Measurement of nuclear DNA content of the genus Trifolium L. as a measure of genebank accession identity

Abstract

The collection, identification and maintenance of genebank accessions of the genus Trifolium is a major task because of the large number of genera and their occasional morphological similarity. We investigated whether the measurement of nuclear DNA content can serve as an additional criterion for identification of mislabeled accessions. Relative nuclear DNA content was determined by flow cytometry measurements for a total of 151 genebank accessions of 23 Trifolium species with notable agronomical value. Among 23 species analyzed, 15 were found to possess a uniform relative nuclear DNA content, with intraspecific variability of the majority of analyzed species lower than 5%. Within six Trifolium species, 1-2 atypical accessions with outstanding differences in relative DNA content, chromosome number and morphological features were found. In T. hybridum and partially in T. ambiguum these outstanding differences could be ascribed to variations in accession ploidy level. For the remaining atypical accessions, the determined nuclear DNA content, chromosome number and morphological features were not related to those characteristic of the species. Additionally taxonomic identity of atypical accessions was determined using ITS region sequencing and morphological observations. We propose flow cytometric measurements of nuclear DNA content as simple and reliable technique which can be used at seedling stage to verify identity and genetic stability of Trifolium genebank accessions.

Genome Size Variation inMalusSpecies

“…This variation within a ploidy level for the genus Malus is rather small when compared to other genera. Comparable studies investigating species within a genus demonstrated 1.7-fold difference of 2C DNA content in 34 Central European diploid species of Cirsium [20], while fourfold difference in DNA content was reported among 25 diploid species of Lactuca [21] and 23 Trifolium species [22]. Our investigations in Pyrus using 17 different species demonstrated only a difference of 0.067 pg (data not published).…”

Genome size stability across EurasianChenopodiumspecies (Amaranthaceae)

“…Both approaches have been widely used (e.g. Bogunic et al ., ; Vižitin & Bohanec, ; Pellicer et al ., ; Cires et al ., ), but the latter artificially decreases the extent of variation (see Table , for comparison). Limited genome size variation was detected during our large‐scale relative genome size screening (individual ranges varied from 2.00% to 7.70%; population means varied from 1.35% to 6.13%).…”

“…a 1.06‐fold difference (Bogunic et al ., ). Only minute intraspecific variation in genome size (1.05‐fold and 1.03‐fold, respectively) has been documented in Trifolium repens L. and T. fragiferum L. (Fabaceae) (Vižitin & Bohanec, ). During a study focused on cultivars of Allium cepa L. from different parts of the world, Bennett et al .…”

Ribosomal RNA Internal Transcribed Regions Identify Possible Misidentification or Mislabeling among Trifolium (Clover) Specimens from Germplasm Collections

“…nigrescens, ssp. Species identification among related clover species based on morphological traits can be difficult even for experts, and while botanists and breeders may be aware that germplasm collections may contain contaminants or seed from misidentified specimens, the published literature contains just a few references to these issues (Scott and Hallam, 2003;Ellison et al, 2006;Vižintin and Bohanec, 2008). meneghinianum) based on both morphological and DNA sequence analyses (Williams et al, 2001;Ellison et al, 2006).…”

“…In the course of a study to examine shared and unique insertions of recently active transposable elements (TE) within and between these species, we generated preliminary TE sequence data from some accessions that were inconsistent with those of other accessions of the same species. Species identification among related clover species based on morphological traits can be difficult even for experts, and while botanists and breeders may be aware that germplasm collections may contain contaminants or seed from misidentified specimens, the published literature contains just a few references to these issues (Scott and Hallam, 2003;Ellison et al, 2006;Vižintin and Bohanec, 2008). The findings of some investigators that examine questions related to phenotypic adaptability, genomic diversity, and evolutionary trajectories may be compromised by incorrect species assignments.…”