Joanne Russell

Food and nutritional security are global challenges exacerbated by an increasing human population and impacted by climate change. Barley is among the top cereal crops grown worldwide and is a strategic crop for food and nutrition security in several geographical domains. However, barley grains are generally limited in iron and zinc, two major micronutrient deficiencies affecting billions of people around the world, but particularly women and children in developing countries. One promising strategy to enhance crop micronutrient status is via biofortification, the identification and use of nutrient-rich natural variants in crop genetic improvement. Germplasm assessed as being rich in essential nutrients are used as parental materials in traditional breeding strategies. While simple in theory, directly assessing grain nutrient concentration as a phenotype in a crop breeding program is not trivial, particularly in lesser developed geographies. As an alternative, genetic diagnostics can simplify the identification of desirable progenies and accelerate the breeding process. Here we explored natural variation for grain zinc concentration within 296 Ethiopian and Eritrean barley landraces using a genome-wide association study. We found strong associations with two SNPs, both of which were located within the barley ortholog of a tonoplast-associated major facilitator superfamily (MFS) transporter gene, Zinc induced facilitator-like 1 (ZIFL1) of Arabidopsis thaliana (AtZIFL1). Sequence-based haplotype analysis of the barley gene (HvZIFL1) extended this association to a 153-162 bp deletion in a non-coding region. The favourable haplotype, associated with higher grain Zn concentration, was found in ~20% of Ethiopian and Eritrean barley germplasm. Markers are designed to the diagnostic SNPs for use as molecular diagnostics in breeding for genotypes with enhanced grain Zn.

Recommended List (RL) is the UK plant variety recommendation system introduced in 1944 for supporting growers in making decisions on variety choices. The current RL system is heavily focused on single-trial analyses developed in the 1980s without making full use of information across varieties and trial sites. Given the statistical advances that have been developed and adopted elsewhere, it is timely to review and update the methods for data analysis in RL. In addition, threats from climate change challenge the prediction of variety performance in future environments. Better variety recommendations, particularly for matching varieties to specific environments can be achieved through the improved modeling of effects from genetics, environments, and genetic-by-environment interactions. Here, we evaluate grain yield data from 153 spring barley varieties that were trialed for RL from 2002 to 2019. Our results show that the current RL system produces poor and inconsistent predictions on variety performance across environments. Improvement in RL can be achieved by using mixed models that account for genetic relationships among varieties, and additional improvement is possible if genetic-by-environment interaction can be modeled accurately. We highlight the relevance and importance of genomics in both variety registration and recommendation.

Recommended List (RL) is the UK plant variety recommendation system introduced in 1944 for supporting growers in making decisions on variety choices. The current analysis for RL is largely based on published works on trial designs and statistical analyses in the 1980s. Given the statistical advances that have been developed and adopted elsewhere, it is timely to review and update the methods for data analysis in RL. In addition, threats from climate change challenge the prediction of variety performance in future environments. Better variety recommendations, particularly for matching varieties to specific environments can be achieved through improved modeling of effects from genetics, environments and genetic by environment interactions. Here, we evaluated grain yield data from 153 spring barley varieties that were trialed for RL from 2002 to 2019. Our results show that the available methods for predicting variety performance are poor and inconsistent across environments without any clearly superior method. However, these shortcomings can be easily overcome by switching the statistical model for analyzing RL data to one that fits variety effects as random and accounts for genetic relationships among varieties. Lastly, we also discuss other possible approaches for analyzing RL data and highlight the relevance of genomics in both variety registration and recommendation.

Silicon (Si) is a beneficial nutrient that has been shown to increase rice productivity and grain quality. Fragrant rice occupies the high end of the rice market with prices at twice to more than three times those of non-fragrant rice. Thus, this study evaluated the effects of increasing Si on the yield and quality of fragrant rice. Also measured were the content of proline and the expression of the genes associated with 2AP synthesis and Si transport. The fragrant rice varieties were found to differ markedly in the effect of Si on their quality, as measured by the grain 2AP concentration, while there were only slight differences in their yield response to Si. The varieties with low 2AP when the Si supply is limited are represented by either PTT1 or BNM4 with only slight increases in 2AP when Si was increased. Si affects the gene expression levels of the genes associated with 2AP synthesis, and the accumulation of 2AP in fragrant rice mainly occurred through the upregulation of Badh2, DAO, OAT, ProDH, and P5CS genes. The findings suggest that Si is a potential micronutrient that can be utilized for improving 2AP and grain yield in further aromatic rice breeding programs.

Barley genomic resources are increasing rapidly, with the publication of a barley pangenome as one of the latest developments. Two-row spring barley cultivars are intensely studied as they are the source of high-quality grain for malting and distilling. Here we provide data from a European two-row spring barley population containing 209 different genotypes registered for the UK market between 1830 to 2014. The dataset encompasses RNA-sequencing data from six different tissues across a range of barley developmental stages, phenotypic datasets from two consecutive years of field-grown trials in the United Kingdom, Germany and the USA; and whole genome shotgun sequencing from all cultivars, which was used to complement the RNA-sequencing data for variant calling. The outcomes are a filtered SNP marker file, a phenotypic database and a large gene expression dataset providing a comprehensive resource which allows for downstream analyses like genome wide association studies or expression associations.

