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.     

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.     

Environmental factors affecting yield variability in spring and winter rapeseed genotypes cultivated in the southeastern Argentine Pampas

Rapeseed yields in Argentina are low (averaging 1400 kg/ha nationwide) with a high inter-annual variability. One of the limiting factors for improving yields is the lack of information on the adaptability of the cultivars, especially in the main rapeseed-producing area, the southeastern Pampas. The objectives of this study were to (i) quantify and analyze the yield variability of winter and spring rapeseed hybrids introduced in Argentina, (ii) identify the main environmental factors that affect the yields of the spring and winter genotypes in the southeastern Pampas, and (iii) model and validate rapeseed yields from environmental variables in the pre- and post-flowering periods. Principal component analysis (PCA) and linear regression methods were used to analyze 129 data points from 16 comparative yield trials in eight sites of southeastern Pampas. The rainfed crops were sown between April and July and from 2007 to 2009. Pre- and post-flowering phases were recorded in each experiment; temperature, frost occurrences, rainfall and radiation were measured during each phase. Yield variability (600–3700 kg ha⁻¹) was slightly lower in spring than in winter genotypes (CV 0.25 versus 0.38). Sixty percent of the winter genotype variability was explained by the first axis which was associated to the pre- and post-flowering durations, while 25% of the variability was explained by the second axis associated to yield. Almost 50% of the spring genotype variability was explained by the first axis associated to pre-flowering and total durations, while 27% of the variability was explained by the second axis in which post-flowering duration was associated to yield. Winter genotypes evidenced vernalization requirements that were either partially or not fulfilled, so, the longer the photoperiod, the longer the pre-flowering phase duration. In the critical period of 30 d post-flowering, yield was not associated to the photothermal quotient. In winter genotypes, yield was associated to a linear model which included rainfall during the crop cycle, radiation and pre-flowering temperatures (R² = 0.50). The model was adequately validated with independent data (n = 116) from official trials. For spring genotypes, only the frost occurrences during the critical period were relevant (R² = 0.26) and placing the flowering time after October decreased the risk of late frost damage. Water use efficiency (WUE) values ranged from 1.6 to 6.7 kg ha⁻¹ per mm of rain without a clear trend between spring and winter genotypes for this trait. In conclusion, winter genotypes did not necessarily yield more than the spring materials. In addition, rainfall during the crop cycle and frost occurrences during flowering were the main limiting factors of the winter and spring genotype yields, respectively, in the southeastern Pampas.     

Cold acclimation of winter and spring peas: carbon partitioning as affected by light intensity

Like most plants, pea (Pisum sativum L.) becomes tolerant to frost if it is first exposed to low non-freezing temperatures, a process known as cold acclimation. Cold acclimation is a complex process involving many physiological and metabolic changes. Two spring dry peas, two winter dry peas and one winter forage line were exposed to cold temperature in a controlled environment in two experiments, one using low light intensity and the other regular light intensity. Plants were harvested throughout the experiment and dry matter accumulation, water content, soluble and insoluble sugar concentrations were determined from shoot and root samples. Cold acclimation did not occur when temperatures were low if light intensity was low, even in winter peas. In contrast, with regular light intensity, the winter peas acquired more freezing tolerance than spring peas and a close relationship was found between the soluble sugar concentration of leaves just before the frost and the degree of freezing tolerance obtained by the different genotypes. Relationships between freezing tolerance and carbon partitioning between shoot and roots are discussed.     

Relevance of Osmotic and Frost Protecting Compounds for the Winter Hardiness of Autumn Sown Sugar Beet

The cultivation of autumn sown sugar beet (winter beet) is supposed to result in a marked yield increase compared with spring sown sugar beet. Although the importance of the growth stage reached before winter for the survival of autumn sown sugar beet has already been shown, it is not clear to which extent osmotic and potentially frost protecting compounds may contribute to winter hardiness. The study thus aimed to analyse the acclimatization process of sugar beet to low temperatures and to identify compounds which are important for survival of frost. Field trials with autumn sown sugar beet were conducted at eleven environments in Germany from 2009/10 to 2012/13, which were accompanied by greenhouse experiments with controlled temperature regimes. In the field trials, the survival rates after winter varied from 0 % to 99 %, but only in four environments differences between the five genotypes occurred. During acclimatization, betaine, glutamine, proline and raffinose were markedly accumulated and osmolality was enhanced. In particular betaine, amino acids and osmolality showed a positive correlation to the survival rate and were thus identified as potentially frost protecting substances for sugar beet. In contrast, raffinose and proline seem to act rather as stress indicators as they were negatively related to survival. Possible frost protecting substances were identified which can be used in breeding to improve the winter hardiness of sugar beet.     

