Evolution Of Grasses Research Articles

Disentangling conflicting molecular phylogenetic signals in nuclear and plastid DNA of the western Eurasian-Mediterranean grass genus Cynosurus and its relatives (Poaceae subtribes Cynosurinae and Parapholiinae)

The western Eurasian-Mediterranean grass genus Cynosurus, comprising about 11 species, is morphologically well delimited by the regular occurrence of conspicuous sterile spikelets distal to the fertile ones on the outer, abaxial side of the inflorescences. However, our molecular phylogenetic study using nuclear ribosomal DNA (ITS, ETS) and plastid DNA sequences (trnL–F, matK) has shown that the genus is not monophyletic in its current delimitation, but consists of three distinct lineages. These lineages were found to be closely related to a group of 6–7 genera taxonomically assigned to the subtribe Parapholiinae. These Parapholiinae genera were consistently monophyletic in our analyses, but the suggested relationships to the three lineages of Cynosurus varied depending on the particular DNA region examined. This was the case for both plastid and nuclear DNA, with cytonuclear discordance and ‘chloroplast capture’ indicating earlier hybridization. Interestingly, hybridization also proved to be the most likely explanation even with regard to the 18S–26S cistrons of the nuclear ribosomal DNA, where an exceptional evolutionary divergence between ITS and ETS was found. The results highlight and illustrate the important role of hybridization in the evolution of grasses. In terms of taxonomy, our findings argue against maintaining a polyphyletic genus Cynosurus s.l. but instead argue for dividing it into three monophyletic genera: Cynosurus s.s., Falona, which is reestablished here, and Ciliochloa, which is described as a new genus. In addition, it is proposed that the two subtribes Cynosurinae and Parapholiinae be combined into a single subtribe Cynosurinae, which is also monophyletic. The possible genetic background of the formation of sterile spikelets and the occasional occurrence of inflorescences with consistently fertile spikelets are discussed. New combinations are Ciliochloa effusa, C. effusa var. obliquata, C. effusa var. fertilis, C. elegans, C. gracilis, C. turcomanica and Falona colorata.

The optimum fire window: applying the fire–productivity hypothesis to Jurassic climate states

Abstract. Present-day fire frequency is related to a productivity–aridity gradient on regional and global scales. Optimum fire conditions occur at times of intermediate productivity and aridity, whereas fire is limited at the high productivity (moisture) and aridity (no fuel) endmembers. However, the current global fire activity pattern is reinforced by the predominant burning of grasslands. Here we test the intermediate fire–productivity hypothesis for a period on Earth before the evolution of grasses, the Early Jurassic, and explore the fire regime of two contrasting climatic states: the cooling of the Late Pliensbachian Event (LPE) and the warming of the Sinemurian–Pliensbachian Boundary (SPB). Palaeo-fire records are reconstructed from fossil charcoal abundance, and changes in the hydrological cycle are tracked via clay mineralogy, which allows inference of changes in fuel moisture status. Large fluctuations in the fossil charcoal on an eccentricity timescale indicate two modes of fire regime at the time. Wildfires were moisture-limited in a high-productivity ecosystem during eccentricity minima for both the SPB and the LPE. During eccentricity maxima fires increased, and an optimum fire window was reached, in which periodically greater seasonality in rainfall and temperatures led to intermediate states of productivity and aridity. The LPE experienced more extreme climatic endmembers compared to the SPB, with the fire regime edging closer to “moisture limitation” during eccentricity minima, and experienced more pronounced seasonality during eccentricity maxima, explained by the overall cooler climate at the time. This study illustrates that the intermediate-productivity gradient holds up during two contrasting climatic states in the Jurassic.

Molecular Evolution of RAMOSA1 (RA1) in Land Plants.

RAMOSA1 (RA1) is a Cys2-His2-type (C2H2) zinc finger transcription factor that controls plant meristem fate and identity and has played an important role in maize domestication. Despite its importance, the origin of RA1 is unknown, and the evolution in plants is only partially understood. In this paper, we present a well-resolved phylogeny based on 73 amino acid sequences from 48 embryophyte species. The recovered tree topology indicates that, during grass evolution, RA1 arose from two consecutive SUPERMAN duplications, resulting in three distinct grass sequence lineages: RA1-like A, RA1-like B, and RA1; however, most of these copies have unknown functions. Our findings indicate that RA1 and RA1-like play roles in the nucleus despite lacking a traditional nuclear localization signal. Here, we report that copies diversified their coding region and, with it, their protein structure, suggesting different patterns of DNA binding and protein-protein interaction. In addition, each of the retained copies diversified regulatory elements along their promoter regions, indicating differences in their upstream regulation. Taken together, the evidence indicates that the RA1 and RA1-like gene families in grasses underwent subfunctionalization and neofunctionalization enabled by gene duplication.