SUMMARY: The distribution of recombination events along large cereal chromosomes is uneven and is generally restricted to gene‐rich telomeric ends. To understand how the lack of recombination affects diversity in the large pericentromeric regions, we analysed deep exome capture data from a final panel of 815 Hordeum vulgare (barley) cultivars, landraces and wild barleys, sampled from across their eco‐geographical ranges. We defined and compared variant data across the pericentromeric and non‐pericentromeric regions, observing a clear partitioning of diversity both within and between chromosomes and germplasm groups. Dramatically reduced diversity was found in the pericentromeres of both cultivars and landraces when compared with wild barley. We observed a mixture of completely and partially differentiated single‐nucleotide polymorphisms (SNPs) between domesticated and wild gene pools, suggesting that domesticated gene pools were derived from multiple wild ancestors. Patterns of genome‐wide linkage disequilibrium, haplotype block size and number, and variant frequency within blocks showed clear contrasts among individual chromosomes and between cultivars and wild barleys. Although most cultivar chromosomes shared a single major pericentromeric haplotype, chromosome 7H clearly differentiated the two‐row and six‐row types associated with different geographical origins. Within the pericentromeric regions we identified 22 387 non‐synonymous SNPs, 92 of which were fixed for alternative alleles in cultivar versus wild accessions. Surprisingly, only 29 SNPs found exclusively in the cultivars were predicted to be ‘highly deleterious’. Overall, our data reveal an unconventional pericentromeric genetic landscape among distinct barley gene pools, with different evolutionary processes driving domestication and diversification.

Rhynchosporium is one of the main biotic stresses on barley production worldwide. A set of 312 spring barley accessions was tested in four different locations over 3 years, to identify novel genetic resistances to rhynchosporium and to explore the allelic diversity for resistance genes present in this global germplasm collection. High-density genotypes from exome capture and RNA-seq were used to conduct high-resolution association mapping. Seven quantitative trait loci (QTL) were detected, including one in the Rrs2 region, amongst five containing known resistances. Relatively short physical intervals harbouring these resistances were proposed, providing a platform for the identification of underlying genes and tightly linked genetic markers for use in marker assisted selection. Genes encoding kinases were present in four of the QTL, in addition to Rrs1 and Rrs18, two loci known to contribute to rhynchosporium resistance. The frequencies and distributions of these novel and known QTL were superimposed on the regional origin of the landrace genotypes comprising the genome-wide association studies (GWAS) panel, highlighting the value of genetic resources as a source of diverse genetically controlled resistance to rhynchosporium. The detected QTL along with their linked genetic markers, could be exploited either directly for breeding purposes or for candidate gene identification in future studies.

Distinctness, Uniformity and Stability (DUS) is an intellectual property system introduced in 1961 by the International Union for the Protection of New Varieties of Plants (UPOV) for safeguarding the investment and rewarding innovation in developing new plant varieties. Despite the rapid advancement in our understanding of crop biology over the past 60 years, the DUS system has not changed and is still dependent upon a set of morphological traits for testing candidate varieties. As the demand for more plant varieties increases, the barriers to registration of new varieties become more acute and thus require urgent review to the system. To highlight the challenges and remedies in the current system, we evaluated a comprehensive panel of 805 UK barley varieties that span the entire history of DUS testing. Our findings reveal the system deficiencies and provide evidence for a shift towards a robust genomics enabled registration system for new crop varieties.

The microbiota thriving in the rhizosphere, the thin layer of soil surrounding plant roots, plays a critical role in plant’s adaptation to the environment. Domestication and breeding selection have progressively differentiated the microbiota of modern crops from the ones of their wild ancestors. However, the impact of eco-geographical constraints faced by domesticated plants and crop wild relatives on recruitment and maintenance of the rhizosphere microbiota remains to be fully elucidated. Here we performed a comparative 16S rRNA gene survey of the rhizosphere of 4 domesticated and 20 wild barley ( Hordeum vulgare ) genotypes grown in an agricultural soil under controlled environmental conditions. We demonstrated the enrichment of individual bacteria mirrored the distinct eco-geographical constraints faced by their host plants. Unexpectedly, Elite varieties exerted a stronger genotype effect on the rhizosphere microbiota when compared with wild barley genotypes adapted to desert environments with a preferential enrichment for members of Actinobacteria. Finally, in wild barley genotypes, we discovered a limited, but significant, correlation between microbiota diversity and host genomic diversity. Our results revealed a footprint of the host’s adaptation to the environment on the assembly of the bacteria thriving at the root-soil interface. In the tested conditions, this recruitment cue layered atop of the distinct evolutionary trajectories of wild and domesticated plants and, at least in part, is encoded by the barley genome. This knowledge will be critical to design experimental approaches aimed at elucidating the recruitment cues of the barley microbiota across a range of soil types.