Freezing Tolerance Of Winter Wheat Research Articles

Comparative Analysis of Antioxidant Accumulation under Cold Acclimation, Deacclimation and Reacclimation in Winter Wheat.

Low temperature during cold acclimation (CA) leads to the accumulation of detrimental reactive oxygen species (ROS) in plant tissues, which are scavenged by antioxidants, such as ascorbate and glutathione. However, there is a lack of studies examining the dynamics of antioxidants throughout CA, deacclimation (DEA), and reacclimation (REA) in winter wheat. Six winter wheat genotypes were selected to assess the effect of CA, DEA, and REA on the concentrations of ascorbate and glutathione in leaf and crown tissues under two CA temperature treatments. Higher levels of total, reduced, and oxidised ascorbate were determined in leaves, whereas crowns accumulated higher concentrations of nicotinamide adenine dinucleotide (NAD+) after CA, DEA, and REA. Constant low temperature (CLT) during CA led to higher contents of ascorbate and glutathione in both tissues at all stages of acclimation, in comparison with prolonged higher low temperature (PHLT). The concentrations of antioxidants increased after CA, tended to decrease after DEA, and returned to CA levels after REA. Significant positive correlations between freezing tolerance (FT) and antioxidants were only determined under the CA at CLT treatment, thus, affirming the negative effect of PHLT during CA on the FT of winter wheat.

The effect of cold acclimation, deacclimation and reacclimation on metabolite profiles and freezing tolerance in winter wheat.

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.

Evaluation of freezing tolerance of winter wheat (Triticum aestivum L.) under controlled conditions and in the field

Freezing tolerance of winter wheat (Triticum aestivum L.) is one of the main factors governing winter survival. To avoid winterkill it is very important to choose freezing tolerant wheat genotypes. Experiments were carried out to evaluate freezing tolerance of winter wheat varieties and breeding lines under field and controlled conditions with cold acclimation and with no cold acclimation stage. Field experiments were done for two years during the winters of 2010–2011 and 2011–2012. The evaluation of winter hardiness was conducted in April of 2011 and 2012 by visual scoring on a 1–9 score basis (score 1 – all plants were killed, score 9 – all plants survived). Wheat genotypes under investigation experienced very different climatic conditions in the field during the two winters. Consequently, no correlation between winter hardiness scores of 2010–2011 and 2011–2012 winters was observed. Winter hardiness scores ranged from 1.0 (WW-8) to 7.6 (‘Zentos’) after 2010–2011 winter, whereas winter hardiness scores varied from 5.8 (WW-31) to 7.8 (‘Kovas DS’) after 2011–2012 winter. Freezing tolerance of winter wheat genotypes was also assessed in the controlled conditions by measuring chlorophyll fluorescence parameter Fv/Fm in leaves and percentage survival of plants after the freezing test. High correlation (r = 0.88, p < 0.01) between freezing test survival of non-acclimated wheat and Fv/Fm ratio showed that this method can speed up the selection for freezing tolerance by evaluating wheat genotypes immediately after the test. Results of our study showed low negative, but significant relationship (r = −0.41, p < 0.05) between 2010–2011 winter hardiness scores in the field and freezing test survival of non-acclimated plants in the laboratory experiment. Wheat genotypes that quickly lose winter hardiness have higher freezing tolerance without hardening stage. Our results support the hypothesis of two separate genetic systems of freezing tolerance in winter wheat which are determined by duration and rate of gene expression during cold acclimation.

Application of natural and synthetic polyamines as growth regulators to improve the freezing tolerance of winter wheat (Triticum aestivum L.)

