Interspecific hybrids between Paspalum plicatulum and P. oteroi: a key tool for forage breeding

Abstract

Grama-tio-pedro (Paspalum oteroi Swallen) is a rare stoloniferous grass of the Plicatula group of Paspalum, well adapted to continuous grazing in areas subject to seasonal flooding in the Pantanal region, in central western Brazil. The species is a facultative apomictic (asexual reproduction by seed) tetraploid, sporadically cultivated in Pantanal farms, either propagated by cuttings or seed. Due to its potential for extensive cultivation and its forage quality, it appears as a good candidate for genetic improvement within the Plicatula group through plant breeding. Taking advantage of a colchicine-induced sexual autotetraploid genotype of P. plicatulum Michx. we obtained interspecific hybrids by using the apomictic species, P. oteroi, as pollen donor. The very similar meiotic chromosome behavior observed in both parents, with mainly quadrivalent and bivalent associations, suggested that P. oteroi is a natural autotetraploid. The hybrids showed less irregular meiotic behavior with fewer quadrivalents and more bivalents than either parent. The fertility among interspecific hybrids varied from complete sterility in some of them, to seed productions in others that were approximately twice as much as for either parent. The great variability of seed set performance may well be a drastic genetic consequence of joining two homologous chromosome sets of P. plicatulum together with two homologous sets of P. oteroi which in turn have some homeology between them. Because most hybrids reproduce by mean of sexuality, they could be used as female parents in backcrosses and in crosses with other species of the Plicatula group for interspecific gene transferring in breeding programs.