Nectar secretion in winter oilseed rape, Brassica napus— quantitative and qualitative variability among 71 genotypes

The genotypic variability in nectar secretion among 71 genotypes of winter oilseed rapes was tested for floral nectar volume, sugar composition and concentration. Differences were found between seed quality genotypes: double low [99] oilseed rape varieties tended to secrete much more nectar than single low [0 +] and double high [++] varieties. Male-sterile lines (Ogura CMS) secreted one-half to one-third the amount of their isogenic male-fertile counterparts. Restored lines behaved as conventional rape varieties. On average, amounts of nectar were 2 μl/flower and ranged from 0.7 to 6 μl/flower. Among the genotypes under test, the male-sterile lines were not the least productive. The analysis of (Samourai) winter oilseed rape showed that total sugar concentrations in nectar were highest at the beginning of the flowering period (30g/100 ml) and lowest towards the end (10g/100 ml). At a given date, total sugar contents in nectar of [0 +] varieties were significantly higher than those of [++] varieties and were due to higher fructose contents. Differences between genotypes within the same type also occurred, depending on the day of sampling. Oilseed rape nectar was confirmed to be predominantly composed of hexose (glucose and fructose). From the results of these investigations, it is concluded that the opportunity exists to select oilseed rape genotypes, including male-sterile lines, that secrete sufficient amounts of nectar to attract honey-bees to ensure pollination of male-sterile lines for hybrid seed production.     

春化、光周期和矮秆基因在不同国家小麦品种中的分布及其效应

为促进国外种质资源在我国的有效利用,将14个国家的100份代表性小麦品种在国内的8个代表性地点种植,调查抽穗期、成熟期和株高,并以4个春化基因(Vrn-A1、Vrn-B1、Vrn-D1和Vrn-B3)、1个光周期基因(Ppd-D1a)及2个矮秆基因(Rht-B1b和Rht-D1b)的分子标记检测所有品种的基因型。春化基因Vrn-A1a、Vrn-B1、Vrn-D1和vrn-A1+vrn-B1+ vrn-D1的分布频率分别为8.0%、21.0%、21.0%和64.0%;显性等位变异Vrn-A1a、Vrn-B1和Vrn-D1主要存在于来自中国春麦区及意大利、印度、加拿大、墨西哥和澳大利亚的品种中,这些品种一般为春性类型;春化位点均为隐性等位变异或vrn-A1+vrn-D1+Vrn-B1的品种主要分布在中国冬麦区、美国冬麦区、俄罗斯冬麦区,以及英国、法国、德国、罗马尼亚、土耳其和匈牙利,这些地区的小麦均为冬性类型。秋播时,供试品种均能正常抽穗,且携带春化显性变异的材料较隐性类型抽穗早,显性等位变异表现加性效应,4个春化位点均为隐性变异的一些欧美材料因抽穗太晚在杨凌和成都不能正常成熟;而春播时,显性等位变异基因型抽穗的频率高,隐性等位变异基因型基本不能抽穗。光周期不敏感基因Ppd-D1a的分布频率为68.0%,主要分布在中国、法国、罗马尼亚、俄罗斯、墨西哥、澳大利亚和印度,而光周期敏感等位变异Ppd-D1b主要分布在英国、德国、匈牙利和加拿大等中高纬度地区;携带Ppd-D1a的品种较携带Ppd-D1b的品种抽穗早,大多数Ppd-D1a品种在长日照和短日照条件下均能成熟,大部分Ppd-D1b品种在短日照条件下不能成熟。Rht-B1b和Rht-D1b基因的分布频率分别为43.0%和35.0%,其中Rht-B1b主要分布于美国、罗马尼亚、土耳其、意大利、墨西哥和澳大利亚,Rht-D1b主要分布于中国、德国、英国、意大利和印度。一般来说,一个国家的品种携带Rht-B1b或Rht-D1b之一,而这2个基因在高纬度地区分布频率较低。Rht-B1b、Rht-D1b和Ppd-D1a的降秆作用均达显著水平,Rht-B1b和Rht-D1b的加性效应突出。     

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.     

