Molecular phylogeny of the genus Hordeum using thioredoxin-like gene sequences

Abstract

Phylogenetic relationships within the genus Hordeum were investigated based on nucleotide sequences of the thioredoxin-like (HTL) gene. We analyzed amplified genomic DNA fragments of the HTL gene from 11 Hordeum species including 16 taxa (25 accessions), which cover mainly diploid accessions together with several tetraploid accessions. Phylogenetic analysis based on the HTL sequences demonstrated a clear divergence of the four basic genomes I (H. vulgare and H. bulbosum), Xa (H. marinum), Xu (H. murinum) and H (other species) in the genus. Phylogenetic clustering also led us to infer two separate clades, one containing the I and Xu, and the other containing the Xa and H genomes. In the diploid H-genome species, American species were confirmed to be closely related and divergent from Asian species. Analysis of the Xa-genome group suggested an alloploid origin of tetraploid H. marinum ssp. gussoneanum by hybridization between the diploid cytotypes of ssp. marinum and ssp. gussoneanum. Our data also supported the hypothesis that two tetraploid cytotypes of H. murinum (ssp. murinum and ssp. leporinum) have an alloploid origin, where one genome was presumably derived from the diploid cytotype ssp. glaucum and the other from an unknown Xugenome species.

Progress in phylogenetic analysis and a new infrageneric classification of the barley genus Hordeum (Poaceae: Triticeae)

“…Particularly DNA sequencing resulted in fast advances in molecular phylogenetics of the genus during the last decade (Komatsuda et al 1999, Nishikawa et al 2002, Petersen and Seberg 2003, Blattner 2004, 2006, Jakob and Blattner 2006, Kakeda et al 2009, Sun et al 2009). …”

“…Taking into account the importance of barley, surprisingly few phylogenetic studies of Hordeum with a complete or at least representative taxon sample were conducted. Studies with higher species numbers or including at least most diploid species have been published by Jørgensen (1986), Doebley et al (1992), Komatsuda et al (1999), Provan et al (1999), Nishikawa et al (2002), Seberg (2003, 2004), Blattner (2004Blattner ( , 2006, Jakob and Blattner (2006), Kakeda et al (2009), andSun et al (2009). The results were partly contradictory, due to (i) inconsistencies between chloroplast and nuclear phylogenies, (ii) differences in taxon sampling, (iii) incongruence among specific loci, and (iv) different analysis methods.…”

“…In the light of other data confirming monophyly and a very close relationship of the three Patagonian species (Blattner 2004, 2006, Jakob and Blattner 2006, Pleines and Blattner 2008, it seems that paralogs of RPB2 occur within this taxon group. Kakeda et al (2009) used the single-copy locus of a thioredoxin-like gene closely linked to the selfincompatibility locus of H. brevisubulatum in a phylogenetic analysis of H, Xa, Xu, and representative I-genome species. They obtained monophyletic genome groups, sister relationships of H/Xu and I/Xa taxa, and American species monophyletic within the Asian I-genome species.…”

“…Thus, for H. capense and H. secalinum the involvement of H. marinum or H. gussoneanum together with an I-genome species could be shown (Petersen and Seberg 2004, Blattner 2006, and in the H. murinum complex polyploids evolved under contribution of diploid subsp. glaucum (Kakeda et al 2009) and two now extinct taxa of the Xu-genome group (Jakob and Blattner 2009, Tanno et al, in press). …”

Genetic diversity and geographic distribution of variation of Hordeum murinum as revealed by retroelement insertional polymorphisms in Iran

“…Most of the studies showed H. murinum as a closely related species to H. vulgare (e.g., Taketa et al 1999;El-Rabey et al 2002;Blattner 2004Blattner , 2009Kakeda et al 2009). H. murinum possessing a center of diversity in Mediterranean region, is an annual, inbreeding di-, tetra-and hexaploid species occurring with three subspecies: murinum (2n = 4x = 28), glaucum (Steudel) Tzvelev (2n = 2x = 14), and leporinum (Link) Arcangeli (2n = 4x,6x = 28,42).…”