Hexaploid Oat Research Articles

Genetic mapping and comparative analysis of heading date in hexaploid oat

Genetic mapping and comparative analysis of heading date in hexaploid oat

Phenotypic characterization and candidate gene analysis of a short kernel and brassinosteroid insensitive mutant from hexaploid oat (Avena sativa).

In an ethyl methanesulfonate oat (Avena sativa) mutant population we have found a mutant with striking differences to the wild-type (WT) cv. Belinda. We phenotyped the mutant and compared it to the WT. The mutant was crossed to the WT and mapping-by-sequencing was performed on a pool of F2 individuals sharing the mutant phenotype, and variants were called. The impacts of the variants on genes present in the reference genome annotation were estimated. The mutant allele frequency distribution was combined with expression data to identify which among the affected genes was likely to cause the observed phenotype. A brassinosteroid sensitivity assay was performed to validate one of the identified candidates. A literature search was performed to identify homologs of genes known to be involved in seed shape from other species. The mutant had short kernels, compact spikelets, altered plant architecture, and was found to be insensitive to brassinosteroids when compared to the WT. The segregation of WT and mutant phenotypes in the F2 population was indicative of a recessive mutation of a single locus. The causal mutation was found to be one of 123 single-nucleotide polymorphisms (SNPs) spanning the entire chromosome 3A, with further filtering narrowing this down to six candidate genes. In-depth analysis of these candidate genes and the brassinosteroid sensitivity assay suggest that a Pro303Leu substitution in AVESA.00010b.r2.3AG0419820.1 could be the causal mutation of the short kernel mutant phenotype. We identified 298 oat proteins belonging to orthogroups of previously published seed shape genes, with AVESA.00010b.r2.3AG0419820.1 being the only of these affected by a SNP in the mutant. The AVESA.00010b.r2.3AG0419820.1 candidate is functionally annotated as a GSK3/SHAGGY-like kinase with homologs in Arabidopsis, wheat, barley, rice, and maize, with several of these proteins having known mutants giving rise to brassinosteroid insensitivity and shorter seeds. The substitution in AVESA.00010b.r2.3AG0419820.1 affects a residue with a known gain-of function substitution in Arabidopsis BRASSINOSTEROID-INSENSITIVE2. We propose a gain-of-function mutation in AVESA.00010b.r2.3AG0419820.1 as the most likely cause of the observed phenotype, and name the gene AsGSK2.1. The findings presented here provide potential targets for oat breeders, and a step on the way towards understanding brassinosteroid signaling, seed shape and nutrition in oats.

The application of Vavilov's approaches to the phylogeny and evolution of cultivated species of the genus Avena L.

The central problem that Vavilov was investigating was the overall concept of global plant genetic resources. The theoretical basis of this concept consisted of the law of homologous series in variation, research on the problem of species as a system, botanical and geographical bases of plant breeding, and the key theory of the centers of origin of cultivated plants. The VIR global collection of plant genetic resources collected by Vavilov and his associates from all over the world reflects the fullness of botanical, morphological and genetic diversity, and can be used for historical, evolutionary, phylogenetic and applied breeding research aimed at unlocking the potential of all the collection material. The whole diversity of cultivated oats, as was proved by Vavilov, had originated from segetal weeds. This process can be clearly traced in Spain on the example of the cultivated diploid species A. strigosa, A. abyssinica in Ethiopia, A. byzantina in Turkey and Iran, and on segetal forms of A. sativa. The studies of the morphological features as a whole do not yield a complete picture of the evolutionary and systematic status of some oat species and forms. The methods and approaches that use DNA markers and genomic technologies, and are promising for the study of oat polymorphism and phylogeny have been actively researched recently. A number of works devoted to the molecular aspects of the evolution and phylogeny of the genus Avena have recently appeared. The research uses various markers of genes, gene regions, intergenic spacers (internal and external), both nuclear and chloroplast and mitochondrial, genomic approaches and other modern methods. On the basis of a comprehensive study of the complete intraspecific diversity from different zones of the distribution range of cultivated oat species as well as on the basis of an analysis of data on the geography of forms and species distribution ranges, it was established that the process of hexaploid species formation also took place in the western part of the Mediterranean, and subsequently, when moving eastward, these forms started occupying all the vast spaces in the region of the Southwest Asian center, forming a large intraspecific diversity of wild forms and weedy ones in transit to cultivated hexaploid oat species. An analysis of the intraspecific diversity of landraces has specified the centers of morphogenesis of all cultivated oat species. The phylogenetic analysis of the representative intraspecific diversity of cultivated and wild Avena species carried out using next generation sequencing (NGS) showed that diploid species with A-genome variants are in fact not primary diploids, but a peculiar Mediterranean introgressive hybridization complex of species that sporadically enter into interspecific hybridization. It was established that the tetraploid cultivated species A. abyssinica had most likely originated from the wild A. vaviloviana. An analysis of the ways of A. sativa and A. byzantina domestication showed that the most widespread ribotype of the A. sativa hexaploid was inherited from A. ludoviciana, and the second most widespread one, from A. magna, while A. byzantina has two unique ribotype families, most likely inherited from an extinct oat species or a still undiscovered cryptospecies.