Genetic relationships among resynthesized,semi-resynthesized and natural <Emphasis Type="Italic">Brassica napus</Emphasis> L. genotypes

The allopolyploidization event that created cultivated oilseed rape Brassica napus L, followed by intense breeding, reduced its genetic diversity. Resynthesized (RS) B. napus L. obtained by interspecific hybridization between genotypes of B. rapa L. and B. oleracea L. can be a valuable source for broadening genetic diversity in cultivated oilseed rape. In this study, we determined the extent of DNA polymorphism among natural accessions of oilseed rape, resynthesized B. napus, their parental species and double-low quality semi-RS lines carrying the Rfo gene. Using 10 selected primer combinations, 522 polymorphic AFLP markers were scored in the complete set of 100 Brassica sp. To detect relationships between these genotypes, a cluster analysis was performed using the Jaccard’s distance. Resynthesized allopolyploids clustered directly between their diploid parents. Cultivated accessions of oilseed rape created a compact group away from resynthesized allopolyploids as well as semi-RS lines. The natural oilseed rape group, which consists of 49 cultivars and breeding lines of oilseed rape, is characterized by lower genetic diversity than the group of 33 accessions of resynthesized oilseed rape, and the analysis showed that the double-low quality semi-RS lines represent a specific genetic variation of B. napus. The de novo resynthesized B. napus lines and the semi-RS lines of double-low quality generated from them, provide a significant opportunity for enrichment the gene pool of oilseed rape.     

Comparison of Vernalization Requirements and Frost Resistance of Winter Rape Lines Derived from Double Haploids

Vernalization requirements and cold resistance of 13 lines of winter rape derived from doubled haploids obtained by androgenesis were investigated. The degree of vernalization requirements was examined in two parallel experiments. In the first experiment seedlings aged 2 weeks were vernalized during 63 and 35 days under controlled conditions, at 5 °C. In the second experiment the natural conditions of vernalization were differentiated by sowing the plants at four different dates in spring: March 15th, April 15th, May 15th, and at the latest date excluding vernalization, June 5th. The lines examined revealed differentiation of vernalization requirements that were similar in both experiments; all the lines required a period of exposure to cold before flowering. Cold resistance of lines was estimated in two successive series at −15 °C and −17 °C. Before testing the plants were kept in natural field conditions from the beginning of September until the middle of November. Testing of cold resistance was preceded by hardening under controlled conditions. Considerable differences in cold resistance was found in the forms investigated.
The results obtained do not show any relation between frost resistance and the degree of vernalization requirements, as the line characterized by the strongest winter habit of growth showed low cold resistance, whereas the lines which were closer to spring growth habit showed the highest level of cold resistance; the lines with the least vernalization requirements revealed the highest level of cold resistance. This conclusion can be confirmed by the significance of the correlation coefficients between the various indices defining the frost resistance and the indices of vernalization requirements.     

Estimating winter survival of winter wheat by simulations of plant frost tolerance

Based on soil temperature, snow depth and the grown cultivar's maximum attainable level of frost tolerance (LT_50c), the FROSTOL model simulates development of frost tolerance (LT₅₀) and winter damage, thereby enabling risk calculations for winter wheat survival. To explore the accuracy of this model, four winter wheat cultivars were sown in a field experiment in Uppsala, Sweden in 2013 and 2014. The LT₅₀ was determined by tests of frost tolerance in November, and the cultivars’ LT_50c was estimated. Further, recorded winter survival from 20 winter wheat field variety trials in Sweden and Norway was collected from two winter seasons with substantial winter damages. FROSTOL simulations were run for selected cultivars at each location. According to percentage of winter damage, the cultivar survival was classified as “survived,” “intermediate” or “killed.” Mean correspondence between recorded and simulated class of winter survival was 75% and 37% for the locations in Sweden and Norway, respectively. Stress factors that were not accounted for in FROSTOL might explain the poorer accuracy at the Norwegian locations. The accuracy was poorest for cultivars with intermediate LT_50c levels. When low temperature was the main cause of damage, as at the Swedish locations, the model accuracy was satisfying.     

