Cytogenetics and Reproductive Behavior of Different Chromosome Races in Six Paspalum Species

Accessions of Paspalum Intermedium, P. quadrifarium, P. brunneum, P. haumanli, P. rufum, and P. maculosum were studied cytologically to determine their potential for use in a hybridization program. Diploid (2n = 2x = 20) and tetraploid (2n = 4x = 40) cytotypes were found for all six species. Two triploid (2n = 3x = 30) P. quadrifarium accessions and an aneuploid (2n = 4x = 39) of P. brunneum were also identified. The diploid accessions were meiotically regular, with primarily bivalent pairing at metaphase I. All diploid cytotypes developed one meiotic (cytologically reduced) embryo sac in each ovule, indicating sexual reproduction. However, most diploids developed an aposporous embryo sac in addition to the meiotic sac, indicating some potential for apomixis. The diploids were highly self-incompatible, and this should be beneficial for hybridization. Meiosis in tetraploids was more irregular, with the chromosomes associating as univalents, bivalents, quadrivalents, and other multivalent associations. The polyploids produced aposporous sacs in most ovules, but some normal meiotlc (Polygonum type) sacs were also present, indicating that most of the tetraploids were facultative apomicts. Polyploids set seed under isolation conditions.