Studies in the Hordeum murinum L. aggregate: disc electrophoresis of seed proteins

Seeds of the H. murinum aggregate were collected from much of the range of the group and soluble protein extracts were subject to gel-electrophoresis analysis. Diploid, tetraploid and hexaploid plants were readily differentiated. Analysis using a similarity matrix and dendrogram revealed further groups within the ploidy levels and indicated inter-group relationships. Evidence obtained supported karyological results, suggesting that tetraploid and hexaploid plants are allopolyploids, and that one of their putative parents is a diploid known from Turkey and adventive in Australia. Within the tetraploids there is little correspondence between groups detected by either gel-electrophoresis or karyology, and the species H. leporinum (mostly southern) and H. murinum (mostly northern).     

The chemotaxonomy ofGeranium (Geraniaceae)

Relationships amongGeranium species constituting sectt.Anemonifolia, Lucida (monotypic) andRuberta together with representatives of sect.Unguiculata were investigated by gas-chromatographic study of essential oils, electrophoretic comparison of seed proteins and chromatographic separation of nectar amino acids. — Essential oil study gave little information.G. macrorrhizum (sect.Unguiculata) had far greater quantities of essential oils in its foliage than other species and differed from them qualitatively. — Species of sectt.Anemonifolia andRuberta, together withG. cataractarum (sect.Unguiculata), between them yielded 19 seed protein bands; the distribution of these indicated close relationship among the species and was consistent with hypotheses for the origin of certain species by alloand autopolyploidy partly within the group. Involvement of an unknown species in the origin of two allopolyploids was implied. Separate origins for the two octoploid species in this set are also inferred. In two instances there was evidence for the transformation of one band into another subsequent to the separation of related species. The inference of allopolyploidy was supported by the occurrence of additivity of parental bands shown by an artificial hybrid between two of the species. A model for the evolutionary divergence of the seed protein patterns is presented. Two species outside the above set appeared less closely related; they wereG. lucidum andG. macrorrhizum (sect.Unguiculata) and between them they showed 6 additional bands, four of which were shared. — Of 18 nectar amino acids found, 4 to 15 occurred in any one species, with low numbers (4 and 8) occurring in the most extreme inbreeders. The spectra of nectar amino acids of two hybrids showed additivity of those of the respective parents. The results echo rather closely those provided by seed proteins, but in the absence of data from outside the group their taxonomic significance is uncertain. However, the divergence between the two octoploids was again evident.     

Plant highly repeated satellite DNA: Molecular evolution,distribution and use for identification of hybrids

Relationships among genomes are often revealed by the occurrence of common or related satellite DNA (satDNA) types. A typical satDNA characterized by specific sites for one (or more) restriction endonuclease(s) is called ‘restriction satellite DNA’. Restriction satDNA comprises ‐ in addition to transposons and retrotransposable elements ‐ often highly repeated genome components present in most higher plants. Large arrays of satDNA elements are concentrated at subtelo‐meric and/or centromeric regions (intermingled with other retrotransposon‐derived elements), however, they can be also located as large intercalating blocks along the chromosome. The head‐to‐tail tandemly arranged repeat units (monomers) of satDNA mostly exhibit lengths of 160 to 180 bp or 320 to 370 bp, but other lengths were also found in plants. In particular, in interspecific hybrids between more distantly related species, which often exist only after polyploidization, the individual repetitive DNA of the crossing partners contribute to recombination and rearrangement processes in the hybrids, thereby stimulating genome evolution. Here, we concentrate on the possible origin, molecular evolution, organization and distribution of highly repeated satDNA in various higher plants with emphasis on hybrids and allopolyploids.     

Serological reactions of Fraction I proteins from interspecific hybrids in the genusNicotiana

The serological reactions of Fraction I proteins from interspecific hybrids in the genusNicotiana have been examined by immunodiffusion in agar gels using antisera to crystalline Fraction I proteins fromN. glutinosa, N. gossei, andN. tabacum. The serological reactions of the proteins from the hybrids resembled the reactions of the proteins from the maternal parent species but not from the paternal species. Changes in ploidy level did not affect the serological reactions of Fraction I proteins from hybrids. It is suggested that serological examination of Fraction I proteins from polyploid species and their known progenitors can indicate the direction of the cross giving rise to the polyploid species.     

