Relationship between vernalization requirement and winter hardiness in doubled haploids of barley

Summary Progeny lines of chromosome-doubled haploids from crosses between one winter and four spring barley varieties were analysed for winter hardiness and vernalization requirement in the field. About one quarter or less of the offspring lines required vernalization under field conditions showing that winter versus spring habit of growth is controlled by at least two pairs of genes. The vernalization requirement could be measured quantitatively by testing a few plants in a greenhouse after artificial cold treatment during germination. The individual winter lines tested required from two to seven weeks of vernalization in order to flower as early as possible. The cold treatment had no effect on the time of flowering in the spring lines.Winter hardiness varied from zero to 100% plant survival in the field. The majority of the lines requiring vernalization survived better than 90% and the survival of the rest was at least 60%. The winter survival of the spring lines varied from zero per cent (about one third of the lines) to 100%. Hence, it is possible to obtain lines of good winter hardiness without requirements for cold treatment. Conversely, a selection for vernalization requirement has a positive effect on winter hardiness.     

Evaluation of Maize Germplasm for Tolerance to Low Temperature Stress under Field and Laboratory Conditions

Sixty-four inbred lines of maize ( Zea mays L.) were evaluated for their tolerance to low temperature stress in three experiments at Punjab Agricultural University, Ludhiana. All the 64 inbred lines were evaluated under laboratory conditions. Forty-four of these were also studied under field conditions. In the laboratory test the materials were exposed for four hours to 1, 0, −1, −2, −3 and −3.5°C on six successive nights. Significant genotypic differences were observed for freezing injury in laboratory test and for frost and non-freezing (yellowing) injuries in field evaluation. Expression of frost injury under field condition and freezing injury in laboratory test at −2, −3 and −3.5 °C showed positive correlation in one experiment. The range and mean square for freezing injury of inbred lines were the largest either at −3 or at −3.5°C. The correlation of yellowing with frost injury in field and freezing injury in laboratory at −3 and 3.5°C was not significant suggesting the lack of association between yellowing and frost/freezing injury.     

Genetic variation for shoot elongation before winter and its correlation with vernalization requirement in winter oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Changing climatic conditions in north-western Europe are accompanied by occasional extreme weather conditions. This requires breeding of winter oilseed rape cultivars which are resilient to diverse abiotic stress factors, e.g. frost, drought and heat. The degree of vernalization requirement of winter oilseed rape has been found to be related to frost tolerance and winter hardiness. Shoot elongation before winter in particular has been identified as one decisive factor for frost tolerance in winter oilseed rape. However, the relationship between vernalization requirement and shoot elongation before winter is not known. In the present study the genetic variation for shoot elongation before winter and vernalization requirement of 19 genetic diverse breeding lines and cultivars were analyzed. Autumn and spring sown field experiments in multiple environments were performed to determine shoot elongation before winter and vernalization requirement, respectively. In spring sown field experiments, genotypes with a low vernalization requirement were characterized by the occurrence of long bolting plants with flower buds. Large and significant genotypic variation was found for shoot length in the autumn sown and spring sown environment. Broad sense heritability was quite high for shoot length in the spring sown environment (h²?=?97%), whereas it was only of medium size for shoot length before winter (h²?=?62%). Although the correlation between shoot length before winter and shoot length in the spring sown environment was positive (Spearman’s rank r_S?=?0.48*), a number of genotypes with reduced shoot elongation before winter and low vernalization requirement were identified. Results indicate that genotypes with a reduced shoot elongation before winter independent of their vernalization requirement can be selected in breeding programs.     

