Chromosome evolution in wild oat grasses (Aveneae) revealed by molecular phylogeny

Abstract

Karyotype structures revealed by in situ hybridization with ribosomal and satellite DNAs and fluorochrome staining of AT- or GC-rich regions are reported for 23 diploid to tetraploid taxa of Aveneae genera Arrhenatherum, Avena, Helictotrichon, and Pseudarrhenatherum. Chromosomal features are compared with a molecular phylogeny generated on nuclear ribosomal (ITS, 5S) and chloroplast (matK) DNA sequences. Ancestral chromosomal character states are (1) two satellite chromosomes per set of x = 7, (2) 5S rDNA localized in nonsatellite chromosomes, (3) large chromosomes with (4) rather equal lengths of their respective chromosome arms, (5) sets with strong variance of chromosome lengths, (6) absence or small amounts of heterochromatin, and (7) absence or no detectable amplification of the satellite DNAs tested. Overall, most karyotype characteristics are species specific, but common patterns were found for the species of two large subgenera of Helictotrichon. Pseudarrhenatherum, although nested in the molecular phylogeny within Helictotrichon subgenus Helictotrichon, deviates strongly in karyotype characters such as Arrhenatherum as sister of Avena. The karyotype of Helictotrichon jahandiezii, sister to the clade of Helictotrichon subgenera Helictotrichon, Avena, and Arrhenatherum, strongly resembles that of Avena macrostachya. Karyotype features suggest that perennial A. macrostachya and H. jahandiezii are close to the C-genome species of annual Avena, whereas the Avena A genome resembles that of Arrhenatherum.

Polyploidy and Hybridization as Main Factors of Speciation: Complex Reticulate Evolution within the Grass Genus <b><i>Helictochloa</i></b>

“…Taketa et al, 2005;Badaeva et al, 2010b]. Comparisons between the molecular data, the results from previous cytogenetic and karyotype studies [Winterfeld, 2006;Winterfeld et al, 2009aWinterfeld et al, , b, 2011Winterfeld et al, , 2012 and the taxonomical treatment of this group, which is based mainly on morphological and anatomical features [e.g. Holub, 1958[e.g.…”

“…Following the rather basal phylogenetic position of the ITS rDNA sequences, it was hypothesized [Winterfeld et al, 2009a] that also karyotype features of these diploids ( fig. 2 ) might be considered as more ancestral, e.g.…”

“…According to morphological, karyological and chorological data, it was suggested that the genus consists of ∼ 6-7 separate species complexes which have evolved independently in parallel and accompanied by polyploidy. Chromosome numbers range from 2n = 2x = 14 up to 2n = 22x = 154 [Gervais, 1973;Romero Zarco, 1984;Sauer, 1984;Röser, 1996Röser, , 1998Winterfeld, 2006;Winterfeld et al, 2009aWinterfeld et al, , b, 2011Winterfeld et al, , 2012.…”

“…For Helictochloa , combined analyses of nuclear rDNA (5S rRNA gene and intergenic spacer, internal transcribed spacers ITS1, ITS2 with interjacent 5.8S rRNA gene) and chloroplast mat K DNA sequences from diploid species and their comparisons with chromosomal features revealed the occurrence of different genomes which are involved in the origins of the numerous polyploids in this genus [Winterfeld et al, 2009a]. Allopolyploid speciations were detected in the west Mediterranean H. bromoides species group with diploid H. bromoides identified as one of the genome donors [Winterfeld et al, 2009b].…”

A plant’s inheritance : Soil legacy effects of crops and wild relatives in relation to plant functional traits

“…Pairs of grasses did consist of closely related species: Festuca and Lolium (Soreng, Davis & Voionmaa 2007), and Avena and Arrhenatherum (Winterfeld, Döring & Röser 2009). …”