Wheat cultivars were grown as soil culture under normal growth conditions. Twoweek- old seedlings were exposed to 4°C for 6 h and then transferred to −12°C for 24 h in the dark. Twenty-four hours before freezing stress, some of the plants were sprayed with aqueous solutions of spermine, spermidine, putrescine, 1,3-diaminopropane (1,3-DAP) and diethylenetriamine (DETA). The data showed that freezing stress caused a decrease in the fresh weight, chlorophyll content and plant survival rate, accompanied by a simultaneous accumulation of free proline and the enhanced leakage of electrolytes. Preliminary treatment with polyamines caused a decline in electrolyte leakage and a considerable augmentation in proline quantity, indicating that the compounds are capable of preventing frost injury. Additionally, the foliar application of polyamines retarded the destruction of chlorophyll, and lessened fresh weight losses due to freezing stress. The synthetic triamine DETA was the most effective, having the most pronounced action in all the experiments, followed by the tetraamine spermine. The application of polyamines to wheat crops could be a promising approach for improving plant growth under unfavourable growth conditions, including freezing temperatures. The results demonstrate that treatment with polyamines could protect winter wheat by reducing the stress injuries caused by subzero temperatures.

Exposure to subfreezing temperature and a freeze-thaw cycle affect freezing tolerance of winter wheat in saturated soil

Winter wheat is sown in the autumn and harvested the following summer, necessitating the ability to survive subfreezing temperatures for several months. Autumn months in wheat-growing regions typically experience significant rainfall and several days or weeks of mild subfreezing temperatures at night, followed by above-freezing temperatures in the day. Hence, the wheat plants usually are first exposed to potentially damaging subfreezing temperatures when they have high moisture content, are growing in very wet soil, and have been exposed to freeze-thaw cycles for a period of time. These conditions are conducive to freezing stresses and plant responses that are different from those that occur under lower moisture conditions without freeze-thaw cycles. This study was conducted to investigate the impact of mild subfreezing temperature and a freeze-thaw cycle on the ability of 22 winter wheat cultivars to tolerate freezing in saturated soil. Seedlings that had been acclimated at +4°C for 5 weeks in saturated soil were frozen to potentially damaging temperatures under three treatment conditions: (1) without any subzero pre-freezing treatment; (2) with a 16-h period at −3°C prior to freezing to potentially damaging temperatures; and (3) with a freeze-thaw cycle of −3°C for 24 h followed by +4°C for 24 h, followed by a 16-h period at −3°C prior to freezing to potentially damaging temperatures. In general, plants that had been exposed to the freeze-thaw cycle survived significantly more frequently than plants frozen under the other two treatments. Plants that had been exposed to 16 h at −3° (without the freeze-thaw cycle) before freezing to potentially damaging temperatures survived significantly more frequently than plants that were frozen to potentially damaging temperatures without a subzero pre-freezing treatment. These results indicated that cold-acclimated wheat plants actively acclimate to freezing stress while exposed to mild subfreezing temperatures, and further acclimate when allowed to thaw at +4°C for 24 h. The cultivar Norstar had the lowest LT50 (temperature predicted to be lethal to 50% of the plants) of the 22 cultivars when frozen with either of the subzero pre-freezing treatments, but several cultivars had lower LT50 scores than Norstar when frozen without a subzero pre-freezing treatment. We conclude it may be possible to improve winterhardiness of wheat grown in saturated soil by combining the ability to effectively respond to mild subzero pre-freezing temperatures with a greater ability to withstand freezing to damaging temperatures without a subzero pre-freezing exposure.

Oligosaccharin and ABA synergistically affect the acquisition of freezing tolerance in winter wheat

In this paper, we continue our studies of the previously discovered [O.A. Zabotina, D.A. Ayupova, O.N. Larskaya, O.N. Nikolaeva, G.I. Petrovicheva, A.I. Zabotin, Physiologically active oligosaccharides, accumulating in the roots of winter wheat during adaptation to low temperature, Russian Journal of Plant Physiology 45 (1998) 262] oligosaccharin (physiologically active oligosaccharide) GXAG, which stimulates the acquisition of freezing tolerance in winter varieties of Triticum aestivum L. The transient accumulation of GXAG in the tissues of winter wheat correlates with the temporal activation of cell wall glycosidases during the first hours of cold acclimation (2 degrees C). This finding suggests that the oligosaccharin is liberated as a result of the intensification of hemicellulose turnover. At low concentrations, GXAG initiates the acquisition of freezing tolerance in winter plants, in a manner similar to ABA, even at room temperature. The resultant effect of ABA and GXAG on the freezing tolerance of winter wheat depends on the sequence of pre-treatments with these two factors. When seedlings are pre-treated with GXAG a few hours before treatment with ABA, the effect is synergistic, and its impact depends on the duration of pre-treatment with GXAG. When ABA is applied first, the resultant effect on freezing tolerance is additive. The results obtained here lead to the conclusion that oligosaccharin, accumulating during the first hours of cold acclimation, functions as a partner of ABA during the initiation of freezing tolerance acquisition in winter plants. We hypothesize that GXAG increases cell receptivity to ABA signaling.

