Revision of Taeniatherum (Poaceae)

Three species are often accepted in Taeniatherum Nevski. Analysis of morphological characters show that indistinct limits occur between them. All taxa are found to be diploid (2n=14), with the same karyotype, but artificial hybridization shows genetical barrier to exist. For these reasons subspecific level is chosen for the taxa, viz. T. caput-medusae (L.) Nevski ssp. caput-medusae, T. caput-medusae ssp. crinitum (Schreb.) Melderis and T. caput-medusae ssp. asperum (Simk.) Melderis. Map showing known distribution of the subspecies is presented.     

Intergeneric hybridization between Taeniatherum and different genera of Triticeae, Poaceae

Intergeneric crosses were carried out between the 3 subspecies of Taeniatherum caput-medusae (2x) and 30 different species (33 different cytotypes) representing 11 genera of the Triticeae. Seed set was obtained in 15 combinations, but only 6 of them resulted in adult plants. In the combination with Hordeum bulbosum (2x), a haploid of T. caput-medusae was obtained as a result of selective elimination of the H. bulbosum chromosomes. All other hybrid plants were morphologically intermediate between the parents. They were highly sterile with low pollen fertility caused by very low chromosome pairing at meiosis and without any seed set.
The few hybrid plants obtained and the lack of pairing at meiosis support that Taeniatherum is a distinct genus within the Triticeae.     

Intergeneric Hybridization between Species of Leymus, Psathyrostachys and Hordeum (Poaceae, Triticeae)

A total of 132 intergeneric crossing attempts (49 combinations)involving species of Leymus Hochst., Psathyrostachys Nevskiand Hordeum L. were performed, of which 103 were between Hordeumand Leymus. Embryo rescue was used throughout the experiment.Hybrids between Leymus and Psathyrostachys were difficult toobtain. Hybrid progeny were relatively easily obtained whencrossing Hordeum and Leymus. Plants from 20 different combinationswere obtained. Nineteen of these have not previously been reported.Meiotic analysis of three hybrid combinations of Hordeum x Leymusis reported. The high frequency of univalents in meiotic interphase(MI) indicates that allosyndetic chromosome pairing did notoccur, supporting the assumption that the genomes of Leymusare non-homologous to the H genomes of Hordeum.Copyright 1994,1999 Academic Press Taxonomy, Triticeae, Leymus, Psathyrostachys, Hordeum, intergeneric hybridization     

Asymmetric Somatic Hybridization Between Wheat (Triticum aestivum) and Bromus inermis

Asymmetric hybridization was conducted between wheat and Brorrats inermis keyss which is a distanfiy related intergeneric plant (belonging to different tribe) of wheat and possesses some favorable traits, such as resistant to cold, drought and disease. Protoplasts isolated from young embryo-derived calli of common wheat ( Triticura aestivum L., tv. 99P, (AABBDD), 2n = 42) were fused with UV-treated protoplasts isolated from young embryo-derived calli of Bromus inermis by PEG method. Three clones (No. 1 ~ No. 3) were regenerated from the fusion products and differentiated into albino seedlings. The clones and the seedlings were all verified as hybrids by chromosome counting, isozyme and RAPD analysis. Their isozyme and RAPD pattern contained the characteristic bands of both parents as well as new band(s). The chromosome numbers of albino were in the range of 42~54 with small chromosomes of Bromus inerm/s and chromosome fragments. The above results confirmed that hybrid albinos were obtained.     

Hybridization between tetraploid species of Alopecurus L. (Poaceae): morphological studies of natural and artificial hybrids

The morphology of individuals of mixed natural populations of three species of Alopecurus, A. pratensis, A. geniculars and A. arundinaceus , is described. It is suggested that plants morphologically intermediate between the parental species are hybrids or of hybrid origin. Hybridization occurs more readily between A. pratensis and A. arundinaceus than between A. pratensis and A. geniculate , since intermediate forms were recovered from all mixed populations of A. pratensis and A. arundinaceus. The intermediate forms occur only in a few populations of A. pratensis and A. geniculars where an appropriate habitat is available. Evidence of backcrossing and therefore introgression comes from the continuum of intermediate forms that exists between the species. Scatter diagrams for individual populations show distinct differences in the degree of introgression. Observations on artificially produced hybrids are similar to those on naturally occurring hybrids.     

