Level Of Low Temperature Tolerance Research Articles

Developmental regulation and metabolic changes of RILs of crosses between spring and winter wheat during low temperature acclimation

Winter survival in wheat requires programmed potential modulations to develop low temperature (LT) acclimation for its growth and yield. The purpose of the present study was to understand the relationships between developmental regulations and metabolic changes during LT acclimation and vernalization under field conditions. Six wheat recombinant inbred lines (RILs) of F8 generation resulted from cross Mironovskaya 808 (winter-habit parent) and Pishtaz (spring-habit parent) with different vernalization requirements and reproductive development, whose growth habits were determined by Vrn-1 loci, were cultivated under greenhouse and field conditions. Plants were sampled on three dates (Dec. 12, Jan. 11, and Feb. 10) as different phenological development stages. Early and rapid transition from vegetative to reproductive phase measured by double ridge (DR) formation and final leaf number (FLN) occurred in spring genotypes, including Pishtaz parent and RILs 4006 and 4014. They also had the lowest enzymatic antioxidants activity and contents of anthocyanins, total phenols, flavonoids, lignin, proline and carotenoids and the highest damage indices (H2O2 and MDA) among genotypes. RILs 4012 and 4016 had higher FLN than Pishtaz and remained in vegetative phase longer and showed higher tolerance (LT50 and metabolites) as compared to spring genotypes. In contrast, Mironovskaya 808 parent and RILs 4005 and 4003 spent the longest time in the vegetative phase and showed the highest level of LT tolerance (confirmed by LT50, damage indices and pigment contents). The highest level of LT tolerance in all genotypes, obtained at the vegetative/reproductive transition, significantly decreased with the onset of the reproductive phase. Our results suggested that LT tolerance was established from developmental regulations and potential metabolic networks following longer vegetative phase in wheat.

The Response of Volvariella volvacea to Low-Temperature Stress Based on Metabonomics.

Low temperature can lead to the autolysis of Volvariella volvacea (V. volvacea), hindering its growth and preservation and severely reducing its yield and quality. This autolysis of V. volvacea at low temperature has been reported, but a metabolomics-based investigation of the underlying mechanisms of the V. volvacea response to low temperature has not been reported. Therefore, this study aimed to explore the changes, levels and expression patterns of V. volvacea metabolites at low temperature. To understand the metabolic differences within V. volvacea, two strains with different levels of low-temperature tolerance were treated in an ice bath at 0°C for 2, 4, 8, and 10 h, while the blank control group was treated for 0 h. Metabonomics analysis was adopted to study the changes in V. volvacea in response to low temperature and the differences between the two different strains. Metabolic curves were analyzed at different time points by high-performance liquid chromatography-mass spectrometry (HPLC-MS). A total of 216 differential metabolites were identified and enriched in 39 metabolic pathways, mainly involving amino acid metabolism, carbohydrate metabolism, the TCA cycle, energy metabolism, etc. In this paper, we report the metabonomic analysis of V. volvacea in response to low temperature and compare the differences in metabolite expression between the low-temperature-resistant strain VH3 and the low-temperature-sensitive strain V23. Finally, the putative low-temperature resistance mechanism of VH3 is revealed at the metabolic level. This study provides a theoretical basis for revealing the regulatory mechanism of low-temperature resistance in V. volvacea and for future molecular breeding efforts.

Survivorship of geographic Pomacea canaliculata populations in responses to cold acclimation.