Factors contributing to enhanced freezing tolerance in wheat during frost hardening in the light

The interaction between light and temperature during the development of freezing tolerance was studied in winter wheat ( Triticum aestivum L. var. Mv Emese). Ten-day-old plants were cold hardened at 5 °C for 12 days under normal (250 μmol m −2 s −1) or low light (20 μmol m −2 s −1) conditions. Some of the plants were kept at 20/18 °C for 12 days at high light intensity (500 μmol m −2 s −1), which also increased the freezing tolerance of winter wheat. The freezing survival rate, the lipid composition, the antioxidant activity, and the salicylic acid content were investigated during frost hardening. The saturation level of hexadecanoic acid decreased not only in plants hardened at low temperature, but also, to a lesser extent, in plants kept under high light irradiation at normal growth temperature. The greatest induction of the enzymes glutathione reductase (EC 1.6.4.2.) and ascorbate peroxidase (EC 1.11.1.11.) occurred when the cold treatment was carried out in normal light, but high light intensity at normal, non-hardening temperature also increased the activity of these enzymes. The catalase (EC 1.11.1.6.) activity was also higher in plants grown at high light intensity than in the controls. The greatest level of induction in the activity of the guaiacol peroxidase (EC 1.11.1.7.) enzyme occurred under cold conditions with low light. The bound ortho-hydroxy-cinnamic acid increased by up to two orders of magnitude in plants that were cold hardened in normal light. Both high light intensity and low temperature hardening caused an increase in the free and bound salicylic acid content of the leaves. This increase was most pronounced in plants that were cold treated in normal light.

Effects of salicylic acid and cold on freezing tolerance in winter wheat leaves

The effects of salicylic acid (SA) (0.01, 0.1 and 1 mM) and cold on freezing tolerance (freezing injury and ice nucleation activity) were investigated in winter wheat (Triticum aestivum cv. Dogu-88) grown under control (20/18 °C for 15, 30 and 45-day) and cold (15/10 °C for 15-day, 10/5 °C for 30-day and 5/3 °C for 45-day) conditions. Cold acclimatisation caused a decrease of injury to leaf segments removed from the plants and subjected to freezing conditions. Exogenous SA also decreased freezing injury in the leaves grown under cold (15/10 °C) and control (15 and 30-day) conditions. Cold conditions (10/5 and 5/3 °C) caused an increase in ice nucleation activity by apoplastic proteins, which were isolated from the leaves. For the first time, it was shown that exogenous SA caused an increase in ice nucleation activity under cold (15/10 and 10/5 °C) and control conditions. These results show that salicylic acid can increase freezing tolerance in winter wheat leaves by affecting apoplastic proteins.

Seasonal changes in the physical state of crown water associated with freezing tolerance in winter wheat

The relationship between freezing tolerance (expressed as LT50, the lethal freezing temperature for 50% of plants) and the amount and physical state (as determined by spin‐lattice [T1] and spin‐spin [T2] relaxation times of protons) of water in crown tissue was examined in contrasting winter wheat (Triticum aestivum L.) varieties grown under field conditions from 1992 to 1994. During acclimation, the LT50 values decreased from around ‐7 to ‐17, ‐20 and ‐27°C in PI 173438, Chihokukomugi and Valuevskaya, respectively. Tissue water content decreased continuously through autumn to reach a plateau around 3 g H2O (g dry weight)‐1 in early winter when LT50 was still decteasing, and then gradually increased under snow cover. A significant negative correlation was found between mean minimum air temperatures and freezing tolerance prior to the establishment of continuous snow cover. In contrast, a positive association between mean minimum temperatures and crown tissue water content was significant only when air temperatures were above 0°C, as water content did not decrease further at sub‐zero temperatures. Seasonal changes in T1 were closely related to changes in freezing tolerance. T1 decreased until January even though water content stopped decreasing. Further tests on 15 field‐grown varieties confirmed a strong negative association between freezing tolerance and T1. The results suggest that cold hardening is comprised of two stages, with the transition occurring at ca 0°C. Development of hardiness was related to (1) a reduction in water content in the first stage (at minimum temperatures &gt; 0°C), and (2) a change in physical state of water without much reduction in water content in the second stage. Varietal differences in hardiness thus arise due to changes in both water content and physical state of water.

