جستجوی مقالات مرتبط با کلیدواژه « cold stress » در نشریات گروه « زراعت »

Changing the chickpea planting system from spring to autumn, due to the increase in the length of the growing period, proper productivity from the late winter and early spring rains, the coincidence of the flowering and podding period with suitable soil moisture, and finally avoiding the dryness at the end of the season, is result in increasing the yield in Mediterranean climates. Wild relatives are useful sources of genetic diversity and resistance genes to biotic and non-biotic stresses, and the wider the base of diversity, the more likely the breeder will be able to find the desired genetic combination.

Photosynthetic efficiency and biochemical response of dryland chickpea genotypes were  evaluated as factorial experiment based on a completely randomized design with two replications under cold stress in two genotypes ILWC109 and ILWC119 along with two genotypes i.e. Ana (resistant control) and ILC533 (sensitive control). In the controlled environment, three different temperature levels including 22°C (as control), 4°C and -4°C were considered to evaluate biochemical characteristics.

The results of the field section showed that genotypes number 5 (ILWC109) and 23 (ILWC119) not only had the highest amount in terms of chlorophyll a content, but also in terms of ELI index and activity levels of CAT and PPO enzymes. They were better than other genotypes and cultivars and were recognized as cold resistant genotypes. In the controlled part, the results showed that the maximum fluorescence, the maximum photochemical efficiency of photosystem II, the efficiency of the water split complex in photosystem II and the photosynthetic efficiency significantly decreased in the studied genotypes under cold stress of -4°C. On the other hand, at -4°C, the amount of light current absorption increased in active reaction centers. The highest level of maximum fluorescence and photochemical efficiency of photosystem II and the lowest amount of light current absorption in the active reactive center were obtained in ILWC109 genotype. It seems that Anna genotypes and ILWC109 line have been able to increase the number of photosystem II active reaction centers under cold stress conditions of -4°C, and by absorbing light photons, electron transfer could take place with better efficiency. The improvement of the photochemical efficiency of photosystem II confirms this mechanism of action in genotypes tolerant to cold stress.

The Gamma aminobutyric acid (GABA) content as a free amino acid which is involved in reduction of oxidative stress damage and stress adaptation in the cell is adjusted by various routes, including the GABA shunt pathway. In this experiment, Gama -aminobutyric acid (GABA), Hydrogen Peroxide (H2O2), activity of GABA transaminase (GABA-T) and relative expression of Glutamate Gecarboxylase1 (GAD1) gene in cold-tolerant (Sel96th11439) and cold-sensitive (ILC533) chickpea (Cicer arietinum L.) genotypes under cold stress (4◦C) as a factorial experiment in a Completely Randomized Design were studied. In tolerant genotype H2O2 content after a significant increase on the first day of cold stress decreased significantly on the sixth day of cold stress compared to control conditions (up to 4.7%) while its accumulation was observed in sensitive genotype (up to 50%). Based on H2O2 adjustment as a damage index, these results indicated a relative acclimation to cold stress in tolerant genotype. Under cold stress, GABA content in tolerant genotype was higher compared to sensitive genotype (up to 14%). In this experiment, under cold stress, in tolerant genotype increasing GABA content was accompanied with an increase in GABA-T activity and relative expression of GAD1 gene as regulatory routes of this metabolite (up to 3- and 17-fold, respectively). The maximum and minimum activities of catabolic and anabolic pathways was observed in tolerant genotype on the sixth day of cold stress, respectively. Therefore, under cold stress, the accumulation of GABA in tolerant genotype led to reduced cell damage (H2O2 results) and improved cold tolerance.

In order to evaluate the diversity of oat genotypes (Avena sativa L.) in response to cold stress, 21 oat genotypes were studied in the Faculty of Agricultural Sciences and Engineering of Razi University, Kermanshah in 2015-2016 under controlled conditions in the greenhouse. Two separate experiments were conducted to determine the 50% plant lethality temperature (LT50) and the effect of short-term cold stress on physiological characteristics and antioxidant enzymes, in the form of a completely randomized design. Variance analysis of LT50 showed that there is a significant genetic variation between the investigated genotypes in terms of LT50 level. The average of LT50 trait showed that the genotypes (Ozark), (UFRGSP 948886), (UPF775456), (Euro), (GA Mitchell), (Mortlock), (OH1022), (Brusher), (Wallaroo) and (Kalott) had the highest LT50 value and can be considered as cold tolerant genotypes, and (Quoll) and (Nasta) genotypes had the lowest values. A positive and significant correlation was observed between the catalase enzyme and chlorophyll content and between the peroxidase enzyme and ion leakage rate. The Ozark and UFRGS 948886 genotypes were placed in the group with the maximum mean LT50, chlorophyll content, carotenoid content, catalase enzyme, peroxidase enzyme and minimum ion leakage rate in the cluster analysis. Therefore, it could be stated that the genotypes of this group have better conditions in terms of cold tolerance than other genotypes.

