Susanne Barth

Sitka spruce (Picea sitchensis (Bong.) Carr.) is the dominant plantation conifer in Atlantic Europe, yet the genomic basis of provenance-level climate adaptation remains poorly resolved. We applied gradient forest analysis to 31,049 genome-wide SNPs from 1106 individual trees representing 79 native-range provenances in the IUFRO collection, using three environmental predictors retained after collinearity screening: Longitude, Temperature Seasonality, and Annual Precipitation. Longitude was the dominant driver of genomic turnover (mean R² = 0.01168), followed by Temperature Seasonality (0.00672) and Annual Precipitation (0.00228), reflecting the long-distance coastal gradient of the native range. A redundancy analysis conditioned on ancestry principal components confirmed a significant multivariate genotype–environment association (F = 8.679, p = 0.001). Genomic offset was negatively correlated with all three provenance-level performance traits measured at the IUFRO common garden after 50 years of growth: height, stem diameter and stem quality, providing empirical validation of the genomic-climatic framework. Projecting the fitted model onto European planting sites using an 8-GCM CMIP6 ensemble showed mean offset increasing from 0.0021 (SSP2-4.5, 2041–2060) to 0.0041 (SSP5-8.5, 2061–2080), with the most climate-exposed cells under the high-emission late-century scenario approaching the upper tail of the source population offset distribution. The European planting region showed a higher projected offset than the North American source range under all scenarios. This supports the hypothesis that provenances from Oregon to southern British Columbia are most suited for planting in regions under future Atlantic European conditions.

Corn poppy ( Papaver rhoeas L.) is a problematic weed in cereal farms in Ireland, necessitating continuous herbicide use to protect crop yields. In 2022, poor control with acetolactate synthase (ALS) inhibitors and auxin-mimic herbicides was reported by growers/advisors in two resistance-suspect populations, namely PAPRH-R1 and PAPRH-R2. In this study, we quantified their resistance to both herbicide modes of action and investigated the underlying mechanisms. ALS inhibitor dose–response experiments revealed that both populations had ED ₅₀ and GR ₅₀ resistance indices (RIs) above 120 to thifensulfuron + tribenuron, mesosulfuron + iodosulfuron + amidosulfuron, and metsulfuron, and values of 4 to 13 to florasulam + pyroxsulam. Results of 2,4-D dose–response assays revealed higher resistance in PAPRH-R2 (ED ₅₀ and GR ₅₀ RI > 9.1) than PAPRH-R1 (ED ₅₀ and GR ₅₀ RI > 3.4). ALS gene sequencing detected Pro-197 mutations in all sequenced plants from both resistant populations. Pretreatment with piperonyl butoxide (PBO, a cytochrome P450 inhibitor) reversed 2,4-D resistance with GR ₅₀ , the more sensitive response parameter, decreasing from 680.8 to 84.9 g ha ⁻¹ in PAPRH-R1 and from 2,508.9 to 456.8 g ha ⁻¹ in PAPRH-R2, both well below the recommended label rate of 1,000 g ha ⁻¹ . The ¹⁴ C-2,4-D assays ruled out reduced absorption or translocation as resistance mechanisms. Sensitivity screening further revealed incomplete control with other postemergence foliar herbicides tested at half and full recommended label rates, except for fluroxypyr + halauxifen, which provided complete control of PAPRH-R1 at the full rate, and glyphosate, which provided complete control of PAPRH-R1 and PAPRH-R2 at both rates. This is the first report of multiple resistance in P. rhoeas in Ireland involving ALS target-site mutations and likely P450-mediated 2,4-D metabolism. As cultural/nonchemical control of broadleaf species is difficult, the continued availability of preemergence or autumn residual herbicides, together with effective auxin mimics and stewardship practices, will remain essential for managing these species, including P. rhoeas , in cereal crops.

Excess water is an abiotic stress in plants, but the level at which excess water becomes varies widely between plant species. We conducted a two growing season replicated excess flooding experiment that was planted with 24 accessions of perenn...