The influence of a spring habit gene, Vrn-D1, on heading time in wheat

The adaptability of wheat cultivars to environmental conditions is known to be associated with a vernalization requirement, that is, spring/winter habit. To clarify the genetic effect of the spring habit gene, Vrn‐D1, on heading time in the field, recombinant inbred lines (RILs) with or without the Vrn‐D1 gene were produced from F₂ plants of the cross between ‘Nanbukomugi’ and ‘Nishikazekomugi’, non‐carrier and carrier cultivars of this gene, respectively. Using growth chambers with a controlled temperature and photoperiod, three components of heading time, i.e. vernalization requirement, photoperiodic sensitivity and narrow‐sense earliness (earliness per se), were evaluated in each RIL. RILs with the Vrn‐D1 gene (E lines) showed greatly reduced vernalization requirements and slightly shorter narrow‐sense earliness than RILs without Vrn‐D1 (L lines), although no difference in photoperiodic sensitivity was observed between the two groups. RILs were planted at four different sites in Japan and examined for their heading time in the field. E lines headed significantly earlier than L lines at all locations, indicating that the earliness of E lines is stable in various environmental conditions. These results indicated that spring habit caused by Vrn‐D1 gene, as well as narrow‐sense earliness, was responsible for heading time in the field.     

Marker-assisted characterization of frost tolerance in barley (Hordeum vulgare L.)

Five molecular markers associated to two frost tolerance QTLs ( Fr-H1 and Fr-H2 ) were tested both on nine Turkish accessions, classified by breeders as highly frost-tolerant, and on a previously described sample of 26 barleys, winter, facultative and spring. Accessions were characterized in terms of frost tolerance under both field conditions and artificial freezing test at −12°C. The Turkish lines resulted to be equal or superior to the most tolerant European genotypes tested, showing that they can be used to improve the frost tolerance of the EU barley germplasm. The marker Hv BM5A ( Vrn-H1 and Fr-H1 ) resulted to be the best predictor for assisted selection within this germplasm, because of its high correlation between allelic variation and phenotypic traits. Only Hv CBF4 of the three Hv CBF markers tested at Fr-H2 was associated to the trait, but at lower significance than HvBM5A . The PCR-based molecular marker of Vrn-H1 can thus be used in barley breeding not only for selection of facultative and winter types, but also for fast routine selection of frost tolerant genotypes.     

Measurement of response to vernalization in Australian wheats with winter habit

Summary Development in wheat is strongly controlled by sensitivity to vernalization and photoperiod, and to a lesser degree by non-vernalizing temperature and intrinsic earliness. A method to measure effect of vernalization in wheats with winter habit is described. Twenty seven wheats with winter habit and eight with spring/facultative habit were studied, comprising breeding lines and cultivars with maturities suited to south-central New South Wales. Effect of vernalization on the development of these wheats was quantified by integrating responses to vernalizing treatments of differing duration. Intrinsic earliness was measured as time for vernalized seedlings to grow to ear emergece in an 18h photoperiod with day/night temperature of 21/16°C, and response to photoperiod as the difference in time to ear emergence between 9 and 18h daylengths. Integrated response to vernalization is sensitive to both cumulative and thresh-hold responses and is applicable to wheats of all habit type. Integrated response to vernalization and intrinsic earliness were positively associated within wheats with winter habit. Wheats were largely of restricted origin, so that there were few allelic differences at Vrn loci to disrupt this association, which suggests intrinsic earliness may modify response to vernalization. Though integrated response to vernalization was measured with artificial treatments, it was strongly associated with ear emergence for wheats with winter habit when grown at a site in New South Wales.     

Winter Hardiness, Frost Resistance and Vernalization Requirement of European Winter Oilseed Rape (Brassica napus var. oleifera) Cultivars within the Last 20 Years

Cultivars of European winter oilseed rape cultivated in the second half of the 1970s and in the mid-1990s were screened for their winter hardiness, frost resistance and vernalization requirement. A strong correlation between winter hardiness and frost resistance in both groups of rape has been noticed. Among oilseed rapes cultivated in the late 1970s, low erucic acid and particularly double zero cultivars were less winter hard than high erucic acid cultivars. Double zero cultivars were characterized by lower frost resistance and lower vernalization requirement. A significant correlation between vernalization requirement and both frost resistance and field survival has also been shown. Frost resistance of the 1990s (double zero) cultivars was higher than that of double low cultivars from the late 1970s. Their vernalization requirement was still small and did not correlate with either frost resistance or winter hardiness. It was concluded that reduction in the content of glucosinolates in the 1970s involved decrease in winter hardiness and vernalization requirement of cultivars. During the following 20 years winter hardiness of double low cultivars has been improved, but vernalization requirements have not changed. As a result no correlation between winter hardiness and vernalization requirement in contemporary canola cultivars has been observed.     

