Global climate change will cause longer and warmer autumns, thus negatively affecting the quality of cold acclimation (CA) and reducing the freezing tolerance (FT) of winter wheat. Insufficient FT and fluctuating temperatures during winter can accelerate the deacclimation (DEA) process, whereas reacclimation (REA) is possible only while the vernalization requirement is unfulfilled. Six winter wheat genotypes with different winter hardiness profiles were used to evaluate the impact of constant low-temperature (2°C) and prolonged higher low-temperature (28 days at 10°C followed by 2°C until day 49) on shoot biomass and metabolite accumulation patterns in leaf and crown tissues throughout 49 days of CA, 7 days of DEA, and 14 days of REA. The FT of winter wheat was determined as LT30 values by conducting freezing tests after CA, DEA, and REA. Shoot biomass accumulation, projected as the green leaf area (GLA), was investigated by non-destructive RGB imaging-based phenotyping. Dynamics of carbohydrates, hexose phosphates, organic acids, proteins, and amino acids were assessed in leaf and crown tissues. Results revealed that exposure to higher low-temperature induced higher accumulation of shoot biomass and had a negative impact on FT of winter wheat. Prolonged higher low-temperature negatively affected the accumulation of soluble carbohydrates, protein content and amino acids, and had a positive effect on starch accumulation in leaf and crown tissues after CA, in comparison with the constant low-temperature treatment. DEA resulted in significantly reduced FT. Lower concentrations of glucose-6-phosphate, sucrose and proline, as well as higher concentrations of starch in leaves and crowns were found after DEA. The majority of the genotypes regained FT after REA; higher concentrations of glucose and malate in leaves, and sucrose in crown tissue were observed, whereas starch accumulation was decreased in both tissues. Negative correlations were determined between FT and starch concentration in leaves and crowns, while proline and proteins, accumulated in crowns, showed positive correlations with FT. This study broadens the knowledge regarding the effect of different low-temperature regimes on the dynamics of metabolite accumulation in winter wheat throughout CA, DEA, and REA, and its relationship to biomass accumulation and FT.

In northern countries, Lolium perenne L. generally survives poorly when grown inland and north of 60°N because of extensive winter damage. With the projected future climate change, it could become a promising option for improving production efficiency of the agricultural sector in these regions. Here, we compare the biomass production potential of cultivars of diverse origin across five locations stretching from Estonia to Iceland over a period of three harvest years, and their freezing tolerance under artificial conditions. The aim was to relate the observed pattern of adaptation to the geographic origin of the cultivars and their response to prevailing agroclimatic conditions. Significant interactions were observed between cultivars and test environments (locations × years), and significant interactions between cultivars and years were detected at four of the five locations. Models of joint regression, additive main effects and multiplicative interaction (AMMI) and factorial regression using several agroclimatic indices showed that cultivars developed in northern countries showed greater yield potential across the test environments and were, thus, generally better adapted than cultivars from Central Europe. Diploid cultivars were more frost tolerant than tetraploid cultivars giving them an advantage in locations which were characterized by low temperatures during the hardening period in autumn and mild and rainy winters, such as at the Icelandic location. Only a few cultivars showed general adaptability to the environmental conditions at the test sites, the most stable cultivar being an admixture of diploids and tetraploids. In future breeding, the best strategy would be to hybridize cultivars developed in northern countries with more exotic materials that combine high yield potential, adequate winter survival and superior disease resistance under northern conditions.

Global warming is predicted to impact many agricultural areas, which will suffer from reduced water availability. Due to precipitation changes, mild summer droughts are expected to become more frequent, even in temperate regions. For perennial ryegrass (Lolium perenne L.), an important forage grass of the Poaceae family, leaf growth is a crucial factor determining biomass accumulation and hence forage yield. Although leaf elongation has been shown to be temperature-dependent under normal conditions, the genetic regulation of leaf growth under water deficit in perennial ryegrass is poorly understood. Herein, we evaluated the response to water deprivation in a diverse panel of perennial ryegrass genotypes, employing a high-precision phenotyping platform. The study revealed phenotypic variation for growth-related traits and significant (P < 0.05) differences in leaf growth under normal conditions within the subgroups of turf and forage type cultivars. The phenotypic data was combined with genotypic variants identified using genotyping-by-sequencing to conduct a genome-wide association study (GWAS). Using GWAS, we identified DNA polymorphisms significantly associated with leaf growth reduction under water deprivation. These polymorphisms were adjacent to genes predicted to encode for phytochrome B and a MYB41 transcription factor. The result obtained in the present study will increase our understanding on the complex molecular mechanisms involved in plant growth under water deficit. Moreover, the single nucleotide polymorphism (SNP) markers identified will serve as a valuable resource in future breeding programs to select for enhanced biomass formation under mild summer drought conditions.

Perennial ryegrass is an important agricultural crop, however, it is susceptible to winterkill. Freezing injury is caused primarily by ice formation. The LpIRI1 protein has the potential to inhibit ice recrystallization, thus minimize the damage. An association study was conducted using single nucleotide polymorphisms obtained through allele sequencing of the LpIRI1 gene and phenotypic data were collected using two phenotyping platforms in a perennial ryegrass association mapping population of 76 diverse genotypes. Winter survival (FWS) was evaluated under field conditions, while tiller survival (PTS) and electrolyte leakage (EL) at -8 and -12°C were determined under controlled-environment conditions. Proline content (PC) in cold-acclimated plants was measured prior to the freezing test. Significant variation in FWS, PTS, EL and PC was observed among genotypes in our panel. EL and PTS revealed significant negative correlations at -8°C (r s = -0.40) and -12°C (r s = -0.49). PC, however, did not show significant correlations with any of the measured traits, while FWS was correlated (r s = -0.48) with EL at -12°C. The LpIRI1 gene was found to be highly polymorphic with an average SNP frequency of 1 SNP per 16 bp. Association analysis revealed two non-synonymous SNPs being associated with increased EL, both located in the LpIRI1 leucinerich repeat. The results indicate that allelic variation in the LpIRI1 gene plays an important role in the cell membrane integrity of perennial ryegrass during freezing, and can be exploited for developing more freezing tolerant cultivars.

Abiotic stresses alter the expression of multiple genes in plants allowing them to accommodate to hostile environmental conditions. Exposure to low temperatures in the autumn prior to winter is a crucial environmental factor determining an increase in freezing tolerance and winter hardiness in temperate plants. The objective of this study was to evaluate transcriptome changes under a short-term low temperature stress using an RNA-Seq approach in winter wheat (Triticum aestivum L.). Significant alterations were observed for nuclear transcriptome of winter wheat, whereas the expression profiles of organellar genes were much less responsive to low temperature stress. In total, there were 15,042 nuclear genes with significantly (FDR < 0.05) altered expression profiles caused by exposure to low temperature. From this number, a total of 2,466 genes had a substantially (log 2 FC > 2 or log 2 FC < −2) affected expression profile. The highest number of upregulated genes was observed from chromosomes in homoeologous group 5, followed by group 2. Differentially expressed genes (DEGs) with the most extreme upregulation encompassed CBFIIId-12.1, WRKY transcription factor 55-like, and a group of genes related to jasmonate signalling pathway.