Pomacea canaliculata, a freshwater snail from South America, has rapidly established natural populations from south to north subtropical region in China, since its original introductions in the 1980s. Low temperature in winter is a limiting factor in the geographic expansion and successfully establishment for apple snail populations. There have been some studies on population level of low temperature tolerance for P. canaliculata, yet little is quantified about its life‐history traits in responses to cold temperatures. Whether these responses vary with the acclimation location is also unclear. We investigated the survivorship and longevity of P. canaliculata in responses to cold temperatures and examine whether these responses vary with the location and snail size. We hypothesized that survival of the snails depends on their shell height and the level of low temperature, and P. canaliculata population from the mid-subtropical zone may exhibit the highest viability over the cold thermal range.We sampled P. canaliculata populations from five latitude and longitude ranges of subtropical China: Guangzhou population in southernmost (SM‐GZ), three populations of Yingtan (MR‐YT), Ningbo (MR‐NB), Ya'an (MR‐YA) in midrange, and Huanggang population in northernmost (NM‐HG) subtropical zone. For each P. canaliculata population, survival and longevity at six cold acclimation temperature levels (12, 9, 6, 3, 0, and −3°C) were quantified, and the effects of location and shell height were examined.The MR‐YA population from mid-subtropical zone of China exhibited the highest survival rate and prolonged survival time regardless of the temperature acclimation treatments, whereas the SM‐GZ population from southern subtropical was the most sensitive to cold temperatures, particular temperatures below 9°C. No individuals of the SM‐GZ population could survive after stressed for 30 days (3°C), 5 days (0°C) and 2 days (−3°C), respectively. For each experimental P. canaliculata population held at 3, 0, and −3°C, individuals with intermediate shell height of 15.0–25.0 mm had significantly higher survivals.The results highlight a request of a more thorough investigation on acclimation responses in each of the life table demographic parameters for P. canaliculata, and pose the question of whether natural selection or some genetic changes may have facilitated adaptation in invasive locations.

Genetic tolerance to low temperatures in irrigated rice

The aim of this study was to characterise genetic variability to low-temperature tolerance in the emergence stage of irrigated-rice genotypes under controlled and field conditions. Thirty-seven genotypes were evaluated, interspersed with controls of different levels of low-temperature tolerance. The design used was of randomised blocks with three replications. The genotypes were submitted to germination and emergence in controlled-temperature trials at 13 oC (Trial I) and 17 oC (Trial II), and in field environments with no cover (Trial III) and with a cover of polyethylene (Trial IV), where the soil temperature was monitored. The evaluations were carried out daily by counting the emerged seedlings and later inferring the speed of emergence index (SEI). The results showed (experiment I to IV) that the SEI varied from 0.61 to 4.23, increasing by 0.4259 for each 1 oC increase in soil temperature. The genotypes Ostiglia, Diamante, Baldo, Carnaroli, Selenio, Loto e Amarelo, of subspecies japonica, and Ringo Miara-AC and Arelate, of subspecies indica, are promising sources of genetic tolerance to low temperature. Temperatures of less than 17 oC reduce the number of emerged seedlings and delay development in each of the rice genotypes under test, with a greater or lesser negative effect on the initial plant stand per unit area.

Developmental regulation of metabolites and low temperature tolerance in lines of crosses between spring and winter wheat

Low temperature (LT) tolerance in cereals needs developmental regulation of metabolites, a process which is associated with vernalization requirement. This study was initiated to investigate the relationships among stage of phenological development, final leaf number (FLN), the activities superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase and polyphenol oxidase, the contents of proline, photosynthetic pigments, and hydrogen peroxide (H2O2) during vernalization and LT acclimation in spring and winter wheat. Six genotypes with different vernalization requirements were grown under greenhouse and field conditions. The spring-habit parent, “Pishtaz” and line 4021, rapidly entered the reproductive phase and had a limited capacities to LT acclimate. They also had the lowest antioxidative activities and accumulation of proline among genotypes. Lines 4002 and 4014, with a short vernalization requirement and higher FLN, remained in the early stages of phenological development longer and developed a higher level of LT tolerance and metabolites compared to spring habit genotypes. In contrast, the winter habit “Norstar” and line 4023 spent a longer time in the vegetative stage and accumulated higher levels of metabolites. Maximum LT tolerance and metabolite accumulations occurred near the vegetative/reproductive transition in all genotypes. The longer periods of vernalization and increased FLN that happened along with increased defense mechanisms and decreased damage indices (H2O2 content and LT50) ensured LT tolerance in wheat. These results demonstrate that both genetic and environmental factors via developmental regulation of metabolites play important roles in creating LT tolerance in long mild winters of Iran. Significant correlations coefficients for many of the metabolites considered in this study and Lethal temperature 50 (LT50) also suggest that they could be useful as indirect measures of plant LT tolerance potential in wheat breeding programs.