内蒙古平原灌区“春麦冬播”种植效应及品种适应性

针对内蒙古春播小麦生育期短、干热风、高温逼熟等因素制约产量提高,且收获后光温资源极大浪费的现状,以及试种冬小麦发现的冬季冻害、春季干旱或“倒春寒”影响返青率及前茬限制等问题,本研究以“春麦冬播”种植模式为切入点,采用不同春化类型小麦品种,通过连续2年的田间试验,系统研究了不同小麦品种越冬出苗、叶片生理、根系性状及产量形成的差异,以期筛选适宜冬播的小麦品种。结果表明:供试的全部春性小麦品种及部分冬性品种可以以种子形式完成春化作用,第2年正常抽穗成熟。冬播条件下春季田间出苗率较春播小麦有所降低,但根系发达,对低温及干旱的适应性强。通过系统聚类筛选出适宜内蒙古平原灌区冬播的3个小麦品种,包括春性品种永良4号、冬性品种宁冬11号和半冬性品种河农7106,其共同特征为越冬出苗率高、抗逆性强、根系发达、产量表现较高,其中永良4号产量可达到与春播相同的水平。     

Effect of Completion of Vernalization on Generative Development of Winter Rape (Brassica napus L. var. oleifera) Plants

Germinating seeds and young plants of winter rape var. Górczañski were vernalized for 56–63 days under conditions of 9-hour day, at the temperature 2 and 5 °C and in continuous darkness at the temperature 2 °C. After vernalization the plants grew under conditions enabling to complete vernalization: in a glass-house at the temperature day/night 15/10 °C and in semi natural conditions of open vegetation hall in the period from June till August. After sub-optimal vernalization further growth of the plants at lowered temperature increased its effectiveness (completion of vernalization). Depending on the degree of the vernalization of the plants the completion of their vernalization was both obligatory, i.e. conditioning the acquisition of the ability of generative development, and facultative i.e. accelerating this development. It has been demonstrated that the population of plants of the examined variety is strongly differentiated not only with respect of vernalization requirements in the particular plants, but also what regards the effectiveness of vernalization completion. New observations have been made indicating that the mechanisms controlling the successive phases of generative development, i.e. phase of forming flower buds and the flowering phase are not identical which may be interpreted as indicating that the "flowering factor" is polymorphous.     

Influence of Warm Intervals on the Effects of Vernalization and the Composition of Phospholipid Fatty Acids in Seedlings of Winter Wheat

Excised embryos of winter wheat were submitted to a different number of vernalization (2 °C) and devernalization (20 °C) cycles of different lengths. In all treatments sum of cold and warm intervals was 50 and 10 days, respectively. The influence of different temperature conditions of seedling growth on the effectiveness of vernalization and correlations between effectiveness of vernalization and final content of phospholipid fatty acids were analyzed.
All indexes of generative development of plants (length of vegetative phase, % of generative plants, number of side shoots) showed the most effective was uninterrupted vernalization beginning immediately after excision of embryos. Increasing the number of 2 ° C/20 °C cycles rapidly depressed effectiveness of vernalization, which reached the minimum with the 8.3 days at 2 °C and 2 days at 20 °C cycle and then improved again as cycles became shorter and more numerous.
Correlations between indexes of generative plant growth and indexes describing composition of fatty acids in seedlings showed that from 50 % to 60 % of variability in the composition of phospholipid can be associated with changes in the degree of generative induction. A higher degree of generative induction was associated with a higher share of < 16, 16: 0 and 18:2 acids and a lower share of 18: 3 acid and also with a lower value of the 16: 0/< 16 ratio of phospholipids.
The relation between the generative induction of plants and the composition of phospholipid fatty acids may however be blurred when induction proceeds under conditions of alternate short spells of vernalization and devernalization temperatures.     

