Biology subjects

Joynson, R.

Publications and source records attributed to Joynson, R..

8 recordsLinked to original sources

bioRxiv2022

Exotic alleles contribute to heat tolerance in wheat under field conditions

Global warming is one of the most significant threats to food security. With temperatures predicted to rise and extreme weather events becoming more common we must safeguard food production by developing crop varieties that are more tolerant to heat stress without compromising yield under favourable conditions. By evaluating 149 spring wheat lines in the field under yield potential and heat stressed conditions, we demonstrate how strategic integration of exotic material significantly increases yield under heat stress compared to elite lines, with no significant yield penalty under favourable conditions. Genome-wide association analysis revealed three marker trait associations, which together increase yield under heat stress by over 50% compared to lines without the advantageous alleles and was associated with approximately 2{degrees}C lower canopy temperature. We identified an Aegilops tauschii introgression underlying the most significant of these associations. By comparing overlapping recombination of this introgressed segment between lines, we identified a 1.49Mbp region of the introgression responsible for this association that increases yield under heat stress by 32.4%. The genes within this region were extracted from diverse Ae. tauschii genomes, revealing a novel Ae. tauschii MAPK gene, a SOC1 orthologue and a pair of type-B two-component response regulators. Incorporating these exotic alleles into breeding programmes could serve as a pre-emptive strategy to produce high yielding wheat cultivars that are resilient to the effects of future climate uncertainty with no yield penalty under favourable conditions.

plant biology↗

bioRxiv2021

Whole genome sequencing uncovers the structural and transcriptomic landscape of hexaploid wheat/Am. muticum introgression lines

Wheat is a globally vital crop, but its limited genetic variation creates a challenge for breeders aiming to maintain or accelerate agricultural improvements over time. Introducing novel genes and alleles from wheats wild relatives into the wheat breeding pool via introgression lines is an important component of overcoming this low variation but is constrained by poor genomic resolution and limited understanding of the genomic impact of introgression breeding programmes. By sequencing 17 hexaploid wheat/Ambylopyrum muticum introgression lines and the parent lines, we have precisely pinpointed the borders of introgressed segments, most of which occur within genes. We report a genome assembly and annotation of Am. muticum that has facilitated the identification of Am. muticum resistance genes commonly introgressed in lines resistant to stripe rust. Our analysis has identified an abundance of structural disruption and homoeologous pairing across the introgression lines, likely caused by the suppressed Ph1 locus. mRNAseq analysis of six of these introgression lines revealed that novel introgressed genes are rarely expressed and those that directly replace a wheat orthologue have a tendency towards downregulation, with no discernible compensation in the expression of homoeologous copies. This study explores the genomic impact of introgression breeding and provides a schematic that can be followed to characterise introgression lines and identify segments and candidate genes underlying the phenotype. This will facilitate more effective utilisation of introgression pre-breeding material in wheat breeding programmes.

genomics↗

bioRxiv2021

A novel approach to develop wheat chromosome-specific KASP markers for detecting Amblyopyrum muticum segments in doubled haploid introgression lines

Many wild relative species are being used in pre-breeding programmes to increase the genetic diversity of wheat. Genotyping tools such as single nucleotide polymorphism (SNP)-based arrays and molecular markers have been widely used to characterise wheat-wild relative introgression lines. However, due to the polyploid nature of the recipient wheat genome, it is difficult to develop SNP-based KASP markers that are codominant to track the introgressions from the wild species. Previous attempts to develop KASP markers have involved both exome- and PCR-amplicon-based sequencing of the wild species. But chromosome-specific KASPs assays have been hindered by homoeologous SNPs within the wheat genome. This study involved whole genome sequencing of the diploid wheat wild relative Amblyopyrum muticum and development of a SNP discovery pipeline that generated [~]38,000 SNPs in single-copy wheat genome sequences. New assays were designed to increase the density of Am. muticum polymorphic KASP markers. With a goal of one marker per 60 Mbp, 335 new KASP assays were validated as functional. Together with assays validated in previous studies, 498 well distributed chromosome-specific markers were used to recharacterize previously genotyped wheat-Am. muticum doubled haploid (DH) introgression lines. The chromosome specific nature of the KASP markers allowed clarification of which wheat chromosomes were involved with recombination events or substituted with Am. muticum chromosomes and the higher density of markers allowed detection of new small introgressions in these DH lines. Key MessageA novel methodology to generate chromosome-specific SNPs between wheat and its wild relative Amblyopyrum muticum and their use in the development of KASP markers to genotype wheat-Am. muticum introgression lines.

genetics↗

bioRxiv2020

Uncovering candidate genes involved in photosynthetic capacity using unexplored genetic variation in Spring Wheat

To feed an ever-increasing population we must leverage advances in genomics and phenotyping to harness the variation in wheat breeding populations for traits like photosynthetic capacity which remains unoptimized. Here we survey a diverse set of wheat germplasm containing elite, introgression and synthetic derivative lines uncovering previously uncharacterised variation. We demonstrate how strategic integration of exotic material alleviates the D genome genetic bottleneck in wheat, increasing SNP rate by 62% largely due to Ae. tauschii synthetic wheat donors. Across the panel, 67% of the Ae. tauschii donor genome is represented as introgressions in elite backgrounds. We show how observed genetic variation together with hyperspectral reflectance data can be used to identify candidate genes for traits relating to photosynthetic capacity using association analysis. This demonstrates the value of genomic methods in uncovering hidden variation in wheat and how that variation can assist breeding efforts and increase our understanding of complex traits.