Cold tolerance in rice varieties at different growth stages

Low temperature is a common production constraint in rice cultivation in temperate zones and high-elevation environments, with the potential to affect growth and development from germination to grain filling. There is a wide range of genotype-based differences in cold tolerance among rice varieties, these differences often reflecting growth conditions in the place of origin, as well as breeding history. However, improving low temperature tolerance of varieties has been difficult, due to a lack of clarity of the genetic basis to low temperature tolerance for different growth stages of the rice plant. Seeds or plants of 17 rice varieties of different origins were exposed to low temperature during germination (15°C), seedling, booting, and flowering stages (18.5°C), to assess their cold tolerance at different growth stages. Low temperature at the germination stage reduced both the percentage and speed of germination. Varieties from China (B55, Banjiemang, and Lijianghegu) and Hungary (HSC55) were more tolerant of low temperature than other varieties. Most of the varieties showed moderate levels of low temperature tolerance during the seedling stage, the exceptions being some varieties from Australia (Pelde, YRL39, and YRM64) and Africa (WAB160 and WAB38), which were susceptible to low temperature at the seedling stage. Low temperature at booting and flowering stages reduced plant growth and caused a significant decline in spikelet fertility. Some varieties from China (B55, Bangjiemang, Lijiangheigu), Japan (Jyoudeki), the USA (M103, M104), and Australia (Quest) were tolerant or moderately tolerant, while the remaining varieties were susceptible or moderately susceptible to low temperature at booting and flowering stages. Three varieties from China (B55, Lijianghegu, Banjiemang) and one from Hungary (HSC55) showed consistent tolerance to low temperature at all growth stages. These varieties are potentially important gene donors for breeding and genetic studies. The cold tolerance of the 17 rice varieties assessed at different growth stages was correlated. Screening for cold tolerance during early growth stages can therefore potentially be an effective way for assessing cold tolerance in breeding programs.

Identification of quantitative trait loci and associated candidate genes for low-temperature tolerance in cold-hardy winter wheat

Low-temperature (LT) tolerance is an important economic trait in winter wheat (Triticum aestivum L.) that determines the plants' ability to cope with below freezing temperatures. Essential elements of the LT tolerance mechanism are associated with the winter growth habit controlled by the vernalization loci (Vrn-1) on the group 5 chromosomes. To identify genomic regions, which in addition to vrn-1 determine the level of LT tolerance in hexaploid wheat, two doubled haploid (DH) mapping populations were produced using parents with winter growth habit (vrn-A1, vrn-B1, and vrn-D1) but showing different LT tolerance levels. A total of 107 DH lines were analyzed by genetic mapping to produce a consensus map of 2,873 cM. The LT tolerance levels for the Norstar (LT(50)=-20.7 degrees C) x Winter Manitou (LT(50)=-14.3 degrees C) mapping population ranged from -12.0 to -22.0 degrees C. Single marker analysis and interval mapping of phenotyped lines revealed a major quantitative trait locus (QTL) on chromosome 5A and a weaker QTL on chromosome 1D. The 5A QTL located 46 cM proximal to the vrn-A1 locus explained 40% of the LT tolerance variance. Two C-repeat Binding Factor (CBF) genes expressed during cold acclimation in Norstar were located at the peak of the 5A QTL.

In vitro screening for low temperature tolerance of wheat genotypes

Low temperature (LT) tolerance of 12 wheat (T. aestivum L.) genotypes was investigated in an in vitro zygotic embryo culture. Isolated embryos were grown on a modified MS medium for two months. Calluses were prepared by gradual decrease of temperatures (17?C-7 days, 5?C-7 days, -5?C-l day, -10?C-1 day) and then exposed to LT treatments (-15?C, 24 h and 48 h). After LT treatments, calluses were acclimated by gradual increase of temperatures and grown for another month. Based on the differences in callus fresh weight between the control group and calluses exposed to the LT treatments, levels of LT tolerance of wheat genotypes were determined. The results have shown that out of the 12 wheat cultivars, 6 had a high level of LT tolerance, 5 had a medium and only one spring cultivar (Venera) had a low level of LT tolerance. These results were compared with the results of the standard in situ test in a cold chamber. Only partial disagreement of results was determined in two cultivars with the medium level of LT tolerance (NSR-2 and Balkan). It can be concluded that the in vitro test can be successfully used for the separation of genotypes with high and low levels of LT tolerance, but for more precise separation within the medium level of LT tolerance, the test should be improved.

