. rufum. All hybrids had 2n = 20 chromosomes, and the degree of meiotic pairing was high in most of them. Excepting P. haumanii x P. brunneum, all other hybrids had some pollen mother cells (PMC) with 10 II. Paspalum haumanii x P. brunneum had the least number of bivalents (mean = 4.7, maximum = 7 II). Almost complete pairing was observed in P. intermedium x P. haumanii and P. quadrifarium x P. brunneum, with a mean of 9.86 and 9.9 bivalents/PMC, respectively. The high degree of meiotic pairing in the hybrids is consistent with morphological and ecological affinities of the species as well as their geographical distribution. The data indicate that the genome of each of these species evolved from an ancestral common basic genome, and each of them may be a particular form of the I genome previously assigned to P intermedium. The low rate of crossability among these five species and the high sterility of the hybrids are important barriers preventing introgression.