Outcrossing frequencies and distribution of transgenic oilseed rape (Brassica napus L.) in the nearest neighbourhood

The outcrossing of transgenic oilseed rape in the neighbourhood is of major concern with regard to the actual EU labelling threshold of 0.9% for transgenic contamination in food and feed and the regulations for the co-existence of cultivation of genetically modified crops, conventional and organic farming. In a two-year field trial, the outcrossing frequencies and distribution from plots with different ratios of transgenic plants (100%, 1.0% and 0.1%) containing the pat-gene for resistance towards the broad-range herbicide glufosinate-ammonium were determined in surrounding acceptor plots within a distance of 3–11 m. Randomly distributed outcrossing with isolated pollination events became apparent, and an average gene flow of 0.28%, 0.01% and 0.0065% was detected for 100%, 1.0% and 0.1% transgenic donor plots, respectively. Significant effects on the distribution of outcrossing were found for distance, but not for the prevailing wind direction. The random distribution in combination with the behaviour of honey-bees and bumble-bees gives strong evidence that insects play an important role for short distance gene dispersal. A curve fit assuming an exponential decline was performed with the experimental outcrossing data as a function of distance and was applied to the actual EU labelling threshold. The contamination limit of 0.9% in food and feed could be kept without cultivation distances to the transgenic source. The impact of effective detection limits of analytical methods on the establishment of specific rules for the co-existence is discussed.     

Occasional loss of expression of phosphinothricin tolerance in sexual offspring of transgenic oilseed rape (Brassica napus L.)

The commercial and economic value of genetically modified crops is determined by a predictable, consistent and stable transmission and expression of the transgenes in successive generations. No gene inactivation is expected after selfings or crosses with non-transformed plants of homozygous transgenic oilseed rape plants if the expression of the transgene in homozygous or hemizygous nature in such plants is stable. The segregation ratios of phosphinothricin (PPT) tolerance in successive generations of selfings and mutual crosses of a few independent transgenic PPT-tolerant oilseed rape plants indicated a dominant, monogenic inheritance. In within-variety and between-variety crosses no transgene inactivation was observed. However, after selfings and backcrosses with non-transgenic oilseed rape infrequent loss of the expression of the PPT tolerance transgene was observed independent from its homozygous or hemizygous nature. Molecular analysis of PPT-susceptible plants showed that the loss of expression was due to gene inactivation and not to the absence of the transgene. Methylation and co-suppression are mechanisms that might cause reduced or even loss of expression of the transgene in later generations. The implications of this observation for seed multiplication of varieties and breeding activities with transgenic oilseed rape are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Gene flow from transgenic wheat and barley under field conditions

In this study the frequency and distance of gene flow from transgenic wheat (Triticum aestivum) and barley (Hordeum vulgare) to non-transgenic wheat and barley crops was investigated under local field conditions. Trials were conducted in the Australian Capital Territory (ACT) and in South Australia (SA). Gene flow from transgenic wheat was confirmed at frequencies of 0.012% and 0.0037% in the ACT and SA, respectively. In both trials gene flow occurred over distances of less than 12 m. Gene flow was also detected from transgenic barley at a frequency of 0.005%, over a distance of less than 12 m. The results show that under Australian field conditions, gene flow occurs at extremely low frequencies and over very short distances. Physical separation of transgenic and non-transgenic cereal crops by greater than 12 m should ensure that contamination of adjacent non-transgenic cereal crops remains less than 0.02%, well below the level permitted under Australian regulations.     

Assessing the risks of wind pollination from fields of genetically modified Brassica napus ssp. oleifera

Summary Intensive research over the past 10 years has produced many genetically-mofified lines of oilseed rape with market potential. Assessment of these lines in statutory trials prior to their release as cultivars is necessary, owing to concern over the likelihood of transgene escape from such crops. Here, we examine the movement of airborne pollen grains from oilseed rape fields and assess their capacity for long-range geneflow.Pollen dispersal from isolated rape fields was monitored over two seasons and related to the distribution of fields and feral (domesticated plants growing outside cultivations) populations of the crop in Tayside and North East Fife regions of Scotland. Airborne pollen density declined with distance and at 360 m was 10% of that at the field margin. Pollen counts of 0–22 pollen grains m³ were observed 1.5 km from source fields and apparently were sufficient in number to allow seed set on emasculated bait plants. Oilseed rape pollen has greater capacity for long-range dispersal than had been suggested by small-scale field trials. Mean separation of oilseed rape fields in the survey area was 410 m and the mean distance from feral populations to commercial fields was 700 m. Sixty percent of feral populations with more than 10 plants occurred downwind and within 2 km of an oilseed rape field. Provided that the flowering biology of genetically-modified oilseed rape does not differ from the conventional crop, these data suggest that transgene movement to non genetically-modified fields or feral populations is likely following commercial release.     