Picea sitchensis (Sitka spruce) occupies a large number of host environments across the Pacific Northwest, stretching from California to Alaska. Populations have become locally adapted to their environmental niche rather than undergoing speciation and these local adaptions can be discovered and utilised for breeding programs. These local adaptions may contain traits which can confer increased resilience against climate change. Here we employed Genome Wide Association Studies (GWAS), Genotype Environment Analysis (GEA) and Canonical correlation analysis to discover adaptive loci. A total of 593 adaptive loci were discovered from the GEA. The GWAS found eight loci involved with height and one with diameter at breast height. The canonical correlation analysis allowed for the discovery of positive and negative correlated loci with traits or environmental variables. We discovered 121 loci positively correlated with environmental values and 10 loci positively correlated with phenotypic traits. We discovered one cluster of adaptive loci involved with snowy winter conditions and two clusters showing adaptation to southern locations characterised with milder conditions. The allelic distribution of positive and negatively correlated loci involved with height showed a north south divide with loci positively correlated with height being distributed below a latitude of 50oN. This shows adaptations for height are generally found south of the 50th latitude. We have discovered signs of local adaptation, with Minor Allele Frequency (MAF) differing between northern and southern populations.

Herbicide-resistant annual bluegrass (Poa annua L.) has become a problem in non-arable land areas. In arable fields, P. annua is frequently of lower priority in weed control program due to the variety of control options available and the relatively modest impact on crop yield compared with other species. In Ireland, postemergence herbicides are not primarily intended for P. annua control, but some herbicides, including the acetolactate synthase (ALS) inhibitor mesosulfuron-methyl + iodosulfuron-methyl, exhibit P. annua activity. In this study, a suspected P. annua population (POAAN-R) that survived mesosulfuron-methyl + iodosulfuron-methyl at 0.75 of the field recommended rate was sampled from a wheat (Triticum aestivum L.) field in County Dublin, Ireland. Single-dose testing confirmed that the suspected POAAN-R had evolved resistance to mesosulfuron-methyl + iodosulfuron-methyl and, additionally, to pyroxsulam (not registered in Ireland for P. annua control), but was sensitive to clethodim, glyphosate, pendimethalin, and flufenacet. Dose–response experiments indicated that POAAN-R was more resistant (GR₅₀ resistance index) to both mesosulfuron-methyl + iodosulfuron-methyl (47.8 times) and pyroxsulam (38.0 times) than sensitive POAAN-S, and this was associated with the mutation at Trp-574 in the ALS protein. Malathion (a cytochrome P450 [P450] inhibitor) pretreatment did not reverse POAAN-R resistance to mesosulfuron-methyl + iodosulfuron-methyl or pyroxsulam at the field rate or above. The natural inherent mutation at Ile-1781 in acetyl-CoA carboxylase protein had no effect on both POAAN-R and POAAN-S sensitivity to clethodim. The glyphosate sensitivity of POAAN-R also corresponded with no known mutation in 5-enolpyruvylshikimate-3-phosphate synthase protein. Based on field histories, poor early-season weed control coupled with intensive use of mesosulfuron-methyl + iodosulfuron-methyl (often at reduced rates) has unintentionally selected for ALS inhibitor–resistant POAAN-R. This is the first report to characterize resistance in P. annua to ALS-inhibiting herbicides mesosulfuron-methyl + iodosulfuron-methyl and pyroxsulam in an arable setting. There is an opportunity to effectively control POAAN-R using herbicides, but this needs a wide-ranging and varied approach, coupled with cultural/nonchemical practices.

Picea sitchensis, Sitka spruce, is of interest to forestry as both a conservation species and a highly productive crop. Its native range stretches from Alaska to California, and it is hence distributed across a large environmental cline with areas of local adaptation. The IUFRO collection, established in 1968–1970, consists of 81 provenances of commercial and scientific interest spanning this native range. We used genotyping-by-sequencing on 1177 genotypes, originating from 80 of the IUFRO provenances which occupy 19 geographic regions of the Pacific Northwest, resulting in an SNP database of 36,567 markers. We detected low levels of genetic differentiation across this broad environmental cline, in agreement with other studies. However, we discovered island effects on geographically distant populations, such as those on Haida Gwaii and Kodiak Island. Using glaciation data, alongside this database, we see apparent post-glacial recolonization of the mainland from islands and the south of the range. Genotyping the IUFRO population expands upon the use of the collection in three ways: (i) providing information to breeders on genetic diversity which can be implemented into breeding programs, optimizing genetic gain for important traits; (ii) serving a scientific resource for studying spruce species; and (iii) utilizing provenances in breeding programs which are more tolerant to climate change.