Seasonal changes in the physical state of crown water associated with freezing tolerance in winter wheat

Seasonal changes in the physical state of crown water associated with freezing tolerance in winter wheat

The effect of fungicides and plant growth regulators applied as a seed treatment on the freezing tolerance of winter wheat

Several plant growth regulators and fungicides, which inhibit gibberellin synthesis, were tested for their effect on the development of freezing tolerance of winter wheats (Triticum aestivum em Thell). Seeds of Norstar and Norwin were treated with either triadimenol; prochloraz, alone or in combination with imazalil; tetcyclasis; and carbathiin. The first four compounds are potent plant growth regulators that inhibit the production of gibberellins. The first three compounds, triadimenol, prochloraz and imazalil are also registered seed fungicides. Carbathiin, also a seed fungicide, has no known plant growth regulator activity. Prochloraz alone or in combination with imazalil and carbathiin initially delayed germination of both cultivars; after 144 h, however, germination was 90% or better for all treatments except the seeds of Norwin treated with carbathiin which were only 84% germinable. None of the fungicides increased the freezing tolerance of the Norstar crowns; however, carbathiin, tetcyclasis, triadimenol, prochloraz alone and in combination with imazalil (intermediate rate) reduced freezing tolerance. The freezing tolerance of Norwin, a semi-dwarf winter wheat, was reduced by tetcyclasis at the low and intermediate rate. In samples collected in the spring, the carbathiin treatment reduced the freezing tolerance of both Norwin and Norstar. None of the treatments affected the growth of the Norstar crowns in late October. Only triadimenol (intermediate rate) and tetcyclasis (intermediate and high rate) increased the crown moisture content. The carbathiin seed treatment increased the growth of Norwin crowns in the autumn. Nearly all of the treatments increased the crown moisture content of the Norwin crowns. In estimating spring vigour, only triadimenol (low rate) and tetcyclasis (intermediate rate) increased the leaf number of Norstar crowns, whereas nearly all treatments except tetcyclasis (intermediate rate) and prochloraz alone or in combination with imazalil increased leaf number of Norwin crowns. All rates of triadimenol and tetcyclasis, at the low rate, stimulated development of more roots for Norwin. The above seed treatment provide little or no benefit for the survival of winter wheats to a freezing stress. Key words: Winter wheat, seed treatment, fungicides, freezing tolerance

EFFECT OF RUSSIAN WHEAT APHID ON COLD HARDINESS AND WINTERKILL OF OVERWINTERING WINTER WHEAT

Russian wheat aphid (RWA) (Diruaphis noxia (Mordvilko)) is a new and cold-hardy pest of temperate cereals in western Canada. In view of the risk of fall infestation of winter wheat (Triticum aestivum L. em. Thell.), this study was made to establish whether feeding by RWA can interfere with cold hardening and plant survival of overwintering winter wheat. Feeding by RWA significantly increased the LT50 of field-hardened Norstar winter wheat by + 2 to + 4 °C. Application of 400 g (a.i.) ha−1 of the insecticide chlorpyrifos in mid-October to control severe RWA infestations in two different fields of Norstar winter wheat significantly improved winter survival of the crop. The pattern of winterkill within the two fields suggested that this protective effect of chlorpyrifos was greatest in areas where microtopography resulted in the least accumulations of snow and cold stress was most intense. It was concluded that heavy RWA infestation in the fall significantly reduced freezing tolerance of winter wheat and increased the likelihood of winterkilling of the crop by severe cold.Key words: Winter survival, cold hardening, Diuraphis noxia, insecticide, chlorpyrifos, Triticum aestivum, crop damage