Natural outcrossing in common buckwheat

Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess the extent of natural outcrossing was undertaken for two years at Morden and Portage la Prairie, Manitoba using the semi-dwarf character, which is due to a homozygous genotype with regard to a single recessive gene, as a marker. The semi-dwarf genotype was grown in 100 m rows running in four directions at 90 ° from a central 36 m² plot of a normal, tall variety. At maturity, seed samples were taken from the semi-dwarf population at designated intervals. At least 200 F₁ seeds from each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwarf plants were immediately next to the normal plants and then the proportion decreased with increasing distance. Although outcrossing occurred throughout the distance tested, there were no significant differences from 12 m onward from the pollen source. Lack of directional influence in outcrossing and a sharp reduction in the proportion of tall plants within a 3 m distance from the pollen source suggested that wind was not a major factor in dispersing the buckwheat pollen over long distances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend the minimum isolation distance required to meet certain standards for buckwheat seed production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Deep Placement of Slow-release Fertilizer (Lime Nitrogen) Applied at Different Rates on Growth, N2 Fixation and Yield of Soya Bean (Glycine max [L.] Merr.)

A new fertilization method with deep placement of slow‐release N fertilizers, such as coated urea and lime nitrogen (LN) (calcium cyanamide) at 20 cm depth was found to promote soy bean seed yield. In the present study, the effect of deep placement of LN was investigated on different parameters such as growth, N accumulation, N₂ fixation activity and yield of soy bean by applying LN at different rates in the rotated paddy field of Niigata, Japan. In addition to the basal fertilizer, ammonium sulphate (16 kg N ha^?1), deep placement of LN was conducted by applying various amounts such as 50 kg N ha^?1 (A50), 100 kg N ha^?1 (A100) and 200 kg N ha^?1 (A200) at 20 cm depth in separate plots. A ¹⁵N‐labelled LN fertilizer was also employed for each of the above treatments to calculate N utilization from LN in separate plots. Soya bean plant growth and N₂ fixation activity were periodically analysed. Both plant growth and N accumulation were found to increase with LN treatment compared with control plants. An increase in N₂ fixation activity was found in the A100 plots. The total seed yield was the highest in the deep placement of LN with A100 (73 g per plant) compared with other treatments. The visual quality of harvested seeds also showed that A100 enhanced the quality of seeds compared with other treatments. Thus, it is suggested that N fertilization management with particular reference to optimum amount of fertilizers is important for maximum growth, N₂ fixation and enhancement of seed yield of soy bean.     

Emergence and performance of volunteer oilseed rape (Brassica napus) in different crops

Volunteer oilseed rape (OSR, Brassica napus L.) causes various agronomic problems in crop rotations and can contribute to gene dispersal by pollen and by seed admixture. A 4-year field experiment (2008–2011) was set up in south-west Germany to investigate the performance of volunteers derived from two OSR cultivars with different levels of seed dormancy. Volunteers of a high-dormancy (HD) and a low-dormancy (LD) OSR cultivar were deliberately generated by spreading 10,000 seeds m⁻² on a field in August 2008 and 2009. Four different crops were grown on that area in the first year following the seed rain: winter wheat (Triticum aestivum L.), winter turnip rape (Brassica rapa L.), spring barley (Hordeum vulgare L.) and field pea (Pisum sativum L.). In the second year, maize (Zea mays L.) was sown uniformly across all plots. Numbers of OSR seedlings emerging in early autumn shortly after seed rain were not connected with the size of the soil seed bank in early spring of the following year. The seeds of the HD-cultivar formed a much greater soil seed bank (up to 14% of the initially spread seed number) compared with the LD-cultivar (up to 1.3%) in the soil layer of 0 to 30 cm in early spring 2009 and 2010). Across all crops, considerably more volunteers of the HD-cultivar than of the LD-cultivar were present at several survey dates in the first year following seed rain. The highest number of volunteers originated from the HD-cultivar with up to 11 volunteers m⁻² in winter turnip rape compared with a maximum of 0.48 plants m⁻² in the other crops. Cultivar-specific differences in volunteer density were observed as well in maize two years after OSR seed rain. Flowering and seed setting volunteers were only present in 2010 and the flowering time was crucially overlapping with that of sown winter OSR. The reproductive ability (seeds produced m⁻²) of the LD-volunteers was five times lower in winter turnip rape than of the HD-volunteer; a similar trend was observed for the OSR volunteers in the other host crops.Strategies to definitely reduce unwanted effects of OSR volunteers, such as gene flow, should include the use of LD-cultivars with a low potential to form a soil seed bank, particularly if selective herbicides are not available, for instance in broad-leaved crops, or if the volunteers are herbicide-tolerant.     

