Auswahl der wissenschaftlichen Literatur zum Thema „Hordeum marinum“

The genus Hordeum consists of three cytotypes (2x, 4x, and 6x). Its reproductive isolation has been incomplete between closely related species and hence the genetic relationship is reticulate and complex. We used 32 taxa of Hordeum and three chloroplast DNA sequences, matK, atpB–rbcL, and trnL–trnF, in the current study. Molecular phylogenetic analysis based on sequence data of the three chloroplast DNA regions clearly demonstrated genetic relationships among taxa and origin of polypoids. The formation of H. secalinum likely involved hybridization between Hordeum marinum subsp. marinum and a Eurasian diploid possessing the H genome. The formation of hexaploid Hordeum brachyantherum involved hybridization between tetraploid H. brachyantherum and diploid H. marinum subsp. gussoneanum. The formation of three tetraploids, H. brachyantherum, Hordeum jubatum, and Hordeum guatemalense, probably involved hybridization between H. brachyantherum subsp. californicum and an altered H genome diploid. The formation of Hordeum arizonicum involved the two taxa Hordeum pusillum and H. jubatum.Key words: chloroplast DNA, phylogeny, Hordeum, barley.

Giemsa C-banding patterns of the predominantly self-pollinating, annual species Hordeum marinum (2x, 4x) and H. murinum (2x, 4x, 6x) showed mostly very small to small bands at centromeric and telomeric positions, at one or both sides of the nucleolar constrictions, and at intercalary positions with no preferential disposition. A similar distribution of bands has been observed in other Hordeum species, suggesting that the pattern is the basic one in the genus Hordeum. Hordeum murinum, especially the hexaploid cytotype, was distinguished from H. marinum by having more numerous and more conspicuous bands, resulting in a significantly higher percentage of constitutive heterochromatin (9–17 vs. 4–8%). The differences in C-banding patterns supported by differences in chromosome morphology confirm that H. marinum and H. murinum are not closely related. Banding-pattern polymorphism was prevalent among populations but unobserved within populations. In spite of this polymorphism, banding patterns in combination with chromosome morphology identified homologous chromosomes of different populations of a taxon and indicated that the chromosome complements of the polyploids of both species comprised the genome of the related diploid as well as one or two "unidentified" genomes. This agrees with an alloploid origin of polyploids. The C-banding patterns of H. marinum ssp. marinum and H. marinum ssp. gussoneanum (2x) showed some divergence in spite of the close relationship. The C-banded karyotypes of H. murinum ssp. murinum and H. murinum ssp. leporinum (4x) were very similar, supporting conspecificity. Chromosome lengths and longest/shortest chromosome ratios were fairly similar to those previously published, supporting the conclusion that linear relationships of chromosomes are normally stable within genomes. The taxonomy of the two species is discussed.Key words: C-banding, karyotypes, Hordeum.

An investigation was made into the relationships between six species or subspecies of the genus Hordeum that grow in the Iberian Peninsula and Balearic Islands. Plant material included samples of 19 populations of the annual species H. marinum subsp. marinum, H. marinum subsp. gussoneanum, H. murinum subsp. murinum, and H. murinum subsp. leporinum, and the perennial species H. bulbosum and H. secalinum. Relationships were analysed using PCR-based molecular markers. Thirteen sets of primers were designed and synthesized based on sequences of mapped RFLPs from genomic libraries and conserved regions of structural genes of known function in cultivated species. Primers were used to amplify genomic DNA from all populations. The number of amplified products ranged from 1 to 18 per primer and a total of 168 markers were scored. The markers revealed different degrees of relationships. Hordeum bulbosum was clearly separated from the rest. The populations of both subspecies of H. murinum were closely related. H. marinum subsp. gussoneanum appeared to be closely related to H. secalinum, yet relatively separated from its conspecific subspecies marinum. The use of a large number of DNA markers in this kind of analysis is discussed.Key words: Hordeum, barley, DNA markers, restriction endonucleases, variability, DNA analysis.

Restriction-site analysis of chloroplast DNA was carried out on a total of 13 North American species of Hordeum, 7 native and 6 introduced. Sites associated with polymorphic banding patterns were omitted so that only invariant sites within species were used in the analyses. A number of taxa whose species status is in dispute can indeed be supported at species rank, i.e., H. brachyantherum, H. californicum, H. pusillum, H. intercedens, H. marinum, and H. geniculatum. The maternal progenitor of H. arizonicum is H. pusillum, and this is further discussed in light of other possibilities. Both phenetic and cladistic analyses indicate a tripartite relationship whereby H. vulgare is distant from the group of H. leporinum, H. glaucum, and H. murinum and from a second group comprising the native species H. brachyantherum, H. californicum, H. arizonicum, H. jubatum, H. pusillum, H. intercedens, and H. depressum. Hordeum marinum and H. geniculatum occupy a central position in this relationship. Speculation that the putative ancient form of Hordeum resembled a H. murinum – H. geniculatum-like species is discussed. Key words: chloroplast DNA, Hordeum, phylogenetic relationships.