The evolution of indigenous grasses and their response to environmental change

The evolution of indigenous grasses and their response to environmental change

GRASSY TILLERS1 (GT1) and SIX-ROWED SPIKE1 (VRS1) homologs share conserved roles in growth repression.

Crop engineering and de novo domestication using gene editing are new frontiers in agriculture. However, outside of well-studied crops and model systems, prioritizing engineering targets remains challenging. Evolution can guide us, revealing genes with deeply conserved roles that have repeatedly been selected in the evolution of plant form. Homologs of the transcription factor genes GRASSY TILLERS1 (GT1) and SIX-ROWED SPIKE1 (VRS1) have repeatedly been targets of selection in domestication and evolution, where they repress growth in many developmental contexts. This suggests a conserved role for these genes in regulating growth repression. To test this, we determined the roles of GT1 and VRS1 homologs in maize (Zea mays) and the distantly related grass brachypodium (Brachypodium distachyon) using gene editing and mutant analysis. In maize, gt1; vrs1-like1 (vrl1) mutants have derepressed growth of floral organs. In addition, gt1; vrl1 mutants bore more ears and more branches, indicating broad roles in growth repression. In brachypodium, Bdgt1; Bdvrl1 mutants have more branches, spikelets, and flowers than wild-type plants, indicating conserved roles for GT1 and VRS1 homologs in growth suppression over ca. 59 My of grass evolution. Importantly, many of these traits influence crop productivity. Notably, maize GT1 can suppress growth in arabidopsis (Arabidopsis thaliana) floral organs, despite ca. 160 My of evolution separating the grasses and arabidopsis. Thus, GT1 and VRS1 maintain their potency as growth regulators across vast timescales and in distinct developmental contexts. This work highlights the power of evolution to inform gene editing in crop improvement.

Genome-wide expansion and reorganization during grass evolution: from 30 Mb chromosomes in rice and Brachypodium to 550 Mb in Avena

BackgroundThe BOP (Bambusoideae, Oryzoideae, and Pooideae) clade of the Poaceae has a common ancestor, with similarities to the genomes of rice, Oryza sativa (2n = 24; genome size 389 Mb) and Brachypodium, Brachypodium distachyon (2n = 10; 271 Mb). We exploit chromosome-scale genome assemblies to show the nature of genomic expansion, structural variation, and chromosomal rearrangements from rice and Brachypodium, to diploids in the tribe Aveneae (e.g., Avena longiglumis, 2n = 2x = 14; 3,961 Mb assembled to 3,850 Mb in chromosomes).ResultsMost of the Avena chromosome arms show relatively uniform expansion over the 10-fold to 15-fold genome-size increase. Apart from non-coding sequence diversification and accumulation around the centromeres, blocks of genes are not interspersed with blocks of repeats, even in subterminal regions. As in the tribe Triticeae, blocks of conserved synteny are seen between the analyzed species with chromosome fusion, fission, and nesting (insertion) events showing deep evolutionary conservation of chromosome structure during genomic expansion. Unexpectedly, the terminal gene-rich chromosomal segments (representing about 50 Mb) show translocations between chromosomes during speciation, with homogenization of genome-specific repetitive elements within the tribe Aveneae. Newly-formed intergenomic translocations of similar extent are found in the hexaploid A. sativa.ConclusionsThe study provides insight into evolutionary mechanisms and speciation in the BOP clade, which is valuable for measurement of biodiversity, development of a clade-wide pangenome, and exploitation of genomic diversity through breeding programs in Poaceae.

Alloteropsis semialata as a study system for C4 evolution in grasses.