Transcriptional and protein structural characterization of homogentisate phytyltransferase genes in barley, wheat, and oat

BackgroundHomogentisate phytyltransferase (HPT) is the critical enzyme for the biosynthesis of tocopherols (vitamin E), which are the major lipid-soluble antioxidants and help plants adapt to various stress conditions. HPT is generally strictly conserved in various plant genomes; however, a divergent lineage HPT2 was identified recently in some Triticeae species. The molecular function and transcriptional profiles of HPT2 remain to be characterized.ResultsIn this study, we performed comprehensive transcriptome data mining of HPT1 and HPT2 in different tissues and stages of barley (Hordeum vulgare), wheat (Triticum aestivum), and oat (Avena sativa), followed by qRT-PCR experiments on HPT1 and HPT2 in different tissues of barley and wheat. We found that the common HPT1 genes (HvHPT1, TaHPT1s, and AsHPT1s) displayed a conserved transcriptional pattern in the three target species and were universally transcribed in various tissues, with a notable preference in leaf. In contrast, HPT2 genes (HvHPT2, TaHPT2, and AsHPT2) were specifically transcribed in spike (developmentally up-regulated) and shoot apex tissues, displaying a divergent tissue-specific pattern. Cis-regulatory elements prediction in the promoter region identified common factors related to light-, plant hormone-, low temperature-, drought- and defense- responses in both HPT1s and HPT2s. We observed the transcriptional up-regulation of HvHPT1 and HvHPT2 under various stress conditions, supporting their conserved function in environmental adaption. We detected a clear, relaxed selection pressure in the HPT2 lineage, consistent with the predicted evolution pattern following gene duplication. Protein structural modelling and substrate docking analyses identified putative catalytic amino acid residues for HvHPT1 and HvHPT2, which are strictly conserved and consistent with their function in vitamin E biosynthesis.ConclusionsWe confirmed the presence of two lineages of HPT in Triticeae and Aveninae, including hexaploid oat, and characterized their transcriptional profiles based on transcriptome and qRT-PCR data. HPT1s were ubiquitously transcribed in various tissues, whilst HPT2s were highly expressed in specific stages and tissue. The active transcription of HPT2s, together with its conserved cis-elements and protein structural features, support HPT2s’ role in tocopherol production in Triticeae. This study is the first protein structural analysis on the membrane-bound plant HPTs and provides valuable insights into its catalytic mechanism.

Population structure analysis and genome-wide association study of a hexaploid oat landrace and cultivar collection.