In order to evaluate the planting date delay on phenological traits, yield components, grain yield, and linoleic and linolenic fatty acids of new sunflower hybrids, an experiment has been conducted as split plot in a randomized, completely block design, with four replicates at the field of oilseed section of seed and plant Improvement during 2014-2016 growing season. The treatments include seven sunflower hybrids (Barzegar, Farrokh, Haysan 36, Qasem, Shams, Azargol, and Haysan 25) on three planting dates (15 days after harvest of autumn (wheat), July 1, July 15, and July 30, respectively). The experimental results show significant effects of planting date on all traits except number of seeds per head and linolenic acid at the level of 1% and on the percentage of oil and linoleic acid at the level of 5%. The studied hybrids are significantly different in all traits except linoleic and linolenic fatty acids. The latest experimental hybrids include Barzegar and Azargol hybrids and the earliest hybrid is Farrokh. The highest grain yield is obtained from the date of the first sowing at the rate of 2840 kg / ha and in the case of delayed sowing the yield is reduced to 41%.

Beans, due to their significant nutritional and crop characteristics, have a high rank in agricultural systems of the world. These plants, by fixing air nitrogen, can increase the amount of nitrogen in the soil. Beans have a long history of cultivation in Iran, and some believe that some of them, such as lentil (Lense culinaris Medik) and chickpea (Cicer arietinum L.), have been domesticated in this country. The lentils are cold and long day and can be cultivated from 0 to 3500 m above sea level, the temperature suitable for growing lentils is 15-25 °C. Spring cultivation of lentils although common in Iran, winter cultivation of lentils has advantages over spring cultivation if successful. Previous research showed that the average plant height of lentils in autumn and winter was 43% higher than spring planting and the highest yield of lentils (1486 kg.ha-1) was obtained from autumn planting. Autumn cultivation is usually accompanied by a low temperature challenge. Low temperatures often affect the growth and productivity of crops, causing significant crop losses. Delay in emergence and decrease in germination percentage of seeds occur due to autumn cold, so priming can be used for seed germination. The purpose of this study was the effects of different priming treatments on reducing cold stress effects on emergence and growth of two lentil genotypes.
 
The experiment was conducted as a factorial based on completely randomized design with four replications under controlled conditions in 2017 at Ferdowsi University of Mashhad. Factors consisted of lentil genotypes (Robat and Calposh), priming (6 levels of control, Gibberellic acid )C19H22O6(, Potassium nitrate (KNO3), Zinc sulphate (ZnSO4), seed priming Dayan and hydropriming) and temperature (5, 10 and 15ºC). To test and apply treatments, 40 seeds were randomly selected for each treatment. After the end of the priming period (16 h), the seeds were removed from the solution and then placed in the laboratory for 24 h until complete drying. The prepared seeds were 10 seeds in pots of 11 cm diameter light soil and transferred to the growth chamber. Then the studied properties were measured. Data were analyzed using SAS 9.4 software and the means were compared with LSD at 5% probability level.
 
The highest emergence percentage (72.5%) was found in Robat in control and 5ºC. Seed vigor in Robat genotype at 15 °C was higher than Calposh genotype, and in both genotypes (with the exception of Calposh genotype the priming primer with zinc sulphate and hydro-priming), the seed vigor increased with temperature. The highest seed vigor (4.91) was found in Robat in 15ºC and priming by seed priming Dayan. The highest plant height was observed in priming by gibberellic acid and 15ºC. In both genotypes, leaf number per plant was increased as temperature increased and was decreased when treated by ZnSO4 and Hydropriming in Calposh. The highest leaf number per plant (4 leaves) was found in Robat in 15ºC and priming by seed priming Dayan. The highest root length (4.04 cm) was observed in seed priming Dayan and 15ºC. The interaction of temperature and priming on root length showed that at 5 °C all priming treatments (with the exception of sulfate priming) compared to the control, at 10 °C priming with Dayan seed solution, potassium nitrate and 15 °C hydropriming. Dayan seed solution and potassium nitrate had more root length than control. Seedlings Robat appear to have higher seed vigor and can compensate for the time elapsed before priming, but seedlings Calposh that are less potent, priming treatments have been able to improve seed vigor.
 
The results of this study showed that the Robat genotype in terms of seed vigor and other emergence characteristics was better than Calposh genotype. As the Robat genotype has higher vigor, so different priming treatments could not have a positive effect. Priming with gibberellic acid and potassium nitrate had the greatest effect in reducing the effects of low temperature (5 °C) on the emergence characteristics of lentil seed. In general, priming with gibberellic acid seeds for autumn or early spring cultivation can be recommended.

In order to identify cold tolerant cultivars in sugarcane, in December 2015 and one week after the occurrence of -1.2 °C, by morphological study of 454 sugarcane cultivars, the reaction of these cultivars and their tolerance to cold were investigated.