Hordeum marinum Huds. is a waterlogging-tolerant wild relative of wheat (Triticum aestivum L.). Greater root porosity (gas volume per root volume) and formation of a barrier to reduce root radial O2 loss (ROL) contribute to the waterlogging tolerance of H. marinum and these traits are evident in some H. marinum–wheat amphiploids. We evaluated root porosity, ROL patterns and tolerance to hypoxic stagnant conditions for 10 various H. marinum (two accessions) disomic chromosome addition (DA) lines in wheat (two varieties), produced from two H. marinum–wheat amphiploids and their recurrent wheat parents. None of the DA lines had a barrier to ROL or higher root porosity than the wheat parents. Lack of a root ROL barrier in the six DA lines for H. marinum accession H21 in Chinese Spring (CS) wheat indicates that the gene(s) for this trait do not reside on one of these six chromosomes; unfortunately, chromosome 3 of H. marinum has not been isolated in CS. Unlike the H21–CS amphiploid, which formed a partial ROL barrier in roots, the H90–Westonia amphiploid and the four derived DA lines available did not. The unaltered root aeration traits in the available DA lines challenge the strategy of using H. marinum as a donor of these traits to wheat.

Several authors have proposed that the European Hordeum secalinum and the morphologically similar South African Hordeum capense are conspecific. In this paper we provide evidence that the two species differ in their 5S DNA unit class composition. We also report on the diversity of 5S DNA units in Hordeum muticum, a South American species. When the 5S rDNA unit class composition for these three species is compared with the unit class composition for all Hordeum species thus far investigated, it appears that H. capense is more closely related to the American Hordeum species containing the long Y2 unit class, than to H. secalinum, which lacks the long Y2 unit class but contains the long X2 unit class found in H. marinum. This analysis suggests H. capense may have originated from a stock common to the South American species, such as H. muticum.Key words: 5S DNA unit class, Hordeum capense, Hordeum secalinum, Hordeum muticum, continental drift.

The meiotic pairing behaviour of 31 interspecific combinations of tetraploid Hordeum species are reported. The autoploid H. bulbosum with the II genomic constitution has no homology to the other species. The constitution of tetraploid H. murinum is not clear, but it is not homologous to other tetraploids. Hordeum marinum is a probable autoploid (XX) but with a very strong genetic regulation of pairing. The X genome is possibly found in H. secalinum and H. capense, both of which also possess the H genome in several diploids. Hordeum fuegianum, H. tetraploidum, H. jubatum, H. brachyantherum, and H. roshevitzii are segmental alloploids all with the same two partly homoeologous genomes. Hordeum depressum is probably a segmental alloploid with the H genome and with a very strong pairing regulation. Hordeum brevisubulatum is a pure autoploid with two homologous H genomes.Key words: Hordeum, interspecific hybrids, meiosis, tetraploids.

Le silicium (Si) est un élément ubiquitaire, présent en grandes proportions dans le sol. Il n’est pas considéré comme un élément essentiel pour les plantes. Cependant l’addition de Si dans des cultures de plantes sous contraintes abiotiques leur confère une meilleure tolérance. Ce travail avait pour premier objectif d’étudier l’effet du silicium sur une espèce végétale (Hordeum marinum) sous déficience ferrique. Cette espèce, accumulatrice de Si, présente un grand intérêt dans la valorisation de zones marginales. Dans une première partie, l’étude des paramètres de croissance, du statut hydrique, échanges gazeux photosynthétiques, des teneurs en pigments photosynthétiques de la fluorescence chlorophyllienne et de l’accumulation du fer, a montré que l’ajout de Si est un traitement très intéressant pour la correction des effets délétères de la déficience ferrique. A l’issue de ces observations, nous avons cherché à savoir si un prétraitement des grains d’H. marinum par du Si était une alternative intéressante à l’amélioration de la croissance de cette espèce en présence d’une carence en fer. Les résultats obtenus montrent que le taux de germination, les paramètres de croissance, l’intégrité membranaire, l’activité d’enzymes antioxydantes et les quantités des sucres solubles sont améliorés par ce pré- traitement au Si tout au long du développement de la plante soumise à un milieu pauvre en Fe. La dernière partie de ce travail avait pour objectif d’étudier la réponse d’Arabidopsis thaliana, une plante n’accumulant pas le Si, en présence d’une concentration toxique en proline. Les résultats montrent que le silicium agit de facon positive sur la germination, le développement et la gestion du stress oxydant d’A. thaliana, et ceci par le biais d’une possible action directe ou indirecte sur le métabolisme de la proline
Silicon (Si) is a ubiquitous element; it is considered to be the second most abundant element in the lithosphere after oxygen. It is not considered as an essential element for plants. However, the addition of Si in crops under abiotic stress gives them a better tolerance to stress. The first objective of this work was to study the effect of Si in Hordeum marinum, a plant species known to accumulate Si, under iron deficiency. This Poaceae species is of interest for livestock fodder and valorization of marginal zones. Our results indicate that growth parameters, water status, photosynthetic gas exchange, photosynthetic pigment contents, chlorophyll fluorescence and iron accumulation are improved by Si treatment when plants are grown under iron deficiency. We also investigated the effect of seed priming with Si in H. marinum seeds as an inexpensive and easy method to alleviate the effect of stress. Our results showed that germination rate, growth parameters, membrane integrity, activities of antioxidant enzymes and soluble sugar content are all improved by Si pre-treatment in plants growing under iron deficiency. The last objective of this work aimed to understand the behavior of Arabidopsis thaliana, a non-accumulating Si species, in response to stress. Interestingly, our results show that silicon acts positively on germination, development and antioxidant stress in A. thaliana, possibly through a modulation of proline metabolism