Oat (Avena sativa L.) is an important cereal crop grown worldwide for grain and forage, owing to its high adaptability to diverse environments. However, the genetic and genomics research of oat is lagging behind that of other staple cereal crops. In this study, a collection of 288 oat lines originating worldwide was evaluated using 2,213 single nucleotide polymorphism (SNP) markers obtained from an oat iSelect 6K-beadchip array to study its genetic diversity, population structure, and linkage disequilibrium (LD) as well as the genotype-phenotype association for hullessness and lemma color. The average gene diversity and polymorphic information content (PIC) were 0.324 and 0.262, respectively. The first three principal components (PCs) accounted for 30.33% of the genetic variation, indicating that the population structure of this panel of oat lines was stronger than that reported in most previous studies. In addition, accessions could be classified into two subpopulations using a Bayesian clustering approach, and the clustering pattern of accessions was closely associated with their region of origin. Additionally, evaluation of LD decay using 2,143 mapped markers revealed that the intrachromosomal whole-genome LD decayed rapidly to a critical r2 value of 0.156 for marker pairs separated by a genetic distance of 1.41 cM. Genome-wide association study (GWAS) detected six significant associations with the hullessness trait. Four of these six markers were located on the Mrg21 linkage group between 194.0 and 205.7 cM, while the other two significant markers mapped to Mrg05 and Mrg09. Three significant SNPs, showing strong association with lemma color, were located on linkage groups Mrg17, Mrg18, and Mrg20. Our results discerned relevant patterns of genetic diversity, population structure, and LD among members of a worldwide collection of oat landraces and cultivars proposed to be 'typical' of the Qinghai-Tibetan Plateau. These results have important implications for further studies on association mapping and practical breeding in high-altitude oat.

Genetic mapping of the powdery mildew resistance gene Pm7 on oat chromosome 5D

Key messageThree independent experiments with different genetic backgrounds mapped the resistance gene Pm7 in the oat genome to the distal part of the long arm of chromosome 5D.Resistance of oat to Blumeria graminis DC. f. sp. avenae is an important breeding goal in Central and Western Europe. In this study, the position of the effective and widely used resistance gene Pm7 in the oat genome was determined based on three independent experiments with different genetic backgrounds: genome-wide association mapping in a diverse set of inbred oat lines and binary phenotype mapping in two bi-parental populations. Powdery mildew resistance was assessed in the field as well as by detached leaf tests in the laboratory. Genotyping-by-sequencing was conducted to establish comprehensive genetic fingerprints for subsequent genetic mapping experiments. All three mapping approaches located the gene to the distal part of the long arm of chromosome 5D in the hexaploid oat genome sequences of OT3098 and ‘Sang.’ Markers from this region were homologous to a region of chromosome 2Ce of the C-genome species, Avena eriantha, the donor of Pm7, which appears to be the ancestral source of a translocated region on the hexaploid chromosome 5D.

Non–B-form DNA tends to form in centromeric regions and has undergone changes in polyploid oat subgenomes

Centromeres are the specialized regions of the chromosomes that direct faithful chromosome segregation during cell division. Despite their functional conservation, centromeres display features of rapidly evolving DNA and wide evolutionary diversity in size and organization. Previous work found that the noncanonical B-form DNA structures are abundant in the centromeres of several eukaryotic species with a possible implication for centromere specification. Thus far, systematic studies into the organization and function of non-B-form DNA in plants remain scarce. Here, we applied the oat system to investigate the role of non-B-form DNA in centromeres. We conducted chromatin immunoprecipitation sequencing using an antibody to the centromere-specific histone H3 variant (CENH3); this accurately positioned oat centromeres with different ploidy levels and identified a series of centromere-specific sequences including minisatellites and retrotransposons. To define genetic characteristics of oat centromeres, we surveyed the repeat sequences and found that dyad symmetries were abundant in oat centromeres and were predicted to form non-B-DNA structures invivo. These structures including bent DNA, slipped DNA, Z-DNA, G-quadruplexes, and R-loops were prone to form within CENH3-binding regions. Dynamic conformational changes of predicted non-B-DNA occurred during the evolution from diploid to tetraploid to hexaploid oat. Furthermore, we applied the single-molecule technique of AFM and DNA:RNA immunoprecipitation with deep sequencing to validate R-loop enrichment in oat centromeres. Centromeric retrotransposons exhibited strong associations with R-loop formation. Taken together, our study elucidates the fundamental character of non-B-form DNA in the oat genome and reveals its potential role in centromeres.