Numerous groups of plants have adapted to CO2 limitations by independently evolving C4 photosynthesis. This trait relies on concerted changes in anatomy and biochemistry to concentrate CO2 within the leaf and thereby boost productivity in tropical conditions. The ecological and economic importance of C4 photosynthesis has motivated intense research, often relying on comparisons between distantly related C4 and non-C4 plants. The photosynthetic type is fixed in most species, with the notable exception of the grass Alloteropsis semialata. This species includes populations exhibiting the ancestral C3 state in southern Africa, intermediate populations in the Zambezian region and C4 populations spread around the palaeotropics. We compile here the knowledge on the distribution and evolutionary history of the Alloteropsis genus as a whole and discuss how this has furthered our understanding of C4 evolution. We then present a chromosome-level reference genome for a C3 individual and compare the genomic architecture with that of a C4 accession of A. semialata. Alloteropsis semialata is one of the best systems in which to investigate the evolution of C4 photosynthesis because the genetic and phenotypic variation provides a fertile ground for comparative and population-level studies. Preliminary comparative genomic investigations show that the C3 and C4 genomes are highly syntenic and have undergone a modest amount of gene duplication and translocation since the different photosynthetic groups diverged. The background knowledge and publicly available genomic resources make A. semialata a great model for further comparative analyses of photosynthetic diversification.

Changes in global DNA methylation under climatic stress in two related grasses suggest a possible role of epigenetics in the ecological success of polyploids

Polyploidization drives the evolution of grasses and can result in epigenetic changes, which may have a role in the creation of new evolutionary lineages and ecological speciation. As such changes may be inherited, they can also influence adaptation to the environment. Populations from different regions and climates may also differ epigenetically; however, this phenomenon is poorly understood. The present study analyzes the effect of climatic stress on global DNA methylation based on a garden collection of two related mountain grasses (the narrow endemic diploid Festuca tatrae and the more widely distributed mixed-ploidy F. amethystina) with different geographic ranges and ecological niches. A lower level of DNA methylation was observed for F. tatrae, while a higher mean level was obtained for the diploid and tetraploid of F. amethystina; with the tetraploids having a higher level of global methylated DNA than the diploids. The weather conditions (especially insolation) measured 24 h prior to sampling appeared to have a closer relationship with global DNA methylation level than those observed seven days before sampling. Our findings suggest that the level of methylation during stress conditions (drought, high temperature and high insolation) may be significantly influenced by the ploidy level and bioclimatic provenance of specimens; however an important role may also be played by the intensity of stress conditions in a given year.

Chromosome-scale genome assembly provides insights into speciation of allotetraploid and massive biomass accumulation of elephant grass (Pennisetum purpureum Schum.).

Elephant grass (Pennisetum purpureum Schum) is an important forage, biofuels and industrial plant widely distributed in tropical and subtropical areas globally. It is characterized with robust growth and high biomass. We sequenced its allopolyploid genome and assembled 2.07Gb into A' and B subgenomes of 14 chromosomes with scaffold N50 of 8.47Mb, yielding a total of 77,139genes. The allotetraploid speciation occurred approximately 15Ma after the divergence between Setaria italica and Pennisetum glaucum, according to a phylogenetic analysis of Pennisetum species. Double whole-genome duplication (WGD) and polyploidization events resulted in large-scale gene expansion, especially in the key steps of growth and biomass accumulation. Integrated transcriptome profiling revealed the functional divergence between subgenomes A' and B. A' subgenome mainly contributed to plant growth, development and photosynthesis, whereas the B subgenome was primarily responsible for effective transportation and resistance to stimulation. Some key gene families related to cellulose biosynthesis were expanded and highly expressed in stems, which could explain the high cellulose content in elephant grass. Our findings provide deep insights into genetic evolution of elephant grass and will aid future biological research and breeding, even for other grasses in the family Poaceae.

Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution in Urochloa (Brachiaria) species.

