Selecting for low concentration of Na+ in the shoot provides one approach for tackling salinity stress that adversely affects crop production. Novel alleles for Na+ exclusion can be identified and then introduced into elite crop cultivars. We have identified loci associated with lower Na+ concentration in leaves of durum wheat landraces originating from Afghanistan. Seedlings of two F2 populations derived from crossings between Australian durum wheat (Jandaroi) and two Afghani landraces (AUS-14740 and AUS-14752) were grown hydroponically and evaluated for Na+ and K+ concentration in the third leaf. High heritability was found for both third leaf Na+ concentration and the K+/Na+ ratio in both populations. Further work focussed on line AUS-14740. Bulk segregant analysis using 9 K SNP markers identified two loci significantly associated with third leaf Na+ concentration. Marker regression analysis showed a strong association between all traits studied and a favourable allele originating from AUS-14740 located on the long arm of chromosome 4B. The candidate gene in the relevant region of chromosome 4B is likely to be the high affinity K+ transporter B1 (HKT1;5-B1). A second locus associated with third leaf Na+ concentration was located on chromosome 3BL, with the favourable allele originating from Jandaroi; however, no candidate gene can be identified.

When introduced to multiple distinct ranges, invasive species provide a compelling natural experiment for understanding the repeatability of adaptation. Ambrosia artemisiifolia is an invasive, noxious weed, and chief cause of hay fever. Leveraging over 400 whole-genome sequences spanning the native-range in North America and 2 invasions in Europe and Australia, we inferred demographically distinct invasion histories on each continent. Despite substantial differences in genetic source and effective population size changes during introduction, scans of both local climate adaptation and divergence from the native-range revealed genomic signatures of parallel adaptation between invasions. Disproportionately represented among these parallel signatures are 37 large haploblocks—indicators of structural variation—that cover almost 20% of the genome and exist as standing genetic variation in the native-range. Many of these haploblocks are associated with traits important for adaptation to local climate, like size and the timing of flowering, and have rapidly reformed native-range clines in invaded ranges. Others show extreme frequency divergence between ranges, consistent with a response to divergent selection on different continents. Our results demonstrate the key role of large-effect standing variants in rapid adaptation during range expansion, a pattern that is robust to diverse invasion histories.

Canola plants suffer severe crop yield and oil content reductions when exposed to water-deficit conditions, especially during the reproductive stages of plant development. There is a pressing need to develop canola cultivars that can perform better under increased water-deficit conditions with changing weather patterns. In this study, we analysed genetic determinants for the main effects of quantitative trait loci (QTL), (Q), and the interaction effects of QTL and Environment (QE) underlying seed yield and related traits utilising 223 doubled haploid (DH) lines of canola in well-watered and water-deficit conditions under a rainout shelter. Moderate water-deficit at the pre-flowering stage reduced the seed yield to 40.8%. Multi-environmental QTL analysis revealed 23 genomic regions associated with days to flower (DTF), plant height (PH) and seed yield (SY) under well-watered and water-deficit conditions. Three seed yield QTL for main effects were identified on chromosomes A09, C03, and C09, while two were related to QE interactions on A02 and C09. Two QTL regions were co-localised to similar genomic regions for flowering time and seed yield (A09) and the second for plant height and chlorophyll content. The A09 QTL was co-located with a previously mapped QTL for carbon isotope discrimination (Δ¹³C) that showed a positive relationship with seed yield in the same population. Opposite allelic effects for plasticity in seed yield were identified due to QE interactions in response to water stress on chromosomes A02 and C09. Our results showed that QTL’s allelic effects for DTF, PH, and SY and their correlation with Δ¹³C are stable across environments (field conditions, previous study) and contrasting water regimes (this study). The QTL and DH lines that showed high yield under well-watered and water-deficit conditions could be used to manipulate water-use efficiency for breeding improved canola cultivars.

When introduced to multiple distinct ranges, invasive species provide a compelling natural experiment for understanding the repeatability of adaptation. Ambrosia artemisiifolia is an invasive, noxious weed and chief cause of hay fever. Leveraging over 400 whole-genome sequences spanning the native range in North America and two invasions in Europe and Australia, we inferred demographically distinct invasion histories on each continent. Despite substantial differences in genetic source and effective population size changes during introduction, scans of both local climate adaptation and divergence from the native range revealed genomic signatures of parallel adaptation between invasions. Disproportionately represented among these parallel signatures are 37 large haploblocks – indicators of structural variation – that cover almost 20% of the genome and exist as standing genetic variation in the native range. Many of these haploblocks are associated with traits important for adaptation to local climate, like size and the timing of flowering, and have rapidly reformed native range clines in invasive ranges. Others show extreme frequency divergence between ranges, consistent with a response to divergent selection on different continents. Our results demonstrate the key role of large-effect standing variants in rapid adaptation during range expansion, a pattern that is robust to diverse invasion histories.

Brassica napus (canola) is a significant contributor to the world's oil production and is cultivated across continents, yet acidic soils with aluminium (Al³⁺) and manganese (Mn²⁺) toxicities limit its production. The genetic determinants underlying natural variation for acidic soil tolerance in canola are unknown and need to be determined. Through genome‐wide association analysis of 326 canola accessions, we identified three QTLs for tolerance to Mn²⁺ toxicity on chromosomes A09, C03, and C09. Allelism tests between four tolerance sources confirmed that at least one locus on A09 controls Mn²⁺ tolerance in canola. Integrated analyses of genomic and expression QTL and Mn²⁺ tolerance data revealed that BnMTP8.A09, possibly in conjunction with BnMATE.C03, BnMTP8.C04 and BnMTP8.C08, play a central role in conferring Mn²⁺ tolerance in canola. Gene expression analysis showed that variation in BnMTP8.A09 expression could account for upto 74% of the variation in Mn²⁺ tolerance between individuals with extreme phenotypes. Yeast complementation assays and ectopic expression in Arabidopsis show that BnMTP8.A09 can complement manganese‐hypersensitive yeast mutant strain PMR1∆ and Arabidopsis atmtp8 mutant background, respectively and restore Mn²⁺ tolerance to wild‐type levels. Our multi‐omics research approach unveils the genetic architecture of Mn²⁺ tolerance and identifies BnMTP8.A09 as a causal gene imparting tolerance to Mn²⁺ toxicity in canola.