Genome-Wide Identification and Characterization of the Oat (Avena sativa L.) WRKY Transcription Factor Family.

The WRKY family is widely involved in the regulation of plant growth and stress response and is one of the largest gene families related to plant environmental adaptation. However, no systematic studies on the WRKY family in oat (Avena sativa L.) have been conducted to date. The recently published complete genome sequence of oat enables the systematic analysis of the AsWRKYs. Based on a genome-wide study of oat, we identified 162 AsWRKYs that were unevenly distributed across 21 chromosomes; a phylogenetic tree of WRKY domains divided these genes into three groups (I, II, and III). We also analyzed the gene duplication events and identified a total of 111 gene pairs that showed strong purifying selection during the evolutionary process. Surprisingly, almost all genes evolved after the completion of subgenomic differentiation of hexaploid oat. Further studies on the functional analysis indicated that AsWRKYs were widely involved in various biological processes. Notably, expression patterns of 16 AsWRKY genes revealed that the response of AsWRKYs were affected by stress level and time. In conclusion, this study provides a reference for further analysis of the role of WRKY transcription factors in species evolution and functional differentiation.

Reference genome assemblies reveal the origin and evolution of allohexaploid oat

Common oat (Avena sativa) is an important cereal crop serving as a valuable source of forage and human food. Although reference genomes of many important crops have been generated, such work in oat has lagged behind, primarily owing to its large, repeat-rich polyploid genome. Here, using Oxford Nanopore ultralong sequencing and Hi-C technologies, we have generated a reference-quality genome assembly of hulless common oat, comprising 21 pseudomolecules with a total length of 10.76 Gb and contig N50 of 75.27 Mb. We also produced genome assemblies for diploid and tetraploid Avena ancestors, which enabled the identification of oat subgenomes and provided insights into oat chromosomal evolution. The origin of hexaploid oat is inferred from whole-genome sequencing, chloroplast genomes and transcriptome assemblies of different Avena species. These findings and the high-quality reference genomes presented here will facilitate the full use of crop genetic resources to accelerate oat improvement.

Oat genome - sequence of a superfood.

The analysis of the 11-gigabase, hexaploid oat genome reveals a mosaic chromosome structure with complex rearrangements related to polyploidization. The high-quality oat reference genome will facilitate the molecular identification of health food traits and the implementation of genomics-based oat breeding.

Analysis of oat seed transcriptome with regards to proteins involved in celiac disease

Oat (Avena sativa L.) is considered to be a healthy food. In contrast to other grain crops, oat is high in protein, lipids, dietary fiber, antioxidants, and uniquely in avenanthramides. The question of whether it can also be consumed by people suffering from celiac disease is still unresolved. The main aim of this study was to extract and sequence genes for potentially harmful avenins, globulins, and α-amylase/trypsin inhibitors in six oat varieties and to establish their variability using PacBio sequencing technology of enriched libraries. The results were compared with sequences of the genes already present in databases. In total, 21 avenin, 75 globulin, and 25 α-amylase/trypsin inhibitor genes were identified and mapped in the hexaploid oat chromosomes. In all of the three gene families, only marginal sequence differences were found between the oat varieties within the individual genes. Avenin epitopes were found in all four types of avenin genes occurring in all oat varieties tested within this study. However, the number of avenin genes was nearly four times lower than of globulin genes and, on the protein level, formed only 10% of storage proteins. Therefore, the question of whether oat is safe to celiac disease people is a question of boundary values.

Cytogenetic evidence supports Avena insularis being closely related to hexaploid oats.