Diploid and polyploid Urochloa (including Brachiaria, Panicum and Megathyrsus species) C4 tropical forage grasses originating from Africa are important for food security and the environment, often being planted in marginal lands worldwide. We aimed to characterize the nature of their genomes, the repetitive DNA and the genome composition of polyploids, leading to a model of the evolutionary pathways within the group including many apomictic species. Some 362 forage grass accessions from international germplasm collections were studied, and ploidy was determined using an optimized flow cytometry method. Whole-genome survey sequencing and molecular cytogenetic analysis were used to identify chromosomes and genomes in Urochloa accessions belonging to the 'brizantha' and 'humidicola' agamic complexes and U. maxima. Genome structures are complex and variable, with multiple ploidies and genome compositions within the species, and no clear geographical patterns. Sequence analysis of nine diploid and polyploid accessions enabled identification of abundant genome-specific repetitive DNA motifs. In situ hybridization with a combination of repetitive DNA and genomic DNA probes identified evolutionary divergence and allowed us to discriminate the different genomes present in polyploids. We suggest a new coherent nomenclature for the genomes present. We develop a model of evolution at the whole-genome level in diploid and polyploid accessions showing processes of grass evolution. We support the retention of narrow species concepts for Urochloa brizantha, U. decumbens and U. ruziziensis, and do not consider diploids and polyploids of single species as cytotypes. The results and model will be valuable in making rational choices of parents for new hybrids, assist in use of the germplasm for breeding and selection of Urochloa with improved sustainability and agronomic potential, and assist in measuring and conserving biodiversity in grasslands.

The Pharus latifolius genome bridges the gap of early grass evolution.

The grass family (Poaceae) includes all commercial cereal crops and is a major contributor to biomass in various terrestrial ecosystems. The ancestry of all grass genomes includes a shared whole-genome duplication (WGD), named rho (ρ) WGD, but the evolutionary significance of ρ-WGD remains elusive. We sequenced the genome of Pharus latifolius, a grass species (producing a true spikelet) in the subfamily Pharoideae, a sister lineage to the core Poaceae including the (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, and Danthonioideae (PACMAD) and Bambusoideae, Oryzoideae, and Pooideae (BOP) clades. Our results indicate that the P. latifolius genome has evolved slowly relative to cereal grass genomes, as reflected by moderate rates of molecular evolution, limited chromosome rearrangements and a low rate of gene loss for duplicated genes. We show that the ρ-WGD event occurred approximately 98.2 million years ago (Ma) in a common ancestor of the Pharoideae and the PACMAD and BOP grasses. This was followed by contrasting patterns of diploidization in the Pharus and core Poaceae lineages. The presence of two FRIZZY PANICLE-like genes in P. latifolius, and duplicated MADS-box genes, support the hypothesis that the ρ-WGD may have played a role in the origin and functional diversification of the spikelet, an adaptation in grasses related directly to cereal yields. The P. latifolius genome sheds light on the origin and early evolution of grasses underpinning the biology and breeding of cereals.

Grassflies of genus Meromyza (Diptera, Chloropidae) and grasses: the evolution of host plant preference

The present and literature data showed that Meromyza flies developed on grasses from 5 tribes: Poeae, Triticeae, Bromeae, Nardeae, Arundinarieae. The preference of host plants for 25, mainly Western Palaearctic species of Meromyza flies was analyzed: 11 species developed on grasses of the tribe Poeae, 4 on Triticeae, 9 on grasses from different tribes, 1 species developed on bamboo. A phylogenetic tree based on the mtDNA CO1 gene locus was constructed in the BEAST for 28 species of Meromyza flies, for 8 species of Drosophila and Campiglossa pygmaea. The host plants were known for 19 species Meromyza flies out of 28 studied species. An overview of the evolution of grasses is given. By the possible time of the genus Meromyza origin (not earlier than the middle of the Miocene), based on the known evolutionary scale of Drosophila, the Pooideae grasses had already been isolated and division into tribes occured. The features of non-specialized phytophage-oligophage (except M. acuminata) confirmed by the wide spectrum of host plants have been supposed for species close to ancestral haplotypes (M. nigriseta, M. pratorum, M. saltatrix, M. variegata) or representing independent branches in their clusters (M. acuminata, M. mosquensis, M. nigriventris). The differentiation of Meromyza genus with formation of new species with narrow oligophagy or monophagy was associated with adaptation to other wild grasses following the formation and increase in the abundance of core pooids (Triticodae + Poodae) grasses and the spread of herbal biomes in the Miocene. Oligophages M. nigriventris, M. nigriseta, M. variegata and monophages M. acuminata, M. grandifemoris damage cereal cultivars.