The evolutionary history of sea barley (Hordeum marinum) revealed by comparative physical mapping of repetitive DNA

Background and Aims Hordeum marinum

is a species complex that includes the diploid subspecies marinum and both diploid and tetraploid forms of gussoneanum. Their relationships, the rank of the taxa and the origin of the polyploid forms remain points of debate. The present work reports a comparative karyotype analysis of six H. marinum accessions representing all taxa and cytotypes.

Methods

Karyotypes were determined by analysing the chromosomal distribution of several tandemly repeated sequences, including the Triticeae cloned probes pTa71, pTa794, pAs1 and pSc119·2 and the simple sequence repeats (SSRs) (AG)₁₀, (AAC)₅, (AAG)₅, (ACT)₅ and (ATC)₅.

Key Results

The identification of each chromosome pair in all subspecies and cytotypes is reported for the first time. Homologous relationships are also established. Wide karyotypic differences were detected within marinum accessions. Specific chromosomal markers characterized and differentiated the genomes of marinum and diploid gussoneanum. Two subgenomes were detected in the tetraploids. One of these had the same chromosome complement as diploid gussoneanum; the second subgenome, although similar to the chromosome complement of diploid H. marinum sensu lato, appeared to have no counterpart in the marinum accessions analysed here.

Conclusions

The tetraploid forms of gussoneanum appear to have come about through a cross between a diploid gussoneanum progenitor and a second, related—but unidentified—diploid ancestor. The results reveal the genome structure of the different H. marinum taxa and demonstrate the allopolyploid origin of the tetraploid forms of gussoneanum.     

Sequence capture: Obsolete or irreplaceable? A thorough validation across phylogenetic distances and its applicability to hybrids and allopolyploids

As whole-genome sequencing has become pervasive, some have suggested that reduced genomic representation approaches, for example, sequence capture, are becoming obsolete. In the present study, we argue that these techniques still provide excellent tools in terms of price and quality of data as well as in their ability to provide markers with specific features, as required, for example, in phylogenomics. A potential drawback of the wide-scale application of reduced representation approaches could be their drop in efficiency with increasing phylogenetic distance from the reference species. While some studies have focused on the degree and performance of reduced representation techniques in such situations, to our knowledge, none of them evaluated their applicability to inter-specific hybrids and polyploids. This highlights a significant gap in current knowledge since there is increasing evidence for the frequent occurrence of natural hybrids and polyploids, as well as for the major importance of both phenomena in evolution. The main aim of the present study was to carry out a thorough validation of SEQcap applicability to (1) a set of non-model taxa with a wide range of phylogenetic relatedness and (2) inter-specific hybrids of various ploidies and genomic compositions. Considering the latter point, we especially focused on mechanisms causing allelic bias and consequent allelic dropout, as these could have confounding effects with respect to the evolutionary genomic dynamics of hybrids, especially in asexuals, which virtually reproduce as a frozen F1 generation.     

Genome relationships between octoploid and decaploid Thinopyrutn ponticum

MOUSTAKAS, M., 1993. Genome relationships between octoploid and decaploid Thinopyrum ponticum . The genomic relationships between octoploid and decaploid Thinopyrum ponticum were determined by computer-aided karyotype analysis. All the chromosome pairs of the octoploid race can be matched with those of the decaploid chromosome race. Four chromosome pairs that were recognized as marker chromosomes in octoploid and decaploid T. ponticum were almost identical. It is suggested that the two chromosome races of T. ponticum are segmental allopolyploids with genome designations J^jJ^jJ^eJ^e and J^jJ^jJ^jJ^eJ^e. Genome designations Jand J^e represent the same genome but with structural differentiation. Phylogenetic relationships between Thinopyrum species may be indicated by the presence or absence and type of marker chromosomes in the different species.