Genetic diversity in sexual diploid and apomictic tetraploid populations of Paspalum notatum situated in sympatry or allopatry

Abstract

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.

Cytogenetic data for Paspalum notatum Flügge accessions

“…If other wild diploids were identified, they could have been used to introduce novel variation in P. notatum, but, until now, no other diploids have been located outside the Argentinian region of P. notatum var. saurae (Pozzobon & Valls, 1997;Daurelio et al, 2004). The objective of the present work was to determine chromosome numbers, chromosome associations at diakinesis and metaphase I, and pollen viability in accessions of P. notatum which are part of a breeding project.…”

“…Moraes-Fernandes et al (1973) found only the tetraploid level among the 16 Brazilian (Rio Grande do Sul) and one introduced accession from P. notatum. Daurelio et al (2004) reported that despite a search in other regions of Argentina, the diploids are all botanically P. notatum var. saurae and restricted to Northeastern and Central-Eastern Argentina.…”

Genetic gain in apomictic species of the genus Paspalum

“…In these conditions, native species of the genus Paspalum have advantages over the exotic species because of the greater adaptation and great intra-and interspecific variability in forage-related traits (Pereira et al, 2012;Daurelio et al, 2014).…”

Unusual chromosome numbers in Paspalum L. (Poaceae: Paniceae) from Brazil

“…Ploidy levels reported include 2x, 3x, 4x, 5x, 6x, 7x, 8x, 10x, and 12x, and species consisting only of sexual-diploid cytotypes are relatively uncommon. Apparently, sexual-diploids are distributed in rather restricted areas, as well as certain hybrid combinations (Quarín and Lombardo, 1986;Urbani et al, 2002;Daurelio et al, 2004). Moreover, groups previously thought of as rather simple autopolyploid assemblages have turned out to be complex interspecific hybrid groups (Vaio et al, 2005).…”

“…According to Bennett and Bashaw (1966), "every desirable characteristic of a forage plant can be found in some Paspalum species". A copious literature on the cytogenetics of Paspalum and its relationship to ploidy levels, reproductive systems, natural hybridization, genomic associations, and anatomical adaptations has accumulated during the last decades (Burson, 1983;Quarín, 1997, 1998;Daurelio et al, 2004;Machado et al, 2005; and references therein), regarding especially some polyploid hybrid complexes that include highly valuable forage species, as in the case of P. dilatatum Poir. Unfortunately, collections and data on genetics and reproduction from non-foraging species are far scarcer.…”