The natural light conditions above the Arctic Circle are unique in terms of annual variation creating special growth conditions for crop production. These include low solar elevations, very long daily photosynthetic light periods, midnight sun/absence of dark nights, and altered spectral distribution depending on solar elevation. All these factors are known to affect the growth and the metabolism of plants, although their influence on northern crop plants has not yet been reviewed. The ongoing global warming is especially affecting the temperature × light interactions in the Arctic, and understanding the impact on crop production and plant metabolism will be important for an Arctic contribution to global food production. Arctic light conditions have a strong influence on the timing of plant development, which together with temperature limits the number of cultivars suitable for Arctic agriculture. This review compiles information from the reports about the effects of light conditions at high latitudes on growth, biomass production, flowering and quality of the crop plants and discusses the gained knowledge and the key gaps to be addressed.

The sustainable production of perennial grasses in Northern Norway is at risk due to the ongoing climate change. The predicted increase in temperatures and variable weather patterns are further expected to create challenges for winter survival of timothy (Phleum pratense L.). Knowledge about the molecular mechanisms underlying freezing tolerance is crucial for developing robust cultivars. The current study is aimed at identifying genes involved in freezing stress response of timothy and studying gene expression differentiation due to field selection in contrasting environments using RNAseq. Four timothy cultivars were field tested for three years in Tromsø and Vesterålen, in Northern Norway. The surviving material from the field tests, along with plants raised from the original seed lots, were subjected to freezing tests. LT₅₀ values varied across cultivars and materials. Many genes coding for transcription factors and proteins known to play an important role in freezing tolerance, like dehydrins, c‐repeat binding factors, and late embryogenesis abundant proteins were upregulated with decreasing temperatures. Moreover, genes associated with glycolysis/gluconeogenesis, TCA cycle, glutathione metabolism, proteasome pathways and genes encoding autophagy‐related proteins, plasma membrane‐associated proteins, sugar and amino acid transporters had elevated expression in field survivors compared to plants raised from the original material. The lower freezing stress tolerance of field survivors despite the elevated expression of several stress‐responsive genes might be due to a combination of selection in the field and the age effect. Furthermore, differences in freezing stress response between northern and southern adapted cultivars and surviving material from two field trial locations are discussed.

Sammendrag Grasdyrking og grovfôr til husdyr er den største landbruksproduksjonen i Nord-Norge – både i dag og for 100 år siden. Å kunne høste inn nok fôr til vinteren er viktig både for dyrene og økonomi.

In Norway, agroclimatic zones (ACZs) are a valuable tool for national analyses in subject areas concerning the optimized management of agricultural land resources. However, current Norwegian ACZs have been criticized for having an outdated standard climate normal (1931–1960), a limited representation of the local climatic variation, a lack of important model parameters, and weak methodological documentation. Therefore, this paper presents new ACZs for Norway that address these weaknesses. The most significant methodological updates are the use of the standard climate normal of 1991–2020, additional weather data variables, the downscaling of weather data to 250 m hexagons, and the incorporation of phenological crop models for spring wheat, spring barley, and forage grass. The grass model was calibrated with the number of grass harvests at research stations, while the grain models were calibrated with subsidy claim data. The modeled zones for the three crops were combined into the general ACZs. Example maps of the crop zones and new ACZs for the selected regions and the whole country are presented. The new ACZs are more robust, agronomically relevant, and better aligned with the current climatic conditions in Norway. The deliberate exclusion of factors other than climate ensures the new ACZs’ national comparability and their applicability in policy development, land-use planning, climate adaptation, and agronomic assessments at the national scale.

Seed multiplication of perennial grasses outside their area of adaptation is common practice globally. This also applies to timothy ( Phleum pratense L.), the most important forage grass in Arctic Norway (67°–71° N). Early research suggests little risk for loss of winter hardiness if seed multiplication of Arctic timothy is limited to one or two generations in the south, but recent experiences by North Norwegian farmers suggest otherwise. A study was conducted in which original seed of two northerly adapted timothy varieties ‘Engmo’ (an old landrace originating at 69° N) and ‘Noreng’ (a synthetic variety consisting of 10 clones of ‘Engmo’ and four clones of the South‐Norwegian variety ‘Grindstad’) was multiplied for one, two or three generations at 70° N, 64° N and 58° N. Plants raised from the different generations at each site were subjected to freezing tests to determine LT ₅₀ and ice encasement (IE) tests to determine LD ₅₀ , both tests followed by the weighing of regrowth of surviving plants. On average for generations and compared with the original seed, we found no changes in freezing tolerance or IE tolerance after seed production at 70° N, but significant losses in freezing tolerance of both varieties after seed production at 64° N and in particular at 58° N. The fact that major shifts occurred already in the first generation and were later, at least to some extent, reversible and influenced by the winter before each seed harvest raises the possibility that epigenetic memory of environmental conditions was transferred to the seed progeny in addition to the classical genetic effects.

Recent experiences suggest only minor differences in dry matter yield between red clover diploid and tetraploid cultivars whilst tetraploids have a lower seed production potential, prompting breeders to reconsider their breeding efforts in this ploidy group. This large‐scale study comparing the productivity of diploid and tetraploid red clover across a European gradient brings new insight for breeders and farmers. Core yield data were obtained from available results of national field trials across Europe testing red clover cultivars and candivars during the period from 2000 to 2023. Data were analysed by analysis of covariance, including the impact of location, harvest year, ploidy, and the interaction harvest year × ploidy. Temperature mean and sum of precipitation over a growing season were used as a covariate. Red clover productivity was twice as high in warmer Central and Western Europe (DMY 15.5 t ha ⁻¹ ), compared to Northern Europe (DMY 7.55 t ha ⁻¹ ). Tetraploids strongly outyielded diploids in Northern Europe (DMY +9.2%) but only marginally in Central and Western Europe (DMY +3.8%). Tetraploids had the highest yield benefit over diploids in years/locations with lower temperature mean and sum of precipitation over the growing season. Our findings indicate that tetraploid red clover still provides DMY benefits over diploids, but these benefits are most pronounced in regions with less favourable growing conditions. Considering the difficulties with seed production in tetraploid red clover, diploid red clover is a good choice for Central and Western Europe, while for Northern Europe the preference for tetraploids is more justifiable.