In the first stage of the experiment (morphology), 54 cultivars were introduced as resistant and tolerant cultivars and 400 cultivars were introduced as cold and very sensitive cultivars. In 2016, to evaluate cultivars based on biochemical indices, out of 54 resistant cultivars, 5 cultivars, and out of 400 susceptible cultivars, 5 cultivars were selected and the amount of free amino acids, Proline and Malondialdehyde, in them before and after the onset of cold, it was measured. Among the selected cultivars of the previous stage, BR00-01 cultivar was selected as the most tolerant cultivar, and TUC66-107 cultivar as the most sensitive cultivar to cold, to apply cold stress in the cold storage and continue the project in the molecular stage. After planting them in plastic pots, leaf sampling was performed in the refrigeration under stress and to extract TotalRNA. After RNA extraction, the quantity and quality of RNA samples were measured. Using the Illumina Hiseq250 platform in the RNAseq technique, after confirming the quantity and quality of the extracted RNAs, the TruSeq cDNA library was constructed by the Chinese company Novogene and sequencing for RNAseq was done as a pair-end with a length of 150 nucleotides. After sequencing, the data were downloaded in compressed files in Fastq format from the Novogene website. The quality of the raw reads was checked using FastQC software. Trimmomatic software was used in the trimming step. After aligning the reads to the sugarcane reference genome, quantified reads were normalized, differential expression analysis was performed, and genes with differential expression were analyzed and pathways were mapped. After analyzing the differential expression of genes and obtaining the values, GO enrichment analysis was performed to classify the genes based on the placement of their products. Next, the path analysis was performed using the kobas database. Then, in order to enrich the pathways, significant pathways were identified with Corrected P-Value <0.05 for genes with increased and decreased expression.

he results of differential expression of genes showed that out of a total of 62285 expressed genes, 12674 genes have differential expression in different comparisons between treatments, of which 6939 genes decreased expression and 5735 genes increased expression. After enriching the pathways, genes that could be 95% probable in 18 treatment comparisons to attribute their change in expression to cold stress were identified, and marker genes were identified in these comparisons. According to the results of the metabolic study, increasing the concentration of free amino acids, Proline and Malondialdehyde increased the plant's tolerance to cold. In this study, due to cold stress, various biosynthetic and metabolic pathways were activated under the influence of the activity of genes controlling these pathways to produce their products. These pathways include the biosynthesis of the amino acids arginine and Proline, the biosynthesis of Phenylpropanoid, the riboflavin metabolism, and the MAPK messenger pathway, in which the genes involved increased expression during cold stress. Meanwhile, the PR1 gene was detected in the MAPK messenger pathway, which showed an increase in expression with decreasing temperature Increased expression of genes in MAPK, Phenylpropanoid, sulfur, Glycerophospholipid, arachidonic acid, lipid ether, riboflavin and Proline signaling pathways indicates that the products of some genes controlling these pathways play a role in increasing cold tolerance of sugarcane.

The results of morphological, metabolic and molecular studies showed that there is a correlation between these indices and their values in resistant cultivar. When screening sugarcane clones for cold, the best clones can be selected by measuring the amount of secondary metabolites. In this study, genes affecting cell physiology pathways were identified and their role in increasing sugarcane tolerance to cold was elucidated. Using these genes, you can use them in a sugarcane breeding program to screen for cold-resistant clones. In the sugarcane breeding program, these genes can be used as markers in the screening of clones.

In order to investigate the effect of salicylic acid application on reducing the effects of cold stress due to delayed planting in rapeseed genotypes, this experiment was conducted as a factorial-split plot during the 2014 and 2015 growing seasons in the Faculty of Agriculture, University of Zanjan, Iran. Interaction of the sowing date (11th September and 7th October) and salicylic acid (control (spray with distilled water), 250 µM and 500 µM) were as the main-plot and rapeseed genotypes (Karaj-3, L14, Okapi, Zarfam) were assigned to subplots. The effect of planting date* salicylic acid* genotype on winter survival percentage, grain yield and its components, harvest index, and biomass was significant. Delayed planting reduced survival percentage of all rapeseed genotypes; but the severity of reduction varied depending on the genotype. It was also found that the decrease in survival percentage due to delay in planting can be partially compensated for by the use of salicylic acid, which varied depending on the salicylic acid concentration and genotype. Delayed planting date reduced grain yield in all genotypes and salicylic acid application had the opposite effect and increased grain yield. Karaj-3 had the highest grain yield on 7th October planting date and 500 µM salicylic acid, while Zarfam had the lowest grain yield on 11 September and 0 µM salicylic acid. Application of salicylic acid compensated for part of the reduction in yield due to delay in planting, so that the lack of application of salicylic acid and the use of 250 and 500 μM salicylic acid in planting on 7 October caused grain yield reduction in Karaj-3 genotype by 36, 31 and 18% respectively, compared to 11 September, while grain yield in L14 genotype showed 26, 21 and 8% reduction respectively, compared to 11 September planting date. The grain yield of Zarfam genotype at delayed planting date decreased by 9% and 5% and increased by 13%, respectively, in conditions of non-application and application of 250 and 500 μM salicylic acid compared to the 11 September planting date. There was a positive significant correlation between grain yield components and winter survival percentage. Although delayed planting reduced grain yield, yeld components, harvest index, and biomass in all genotypes, the severity of the decrease varied among the genotypes. Consumption of salicylic acid moderated the effect of delay in planting and this modulatory effect was higher in the application of salicylic acid with a concentration of 500 μM than 250 μM. In general, the results showed that in both planting dates, the Karaj-3 genotype had the highest grain yield in all salicylic acid levels, so it is recommended for planting in areas with similar conditions.

