The Baltic Sea is one of the largest brackish water bodies in the world. Eutrophication is a major concern in the Baltic Sea due to the leakage of nutrients to the sea with agriculture being the primary source. Wheat (Triticum aestivum L.) is the most widely grown crop in the countries surrounding the Baltic Sea and thus promoting sustainable agriculture practices for wheat cultivation will have a major impact on reducing pollution in the Baltic Sea. This approach requires identifying and addressing key challenges for sustainable wheat production in the region. Implementing new technologies for climate-friendly breeding and digital farming across all surrounding countries should promote sustainable intensification of agriculture in the region. In this review, we highlight major challenges for wheat cultivation in the Baltic Sea region and discuss various solutions integrating transnational collaboration for pre-breeding and technology sharing to accelerate development of low input wheat cultivars with improved host plant resistance to pathogen and enhanced adaptability to the changing climate.Abbreviations -DDT, dichlorodiphenyltrichloroethane; DK, Denmark; ECPGR, European Cooperative Programme for Plant Genetic Resources; EE, Estonia; FI, Finland; HCB, hexachlorobenzene; HCH, hexachlorocyclohexane; ICM, Integrated Crop Management; IWYP, International wheat yield potential; LT, Lithuania; N, Nitrogen; NPPN, Nordic plant phenotyping network; NUE, nitrogen use efficiency; PL, Poland; PPP, plant protection product; SE, Sweden; STB, Septoria tritici Blotch; WUE, water use efficiency. † These authors contributed equally and are presented alphabetically by their last name. 442

Septoria tritici blotch (STB) caused by the fungal pathogen Zymoseptoria tritici and powdery mildew (PM) caused by Blumeria graminis f.sp tritici (Bgt) are among the forefront foliar diseases of wheat that lead to a significant loss of grain yield and quality. Resistance breeding aimed at developing varieties with inherent resistance to STB and PM diseases has been the most sustainable and environment-friendly approach. In this study, 175 winter wheat landraces and historical cultivars originated from the Nordic region were evaluated for adult-plant resistance (APR) to STB and PM in Denmark, Estonia, Lithuania, and Sweden. Genome-wide association study (GWAS) and genomic prediction (GP) were performed based on the adult-plant response to STB and PM in field conditions using 7,401 single-nucleotide polymorphism (SNP) markers generated by 20K SNP chip. Genotype-by-environment interaction was significant for both disease scores. GWAS detected stable and environment-specific quantitative trait locis (QTLs) on chromosomes 1A, 1B, 1D, 2B, 3B, 4A, 5A, 6A, and 6B for STB and 2A, 2D, 3A, 4B, 5A, 6B, 7A, and 7B for PM adult-plant disease resistance. GP accuracy was improved when assisted with QTL from GWAS as a fixed effect. The GWAS-assisted GP accuracy ranged within 0.53–0.75 and 0.36–0.83 for STB and PM, respectively, across the tested environments. This study highlights that landraces and historical cultivars are a valuable source of APR to STB and PM. Such germplasm could be used to identify and introgress novel resistance genes to modern breeding lines.

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Untargeted metabolomic strategy was chosen to investigate as many small metabolites as possible in a collection of 13 varieties of conventionally grown spring and winter wheat and organic wheat (Triticum aestivum). Metabolites were separated by high-performance liquid chromatography on a reversed-phase column (RP-HPLC) coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The procedure includes extraction of metabolites followed by chromatographic separation using the linear gradient of aqueous formic acid and acetonitrile with subsequent identification of compounds by MS/MS. Discrimination of the metabolomic patterns of different wheat varieties was achieved by principal component analysis (PCA). Results of PCA indicated clear differences in the patterns of wheat varieties.The winter wheat grown in conventional conditions and the spring wheat grown in organic conditions differed from the spring wheat grown in conventional conditions by the higher content of carbohydrates. It could be explained by osmotic stress resistance. Varieties grown under organic conditions could be well distinguished from others by the results of PCA, which points to the existence of an impact of different farming systems.

The objective of this field crop study was to compare the effect of organic (cattle manure, off-season cover crop) and mineral N (NH4NO3; 0, 50, 100° 150 kg N ha−1) fertilizers on (i) gluten-starch interaction, and (ii) rheological properties of winter wheat dough. Data were collected from the long-term field experiment located in the Baltic Sea region (58°22’ N, 26°40’ E) in years 2013–2017. The amount of minuppueral N 150 kg ha–1 applied in two parts before flowering ensured higher gluten content (31 ± 3.3%) and dough quality (81 ± 7.4 mm) due to more positive interactions between gluten proteins and starch granules. The quality of dough was more variable in organic treatments (ranged up to 33%) because the availability of organic N was more variable and sensitivity to the weather conditions was higher. The mean variability of different dough properties over trial years under organic treatments was 1.4–2.0 times higher than in the treatment with 150 kg N ha−1.