Cytogenetic observations, phylogenetic studies and genome analysis using high-density genetic markers have suggested a tetraploid Avena species carrying the C and D genomes (formerly C and A) to be the donor of all hexaploid oats (AACCDD). However, controversy surrounds which of the three extant CCDD tetraploid species—A. insularis, A. magna and A. murphyi—is most closely related to hexaploid oats. The present work describes a comparative karyotype analysis of these three CCDD tetraploid species and two hexaploid species, A. sativa and A. byzantina. This involved the use of FISH with six simple sequence repeats (SSRs) with the motifs CT, AAC, AAG, ACG, ATC and ACT, two repeated ribosomal sequences, and C genome-specific repetitive DNA. The hybridization pattern of A. insularis with oligonucleotide (AC)10 was also determined and compared with those previously published for A. sativa and A. byzantina. Significant differences in the 5S sites and SSR hybridization patterns of A. murphyi compared to the other CCDD species rule out its being directly involved in the origin of the hexaploids. In contrast, the repetitive and SSR hybridization patterns shown by the D genome chromosomes, and by most of the C genome chromosomes of A. magna and A. insularis, can be equated with the corresponding chromosomes of the hexaploids. Several chromosome hybridization signals seen for A. insularis, but not for A. magna, were shared with the hexaploid oats species, especially with A. byzantina. These diagnostic signals add weight to the idea that the extant A. insularis, or a direct ancestor of it, is the most closely related progenitor of hexaploid oats. The similarity of the chromosome hybridization patterns of the hexaploids and CCDD tetraploids was taken as being indicative of homology. A common chromosome nomenclature for CCDD species based on that of the hexaploid species is proposed.

Adaptation and Agronomic Performance of Domesticated Moroccan Oat (Avena magna ssp. domestica) Lines under Subsistence Farming Conditions at Multiple Locations in Morocco

Common hexaploid oat (Avena sativa L.) is an important global cereal crop. A Moroccan tetraploid sister species, A. magna Murphy et Terrel, was exclusively a wild species until recently. The goal of domestication was to exploit its superior groat-protein content and climatic tolerances. We set up replicated trials of 41 domesticated A. magna lines on eight Moroccan farms during the 2017–2018 and 2018–2019 growing seasons. Twenty traits were measured and analyses of variance detected significant differences among lines. The highest grain yield was at Berrechid in 2017–2018 (63.56 q/ha), with an average annual yield across sites of 43.50 q/ha, the site factor explaining 82% and the genotype-environment interaction explaining 15% of the variability. In the second year, El Kebab recorded the highest yield at 20.03 q/ha over the annual average of 14.78 q/ha. In this second year, the site factor was highly significant, explaining 42.25% of the variation, with the genotype-environment interaction explaining 26.61% of the variability. An additional main effect and multiplicative interaction analysis of the eight two-year trials identified several accessions with good yield stability. Twelve lines exhibited a ASVs ≤ 1.50, with five accessions (A34, A40, A23, A05, A04) exceeding the overall average yield of 29.53 and A34 having the greatest mean grain yield and stability. The versatility and stability of A. magna can provide a sustainable protein source and an economic resource for farmers seeking products that are resilient to climatic instability.

New evidence confirming the CD genomic constitutions of the tetraploid Avena species in the section Pachycarpa Baum.

The tetraploid Avena species in the section Pachycarpa Baum, including A. insularis, A. maroccana, and A. murphyi, are thought to be involved in the evolution of hexaploid oats; however, their genome designations are still being debated. Repetitive DNA sequences play an important role in genome structuring and evolution, so understanding the chromosomal organization and distribution of these sequences in Avena species could provide valuable information concerning genome evolution in this genus. In this study, the chromosomal organizations and distributions of six repetitive DNA sequences (including three SSR motifs (TTC, AAC, CAG), one 5S rRNA gene fragment, and two oat A and C genome specific repeats) were investigated using non-denaturing fluorescence in situ hybridization (ND-FISH) in the three tetraploid species mentioned above and in two hexaploid oat species. Preferential distribution of the SSRs in centromeric regions was seen in the A and D genomes, whereas few signals were detected in the C genomes. Some intergenomic translocations were observed in the tetraploids; such translocations were also detected between the C and D genomes in the hexaploids. These results provide robust evidence for the presence of the D genome in all three tetraploids, strongly suggesting that the genomic constitution of these species is DC and not AC, as had been thought previously.