Hybridization between tetraploid species of Alopecurus L. (Poaceae): chromosome behaviour of natural and artificial hybrids

The meiotic behaviour of plants from mixed populations of Alopecurus pratensis × A. geniculatus and of A. pratensis × A. arundinaceus ( 2n = 4×(= 28) is reported together with observations on some artificially produced hybrids. This meiotic behaviour is correlated with the degree of hybridity as shown by the hybrid index values of the plant. In A. pratensis × A. geniculatus hybrids there are marked differences between populations in the degree of meiotic disturbance and in one population there was an almost complete breakdown of meiosis. Alopecurus pratensis × A. arundinaceus hybrids show fairly regular meiotic pairing but in most plants there are a few univalent chromosomes at metaphase I. Artificially produced hybrids of A. pratensis × A. aequalis gave meiotic configurations that suggest that the genomes of the parent species are very similar. Taken together with the results from artificially produced hybrids of A. pratensis × A. geniculatus , it is suggested that bivalent-promoting mechanisms reduce multivalent formation both in the species and the hybrids. The interaction of different genotypes involved in the control of meiosis may account for the variation in meiotic behaviour in the different populations of hybrids. Pollen fertility is reduced in most populations of hybrids and likely to be an important factor permitting introgressive hybridization.     

On the leafy nature of lodicules in the genus Triticum (Poaceae)

Lodicules are important organs creating the mating system in grasses, in a range between autogamy in clestogamous flowers and allogamy in chasmogamous flowers. This balance is the main factor determining variation patterns in plant populations. Recognition of variation in lodicule morphology is especially important in wheat, the main crop of the world. For this reason, a broad range of species of wheat was evaluated by means of characters showing the leafy nature of lodicules. The characters were studied under polarizing and epifluorescence microscopes. Development of lodicule stomata is different than that in leaves. Development of stomata and xylem, is distinctly correlated. Other short cells created by epidermal meristemoids are developmentally rather independent of both stomata and xylem. Interrelations between stomata, xylem and morphogenetic traits of the abaxial epidermis of the lodicule are illustrated by pictures and diagrams of numerical analyses, including a non‐metric multidimensional scaling method. Some unthreshable wheats, such as Triticum diccocum, T. ispahanicum and T. spelta, have more leafy lodicules, but intraspecific variation appears in the form of +leafy vs. ?leafy lodicules. Formation of leafy lodicule morphs does not depend on the ploidy level of wheat. An intraspecific mosaic of + or ?leafy lodicules proves a mutational origin of their leafy characters. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 303–316.     

Hybridization between introduced smooth cordgrass (Spartina alterniflora; Poaceae) and native California cordgrass (S. foliosa) in San Francisco Bay, California, USA

Introduced Spartina alterniflora (smooth cordgrass) is rapidly invading intertidal mudflats in San Francisco Bay, California. At several sites, S. alterniflora co-occurs with native S. foliosa (California cordgrass), a species endemic to California salt marshes. In this study, random amplified polymorphic DNA markers (RAPDs) specific to each Spartina species were identified and used to test for hybridization between the native and introduced Spartina species in the greenhouse and in the field. Greenhouse crosses were made using S. alterniflora as the pollen donor and S. foliosa as the maternal plant, and these crosses produced viable seeds. The hybrid status of the crossed offspring was confirmed with the RAPD markers. Hybrids had low self-fertility but high fertility when back-crossed with S. foliosa pollen. Hybrids were also found established at two field sites in San Francisco Bay; these hybrids appeared vigorous and morphologically intermediate between the parental species. Field observations suggested that hybrids were recruiting more rapidly than the native S. foliosa. Previous work identified competition from introduced S. alterniflora as a threat to native S. foliosa. In this study, we identify introgression and the spread of hybrids as an additional, perhaps even more serious threat to conservation of S. foliosa in San Francisco Bay.     