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.     

Evaluation of a semi‐controlled test as a selection tool for frost tolerance in durum wheat (Triticum durum)

Most durum wheat (Triticum durum) varieties possess only low winter hardiness due to their frost susceptibility. In North America and Central Europe, durum wheat is therefore typically sown in spring to circumvent the local winter conditions. However, the yield potential of durum in these regions could be much better exploited if durum varieties with increased frost tolerance were available, which could be sown in autumn. A factor limiting breeding for increased frost tolerance is the variation in the occurrence of frost stress across years. The ‘Weihenstephaner Auswinterungsanlage’ is a semi‐controlled test that exposes the plants to all weather conditions. Snow coverage of the plants, serving as frost protection, is prevented by the movable glass lid of the semi‐controlled test. In this study, different scorings for frost tolerance based on this semi‐controlled test were evaluated and compared with frost tolerance data in the field. Our results illustrate the potential of the ‘Weihenstephaner Auswinterungsanlage’ as an indirect selection tool for frost tolerance in durum breeding programmes, especially when regular frost tolerance data from the field are not available.     

Environmental variability and heritability of high oleic acid content in winter oilseed rape

Winter oilseed rape, with high oleic (HO) acid contents (C18:1) is of interest for nutritional as well as for industrial purposes. HO mutants have been described, but only limited information is available on any environmental influence on the expression of oleic acid content in these mutants. Therefore, a population of 60 doubled‐haploid (DH) lines segregating for oleic acid content (56‐75% C18:1) was grown in two years at three locations in northern Germany. Analysis of variance revealed a high heritability for oleic acid content of h²= 0.99. Subdividing the DH population into a high (> 64% C18:1) and a low (< 64% C18:1) oleic acid class showed high heritabilities (h²= 0.94) for C18:1 contents within both the high and low oleic acid types. The oleic acid contents in HO types of winter oilseed rape were environmentally stable at the three locations tested.     

Mechanical wounding under field conditions: A potential tool to increase the allelopathic inhibitory effect of cover crops on weeds?

To increase the inhibitory effect of soil-incorporated cover crop residues on germination and early growth of weeds, the allelochemical content of the cover crop at the time of soil incorporation should be maximal. We investigated whether mechanical damaging in spring induced the production of allelochemicals in late-summer sown lucerne, winter rye and winter oilseed rape. Allelopathic activity and biomass of intact cover crop plants were determined throughout spring, and mechanically damaged plants were monitored till 14 days after wounding. Allelopathic activity was determined directly by lettuce seedling bioassays (lucerne and winter rye) or indirectly by glucosinolate quantification (winter oilseed rape). During spring, the allelopathic activity per unit biomass of intact plants showed a gradual decline for winter rye and lucerne, and a steep decline at the onset of flowering for winter oilseed rape. All cover crop species attained the highest allelopathic activity per unit area at the end of the sampling period as the increase in biomass surpassed the decline in allelopathic activity per unit biomass. Although mechanical wounding enhanced the allelopathic activity per unit biomass of all three species, the effect was only minor and often just sufficient to compensate for the loss in biomass resulting from wounding. This study therefore indicates that the best option for maximizing the inhibitory effect is to incorporate residues of intact cover crops as late as possible.     

Superior performance of two homozygous diploid lines from naturally occurring polyhaploids in oilseed rape (Brassica napus)

Summary Homozygous diploids in oilseed rape were produced by pipetting drops of 0.1 per cent colchicine into the leaf axils of rooted cuttings from naturally occurring polyhaploids after removing the waxy covering with a scalpel. Trial results from spring and winter rape showed that occasional homozygous diploid lines yielded consistently more oil per ha than the parental varieties. Prospects for breeding oilseed rape as a self-fertilised crop are discussed.     