Physiological Effects of Winter Rape (Brassica napus var. oleifera) Prehardening to Frost. I. Frost Resistance and Photosynthesis during Cold Acclimation

The objective of the research was to define the changes in photosynthetic activity induced by prehardening and to determine their involvement in frost tolerance of winter rape.
Prehardening of winter rape, consisting of keeping the plants at + 12°C during the light periods from sprouting until the beginning of the 1st stage of cold hardening, contributed to increasing its effectiveness. After 42 days of hardening at + 2°C the resistance of the prehardened plants equalled that attained by winter rape in the most favourable seasons of vegetation in the field. Prehardening stimulated the efficiency of photosynthesis at chill temperatures (+ 2–5°C). Differences in photosynthetic efficiency, like those in frost resistance, increase with successive weeks of hardening. They also concern the leaves already developed at the hardening temperature. A prehardened photosynthetic apparatus is less susceptible to the progress of photoinactivation taking place when the seedlings are kept at + 2°C. It also demonstrated greater activity even during the first hour of hardening or in the newly expanding leaves, and also at higher temperatures, most probably because of the more efficient progress of the dark, processes. The described changes in the functioning of the photosynthetic apparatus induced by prehardening were thus qualitatively very similar to those observed during long-term growth at + 5°C. already described in the literature.     

Induction of Generative Development of Winter Rape (Brassica napus L. var. oleifera) in Relation to Vernalization Conditions and Age of Vernalized Plants

Germinating seeds and young winter rape plants were vernalized 56–63 days at 5 or 2°C under nine-hour days or in darkness. The highest percentage of generative plants and the most rapid flowering were obtained following the vernalization of young seedlings and germinating seed under conditions of nine-hour day, at 5°C. The least effective induction of generative development followed the vernalization at 2°C in continuous darkness. The vegetation period from the end of vernalization till the beginning of flowering was the shortest when four-week-old plants were vernalized under conditions of nine-hour day, yet the vegetation period from the beginning of germination to flowering was the shortest when seed germinating under conditions of nine-hour day were vernalized. The period was extending as older plants were being vernalized. Data indicating that the optimal temperature for vernalization of older plants is higher than for germinating seed and young seedlings were obtained.     

Relationship between Prehardening, Photosynthetic Activity at Cold Acclimation Temperatures and Frost Tolerance in Winter Rape (Brassica napus var. oleifera). The Consequences for the Reliability of Frost Resistance Estimation under Controlled Conditions

The effect of prehardening (early stage of growth at moderate low temperatures (+12°C) during the day) on the reliability of frost resistance estimation in a controlled environment has been studied on three winter oilseed rape cultivars differing markedly in their field survival rate (Leo, Górczański and Idol). It has been also examined the relationship between the photosynthetic activity during the first stage of cold acclimation and the level of frost resistance observed in investigated cultivars. Presented results demonstrated that prehardening, which increases to a significant degree the effectiveness of the cold acclimation process, also increases the differences in cold hardiness between cultivars, and limits the magnitude of experimental errors made during frost resistance estimation under controlled conditions. In all studied cultivars, prehardening increases significantly the photosynthetic activity during cold acclimation. On the other hand, both in the prehardened and in the non-prehardened plants, no relation has been found between either gas exchange rates or chlorophyll 'a' fluorescence characteristics at low temperatures and cultivar ability for acclimation. Neither the existing differences in photosynthetic activity, nor the degree of photosynthetic apparatus acclimation to cold, which occurs during prehardening, are the factors responsible for the frost resistance variation observed between studied cultivars.     

Multivariate analysis of traits determining adaptation in cultivated barley

Thirty‐nine barley varieties of different origin, representing different growth types, were included in a series of experiments aimed at analysing the variability in vernalization response, photoperiod sensitivity and earliness per se and establishing the types of ecoclimatic adaptability using multivariate analysis. In the case of spring barley varieties there was no correlation between any of the three traits. For winter barleys, a negative correlation was found between photoperiod sensitivity and vernalization response and between photoperiod sensitivity and earliness per se. Vernalization response and earliness per se showed a positive correlation. Among the winter barley varieties large variations were apparent in photoperiod sensitivity, vernalization response and earliness per se, which resulted in a tremendous variation in flowering patterns and frost tolerance. Between the spring barley varieties only wider variations in photoperiod sensitivity were detected. Based on the cluster analysis, the 39 varieties could be separated into seven groups. The spring barley varieties were placed in two groups, and the winter barleys in five groups representing different adaptational types. Among these five groups two represented the two opposing extreme combinations of photoperiod sensitivity and vernalization response. The combination of large photoperiod sensitivity and no vernalization response resulted in better frost tolerance than did the combination of photoperiod insensitivity and large vernalization response.     

