Diversity in Diploid, Tetraploid, and Mixed Diploid–Tetraploid Populations of Paspalum simplex

Abstract

The tetraploid cytotype of Paspalum simplex Morong has a wide geographical distribution and reproduces by apomixis while the diploid grows in a restricted area in northern Argentina and behaves as cross‐pollinated. The objective was to evaluate the genetic diversity among and within natural diploid and tetraploid populations of P. simplex growing in sympatry and allopatry by studying the phenotypic variability and DNA polymorphisms. Twenty‐three phenotypic traits and 10 inter‐simple sequence repeat (ISSR) molecular markers were used for evaluating the variability present in six populations of P. simplex. Two populations were diploid and four were tetraploid. One of the tetraploid populations was sympatric to a diploid population while the rest of the populations were allopatric. A rich diversity was observed for specific traits, especially for seasonal biomass yield, presence of a terminal raceme in the inflorescence, and leaf pubescence. The 2x and 4x populations growing in proximity were closely related. Diversity was higher within diploid populations when compared with the evaluated tetraploid populations. Among the tetraploid populations, the one sympatric with a diploid population exhibited the greatest diversity. Gene flow occurs between 2x sexual and 4x apomictic populations of P. simplex. Diploid populations seem to be the main source of the diversity observed among tetraploid populations.

Diversity in Apomictic Populations of Paspalum simplex Morong

“…These results indicate that most of the diversity present in polyploid germplasm is allocated among populations (Fig. These polyploid genotypes are expected to have originated within the sexual 2x populations (Brugnoli et al, 2013) and distributed throughout the rest of the region. Preliminary observations about this phenomenon have been previously reported for Paspalum notatum (Daurelio et al, 2004), P. simplex (Brugnoli et al, 2013), and P. denticulatum (Sartor et al, 2013).…”

“…As in many other genera, apomixis is always linked to polyploidy (Ortiz et al, 2013). Most importantly, tetraploid populations living in proximity to diploid populations are highly variable and share most of the contained variability with the neighboring 2x population (Daurelio et al, 2004;Brugnoli et al, 2013). Paspalum notatum and P. simplex have been the best characterized species of the genus since they share genetic characteristics that represent a high proportion of the Paspalum species.…”

“…They both are also considered good forages by the local ranchers, and P. notatum is also cultivated in several countries. Moreover, variation for the within-population diversity has been observed among three allopatric populations of P. simplex (Brugnoli et al, 2013). The diploid cytotype is sexual and cross-pollinated, while the polyploid plants are apomictic.…”

“…The diploid and mixed diploid-tetraploid populations were previously reported in Crop Science(Brugnoli et al, 2013). Only the 17 pure polyploid populations were used in this research.…”

Inference of individual ploidy level using codominant markers

“…A significant portion of plant species are polyploids, with 24% of all plant taxa being polyploid (Barker, Arrigo, Baniaga, Li, & Levin, ), and 47% to 100% of angiosperm species traced to a polyploidy event in the past (Wood et al, ). Ploidy levels sometimes vary among individuals or populations (Gompert & Mock, ), with mixed‐ploidy populations also occurring (e.g., Spartina pectinata [Kim, Rayburn, Boe, & Lee, ], Chamerion angustifolium [Martin & Husband, ], Paspalum simplex [Brugnoli, Urbani, Quarin, Martínez, & Acuña, ], Aster amellus [Castro, Loureiro, Procházka, & Münzbergová, ], Lycoris radiata [Liu, Xia, Zheng, Zhi, & Zhou, ]).…”