Domestication of <i>Avena magna</i> Murphy et Terrell: a wild tetraploid oat species endemic of Morocco

Avena magna Murphy et Terrell (2n = 4x = 28), a tetraploid oat species endemic of Morocco, has a high groat protein content (more than 20%), good resistance to diseases and good adaptability to the Mediterranean edaphic and climate conditions. Moreover, this taxon is morphologically similar to the hexaploid oat species A. sativa and promising for interspecific crosses with A. sativa in order to transfer the domestication syndrome into it. Four hybridization cycles employing four accessions of A. magna and five Moroccan hexaploid oat cultivars of A. sativa were accomplished to domesticate A. magna. Morphological characterization and cytogenetic analysis of derivative hybrid seeds were made to determine their ploidy level and select the seeds with 2n = 28. The overall combinations yielded 81 hybrid plants with 2n varying from 28 to 29, with 58% having 2n = 28, and pollen fertility over 85%. However, 27 hybrids yielded a seed set ranging from 20 to 80%. Selected hybrid plants were subjected to pedigree selection in the field until they reached the 8th generation and assessed for agronomic performance. Three domesticated lines of tetraploid oat A. magna were selected for their good disease resistance. Analysis of groat protein content in the selected hybrids using the Kjeldahl method showed that it was 2 to 3% higher than in their parents.

Identification of molecular markers for the Pc39 gene conferring resistance to crown rust in oat

Key messageSix new PCR-based markers for the Pc39 crown rust resistance gene in Avena sativa L. were developed. Pc39 was mapped to Mrg11 of the oat consensus map using BLASTn analysis.The aim of this study was the identification of molecular markers for the Pc39 gene in cultivated oat (Avena sativa L.). Pc39 is a major race-specific crown rust resistance gene originally found in an Israeli accession of the wild hexaploid Avena sterilis. The effectiveness of this gene in Europe has decreased in recent years, but is still relatively high and breeding programs would benefit from the availability of molecular markers to aid in its mapping and deployment. The complexity of the oat genome poses a significant obstacle to genetic research. No oat rust resistance genes have yet been cloned, and even the number of relevant molecular markers is very limited. Here, genotyping of a segregating population derived from a cross ‘Celer’ (Pc39)/STH9210 (susceptible) was conducted using RAPD- and SRAP-PCR-based methods, as well as microarray-based DArT™ and next-generation sequencing DArTseq™ techniques. Markers associated with Pc39 were placed on the hexaploid oat consensus linkage group Mrg11 at 3.7–6.7 cM. Six new PCR-based markers were developed to allow identification of the resistant Pc39 allele. These tightly linked markers will be useful in marker-assisted selection, with the closest, SCAR_3456624, being within 0.37 cM of Pc39. The newly developed markers could find applications in the fine mapping or positional cloning of this gene. Moreover, easy-to-use PCR-based markers linked to Pc39 could facilitate the utilization of this gene in oat breeding programs, especially as a component of crown rust resistance gene pyramids.

Heritable temporal gene expression patterns correlate with metabolomic seed content in developing hexaploid oat seed.