Most of the plants in the citrus family are sensitive to cold stress. Therefore, the inevitable occurrence of periodic frost causes extensive damage to their functions. With the purpose of comparing 110 citrus genotypes’ reaction to the two levels of cold stress (-3°C and -6°C), 76 unknown natural genotypes and 34 known genotypes from Ramsar citrus and sub-tropical fruits research institute were studied based on the split-plot design with three replications. The results of variance analysis for the eight traits related to cold tolerance showed that there was a significant difference between the examined accessions. According to cluster analysis, the genotypes in each temperature demonstrated a relatively different grouping pattern after the employment of Euclidean distance squares and the furthest neighbors’ method. The highest amount of electrolyte leakage (55.84%), leaf water soaking (2.70) and lipid peroxidation (2.12 μg/g leaf fresh weight) were estimated at -6°C and recorded at -3°C for other traits. The relationship between the studied panels was determined by considering the common group and the traits in question. G32 and G71 genotypes were merely found to be close to the tolerant genotypes. Regarding the negative deviation from the standardized mean for electrolyte leakage (-1.367), leaf water soaking (-1.423) and lipid peroxidation (-0.684), along with the positive values of other traits (proline content, antioxidant capacity, total soluble carbohydrates and antioxidant enzymes), genotypes Poncirus, Citrumelo, off type sour orange, Sour orange, Satsuma mandarin, and Okitsu are of great usage value in cold tolerance breeding programs.

To study of inheritance of oilseed rape quality traits in normal and late sowing date conditions, 31 genotypes including 7 winter lines as females, and 3 winter testers and their 21 F1 generation were grown under normal sowing date (early October) and late sowing date (early November) conditions in two separate RCB designs with two replications at the field of Seed and Plant Improvement Institute, Karaj (2011-12). Combined analysis of variance showed significant differences between treats of oil seed content and most fatty acids traits in both sowing dates. Therefore, significant genetic variation existed for all traits among the genotypes studied. Estimates of broad and narrow heritability of most traits under late sowing date were less than the normal sowing date and this was mainly due to less esti mation of variance components under late sowing date conditions. In addition, broad heritability was estimated to be generally medium to high (between 72.01 to 100) in both normal and late sowing date conditions. The narrow heritability of traits in both sowing conditions ranged from 20.81% to 80.20%. Therefore, selection for traits with moderate to low narrow heritability in early generations would not be much useful, and it is preferable to use heterosis to improve these traits. In both sowing dates non-additive effect was more evident in control of quality traits. Therefore, selection for these traits would not be effective without using the effect of gene dominance.

Cold stress is one of the main limiting factors for autumn planting of chickpea. The probability of presence of cold tolerant genes is considered to be higher in accessions originating from cold and highlands areas due to natural selection process. With this purpose, 812 Desi chickpea accessions of the National Plant Gene Bank of Iran (NPGBI) originated from cold and high altitude regions (altitude more than 1200 m) were screened for cold tolerance. The experiment was set up as augmented design and carried out in dryland agricultural research station in Maragheh, Iran, in 2018-19 cropping season. The reaction of these accessions to the natural cold temperatures in the region was investigated in comparison to tolerant cultivars (Saeed and Saral), and susceptible line (ILC533). Accessions were scored based on the percentage of frost resistance ratio (FRR). Considerable variation was observed among accessions, while the average FRR was estimated 30% and 50% in Saeed and Saral cultivars, respectively, and ILC533 was completely killed by frost. Frost resistance ratio ranged between 0 and 70 percent in NPGBI Desi chickpea accessions. In total, 114 accessions could survive natural cold temperatures and completed their life cycle. The accessions number KC215724, KC215443, KC215712, KC215905, KC215911, KC216223, KC215458, KC215468 and KC215856 showed 60% FRR, and accession number KC215724 obtained 70% FRR, and were more cold tolerant than the other accessions. Therefore, these accessions can be used for being selected and released as new cold tolerant cultivars as well as in chickpea breeding programs for target environments.