A multilayered cross-species analysis of GRAS transcription factors uncovered their functional networks in plant adaptation to the environment

IntroductionEnvironmental stress is both a major force of natural selection and a prime factor affecting crop qualities and yields. The impact of the GRAS [gibberellic acid-insensitive (GAI), repressor of GA1–3 mutant (RGA), and scarecrow (SCR)] family on plant development and the potential to resist environmental stress needs much emphasis. ObjectivesThis study aims to investigate the evolution, expansion, and adaptive mechanisms of GRASs of important representative plants during polyploidization. MethodsWe explored the evolutionary characteristics of GRASs in 15 representative plant species by systematic biological analysis of the genome, transcriptome, metabolite, protein complex map and phenotype. ResultsThe GRAS family was systematically identified from 15 representative plant species of scientific and agricultural importance. The detection of gene duplication types of GRASs in all species showed that the widespread expansion of GRASs in these species was mainly contributed by polyploidization events. Evolutionary analysis reveals that most species experience independent genome-wide duplication (WGD) events and that interspecies GRAS functions may be broadly conserved. Polyploidy-related Chenopodium quinoa GRASs (CqGRASs) and Arabidopsis thaliana GRASs (AtGRASs) formed robust networks with flavonoid pathways by crosstalk with auxin and photosynthetic pathways. Furthermore, Arabidopsis thaliana population transcriptomes and the 1000 Plants (OneKP) project confirmed that GRASs are components of flavonoid biosynthesis, which enables plants to adapt to the environment by promoting flavonoid accumulation. More importantly, the GRASs of important species that may potentially improve important agronomic traits were mapped through TAIR and RARGE-II publicly available phenotypic data. Determining protein interactions and target genes contributes to determining GRAS functions. ConclusionThe results of this study suggest that polyploidy-related GRASs in multiple species may be a target for improving plant growth, development, and environmental adaptation.

The elephant grass (Cenchrus purpureus) genome provides insights into anthocyanidin accumulation and fast growth.

Elephant grass (2n = 4x = 28; Cenchrus purpureus Schumach.), also known as Napier grass, is an important forage grass and potential energy crop in tropical and subtropical regions of Asia, Africa and America. However, no study has yet reported a genome assembly for elephant grass at the chromosome scale. Here, we report a high‐quality chromosome‐scale genome of elephant grass with a total size of 1.97 Gb and a 1.5% heterozygosity rate, obtained using short‐read sequencing, single‐molecule long‐read sequencing and Hi‐C chromosome conformation capture. Evolutionary analysis showed that subgenome A' of elephant grass and pearl millet may have originated from a common ancestor more than 3.22 million years ago (MYA). Further, allotetraploid formation occurred at approximately 6.61 MYA. Syntenic analyses within elephant grass and with other grass species indicated that elephant grass has experienced chromosomal rearrangements. We found that some key enzyme‐encoding gene families related to the biosynthesis of anthocyanidins and flavonoids were expanded and highly expressed in leaves, which probably drives the production of these major anthocyanidin compounds and explains why this elephant grass cultivar has a high anthocyanidin content. In addition, we found a high copy number and transcript levels of genes involved in C4 photosynthesis and hormone signal transduction pathways that may contribute to the fast growth of elephant grass. The availability of elephant grass genome data advances our knowledge of the genetic evolution of elephant grass and will contribute to further biological research and breeding as well as for other polyploid plants in the genus Cenchrus.

Pilar Catalán.

Pilar Catalán.

The reconstruction and biochemical characterization of ancestral genes furnish insights into the evolution of terpene synthase function in the Poaceae

Key MessageDistinct catalytic features of the Poaceae TPS-a subfamily arose early in grass evolution and the reactions catalyzed have become more complex with time.The structural diversity of terpenes found in nature is mainly determined by terpene synthases (TPS). TPS enzymes accept ubiquitous prenyl diphosphates as substrates and convert them into the various terpene skeletons by catalyzing a carbocation-driven reaction. Based on their sequence similarity, terpene synthases from land plants can be divided into different subfamilies, TPS-a to TPS-h. In this study, we aimed to understand the evolution and functional diversification of the TPS-a subfamily in the Poaceae (the grass family), a plant family that contains important crops such as maize, wheat, rice, and sorghum. Sequence comparisons showed that aside from one clade shared with other monocot plants, the Poaceae TPS-a subfamily consists of five well-defined clades I–V, the common ancestor of which probably originated very early in the evolution of the grasses. A survey of the TPS literature and the characterization of representative TPS enzymes from clades I–III revealed clade-specific substrate and product specificities. The enzymes in both clade I and II function as sesquiterpene synthases with clade I enzymes catalyzing initial C10-C1 or C11-C1 ring closures and clade II enzymes catalyzing C6-C1 closures. The enzymes of clade III mainly act as monoterpene synthases, forming cyclic and acyclic monoterpenes. The reconstruction and characterization of clade ancestors demonstrated that the differences among clades I–III were already present in their ancestors. However, the ancestors generally catalyzed simpler reactions with less double-bond isomerization and fewer cyclization steps. Overall, our data indicate an early origin of key enzymatic features of TPS-a enzymes in the Poaceae, and the development of more complex reactions over the course of evolution.

