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Paspalum notatum Flügge is a warm-season forage grass with sexual diploid and apomictic tetraploid races. Genetic improvement was achieved in out-breeding diploids. The acquisition of artificial sexual tetraploids has raised the possibility of performing crosses and plant improvement at the tetraploid level. The objective of our study was to obtain a genetic and cytoembryological characterization of a germplasm collection of P. notatum, including 31 accessions from seven countries of America and 11 experimentally obtained genotypes. Morphology of mature gametophytes was observed to assess the mode of reproduction of the accessions. A total of 1342 AFLP fragments were generated across the 42 genotypes and from two reference taxa: P. urvillei and P. procurrens. AFLP data were converted into a binary matrix and similarity relationships were established. The genetic distance among all the accessions showed a maximum value of 0.36. In addition, eleven AFLP fragments were observed exclusively in apomictic plants, which could be linked to genomic regions implicated in the control of apospory. [ABSTRACT FROM AUTHOR]

Paspalum notatum is a subtropical grass widely distributed in the temperate areas of America. Diploids are sexual while polyploids give rise to clonal seeds through aposporous apomixis. RAPD markers were used to analyze the genetic structure of three natural populations: i) diploids reproducing sexually (R2X); ii) sympatric apomictic tetraploids collected in the vicinity of the diploids (R4X); iii) allopatric apomictic tetraploids growing in isolation (C4X). The apomictic reproduction rate was evaluated by the use of molecular markers in progeny tests, while chromosome-counting allowed the verification of ploidy levels. Data revealed that the R4X group presented a variation considerably higher than that observed for C4X. Jaccard’s coefficients were used to produce a cluster diagram using the UPGMA method. All but one tetraploid genotypes grouped together and were associated to diploid genotype A21. The possibility of occasional generation of novel tetraploid clones from the interaction between tetraploid and diploid individuals is discussed. [ABSTRACT FROM AUTHOR]