Regulation of low-temperature tolerance in barley under field conditions in northwest Iran

Low-temperature (LT) stress is a major factor limiting the over-winter survival of barley (Hordeum vulgare L.). The objective of this study was to determine the relationship between vegetative/reproductive transition and expression of LT tolerance in barley cultivars acclimated under field conditions. Three cultivars with different vernalization response and photoperiod sensitivity were planted in the field at the Maragheh Dryland Agricultural Research Station (37°15′N, 46°15′E; 1720m) in Iran in the autumns of 2002 and 2003. LT tolerance, as measured by LT50, and stage of phenological development, as estimated from final leaf number (FLN) and shoot apex developmental morphology, were determined during the autumn and winter seasons. The short-day insensitive spring-habit cultivar Rihane-03 had a limited ability to acclimate to LT and it reached its maximum level of LT tolerance very quickly. The winter-habit cultivar Dobrinya reached its maximum LT tolerance at the point of vernalization saturation. The very short-day (SD) sensitive spring-habit cultivar Dicktoo entered the double ridge (DR) stage at about the same time as the winter-habit Dobrinya. The delay in the phenological development of both Dobrinya and Dicktoo was accompanied by increased expression of LT tolerance confirming that the length of the vegetative phase determines a plant’s ability to maintain a high level of cold-tolerance gene expression when temperatures are in the acclimation range. These observations suggest that more detailed studies should be initiated to establish the importance of interactions between photoperiod sensitivity and vernalization requirement with the objective of identifying genetic combinations and management systems that extend the vegetative stage and provide longer-term protection from LT stress in regions with long mild winters like those normally experienced in north-west Iran. Key words: Vernalization, photoperiod, phenological development, freezing resistance, barley

The regulatory role of vernalization in the expression of low-temperature-induced genes in wheat and rye

Low temperature is one of the primary stresses limiting the growth and productivity of wheat (Triticum aestivum L.) and rye (Secale cereale L.). Winter cereals low-temperature-acclimate when exposed to temperatures colder than 10°C. However, they gradually lose their ability to tolerate below-freezing temperatures when they are maintained for long periods of time in the optimum range for low-temperature acclimation. The overwinter decline in low-temperature response has been attributed to an inability of cereals to maintain low-temperature-tolerance genes in an up-regulated state once vernalization saturation has been achieved. In the present study, the low-temperature-induced Wcs120 gene family was used to investigate the relationship between low-temperature gene expression and vernalization response at the molecular level in wheat and rye. The level and duration of gene expression determined the degree of low-temperature tolerance, and the vernalization genes were identified as the key factor responsible for the duration of expression of low-temperature-induced genes. Spring-habit cultivars that did not have a vernalization response were unable to maintain low-temperature-induced genes in an up-regulated condition when exposed to 4°C. Consequently, they were unable to achieve the same levels of low-temperature tolerance as winter-habit cultivars. A close association between the point of vernalization saturation and the start of a decline in the Wcs120 gene-family mRNA level and protein accumulation in plants maintained at 4°C indicated that vernalization genes have a regulatory influence over low-temperature gene expression in winter cereals.

Ontogenetic patterns of cold-hardiness and glycerol production in Sarcophaga crassipalpis

Developmental patterns of low-temperature tolerance and glycerol production were determined for larval, pupal and adult stages of the flesh fly Sarcophaga crassipalpis Macquart (Diptera: Sarcophagidae). Both diapause and non-diapause-destined flies were reared at relatively high temperatures, 20° or 25°C, prior to testing. Cold tolerance was greatest for diapause pupae aged 12–35 days after pupariation. Among non-diapause-destined flies, pupae exhibited a greater level of low temperature tolerance than larvae or adults. Although diapause pupae were more tolerant than non-diapause pupae maximal cold tolerance was not attained in either group until 10 days after pupariation. Non-diapause-destined feeding and wandering larvae had higher glycerol levels than larvae destined for diapause. During the first 6 weeks after pupariation glycerol titres increased steadily in diapause pupae. Rapid loss of glycerol is associated with the termination of pupal diapause.