Plant science's next top models.

Model organisms are at the core of life science research. Notable examples include the mouse as a model for humans, baker's yeast for eukaryotic unicellular life and simple genetics, or the enterobacteria phage λ in virology. Plant research was an exception to this rule, with researchers relying on a variety of non-model plants until the eventual adoption of Arabidopsis thaliana as primary plant model in the 1980s. This proved to be an unprecedented success, and several secondary plant models have since been established. Currently, we are experiencing another wave of expansion in the set of plant models. Since the 2000s, new model plants have been established to study numerous aspects of plant biology, such as the evolution of land plants, grasses, invasive and parasitic plant life, adaptation to environmental challenges, and the development of morphological diversity. Concurrent with the establishment of new plant models, the advent of the 'omics' era in biology has led to a resurgence of the more complex non-model plants. With this review, we introduce some of the new and fascinating plant models, outline why they are interesting subjects to study, the questions they will help to answer, and the molecular tools that have been established and are available to researchers. Understanding the molecular mechanisms underlying all aspects of plant biology can only be achieved with the adoption of a comprehensive set of models, each of which allows the assessment of at least one aspect of plant life. The model plants described here represent a step forward towards our goal to explore and comprehend the diversity of plant form and function. Still, several questions remain unanswered, but the constant development of novel technologies in molecular biology and bioinformatics is already paving the way for the next generation of plant models.

Phylogenetic lineages and the role of hybridization as driving force of evolution in grass supertribe Poodae

AbstractTo investigate the evolutionary diversification and morphological evolution of grass supertribe Poodae (subfam. Pooideae, Poaceae) we conducted a comprehensive molecular phylogenetic analysis including representatives from most of its accepted genera. We focused on generating a DNA sequence dataset of plastid matK gene–3′trnK exon and trnL‐trnF regions and nuclear ribosomal (nr) ITS1–5.8S gene–ITS2 and ETS that was taxonomically overlapping as completely as possible (altogether 257 species). The idea was to infer whether phylogenetic trees or certain clades based on plastid and nrDNA data correspond with each other or discord, revealing signatures of past hybridization. The datasets were analysed separately, in combination, by excluding taxa with discordant placements in the individual gene trees and with duplication of these taxa in a way that each duplicate has only one data partition (plastid or nrDNA). We used maximum likelihood, maximum parsimony and Bayesian approaches. Instances of severe conflicts between the phylogenetic trees derived from both datasets, some of which have been noted earlier, point to hybrid origin of several lineages such as the ABCV clade encompassing several subtribes and subordinate clades, subtribes Airinae, Anthoxanthinae, Antinoriinae, subtr. nov., Aristaveninae, Avenulinae, subtr. nov., Helictochloinae, subtr. nov., Holcinae, Phalaridinae, Scolochloinae, Sesleriinae, Torreyochloinae and genera Arctopoa, Castellia, Graphephorum, Hyalopodium, Lagurus, Macrobriza, Puccinellia plus Sclerochloa, Sesleria, Tricholemma, Tzveleviochloa, etc. ‘Calamagrostis’ flavens appears to be an intergeneric hybrid between Agrostis and Calamagrostis. Analyses excluding all lineages with demonstrably cytonuclear discordance revealed three supported main clades within Poodae that were present in both the plastid and nrDNA trees. They fully corresponded in their delineation but were phylogenetically differently arranged, pointing to hybrid origin of one of them. We propose to consider these main clades in classification as separate tribes Aveneae, Poeae s.str. and Festuceae with a phylogenetic arrangement of Aveneae(Poeae,Festuceae) in plastid versus Festuceae(Aveneae,Poeae) in nrDNA trees. Phylogenetic incongruence of the plastid and nuclear markers extends across all hierarchical taxonomic levels of Poodae, ranging from species (not studied here) to genera, subtribes and tribes, therefore the deepest taxonomic levels, emphasizing the enormous significance of reticulate evolution in this large group of grasses. A partly revised classification is presented, including the introduction of a new tribe Festuceae and a re‐instatement of tribe Aveneae. Following a comparatively narrow delineation of preferably monophyletic subtribes, Antinoriinae, Avenulinae, Brizochloinae, Helictochloinae and Hypseochloinae are described as new. New genera are Arctohyalopoa and Hyalopodium. New combinations are Anthoxanthum glabrum subsp. sibiricum, A. nitens subsp. kolymense, Arctohyalopoa ivanovae, A. jurtzevii, A. lanatiflora, A. momica, Colpodium biebersteinianum, C. kochii, C. pisidicum, C. trichopodum, C. verticillatum, Dupontia fulva, Festuca masafuerana, F. robinsoniana, Graphephorum canescens, G. cernuum, Hyalopodium araraticum, Paracolpodium baltistanicum, Parapholis cylindrica, P. ×pauneroi. Festuca dolichathera and F. masatierrae are new names.