Floral transition through vernalization has a large influence on cold tolerance and agronomic traits in winter cereals. It is now apparent that in many plants small RNAs play critical roles in determination of the flowering time. There is evidence suggesting that the miR156 and miR172 families play a key role in the flowering transition of plants. In this study, the expression of two temporally regulated miRNA (miR156 and miR172) and their targeted genes (SPL3, AP2) were investigated in the winter bread wheat cv. Norstar and the spring bread wheat cv. Baj in 2017-2018 cropping season. The vernalization was exposed to the cold treatments (4°C) for 2 and 14 days at seedling stage. Time to flowering was estimated using the final leaf number (FLN), which significantly decreased under vernalization treatments, only in winter cultivar 'Norstar'. Moreover, analysis of variance showed that vernalization treatments × cultivarsv interaction effect was significant on FLN. Comparison of gene expression using bootstrapping method showed that the expression of miR172 was significantly down-regulated only in Norstar under vernalization treatments. Similarly, the expression of miR156 was completely different under vernalization treatment in two cultivars. Increased expression of miR156 in Baj cultivar was not significant, but vernalization treatment significantly decreased the expression of this gene in cv. Norstar. Although the induction of AP2 expression during vernalization (14 days) was observed in both cultivars, but, the expression levels of SPL3 were only significantly decreased in cv. Norstar, and this reduction was more in two-day vernalization. Unexpectedly, in this experiment, there was no relationship between up-regulation of both miRNA and down-regulation of their targeted genes in two bread wheat cultivars. These results demonstrated that molecular mechanism of flowering time in bread wheat is complex and still largely unknown.

Cold stress is one of the main limiting factors which decrease crop production and even lead to plant death. Temperatures between 0 to 15 ºC can cause physiological injury in plants. One of these injuries is increasing the generation of reactive oxygen that adversely affect the photosynthetic pigments, protein and thylakoid membrane lipids. Also, light affects on growth, development, plant productions including primary and secondary metabolites, so that leaf area, leaf area duration and plant biomass positively response to increasing light intensity while in low light intensity respiration rate is more than photosynthesis rate. Since light intensity can effect in plant resistance to environmental stress especially cold stress and stevia is sensitive to cold stress and it cannot tolerate temperature below 9ᵒC, therefore, the purpose of this study was to determine how vegetative and physiological traits and soluble sugar of the plant response to cold stress in different light intensities.

This study was done in a factorial arrangement based on a randomized complete block design with three replicates. Treatments were five levels of cold stress (0, 4, 8, 12 and 16 days) at 6±2 ᵒC and three light intensity levels of normal light, 50 and 10 % of normal light (240, 120 and 24 µm.m-2.s-1, respectively). The seedlings of stevia plant from in vitro were planted in the plastic pots after acclimation period (40 days). The seedlings were kept in favorite growth conditions at 20-24ºC and 15 h light photoperiod for 30 days. Then, the mentioned light and temperature treatments were applied. Then chlorophyll a, b, total chlorophyll, chlorophyll a/b ratio and carotenoid were measured. Also, plants were harvested and physiological traits and vegetative dry weights were measured. Finally, plant soluble sugar was measured by dry leaf sample.

The results showed that root length, number of nodes, leaf area, leaf, root, shoot and total dry weights decreased as segmental model while stem dry weight decreased linearly when cold stress duration increased. Also traits like leaf area, plant height, vegetative organs dry weight and soluble sugar content (from 10 to 48%) were decreased by reducing light intensity from 240 to 24 µm.m-2.s-1. Moreover, 16 days after cold stress in all light intensities, chlorophyll a (between 18 to 91% ), b (between 16 to 76%), a+b (between 17 to 86%), a/b (between 1 to 60%) and carotenoid (between 16 to 91%) reduced as compared to the control in either segmental or linear models. The most reduction was recorded at low light intensity. Soluble sugar and total dry weight had the most correlation with leaf area and shoot dry weight, respectively.

the results demonstrated that physiological parameters are more sensitive to prolonged cold stress under lower light intensity.

