The Pattern of Genetic Variability in Apomictic Clones of Taraxacum officinale Indicates the Alternation of Asexual and Sexual Histories of Apomicts

Abstract

Dandelions (genus Taraxacum) comprise a group of sexual diploids and apomictic polyploids with a complicated reticular evolution. Apomixis (clonal reproduction through seeds) in this genus is considered to be obligate, and therefore represent a good model for studying the role of asexual reproduction in microevolutionary processes of apomictic genera. In our study, a total of 187 apomictic individuals composing a set of nine microspecies (sampled across wide geographic area in Europe) were genotyped for six microsatellite loci and for 162 amplified fragment length polymorphism (AFLP) markers. Our results indicated that significant genetic similarity existed within accessions with low numbers of genotypes. Genotypic variability was high among accessions but low within accessions. Clustering methods discriminated individuals into nine groups corresponding to their phenotypes. Furthermore, two groups of apomictic genotypes were observed, which suggests that they had different asexual histories. A matrix compatibility test suggests that most of the variability within accession groups was mutational in origin. However, the presence of recombination was also detected. The accumulation of mutations in asexual clones leads to the establishment of a network of clone mates. However, this study suggests that the clones primarily originated from the hybridisation between sexual and apomicts.

New chromosome counts and genome size estimates for 28 species of Taraxacum sect. Taraxacum

“…Such unusual homogeneity among species in T. sect. Taraxacum rather than great morphological (and ecological) variability might reflect a young evolutionary origin, which is likely in contrast to sections Palustria , Erythrosperma and others that may partly consist of evolutionarily older species (Wittzell 1999, Majeský et al 2012, Kirschner et al 2015). Although there is no evidence for the potential evolutionary scenario in European Taraxacum sections, we can speculate that the origin of apomictic species of T. sect.…”

Genetic structure and diversity in natural populations of three predominantly self-pollinating wild Lactuca species in Israel

“…These EST-SSR loci were chosen for their high diversity values. Preparation of the PCR mix was performed according to Majeský et al (2012). The number of cycles and the annealing temperatures were adjusted for each locus, in order to obtain unambiguously scorable products.…”

Sexual reproduction efficiency and genetic diversity of endangered Betula humilis Schrk. populations from edge and sub-central parts of its range

“…Genetic diversity in the populations studied was assessed using the amplified fragment length polymorphism (AFLP) method. Of eleven populations, nuclear microsatellites had previously been investigated at ten sites (Jadwiszczak et al 2011a,b), but the AFLP method, which can discover hundreds of DNA loci throughout the whole genome, is a more effective tool than microsatellites to test for clonal identity between individuals and thus to draw conclusions about sexual and asexual modes of reproduction (Mueller and Wolfenbarger 1999;Kameyama and Ohara 2006;Majeský et al 2012). …”