Increased precipitation during winter months in Western Europe is predicted from climate change. This is expected to increase the frequency of flooding events, with waterlogged conditions becoming more prevalent. A consequence of waterlogging is hypoxic conditions and dying back of roots, thereby negatively affecting plant nutrient uptake, growth, and development. Barley (Hordeum vulgare L.) forms lysigenous aerenchyma, which are air‐filled pockets within the root to facilitate O₂ transport and support root respiration. Current methods for visualizing aerenchyma formation in roots are largely 2D and involve embedding a fixed root segment in resin, followed by destructive sectioning for microscopy. Here, we report the development of an X‐ray computed tomography (CT) acquisition and analytical method for spatio‐temporal identification and quantitation of aerenchyma in 2D and 3D in barley roots without the requirement for chemical fixation, resin embedding, followed by physical sectioning of the root. We demonstrated that the method we have developed can facilitate the identification and quantitation of aerenchyma in barley as early as 9 d post‐waterlogging. The method we have developed can be potentially applied to different plant species and has the potential to support the selection of breeding markers through X‐ray CT phenotyping of aerenchyma.

Understanding the resistance spectrum and underlying genetic mechanisms is critical for managing herbicide-resistant populations. In this study, resistance to acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors was investigated in four suspected resistant populations of Alopecurus myosuroides (ALOMY-001 to ALOMY-004) and Lolium multiflorum (LOLMU-001 to LOLMU-004), collected from cereal production fields in Ireland. Glasshouse assays with three ALOMY-active herbicides [propaquizafop, cycloxydim (ACCase) and mesosulfuron + iodosulfuron (ALS)] or five LOLMU-active herbicides [pinoxaden, propaquizafop, cycloxydim (ACCase) and mesosulfuron + iodosulfuron, pyroxsulam (ALS)], and target-site resistance mechanism studies, based on pyrosequencing, were carried out in each of those populations. For A. myosuroides, Ile-1781-Leu ACCase mutation contributed to propaquizafop and cycloxydim resistance (shoot dry weight GR₅₀ resistance factor (RF) = 7.5–35.5) in all ALOMY populations, and the independent Pro-197-Thr or Pro-197-Ser ALS mutation contributed to mesosulfuron + iodosulfuron resistance (RF = 3.6–6.6), in ALOMY-002 to ALOMY-004. Most of the analyzed plants for these mutations were homo/heterozygous combinations or only heterozygous. For L. multiflorum, phenotypic resistance to mesosulfuron + iodosulfuron (RF = 11.9–14.6) and pyroxsulam (RF = 2.3–3.1) was noted in all LOLMU populations, but the Pro-197-Gln or Pro-197-Leu ALS mutation (mostly in homozygous status) was identified in LOLMU-001, LOLMU-002 and LOLMU-004 only. Additionally, despite no known ACCase mutations in any LOLMU populations, LOLMU-002 survived pinoxaden and propaquizafop application (RF = 3.4 or 1.3), and LOLMU-003 survived pinoxaden (RF = 2.3), suggesting the possibility of non-target-site resistance mechanisms for ACCase and/or ALS resistance in these populations. Different resistance levels, as evidenced by a reduction in growth as dose increased above field rates in ALOMY and LOLMU, were due to variations in mutation rate and the level of heterozygosity, resulting in an overall resistance rating of low to moderate. This is the first study confirming cross- and multiple resistance to ACCase- and ALS-inhibiting herbicides, highlighting that resistance monitoring in A. myosuroides and L. multiflorum in Ireland is critical, and the adoption of integrated weed management strategies (chemical and non-chemical/cultural strategies) is essential.