Cytogenetics and Reproduction of Paspalum dasypleurum and Its Hybrids with P. urvillei and P. dilatatum Ssp. Flavescens

Abstract

Paspalum dasypleurum has the southernmost distribution of the Paspalum species in South America. It is a sexual, self-fertile tetraploid with 40 chromosomes that pair as 20 bivalents at meiosis. This is the first report concerning its cytology and reproductive behavior. Morphologically, this species belongs to the Dilatata group and was crossed with two other tetraploid taxa of the same group: Paspalum urvillei (Vaseygrass) and Paspalum dilatatum ssp. flavescens (yellow-anthered Dallisgrass), both with the genome formula II JJ. Crossability between P dilatatum ssp. flavescens (female) and P. dasypleurum (male) was 0.8%, and their hybrids showed regular meiotic behavior with 20 bivalents. All hybrids were male-sterile, but approximately 8% of the spikelets set seed after backcrossing with pollen from either parent. Crossability between P. dasypleurum (female) and P. urvillei (male) was 53.9%, and their hybrids had regular meiotic behavior with 20 bivalent at diakinesis and metaphase I. All hybrids had indehiscent anthers, and none produced seed when selfed. Backcrosses to P. dasypleurum set a mean of 4.8% seed, and 18.6% (mean of five F1 plants) to P. urvillei. The regular meiotic chromosome pairing in P. dilatatum ssp. flavescens x P. dasypleurum and P. dasypleurum x P. urvillei hybrids indicated that P. dasypleurum has the I and the J genomes that were previously described for tetraploid biotypes of P dilatatum and for P. urvillei. The ability of the hybrids to produce seed following backcrossing suggests that gene exchange through hybridization may be a feasible method for plant improvement among these species.