Genetic variation for secondary seed dormancy and seed longevity in a set of black‐seeded European winter oilseed rape cultivars

Secondary seed dormancy in oilseed rape is a phenomenon that allows seeds to survive in the soil for many years without germination. Following soil cultivation, dormant seeds may germinate in subsequent years, and they are the main reason for the occurrence of volunteer oilseed rape plants in successive crops. Inheritance of secondary dormancy may be related to seed longevity (SL) in the soil. Genetic reduction in secondary dormancy and SL could provide a mean to reduce the frequency of volunteer plants and especially the dispersal of transgenic oilseed rape. The aim of the present study was to analyse secondary dormancy, germination rate and SL of 28 black‐seeded winter oilseed rape cultivars using in vitro laboratory tests. The material was tested in field experiments at six different locations in Germany in 2008/2009. Significant effects of the genotype and the location on all traits were found. Heritability was high for secondary dormancy (0.97) and moderate for germination rate (0.70) and SL (0.71). Results indicate that a selection for low secondary dormancy would be effective.     

转BADH基因玉米植株的获得及其耐盐性分析

采用超声波辅助花粉介导植物转基因方法, 将甜菜碱醛脱氢酶(BADH)基因导入玉米自交系郑58, 获得了耐盐性强的转基因玉米植株。经卡那霉素抗性初筛、PCR扩增、Southern blot杂交分析, 证明BADH基因已导入转化植株并整合到其基因组中。用不同浓度的NaCl溶液对T₂代转基因玉米植株与对照进行盐胁迫处理, 结果表明, 转BADH基因玉米植株表现出一定的抗逆性, 生长状况明显优于对照; 根据非转化苗对NaCl的反应以及生长状况, 确定250 mmol L^-1 NaCl溶液为玉米幼苗耐盐性筛选的适宜浓度; 依据此临界浓度下形态指标和生理生化指标的测定结果, 与对照相比, 转基因植株的株高提高10.94%~25.7%, 鲜重增加8.62%~18.2%, 干重增加9%~18.18%, 相对电导率降低37.21%~58.14%, 叶绿素含量增加15.89%~90.65%, 超氧化物歧化酶(SOD)活性提高64.92%~148.29%, 丙二醛(MDA)含量减少26.97%~48.05%。综上所述, 转入甜菜碱醛脱氢酶(BADH)基因提高了玉米的耐盐性。这是首例将BADH基因导入优良玉米自交系郑58的报道。超声波辅助花粉介导法是一种经济、高效、实用和无基因型依赖性的植物基因转化方法。     

Recommended isolation distances for the field multiplication of diploid tuber-bearing Solanum species

The sexual propagation of genebank accessions by hand pollination in the greenhouse is a very expensive and time-consuming routine task. The self-incompatibility of most diploid potato species allows their multiplication in isolated field plots, which is coupled with the advantage of the presence of natural pollinators and maintaining a high level of heterozygosity. The aim of this study was to determine the isolation distance required for minimizing pollen flow between neighbouring multiplication plots. The Solanum phureja clone IVP48 was used as the pollen donor since it possesses a dominant seed marker (‘embryo spot’). The centrally located pollen donor was surrounded by S. phureja recipient plots at distances of 10,20,40, and 80 m, respectively. The average pollen contamination ranged from 0.2% in the plots 80 m from the pollen donor to 5.1% in those 10 m away. In this study, procedures are suggested which will help to reduce cross-pollination between accessions.     

长江流域直播冬油菜氮磷钾硼肥施用效果

冬油菜直播种植的推广应用对提高我国油菜籽总产量和保障食用油安全有重要意义。2009-2010年度在长江流域6个冬油菜主产省布置36个大田试验,研究当前生产条件下我国直播冬油菜的氮磷钾硼肥施用效果和肥料利用率,比较农民习惯施肥与推荐施肥的差异,并与移栽油菜施肥效果进行对比,以探讨直播冬油菜的施肥管理措施。结果显示,在推荐施肥量和施肥方法条件下,氮磷钾硼肥配合施用(NPKB)处理直播冬油菜的油菜籽产量和产值平均分别为2001 kghm^–2和8205元hm^–2,显著高于农民习惯施肥(FFP)处理,施用效果为N > P > B > K。NPKB配合施用显著促进直播冬油菜的养分吸收,N、P、K累积量分别为104.2、20.4和160.2 kg hm^–2。NPKB配施条件下,直播冬油菜的氮、磷、钾肥表观利用率平均分别为35.8%、22.3%和45.9%,明显高于农民习惯施肥的20.8%、7.2%和28.0%。说明合理施肥对直播冬油菜生产有重要作用,现阶段应积极推行氮磷钾硼肥配施技术,并根据生长发育特点和养分吸收规律调整肥料的施用时期和比例。     