Vegetative Performance of Tropical Highland Maize (Zea mays L.) in the Field

An attempt has been made to work out a simple and reliable method of fast frost resistance evaluation of winter oilseed rape using in vitro cultures. In winter rape cv. Górczański, there was investigated cold acclimation ability of hypocotyle sections from 5-days old seedlings and also of callus tissue formed on these sections after subsequent 4 weeks growth on induction medium. It has been found that hypocotyle sections are unable to cold-acclimate. Winter rape calli acclimated well and optimum conditions for acclimation is fortnight's growth at +2°C. Exposure to light during hardening was not necessary for acquiring maximum resistance. On five winter rape cultivars freezing tests were performed using the best cold acclimation conditions. The differences in resistance between hypocotyle sections did not match the differences in field survival or frost resistance of whole plants. As distinct from hypocotyle sections callus tissue appeared to be suitable for evaluation of frost resistance. However, to ensure the objectiveness of assessment in this method is not so easy. The testing temperature must be chosen carefully, because the results can be reliable only at sufficiently low temperature. For correct estimation of the frost resistance level, it is possible to use both the decrease of triphenyltetrazolium chloride reduction rate during freezing and the increase of callus dry weight during 14 days after freezing.
(Abbreviations: BAP — 6-Benzylaminopurine; 2,4-D — 2,4-dichlorophenoxyacetic acid; LT50 — temperature at which 50 % of the plants (or plant material) has been frost killed; MS(0.5;2) — Moorashige and Skoog Basic Medium with addition of 0.5 mg 2.4-D and 2 mg BAP; PPFD — photosynthetic photon flux density; TTC — 2,3,5 triphenyltetrazolium chloride)     

Evaluation of cold hardiness in two sets of near-isogenic lines of wheat (Triticum aestivum) with polymorphic vernalization alleles

In wheat, variation at the orthologus Vrn‐1 loci, located on each of the three genomes, A, B and D, is responsible for vernalization response. A dominant Vrn‐1a allele on any of the three wheat genomes results in spring habit and the presence of recessive Vrn‐1b alleles on all three genomes results in winter habit. Two sets of near‐isogenic lines (NILs) were evaluated for DNA polymorphisms at their Vrn‐A1, B1 and D1 loci and for cold hardiness. Two winter wheat cultivars, ‘Daws’ and ‘Wanser’ were used as recurrent parents and ‘Triple Dirk’ NILs were used as donor parents for orthologous Vrn‐1 alleles. The NILs were analysed using molecular markers specific for each allele. Only 26 of 32 ‘Daws’ NILs and 23 of 32 ‘Wanser’ NILs had a plant growth habit that corresponded to the marker genotype for the markers used. Freezing tests were conducted in growth chambers programmed to cool to ?21.5°C. Relative area under the death progress curve (AUDPC), with a maximum value of 100 was used as a measure of death due to freezing. The average relative AUDPC of the spring habit ‘Daws’Vrn‐A1a NILs was 86.15; significantly greater than the corresponding winter habit ‘Daws’Vrn‐A1b NILs (42.98). In contrast, all the ‘Daws’Vrn‐A1bVrn‐B1aVrn‐D1b and Vrn‐A1bVrn‐B1bVrn‐D1a NILs (spring habit) had relative AUDPC values equal to those of their ‘Daws’ sister genotypes with Vrn‐A1bVrn‐B1bVrn‐D1b NILs (winter habit). The average AUDPC of spring and winter habit ‘Wanser’ NILs differed at all three Vrn‐A1, Vrn‐B1 and Vrn‐D1 locus comparisons. We conclude that ‘Daws’ and ‘Wanser’ have different background genetic interactions with the Vrn‐1 loci influencing cold hardiness. The marker for Vrn‐A1 is diagnostic for growth habit and cold hardiness but there is no relationship between the Vrn‐B1 and Vrn‐D1 markers and the cold tolerance of the NILs used in this study.     

