Karyotypes of two cytotypes of Paspalum quadrifarium Lam. (Poaceae): an alternative technique for small chromosomes in plants

Abstract

Paspalum quadrifarium Lam. is a bunchgrass native to Uruguay, Argentina, and southern Brazil. Diploid, triploid, tetraploid and hexaploid cytotypes have been reported for this species of the Quadrifaria group of Paspalum. In this group, a high degree of cytogenetic homology between the genomes of several diploid species has been reported, based on meiotic pairing in interspecific hybrids; multivalent associations would thus be expected in polyploid hybrids. Karyotype analysis could provide useful information about the genomic architecture of polyploid plants; however, the fully condensed mitotic chromosomes of Paspalum do not provide enough morphological features for such an analysis. In this paper, we used mitotic prometaphase chromosomes treated with 70% acetic acid at 40°C after cover slip removal. This process removes cytoplasm that remains from chromosome squashes and makes prometaphases available for karyological analysis. The karyotypes of a triploid (2n = 3x = 30) and a tetraploid (2n = 4x = 40) accession of Paspalum quadrifarium were studied using this technique, and evidence of segmental allopolyploidy was found in both cases. In both accessions, meiotic behavior was in accordance with that origin. This technique greatly improved the number and quality of analyzable metaphases and prometaphases on otherwise conventional slides and is recommended for plants with small chromosomes.

Lippia alba (Verbenaceae): A new tropical autopolyploid complex?

“…Intraspecific variation has been reported in natural populations of Paspalum quadrifarium , Poaceae (Speranza et al, 2003); Senecio carniolicus , Asteraceae (Suda et al, 2007); Solidago altissima , Asteraceae (Halverson et al, 2008); Medicago sativa , Fabaceae (Havananda et al, 2011); Turnera sidoides , Turneraceae (Kovalsky and Neffa, 2012); and Phragmites australis , Poaceae (Nakagawa et al, 2013), among others. Although intraspecific variation has been reported for several species (Keeler and Davis, 1999; Kao, 2007; Duchoslav et al, 2014) it is not always possible to understand or even suggest the mechanism involved in the formation of cytotypes.…”

Chromosome numbers, DNA content, morphological data, and nrITS sequence analyses in some species of Nassella (Trin.) E. Desv. and related genera (Stipeae, Poaceae)

“…Roots tips were fixed in freshly prepared Carnoy (3:1 ethanol:acetic acid) for at least 24 h at room temperature and then stored at -20°C. Slides were prepared according to Speranza et al (2003) and Vaio et al (2005). For chromosome numbers, cells were stained with 2% lacto-propionic orcein and examined with an Olympus AHBS3 microscope.…”

Nuclear and cytoplasmic microsatellite markers for the species of the Dilatata group of Paspalum (Poaceae)

“…Recently, Machado et al (2005) have shown that there may be several additional pentaploid apomictic entities in the group which have not yet been described or named. Most of our knowledge of the group has been derived from chromosome numbers and pairing behaviour in hybrids between biotypes; however, only recently has it been possible to obtain further cytological information through the modification of cytological techniques that allow chromosome identification and karyotyping (Speranza et al , 2003; Vaio et al , 2005). In spite of this, cytogenetics alone cannot answer many of the questions that must be addressed in this group.…”