Hybridization between Triticum aestivum L. and Agropyron michnoi Roshev.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring (2n=6x=42, AABBDD) and Agropyron michnoi Roshev. (2n=4x=28, PPPP) were obtained by embryo culture. Their spike characteristics were similar to those of common wheat but, unlike their parents, they were long-awned. The average meiotic chromosome pairing at MI of F₁ hybrids was: 6.39 I +3.75 rodII+8.64 ringII+0.81 III+0.30 IV+0.04 V, the bivalent and multivalent formation of which was much higher than expected from the genomic formulae. It is especially worthwhile to note that the F₁ hybrids were self-fertile, self set being 0.15%, and seeds were easily obtained from the backcross of f₁ plants with hexaploid and tetraploid wheats; here the seed set was more than 20.0%. The polyploid taxa and the position of A. Michnoi in Agropyron are discussed.     

The configuration of the seminal roots of Triticum aestivum L. (Poaceae)

The seminal root system of wheat (Triticum aestivum L.) is composed of the primary seminal root, the first pair of seminal roots, and the second pair of seminal roots, which are known to grow in different directions. The direction of root growth, which can be expressed by theta (the angle between the root and the plumb line) and phi (the angle between the root and a vertical plane including the primary seminal root), was studied with special attention to the latter. It was measured on seedlings grown in a small hemispherical soil-filled mesh basket. There were varietal differences in the phi of the first pair of roots (phi f) and in the phi of the second pair of roots (phi s). phi f and phi s were significantly correlated. The mean distance (MD), a measure to evaluate the efficiency of root spacing, was correlated with the difference between phi f and phi s. Neither experimentally applied low soil water potential nor the excision of the primary seminal root affected phi. When the grain was sown vertically with the tip of the embryo pointing downwards, it was found that the growth movement into a direction different from the plumb line and phi s was greatly modified. It is suggested that certain internal mechanisms, possibly involving gravitropic reactions, are operating to control the direction of root growth. The significance of root growth direction at the seedling stage is discussed.     

Development of chromosome-arm-specific microsatellite markers in Triticum aestivum (Poaceae) using NGS technology

? Premise of the study: The aim of this study was to assess the feasibility of developing chromosome-arm-specific microsatellite markers in wheat on a large scale based on chromosome survey sequences obtained with next-generation sequencing (NGS) technology. ? Methods and Results: The Illumina Hi Seq2000 sequencing platform was used to sequence DNA of isolated wheat chromosome-arm 7DL. The data were assembled and microsatellite loci were identified computationally. In total, 16315 microsatellites were identified from 161061 assembled contigs. Thirty-three markers were randomly selected for validation across 20 diverse wheat cultivars. Two nulli-tetrasomic stocks were also screened to validate the specificity of the newly developed markers. ? Conclusions: This is the first study on identification of chromosome-arm-specific microsatellite markers using NGS technology. These new chromosome-arm-specific markers will facilitate saturation of the 7DL genetic map, and their availability will support genetic mapping and positional cloning in wheat.     

Intergeneric hybridization between Hordeum and Hordelymus (Poaceae)

Intergeneric hybridization between the monotypic Eurasian genus Hordelymus and species of Hordeum was performed. Hybrids were obtained in nine combinations and the meiotic pairing was analyzed in four combinations (6 families). Hordelymus europaeus is probably an alloploid with two different genomes. The very low pairing in the hybrids with H. jubatum, H. brachyantherum , and H. pusillum indicates that these species do not have any genomes in common with Hordelymus. The hybrids with H. depressum have an intermediate pairing which suggests that there is a certain homoeology in one genome.     

Hybridization between invasive Spartina densiflora (Poaceae) and native S. foliosa in San Francisco Bay, California, USA

Rapid evolution in contemporary time can result when related species, brought together through human-aided introduction, hybridize. The significant evolutionary consequences of post-introduction hybridization range from allopolyploid speciation to extinction of species through genetic amalgamation. Both processes are known to occur in the perennial cordgrass genus, Spartina. Here we report the existence of a third recent Spartina hybridization, discovered in 2002, between introduced S. densiflora and native S. foliosa in San Francisco Bay, California, USA. We used nuclear and chloroplast DNA analysis and nuclear DNA content with chromosome counts to examine plants of morphology intermediate between S. densiflora and S. foliosa in a restored marsh in Marin County, California. We found 32 F(1) diploid hybrids and two triploid plants, all having S. densiflora and S. foliosa as parents; there is also evidence of a genetic contribution of S. alterniflora in some hybrids. None of these hybrids set germinable seed. In 2007 we found a hybrid over 30 miles away in a marsh where both parental species occurred, suggesting hybridization may not be a localized phenomenon. The presence of diploid and triploid hybrids is important because they indicate that several avenues existed that may have given rise to a new allopolyploid species. However, such an event is now unlikely because all hybrids are targets of eradication efforts.     