plant biology↗

bioRxiv2019

Circadian diversity in Swedish Arabidopsis accessions is associated with naturally occurring genetic variation in COR28

Circadian clocks have evolved to resonate with external day and night cycles. However, these entrainment signals are not consistent everywhere and vary with latitude, climate and seasonality. This leads to divergent selection for clocks which are locally adapted. To investigate the genetic basis for this, we used a Delayed Fluorescence (DF) imaging assay to screen 191 naturally occurring Swedish Arabidopsis accessions for their circadian phenotypes. We demonstrate period variation with both latitude and sub-population. Several candidate loci linked to period, phase and Relative Amplitude Error (RAE) were revealed by genome-wide association mapping and candidate genes were investigated using TDNA mutants. We show that natural variation in a single non-synonymous substitution within COR28 is associated with a long-period and late-flowering phenotype similar to that seen in TDNA knock-out mutants. COR28 is a known coordinator of flowering time, freezing tolerance and the circadian clock; all of which may form selective pressure gradients across Sweden. Finally, we tested circadian variation under reduced temperatures and show that fast and slow period phenotypic tails remain diverged and follow a distinctive arrow-shaped trend indicative of selection for a cold-biased temperature compensation response.

plant biology↗

bioRxiv2019

Analysis of the recombination landscape of hexaploid bread wheat reveals genes controlling recombination and gene conversion frequency

Sequence exchange between homologous chromosomes through crossing over and gene conversion is highly conserved among eukaryotes, contributing to genome stability and genetic diversity. Lack of recombination limits breeding efforts in crops, therefore increasing recombination rates can reduce linkage-drag and generate new genetic combinations. We use computational analysis of 13 recombinant inbred mapping populations to assess crossover and gene conversion frequency in the hexaploid genome of wheat (Triticum aestivum). We observe that high frequency crossover sites are shared between populations and that closely related parental founders lead to populations with more similar crossover patterns. We demonstrate that gene conversion is more prevalent and covers more of the genome in wheat than in other plants, making it a critical process in the generation of new haplotypes, particularly in centromeric regions where crossovers are rare. We have identified QTL for altered gene conversion and crossover frequency and confirm functionality for a novel RecQ helicase gene that belongs to an ancient clade that is missing in some plant lineages including Arabidopsis. This is the first gene to be demonstrated to be involved in gene conversion in wheat. Harnessing the RecQ helicase has the potential to break linkage-drag utilizing widespread gene conversions.

genetics↗

bioRxiv2018

Elucidating the genetic basis of biomass accumulation and radiation use efficiency in spring wheat and its role in yield potential

One of the major challenges for plant scientists is increasing wheat (Triticum aestivum) yield potential (YP). A significant bottleneck for increasing YP is achieving increased biomass through optimization of Radiation Use Efficiency (RUE) along the crop cycle. Exotic material such as landraces and synthetic wheat has been incorporated into breeding programs in an attempt to alleviate this, however their contribution to YP is still unclear. To understand the genetic basis of biomass accumulation and RUE we applied genome-wide association study (GWAS) to a panel of 150 elite spring wheat genotypes including many landrace and synthetically derived lines. The panel was evaluated for 31traits over two years under optimal growing conditions and genotyped using the 35K Wheat Breeders array. Marker-trait-association identified 94 SNPs significantly associated with yield, agronomic and phenology related traits along with RUE and biomass at various growth stages that explained 7-17 % of phenotypic variation. Common SNP markers were identified for grain yield, final biomass and RUE on chromosomes 5A and 7A. Additionally we show that landrace and synthetic derivative lines showed higher thousand grain weight (TGW), biomass and RUE but lower grain number (GNO) and harvest index (HI). Our work demonstrates the use of exotic material as a valuable resource to increase YP. It also provides markers for use in marker assisted breeding to systematically increase biomass, RUE and TGW and avoid the TGW/GNO and BM/HI trade-off. Thus, achieving greater genetic gains in elite germplasm while also highlighting genomic regions and candidate genes for further study.

plant biology↗

bioRxiv2017

Epigenomic variation across a polyploid wheat diversity collection

Wheat has been domesticated into a large number of agricultural environments and has a remarkable ability to adapt to diverse environments. To understand this process, we survey genotype, repeat content and DNA methylation across a bread wheat landrace collection representing global genetic diversity. We identify independent variation in methylation, genotype and transposon copy number. We show that these, so far unexploited, sources of variation have had a massive impact on the wheat genome and that ancestral methylation states become preferentially hard coded as SNPs via 5-methylcytosine deamination. These mechanisms also drive local adaption, impacting important traits such as heading date and salt tolerance. Methylation and transposon diversity could therefore be used alongside single nucleotide polymorphism (SNP) based markers for breeding.

genomics↗