Diversity and evolution of the Hordeum murinum polyploid complex in Algeria

Abstract

Population diversity and evolutionary relationships in the Hordeum murinum L. polyploid complex were explored in contrasted bioclimatic conditions from Algeria. A multidisciplinary approach based on morphological, cytogenetic, and molecular data was conducted on a large population sampling. Distribution of diploids (subsp. glaucum) and tetraploids (subsp. leporinum) revealed a strong correlation with a North-South aridity gradient. Most cytotypes exhibit regular meiosis with variable irregularities in some tetraploid populations. Morphological analyses indicate no differentiation among taxa but high variability correlated with bioclimatic parameters. Two and three different nuclear sequences (gene coding for an unspliced genomic protein kinase domain) were isolated in tetraploid and hexaploid cytotypes, respectively, among which one was identical with that found in the diploid subsp. glaucum. The tetraploids (subsp. leporinum and subsp. murinum) do not exhibit additivity for 5S and 45S rDNA loci comparative with the number observed in the related diploid (subsp. glaucum). The subgenomes in the tetraploid taxa could not be differentiated using genomic in situ hybridization (GISH). Results support an allotetraploid origin for subsp. leporinum and subsp. murinum that derives from the diploid subsp. glaucum and another unidentified diploid parent. The hexaploid (subsp. leporinum) has an allohexaploid origin involving the two genomes present in the allotetraploids and another unidentified third diploid progenitor.

Chromosomal Characterization of the Three Subgenomes in the Polyploids of Hordeum murinum L.: New Insight into the Evolution of This Complex

“…This agrees with the fact that diploid glaucum has two pairs of satellited chromosomes (F and G), as revealed by the presence of secondary constrictions and major 45S rDNA signals (Fig. 1k, [24]), while only one such pair (chromosome F) is present in the Xu subgenome of the polyploids [15], [18]. Genome remodelling after polyploidization could have led to the replacement of the satellited chromosome G observed in the diploids (with major 45S rDNA sites) by the small metacentric chromosome with only minor 45SrDNA signals found in the tetraploid and hexaploid cytotypes.…”

“…The identification of each H. murinum chromosome pair, including its hexaploids, is here reported for the first time. As indicated by other authors, the five Triticeae probes used (pTa71, pTa794, pAs1, pHch959 and pSc119.2) were insufficient for the reliable identification of most chromosomes [15], [18], [24]. However, the pattern of distribution of several SSRs was shown very useful in chromosome identification.…”

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

“…Correlation between ecological variability and genetic diversity in H. murinum (Ourari et al 2011) and in its allies such as H. vulgare subsp. spontaneum (see for example Nevo et al 1986;Graner et al 2003) are documented.…”

“…Hordeum murinum has been investigated using different characters (see for example Booth & Richards 1978;Giles 1984;Giles & Lefkovitch 1986;LindeLaursen et al 1989;Jaaska 1992;Taketa 2001;Jakob & Blattner 2010;Ourari et al 2011). The auto-or allopolyploid origin of polyploid cytotypes within this complex was subject of many systematic and phylogenetic studies.…”

“…The auto-or allopolyploid origin of polyploid cytotypes within this complex was subject of many systematic and phylogenetic studies. Rajhathy & Morrison (1962) and Bothmer et al (1987Bothmer et al ( , 1988Bothmer et al ( , 1995 believed that the tetra and hexaploid cytotypes of H. murinum are autopolyploid, whereas Blattner (2004), Jakob & Blattner (2010), Tanno et al (2010) and Ourari et al (2011) provided evidences for allopolyploidy origin of 4x and 6x cytotypes.…”