Autopolyploidy in Dactylis glomerata L.: further evidence from studies of chloroplast DNA variation

Abstract

Chloroplast DNA variation has been used to examine some of the maternal lineages involved in the evolution of the intraspecific polyploid complex, Dactylis glomerata L. Diploid (2x) and tetraploid (4x) individuals were collected from natural populations of the subspecies glomerata (4x), marina (4x) and lusitanica (2x), as well as from sympatric 2x/4x populations of the Galician type. Digestion of their ctDNA with 11 restriction endonucleases revealed enough variation to characterise three ctDNA variants, designated MBMK, MBmK and mBMK. The distribution of these ctDNA variants reflects different stages in their spread among the populations. The MBMK ctDNA variant predominated at both ploidy levels in subspecies glomerata, lusitanica and marina, and in recent tetraploid Galician/glomerata hybrids. The MBmK variant was detected in a single tetraploid individual and probably results from a relatively recent mutation. Fixation of the mBMK minority variant in the diploid and tetraploid Galician populations adds to the evidence concerning the possible origin of the Galician tetraploids. It means that the Galician diploids were maternal ancestors of the tetraploids. This result complements evidence from earlier studies based on morphology or biochemical markers, and reduces the likelihood that the tetraploids arose by hybridisation between an ancient Galician diploid and an alien tetraploid. It is, however, consistent with a true autopolyploid origin of the tetraploids.

Orchardgrass (Dactylis glomerata L.) EST and SSR marker development, annotation, and transferability

“…Thus, subspecies can act as a secondary gene pool (Stuczynski 1992). Relationships among the subspecies have been evaluated using morphological traits (Stebbins and Zohary 1959), chloroplast and ITS sequences (Lumaret et al 1989;Stewart and Ellison 2010), isozymes (reviewed in Lumaret 1988), and flavonoid compound diversity (Fiasson et al 1987), and each method has shown commonalities and differences. The SSR markers described herein have great resolution within the genus, which can aid in understanding the more recent genetic history of this species.…”

“…Previous studies have used a variety of tools: chloroplast and ITS sequences have been used to describe phylogenetic relationships (Lumaret et al 1989;Catalan et al 2004;Stewart and Ellison 2010), dominant markers (e.g., RAPD, ISSR, SRAP) used in discreet studies (Koelliker et al 1999;Tuna et al 2004;Peng et al 2008;Zeng et al 2008), and heterologous markers tested from other forage grass species Litrico et al 2009), However, the openplatform dominant markers generally have the inability to add samples to a study without re-analyzing all previous samples due to the large number of bands genotyped per primer. Heterologous marker transferability also decreases as species diverge (Thiel et al 2003;Zhang et al 2005;Litrico et al 2009), and are accompanied by higher likelihood of homoplasy and polymorphism due to mutations that exist among the species (Thiel et al 2003;Saha et al 2004;Zhang et al 2006).…”

Diversity comparison and phylogenetic relationships of cocksfoot (Dactylis glomerata L.) germplasm as revealed by SSR markers

“…A strong genetic similarity between the Galician diploids and the tetraploids was revealed by means of isozyme profile and cpDNA restriction patterns (Lumaret 1984;Lumaret et al 1989). These results were also in good agreement with reports by Lumaret and Borrientos (1990), who assessed phylogenetic relationships between sympatric diploid and tetraploid plants of cocksfoot.…”

Ecotype differentiation and coexistence of two parapatric tetraploid subspecies of cocksfoot (Dactylis glomerata) in the Alps

“…In areas where taxa of the same ploidy level of a single species occur sympatrically, habitat differentiation and\or reproductive isolation (say, differences in flowering time) may occur but generally, hybridization is possible, and might include subsequent genetic introgression between the taxa (Rieseberg & Wendel, 1993). These can become interconnected by a hybrid zone of genetically intermediate plants (Levin, 1983 ;Lumaret, Bowman & Dyer, 1989). The size of hybrid zone reflects the balance between random dispersal and the effect of selection.…”