IEvaluation of cold-tolerance in genetic resources of some annual forage crops under cold climatic conditions Introduction Temperature influences plant physiological processes, cellular structure and development. Habitat from which plants originate has undeniable effects on plant tolerance to cold temperatures. Plants from higher latitudes exhibit more tolerance to cold stress than plants from lower latitudes. When plants are exposed to cold stress, a sequence of events is triggered inside them, leading to an improved tolerance to the environmental condition. This phenomenon is known as plant hardening. Having access to winter-hardened species and cultivars is one of the important necessities for the development of crop production systems in local microclimates of cold regions. Utilizing genetic diversity in crop plant resources is an important approach towards achieving sustainable agriculture. Diversity in Iran`s forage germplasm for traits such as early maturity, high ratio of leaf to stem, dense ground cover and high yield has been shown in temperate regions such as Karaj and Mashhad (Abbasi, 2009, Abbasi et al., 2017). Testing a selection of these germplasm accessions can determine their potential for growing under water-limited conditions in cold regions. Hence, different genera and species of legumes in national plant gene bank of Iran originated from high latitudes were used to be evaluated under cold growing conditions. Materials and Methods A total of 124 annual-forage accessions from 40 species and 10 genera were selected based on the previous research works and were planted in an experimental filed at Jolge-Rokh agricultural research station. The number of accessions in each genus included Trifolium (36 accessions), annual medics (28 accessions), Onobrychis (9 accessions), Vicia (21 accessions), Melilotus (17 accessions), Lolium (6 accessions), Bromus (5 accessions), and Phalaris (1 accession), Lathyrus (1 accession) and barley (1 accession). Each accession was planted in two 2-meter long rows spaced 50 cm apart using an augmented experimental design. Some of the traits characterized in this study from autumn to spring included growth rate in spring and autumn, cold-tolerance score, plant height etc (IPIGRI, 1984). Statistical descriptive parameters were determined for the evaluated traits. One-way ANOVA (analysis of variance) and Duncan's multiple tests were performed on data of each trait. The analyses were carried out by SPSS 15. Results and Discussion Meteorological data showed that there were a total of 68 days of freezing temperatures in the region from November till March. The lowest absolute temperature recorded was - 17.4 °C in December. Also, the mean of daily minimum temperature for December, January, February and March was below zero and the mean of daily maximum temperature for December, January and February was -10 °C, indicating the occurrence of cold stress in the region. The results of one-way ANOVA analysis for the investigated genera and species showed that there were significant differences among their traits at 1 % probability level, particularly prior to cold stress. Lolium and Bromus were the most tolerant species among the narrow-leaved forages and the tested germplasm. Among forage legumes, sweet clover exhibited the highest tolerance to cold temperatures. Although the species vicia, Lathyrus and Iranian clover were not tolerant to cold, they were found to be beneficial in terms of soil conservation and sustainability due to the production of proper vegetative cover prior to the cold spell, which lasted till the spring of the next year. Based on the results of this investigation, the studied species and genera can be classified into the following groups: 1- Cold-tolerant forage grasses including accessions of Lolium: 14TN00072, 14TN00038, 14TN00052, 14TN00054 and accessions of Bromus: 10TN00049, 10TN00012, 10TN00036, 10TN00039, and 10TN00026. 2- Cold-susceptible forage grasses such as accessions: KC126013 (L. temelentum) and barley. Although this group was sensitive to cold, they produced good vegetative cover on ground before the occurrence of cold, which can be used as mulch for soil protection throughout the year. 3- Cold-tolerant legumes, such as accessions of Melilotus: 58TN00025, 58TN00047, MahNo313, 58TN00182, 58TN00223, 58TN00140, 58TN00181, 58TN00080, and 58TN00190 4- Cold-susceptible forage legumes: they were categorized into two groups, one group produced good vegetative cover on ground before the cold spell such as accessions 44TN00047, 44TN00041, and 44TN00005, and the other group failed to produce enough vegetative cover on ground such as some accessions of annual medics, Onobrychis, and Trifolium.

In order to study the response of 120 genotypes of rapeseed (including 100 hybrids and 20 parents) in terms of cold stress tolerance, an experiment was conducted in α-lattice design with two replications under normal (September) and late sowing (October) conditions during two years. Combined analysis of variance showed that genotypes were significantly different at 1% and there was a significant genetic variation among the studied genotypes. In addition, there was a significant difference between the environments (normal and late sowing) at 1% in both years and the effect of late sowing on the yield of rapeseed was different from that of normal sowing. Total mean of seed yield in non-stressed condition was 4.9 ton/ha and in cold stress condition was 2.72 t/ha (34% reduction compared to normal sowing conditions). Principal component analysis (PCA) using six indices of cold stress tolerance (MP, GMP, HARM, TOL, SSI and STI) showed that the first two components justify about 99.85% of the variation in the population. The biplot of first and second components divided the genotypes into four different groups and identified 29 high yielding and cold tolerant genotypes. Similarly, cluster analysis divided the genotypes into four different groups and grouping of genotypes using cluster analysis showed good agreement with the results of principal component analysis. Correlation between different indices of stress tolerance and yield in stress (YP) and non- stress (YS) condition showed that TOL and SSI had positive correlation with YP and negative correlation with YS. Furthermore, the four indices of MP, GMP, HARM and STI showed positive and significant correlation with yield in both stressed and non-stress conditions. The results of this study showed that the STI index has a high efficiency in selection of rapeseed genotypes for cold tolerance and can be successfully applied in breeding programs.