Relationships between seven species ofVulpia (Poaceae)

Seven species ofVulpia were subjected to morphological and protein studies using principal component and cluster analysis and theJaccard's Similarity Coefficient. Studies showed all species were uniform and distinct from each other. Species of sect.Loretia were very dissimilar from those of sect.Monachne and sect.Vulpia. The latter section comprises taxa of high mutual affinity.     

Relationships between five species ofLolium (Poaceae)

Morphological analysis and electrophoresis of seed proteins of fiveLolium species disclosed that they form two distinct groups corresponding to those recognized from compatibility data.Lolium temulentum andL. remotum of the self-pollinated group were shown to be distinct but closely related species. Morphological intergradation and high similarities between protein profiles ofL. perenne, L. multiflorum andL. rigidum (cross-pollinated species) suggest little genetic differentiation between these taxa. This implies that treatment at the infraspecific level might better accomodate the data.     

Participation of the enzymes involved in the biosynthesis of biogenic amines in biochemical interactions between wheat (Triticum aestivum; Poaceae) and bird cherry-oat aphid (Rhopalosiphum padi; Aphididae)

The studies concerned changes in the activities of ornithine decarboxylase (ODC), lysine decarboxylase (LDC) and tyrosine decarboxylase (TyDC) in tissues of wheat (Triticum aestivum L.) infested with bird cherry-oat aphid (Rhopalosiphum padi L.).Obtained results showed that the activities of the enzymes were stimulated in the less susceptible wheat Kontesa cv. infested by the aphids. In the case of the more susceptible Tonacja cv., on most occasions a decrease in the enzyme activities occurred. Such responses were especially clear for TyDC in both analysed cvs., and for LDC and ODC in the case of Kontesa cv. Thus it may be concluded that amino acid decarboxylation plays an important part in the biochemical defence developed in wheat tissues in response to R. padi infestation. The changes in the activities of the decarboxylases were dependent on the wheat genotype as well as the duration of the infestation.     

一粒小麦-葡萄牙野燕麦远缘杂交后代衍生系GISH研究

以一粒小麦-葡萄牙野燕麦杂交后代一粒葡为实验材料,以地高辛标记的葡萄牙野燕麦基因组DNA为探针、一粒小麦基因组DNA为封阻对一粒葡及其衍生系根尖染色体进行基因组原位杂交(GISH)分析,探讨了影响一粒葡GISH效果的主要因素.建立并优化了一粒葡GISH分析的实验体系,即探针DNA与封阻DNA比例为1∶50时可有效分开双方染色体组.优化GISH分析显示,在一粒葡后代衍生系中均检测到燕麦染色质的存在,且不同选系间带有燕麦染色体的数目不同,进一步证明一粒葡是一粒小麦-葡萄牙野燕麦远缘杂交的后代.     

Hybridization in the genera Vulpia and Festuca (Poaceae): the characteristics of artificial hybrids

The chromosome numbers and morphological characteristics, including life–form, vegetative and floral measurements and pollen fertility, of 70 artificial interspecific Vulpia hybrid plants and 49 artificial intergeneric Festuca rubra agg. x Vulpia hybrid plants are presented, together with comparable data from 60 artificial Festuca rubra agg. x Vulpia fasciculata plants produced by R. Cotton. The inheritance of various characters is summarized. It is concluded that most characters of the tetraploid Vulpia fasciculata are dominant over those of diploid species of Vulpia , but that most characters of the hexaploid Festuca rubra agg. are dominant over those of diploid and tetraploid species of Vulpia. In diploid x diploid Vulpia crosses the pubescent ovary tip is dominant to the glabrous state, but the inheritance of lemma pubescence is more complicated. The keeled lemmas of V. fasciculata and V. pyramidata are dominant to the rounded ones of other Vulpia species, but recessive to the rounded ones of F rubra agg. Bearing in mind such generalizations as these, the parentage of wild hybrids should be capable of correct interpretation. The significance of the results in our understanding of the origin of V. fasciculata is discussed.