Using Hemispherical Radiation Measurements to Predict Weight-Related Growth Traits in Oilseed Rape (Brassica napus L.) and Barley (Hordeum vulgare L.) Canopies

Methods for determining growth traits in the field are mostly work‐intensive and/or often erroneous. Further development of multi‐temporal techniques of growth analyses provided by fast and non‐destructive tools for monitoring canopy properties may result in a substantial gain for practical use. Among them, the LAI‐2000 Canopy Analyzer can be used to determine the canopy area index (CAI) resulting from radiation measurements. In plant breeding, single‐date measurements were usually made across a wide number of genoptypes. In contrast, multi‐temporal information on canopy status is needed in agronomy. In our study, data of the CAI based on hemispherical radiation measurements with the LAI‐2000 were used to estimate developmental courses of weight‐related growth traits. For this purpose, seasonal courses of shoot fresh matter, shoot dry matter, shoot N and water content and CAI of winter oilseed rape (Brassica napus L.) and spring barley (Hordeum vulgare L.) were investigated simultaneously in field experiments from 2002 to 2006 in northern Germany with and without nitrogen (N) fertilization. Courses of 2003 and 2004 were used to calculate relationships between CAI and growth traits. Results show that each of the weight‐related growth trait is related to the CAI. In this mechanistic approach relationships were found gathered across 2 years, two N‐treatments and several growth stages being unaffected by N‐fertilization, cultivar and experimental year. These relationships were verified using independent data sets of the years 2005 (winter oilseed rape and spring barley) and 2006 (winter oilseed rape). The results of the current study show that the use of LAI‐2000 and its rapid and non‐destructive determination of weight‐related growth traits over the entire growth period will substantially improve the determination of weight‐related growth traits in agriculture.     

Genetic variation for saturated fatty acid content in a collection of European winter oilseed rape material (Brassica napus)

Oil quality is an important issue in oilseed rape breeding programmes. Recently, the seed oil content of saturated fatty acids has received substantial interest, because in a number of industrialized countries dietary recommendations not only limit total fat intake but also intake of saturated fatty acids. The aim of the present study was to analyse the genetic variation for saturated fatty acid content in two sets of modern winter oilseed rape cultivars ( Brassica napus L.) tested in field experiments under typical German growing conditions. The results showed highly significant genetic differences among the cultivars for total saturated fatty acid content, which ranged from 6.8% to 8.1%, with a mean of 7.4%. For both sets medium to high genotypic heritabilities were found for most fatty acids and for oil and protein content. Close negative correlations between palmitic acid, the predominant saturated fatty acid, and oleic acid as well as oil content were found.     

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.     

Energy balance of winter oilseed rape (Brassica napus L.) cropping as related to nitrogen supply and preceding crop

Data from a field experiment (1995–2000) conducted on a fertile sandy loess in the Hercynian dry region of central Germany were used to determine the energy efficiency of winter oilseed rape (Brassica napus L.) as affected by previous crop and nitrogen (N) fertilization. Depending on the previous crop, winter oilseed rate was cultivated in two different crop rotations: (1) winter barley (Hordeum vulgare L.)–winter oilseed rape–winter wheat (Triticum aestivum L.), and (2) pea (Pisum sativum L.)–winter oilseed rape–winter wheat. Fertilizer was applied to winter oilseed rape as either calcium ammonium nitrate (CAN) or cattle manure slurry. The N rates applied to winter oilseed rape corresponded to 0, 80, 160 and 240 kg N ha⁻¹ a⁻¹.Results revealed that different N management strategies influenced the energy balance of winter oilseed rape. Averaged across years, the input of energy to winter oilseed rape was highly variable ranging from 7.42 to 16.1 GJ ha⁻¹. Lowest energy input occurred when unfertilized winter oilseed rape followed winter barley, while the highest value was obtained when winter oilseed rape received 240 kg N ha⁻¹ organic fertilization and followed winter barley. The lowest energy output (174 GJ ha⁻¹), energy from seed and straw of winter oilseed rape, was observed when winter oilseed rape receiving 80 kg N ha⁻¹ as organic fertilizer followed winter barley. The energy output increased to 262 GJ ha⁻¹ for winter oilseed rape receiving 240 kg N ha⁻¹ as mineral fertilizer followed pea. The energy efficiency was determined using the parameters energy gain (net energy output), energy intensity (energy input per unit grain equivalent GE; term GE is used to express the contribution that crops make to the nutrition of monogastric beings), and output/input ratio. The most favourable N rate for maximizing energy gain (250 GJ ha⁻¹) was 240 kg N ha⁻¹, while that needed for minimum energy intensity (91.3 MJ GE⁻¹) was 80 kg N ha⁻¹ and for maximum output/input ratio (29.8) was 0 kg N ha⁻¹.