To evaluate the cold tolerance potential of bread wheat promising lines, an experiment was conducted based on the alpha-lattice design with two replications during 2015-16 at the Seed and Plant Improvement Institute, Karaj, Iran. In this study, 16 promising lines obtained from the adaptation trial of temperate agro- climatic zone, and 12 promising lines obtained from the adaptation trial of cold agro- climateic zone, were evaluated for cold stress tolerance using an integrated method (laboratory and field). The cold-acclimated plants were sampled from the field in the early January 2015, and the potential of cold strss tolerance in plants was determined by measuring LT50 (the temperature at which 50% of plants are killed) using a regulatable freezer. The results showed that among the temperate adapted lines, eight lines and cv. Baharan had a lower LT50 than Parsi (check cultivar) with LT50 = -6°C and the lowest LT50 (-12°C) was related to line M-94-7. Among the cold adapted lines, eight lines had a lower LT50 than Mihan (check cultivar) with LT50 = -12°C and the lowest LT50 (-15°C) was related to lines C-94-11 and C-94-13. Cold stress tolerance in cultivars Heydari (-9.5°C) and Orum (-11.5°C) was lower and in Zarea (-13°C) was more than the cv. Mihan. Six lines from temperat agro- climatic zone and nine lines from cold agro- climatic zone had lower LT50 (cold tolerance), and higher grain yield than Parsi and Mihan, respectively.

Plants grow well only within a specific temperature range. Getting out of this range is regarded as a stress. Low temperature is regarded as one of the important abiotic stress among the main factors threatening the growth of plants in temperate regions that causes disorder in the growth, development and operation of the plant by affecting some of vital processes of the plant. Environmental stresses especially cold stress affects the morphological and physiological features of the plant. Among these effects are damage to the cell membrane and change in its properties, reduction in photosynthesis and carbon dioxide efficiency, change in chlorophyll fluorescence characteristics, synthesis of chlorophyll and reducing the relative amount of water content. Since rapid and effective assessment of plant cold tolerance is important for researchers and also field trials have no regular process and have high error, different kinds of artificial freeze tests such as survival percentage test and regrowth after using stress has been developed.
In order to investigate the cold tolerance of Fenugreek, an investigation was done in factorial arrangement and in a completely random design in three replications in 2013-2014, in College of Agriculture in Ferdowsi University of Mashhad. The investigated factors include sowing date in four levels ( September 13, October 14, March 5, and April 3), ecotype in 10 levels (Azari, Ardestan, Tall, Dwarf, Shiraz, Shirvan, Mashhad, Neishabur, Hamedan and Hendi) and freezing temperature in seven levels ( control, 0, -3, -6, -9, -12, -15 °C). The plants grew in pots and cold acclimation in outside conditions then the plants which were planted in September and October as well as March and April. The pots were transferred to the freezer thermo gradient to apply the cold temperature in the middle of January and in the middle of May, respectively. Four weeks after applying the stress, survival percentage, Lethal Temperature 50% of Plant according to the Survival Percentage (LT50su), height, leaf area, Reduced Leaf Area Temperature (RLAT50), dry weight and Reduced Dry Matter Temperature 50 (RDMT50) were measured.
All ecotypes (except for Azari and Ardestan ecotypes) in the third sowing date could tolerate lowering temperature to -9 °C in every four sowing date. Lowering temperature to -12 °C also led to the death of all ecotypes in March and April sowing dates, while in September sowing date despite the death of most Fenugreek ecotypes, both Neyshabur and Mashhad ecotypes could tolerate this temperature. Also, in October 14 sowing date, in Neyshabur, Mashhad and Shirvan ecotypes the survival percentage was high, but the survival percentage of Azari, Ardestan and Tall compared with the control treatment decreased 61, 50 and 39, respectively, and the other ecotypes were destroyed completely. Ecotypes of Mashhad and Neyshabur had the lowest LT50su in the first and second sowing dates but in the third and fourth sowing date no significant differences was seen in this respect. In March 5 sowing date, after lowering temperature to -9 °C, the maximum percentage of decrease in height compared with control was in Dwarf ecotype (71 percent) and the minimum was seen in Shiraz (33 percent). In spite of this, Dwarf ecotype in the other sowing dates assigned to itself the lowest decrease percentage of height (respectively 35, 24 and 33 percent) and had a better ability to recovery. In every four sowing date lowering the temperature to -12 °C caused the total mortality of Hamedan, Hendi and Shiraz and they didnt have any leaf surface, but the response of the other ecotypes in October 14 sowing date was different. Two ecotypes Tall and Neyshabur having the highest (92 percent) and the lowest (66 percent) decrease in leaf surface compared with the control temperature were known as the most sensitive and the most tolerant ecotypes in this sowing date. In October 14 sowing date the response of the ecotypes to -6 °C compared with the other sowing date was better and the highest dry weight was associated with this date by lowering the temperature to -9 °C two ecotypes of Shirvan and Azari had the highest and the lowest decrease in dry weight (respectively 33 and 14 percent) in the second sowing date.
Lowering the temperature to less than -9 °C causes a decrease in the plant survival percentage and recovering in most of the ecotypes of Fenugreek. In spite of this, percentage of the plant survival depending on the sowing date, so that in the second sowing date the percentage of survival was more than the other sowing dates and except for Shiraz, Hamedan and Hendi ecotypes, the other ecotypes were able to tolerate -12 °C. Ecotypes of Shirvan, Mashhad, Neyshabur and Dwarf under both of spring and fall sowing dates had a better regrowth than the other ecotypes, while Azari and Ardestan ecotypes under the fall sowing showed a better regrowth than spring sowing date. There was a significant correlation between RLAT50 and RDMT50 with LT50su (r =0.53** and r = 0.64**, respectively), probably this subject shows the efficiency and the possibility of replacing each of these indexes in the investigation of the cold tolerance in Fenugreek. To sum up, the ecotypes of Mashhad, Neyshabur, Shirvan and Dwarf showed a better tolerance to freezing than the other ecotypes.