SummaryOat ranks sixth in world cereal production and has a higher content of health‐promoting compounds compared with other cereals. However, there is neither a robust oat reference genome nor transcriptome. Using deeply sequenced full‐length mRNA libraries of oat cultivar Ogle‐C, a de novo high‐quality and comprehensive oat seed transcriptome was assembled. With this reference transcriptome and QuantSeq 3′ mRNA sequencing, gene expression was quantified during seed development from 22 diverse lines across six time points. Transcript expression showed higher correlations between adjacent time points. Based on differentially expressed genes, we identified 22 major temporal co‐expression (TCoE) patterns of gene expression and revealed enriched gene ontology biological processes. Within each TCoE set, highly correlated transcripts, putatively commonly affected by genetic background, were clustered and termed genetic co‐expression (GCoE) sets. Seventeen of the 22 TCoE sets had GCoE sets with median heritabilities higher than 0.50, and these heritability estimates were much higher than that estimated from permutation analysis, with no divergence observed in cluster sizes between permutation and non‐permutation analyses. Linear regression between 634 metabolites from mature seeds and the PC1 score of each of the GCoE sets showed significantly lower p‐values than permutation analysis. Temporal expression patterns of oat avenanthramides and lipid biosynthetic genes were concordant with previous studies of avenanthramide biosynthetic enzyme activity and lipid accumulation. This study expands our understanding of physiological processes that occur during oat seed maturation and provides plant breeders the means to change oat seed composition through targeted manipulation of key pathways.

URS MONARCA - a new hexaploid oat cultivar with excellent grain yield and wide adaptation

Abstract The Oat Breeding Program of the Federal University of Rio Grande do Sul (UFRGS) release in 2019 a new cultivar URS MONARCA developed from the single cross UFRGS 06 6083-3 / UFRGS 00 6183-2. URS MONARCA presents high grain yield, high grain quality, wide adaptation, short plant height and excellent milling yield.

Phenotypic variation and heritability of heading date in hexaploid oat

Abstract The onset of flowering is decisive to the reproductive success of plants. The objectives of this study were to characterize the phenotypic variation in heading date and estimate its heritability in segregating populations of oat (Avena sativa L.). F2 and F3 generations of two large populations, derived from crosses ‘URS Taura × Leggett’ and ‘FL0206B-S-B-S1 × UFRGS 078030-1’, were evaluated. A wide phenotypic variation in the number of days to heading was observed in both populations. Heritability coefficients of 0.68 and 0.46 were estimated for the ‘URS Taura × Leggett’ and ‘FL0206B-S-B-S1 × UFRGS 078030-1’ populations. Our results demonstrate that genetic differences derived from parents in response to photoperiod and temperature explain most of the phenotypic variation in heading date of oat populations. Understanding genetic and environmental effects on flowering expression is essential to increase the response to selection for well-adapted and high-yielding oat cultivars.

Genomic insights from the first chromosome-scale assemblies of oat (Avena spp.) diploid species

BackgroundCultivated hexaploid oat (Common oat; Avena sativa) has held a significant place within the global crop community for centuries; although its cultivation has decreased over the past century, its nutritional benefits have garnered increased interest for human consumption. We report the development of fully annotated, chromosome-scale assemblies for the extant progenitor species of the As- and Cp-subgenomes, Avena atlantica and Avena eriantha respectively. The diploid Avena species serve as important genetic resources for improving common oat’s adaptive and food quality characteristics.ResultsThe A. atlantica and A. eriantha genome assemblies span 3.69 and 3.78 Gb with an N50 of 513 and 535 Mb, respectively. Annotation of the genomes, using sequenced transcriptomes, identified ~ 50,000 gene models in each species—including 2965 resistance gene analogs across both species. Analysis of these assemblies classified much of each genome as repetitive sequence (~ 83%), including species-specific, centromeric-specific, and telomeric-specific repeats. LTR retrotransposons make up most of the classified elements. Genome-wide syntenic comparisons with other members of the Pooideae revealed orthologous relationships, while comparisons with genetic maps from common oat clarified subgenome origins for each of the 21 hexaploid linkage groups. The utility of the diploid genomes was demonstrated by identifying putative candidate genes for flowering time (HD3A) and crown rust resistance (Pc91). We also investigate the phylogenetic relationships among other A- and C-genome Avena species.ConclusionsThe genomes we report here are the first chromosome-scale assemblies for the tribe Poeae, subtribe Aveninae. Our analyses provide important insight into the evolution and complexity of common hexaploid oat, including subgenome origin, homoeologous relationships, and major intra- and intergenomic rearrangements. They also provide the annotation framework needed to accelerate gene discovery and plant breeding.