Observations of Effects of Partial Vernalization in Winter Rape Plants Grafted Onto Generative Stock

Winter rape plants vernalized under natural conditions were used as stock for grafting apical and subapical parts of rape seedlings vernalized at 5 °C in light during different periods ranging from 0 to 10 weeks. Acceleration of generative development in both kinds of grafts occurred already after 3 weeks of their vernalization, i.e. after cold treatment of insufficient length to induce flowering in plants developing independently. Effectiveness of vernalization — measured by acceleration of flowering in grafts was highest from 3rd to 5th week of cold treatment and then it declined. Processes occurring during an early stage of vernalization, though insufficient to allow independent generative development, become manifest in grafts made on vernalized stock. This allows investigations of very early stages of vernalization processes inaccessible to observation by other methods.     

Relationship between cold resistance,heading traits and ear primordia development of wheat cultivars

Summary For breeding early heading wheat cultivars with resistance to frost damage which are well adapted to dry areas of West Asia and North Africa, the relationships between winter hardiness, ear primordia development and heading traits, i.e. veernalization requirement, photoperiodic response and narrow-sense earliness, were assessed using a total of 30 genotypes of wheat (Triticum aestivum L.) grown in an experiment in Syria. The results of artificial freezing tests indicated that cultivars with good winter hardiness were to be found only in the winter wheat cultivars which required 50 or more days of vernalization treatment. These winter wheat cultivars did not initiate internode elongation without vernalization even at 95 days after planting. Thus their ear primordia were still underground and were protected from frost injury at this stage. Photoperiodic response and narrow-sense earliness were not associated with winter hardiness and earliness of internode elongation, but were related to the number of days to heading after planting. This indicated the possibility for breeding early heading cultivars with winter hardiness and tiller frost avoidance by combining high vernalization requirement, short narrow-sense earliness and neutral response to photoperiod.     

Relationship between Frost Tolerance and Cold-Induced Resistance of Spring Barley, Meadow Fescue and Winter Oilseed Rape to Fungal Pathogens

Plants exposed to one stress factor may become more tolerant to another. Cold is the most often documented factor inducing plant resistance to pathogens. The aim of this work was to investigate whether resistance of spring barley and meadow fescue to Bipolaris sorokiniana and resistance of winter oilseed rape to Phoma lingam induced at 5 °C for 2, 4 or 6 weeks are associated with frost tolerance, water potential and soluble carbohydrate content. Cold‐acclimated plants of each species showed increased resistance to the studied pathogens. Barley, fescue and rape plants demonstrated higher frost tolerance after hardening, but only in the case of fescue a correlation between resistance to frost and resistance to B. sorokiniana was found. A significant decrease in the water potential of leaf cells was observed in cold‐acclimated barley and fescue. In these two species, water potential greatly affected resistance to B. sorokiniana. However, only in barley did accumulation of fructose, glucose and sucrose correlate as well with changes in water potential as with cold‐induced resistance to the pathogen. In the case of hardened rape, no correlation between the studied parameters was found. The results obtained indicated that the temperature of 5 °C used during cold acclimation was not favourable for hardening of this plant species.     

Influence of vernalization and photoperiod to the vegetation period of wild species of oats (Avena spp.)

This paper presents the results of a six year field study of wild Avenaspecies and their response to vernalization and photoperiod. The accessions of twenty one wild and weedy species were tested under 12-hr and 18-hr daylength and cold temperatures (for 40 days at +2 ^°C) treatments and without it (as a control). The results demonstrate that for the majority of species evaluated, cold temperature requirements had a greater influence on heading date and the duration of the vegetative period than daylength. Genotypes with neutral, weak and strong reactions to all treatments were found and spring and winter types were selected. The results further demonstrated that daylength-insensitive forms occurred in the south Mediterranean region and adjacent southern territories.