In this experiment, some physiological responses such as electrolyte leakage index (ELI) and relative expression of receptor-like kinase (RLK), ethylene response transcription factor (ERF) and vacuolar sorting receptor 6 (VSR-6) by real time PCR were studied in two genotypes of chickpea (Cicer arietimun L.) which are different in cold sensitivity (tolerant, Sel96Th11439 and susceptible, ILC533) during cold stress (4°C) and TiO2 nanoparticles (NPs) (5 ppm). Under cold stress, TiO2 NPs caused a significant decrease in ELI, so that tolerant plants had lower ELI than susceptible ones. Therefore, the applied nanoparticles not only did not disturb the cell membrane but also are caused to decline of damages during cold stress. During cold stress, tolerant plants compared to susceptible ones, as well as in plants treated with TiO2 NPs compared to control plants showed significant increase in transcription levels of RLK, ERF and VSR-6 genes. An increase in expression of these genes is probably effective in the survival or recovery of plant because along with their increase, cell damages (ELI) resulted from reactive oxygen species (ROS) are decreased. Therefore, rapid and transient up-regulation of these genes particularly may be considered as functional markers in acclimation process in chickpea against cold stress. This finding that chickpea plants treated with TiO2 show more tolerance against cold stress has created new application for nanoparticles and may be led to the stable yield under stress in these plants.

Food productivity is declining due to the effect of different abiotic stresses. Stress is the result of abnormal physiological processes that influence by one or a combination of biological and environmental factors. Cold, salinity and drought are important among the other stresses. Three types of cold stress has been identified that include: Frost, Freezing and Chilling Stress. The relationship between plant growth and climate change is a seemingly contradictory event. In fact, warming increases danger of cold stress. In the spring, at the same time of started wheat growth, it is increase its sensitivity to low temperatures and it damaged. This model of cold stress called rapidly falling temperatures in the spring or in short term called "chilling". Chilling stress reduced leaf expansion, wilting, chlorosis (yellowing of leaves) and may lead to necrosis (death of tissue) and strongly disturbed the reproductive development of plants. Low temperature stress limit the grain production in cold and ultra-cold climates and makes high damages in some years. Therefore produce resistant cultivars is necessary. Management of genetic resources, and knowledge of the genetic diversity are tow important principles of breeding projects. This study examines the genetic diversity of some of bread wheat cultivars for some physiological characteristics associated with chiling stress using multivariate statistical methods and compare these methods.
This survey performed in 2013 at the Faculty of agriculture, Tarbiat Modares University. In this study an experiment with 20 varieties of wheat with four treated cold levels of stress (8 (control), , 0, -2 Celsius) in factorial arrangement in randomized completely design implemented. In early of reproductive stages (Zydaky code 50 to 68), the plant transferred to growth chamber under 14/10 hours and 16/8 °C day/night photoperiod. To impose stress, temperature reduced 2°C per one hours from 8 °C then the pots were placed for 2 h under stress in each of stress temperature levels (2, 0 and -2 °C). After stress, temperature up to 8 °C with ramp 2 °C per hours. Sampling was done after 24 h and then electrolyte leakage, chlorophyll (a, b, ab and cartenoids), proline and fructan, were assessed.
The results of this study showed that the effects of interaction between gentopyes and chiling stress were significant at 1% level. Based on results of the cluster analysis twenty genotypes were classified into four groups in -2 celsius temperature and two groups in control temperature. The principal component and principal coordinate ,confirmed grouping created based on of cluster analysis. The principal component analysis decrease all treats in to 3 components in control (with cumulative of variance 80) and sever stress (with cumulative of variance 85). Also the principal coordinate analysis decrease all component to 3 components with cumulative variance 94.11 (for control) and 96.59 (for sever stress). Based on cluster analysis Pishgam and Aflak genotypes in control condition and Alvand and Sivand in -2°C had the maximum genetic distance. The minimum genetic distance was observed between Mv17 and Navid genotypes (in control condition) and Kaskojen and Pishgam (sever stress).
(1) Chiling stress detects the diversity amoung studied gentopyes; (2) In order to grouping of genotypes, cluster analysis provided more accurate grouping than principal component analysis and principal coordinate analysis ; (3) Alvand and Sivand cultivars can be use as potential parents to provide the necessary population in classical breeding programs, in order to detect of QTLs for chiling tolerance and also for marker assisted selecion.