Citoembriología y comportamiento reproductivo de un citotipo diploide de Paspalum hydrophilum y sus híbridos con P. palustre.

MARTÍNEZ, ERIC J.; QUARIN, CAMILO L.

DARWINIANA

Instituto de Botánica Darwinion (Academia Nacional de Ciencias Exactas, Físicas y Naturales y Consejo Nacional de Investigaciones Científicas y Técnicas)

Lugar: Albarden 200, 1642 San Isidro, Buenos Aires, Argentina; Año: 1999 vol. 37 p. 243 - 251

0011-6793

Paspalum hydrophilum is a tetraploid, facultative apomictic, pseudogamous and self-compatible species for which  occasional diploid and triploid plants have also been found. Three  new plant collections from Mato Grosso, Brasil, were cytologically and embryologically surveyed. All three accessions were diploid (2n=2x=20), sexual, and allogamous due to self-incompatibility. Reciprocal crosses concerning two diploid P. hydrophilum accessions and one plant of diploid P. palustre produced several interspecific hybrids. Crossability, the number of hybrids obtained every 100 pollinated spikelets, ranged from approximately 8% to 28%. The hybrids showed regular meiotic behaviour with 10 bivalent chromosome associations at meiosis, indicating a high chromosome homology among these species. The F1 hybrids inherited self-incompatibility from both parents, attributable to pollen-pistil interactions that arrested pollen tube growth  at the central axe of the stigma. Low seed fertility was observed under open pollination. Seed performance ranged up to approximately 23% when parental pollen was dusted on hybrids. This performance may allow  to transfer genes among these species. Our results showed a close phylogenetic relationship among P. hydrophilum and P. palustre and indicate the feasibility  of  genetic exchange between them. Though the distribution area of P. palustre overlap the more extensive area of P. hydrophilum, natural hybridisation was not observed. Allopatry of the diploid cytotypes of these species  may account for lack of natural introgression.