QTL mapping of yield component traits on bin map generated from resequencing a RIL population of foxtail millet (Setaria italica)

BackgroundFoxtail millet (Setaria italica) has been developed into a model genetical system for deciphering architectural evolution, C4 photosynthesis, nutritional properties, abiotic tolerance and bioenergy in cereal grasses because of its advantageous characters with the small genome size, self-fertilization, short growing cycle, small growth stature, efficient genetic transformation and abundant diverse germplasm resources. Therefore, excavating QTLs of yield component traits, which are closely related to aspects mentioned above, will further facilitate genetic research in foxtail millet and close cereal species.ResultsHere, 164 Recombinant inbreed lines from a cross between Longgu7 and Yugu1 were created and 1,047,978 SNPs were identified between both parents via resequencing. A total of 3413 bin markers developed from SNPs were used to construct a binary map, containing 3963 recombinant breakpoints and totaling 1222.26 cM with an average distance of 0.36 cM between adjacent markers. Forty-seven QTLs were identified for four traits of straw weight, panicle weight, grain weight per plant and 1000-grain weight. These QTLs explained 5.5–14.7% of phenotypic variance. Thirty-nine favorable QTL alleles were found to inherit from Yugu1. Three stable QTLs were detected in multi-environments, and nine QTL clusters were identified on Chromosome 3, 6, 7 and 9.ConclusionsA high-density genetic map with 3413 bin markers was constructed and three stable QTLs and 9 QTL clusters for yield component traits were identified. The results laid a powerful foundation for fine mapping, identifying candidate genes, elaborating molecular mechanisms and application in foxtail millet breeding programs by marker-assisted selection.

Евразийский степной пояс: статус-кво, происхождение и эволюция

We present a comprehensive review of the characteristics and structure of the Eurasian steppe and of its evolutionary history in space and time. During the last decades, tremendous advances in research methods in earth and palaeontological sciences have greatly increased knowledge on palaeoclimates and palaeoenvironments of the Cenozoic era. We discuss well-known facts against the background of the recent progress made in these fields and others related to our topics, and address open questions. In Part I (Status quo), we deal with steppe classification systems, human impact and present state of the Eurasian steppe. Here, we concentrate on prehistoric times when the first human cultures emerged, and on the last 100 to 200 years when drastic changes occurred and in many regions steppe nearly completely disappeared. In Part II (Origin and evolutionary history of the Eurasian steppe) we attend to the origin and evolution of grasses and grassland in general, and to the evolution and climate/landscape history of the Eurasian steppe belt in particular. Uplift of the Himalayan-Tibet Plateau, changes in land-sea distribution and global climate trends have been invoked as driving forces behind Cenozoic paleoclimate changes, but there is little consensus which one is the most important driver. We finally identify gaps/challenges in our knowledge about the evolutionary history of the Eurasian steppe and discuss research directions, which might help to unravel the florogenetic and steppe habitat dynamics from the beginning of steppe formation to the present time.