蛋白激发子Hrip1基因在拟南芥中表达可提高植株的耐盐耐旱能力

Hrip1是从极细链格孢(Alternaria tenuissima)代谢物中分离的一种蛋白激发子。将蛋白激发子基因Hrip1转化到拟南芥,对5个T₁代转基因拟南芥株系进行分子检测, 证明Hrip1基因能够在拟南芥中转录和表达。转基因植株对盐和干旱胁迫的抗性显著增强, 75 mmol L⁻¹ NaCl和50 mmol L⁻¹甘露醇渗透胁迫2 d, 转基因植株种子平均相对发芽率为32.1%和77.9%, 分别比野生型的增加3.72倍和5.61倍; 150 mmol L⁻¹ NaCl和50 mmol L⁻¹甘露醇处理拟南芥幼苗7 d后, 转基因植株平均相对根长为81.79%和93.25%, 分别是野生型的1.53倍和1.34倍。3周龄的转基因植株在250 mmol L⁻¹ NaCl条件下胁迫20 d, 平均存活率为67%, 显著高于野生型(42%)(P<0.05); 干旱胁迫25 d后, 复水5 d转基因植株平均存活率为72%, 而野生型仅为44%。检测结果显示转基因植株叶片的抗氧化酶活性明显高于野生型, 用200 mmol L⁻¹ NaCl和200 mmol L⁻¹甘露醇处理24 h后, POD活性分别比野生型植株提高1.56倍和1.85倍, CAT活性分别比野生型植株提高1.64和1.86倍。说明蛋白激发子Hrip1基因在拟南芥中的表达能够改善和提高植株的耐盐抗旱能力。     

风、蜜蜂因素对转Cry1Ac基因棉花花粉介导的基因漂移的影响

在温室内人工创造风力和释放传粉昆虫蜜蜂的条件下,应用PCR和蛋白试纸条结合的方法检测外源Cry1Ac基因通过花粉漂移至非转基因棉的频率和距离.结果表明:风力处理和蜜蜂处理的基因漂移频率均显著高于空白对照.漂移至非转基因亲本棉石远321的频率显著高于陆地棉中棉所35和海岛棉吉扎1号.漂移至石远321的频率随距离远近差异显著,而漂移至中棉所35和吉扎1号的频率在不同距离上差异不显著.风力处理共检测到阳性样本72个,在检测范围内,漂移至石远321的最远距离为25.6 m,漂移至中棉所35和吉扎1号的最远距离均为19.2 m.蜜蜂处理中共检测到阳性样本75个,在检测范围内,漂移到常规棉的最远漂移距离均达到设置最远处36 m,并在此处达到峰值.本研究可为转基因棉花基因漂移生态风险性评估提供参考.     

Yield components,harvest index and plant type in relation to yield differences in field pea genotypes

Summary The effectiveness of yield components, harvest index and morphological characteristics as selection criteria among four field pea (Pisum sativum L.) genotypes was examined. Genotypes were grown at a wide range of plant populations (9 to 400 plants m^-2) to maximise environmental diversity.Both biological and seed yields approximately doubled from 9 to 100 plants m^-2. This response flattened from 100 to 400 plants m^-2. Differences among the genotypes were found only at 225 and 400 plants m^-2. Analysis of the yield components highlighted the plasticity and large genotype by environment interactions of field peas. The numbers of pods per plant and peas per pod were maximised when each genotype was grown as spaced plants, but the low plant numbers meant seed yields per unit area were at their lowest.Genotypic differences for plant harvest index (PHI) were also only found at 225 and 400 plants m^-2. Broad sense heritability estimates indicated that direct selection for PHI was not feasible. The inference from the yield component and PHI results was that alternative selection criteria such as physiological or morphological characteristics may be necessary for improved yield potential. Classification of each genotype indicated that low seedling vigour may be a positive attribute for crop plants of semi-leafless and conventionally leafed field peas. Selection based on any single plant attribute is unlikely to lead to dramatic improvements in the yield potential of field peas. Selection should be based on plant characteristics rather than on differences in yield components.     

Evidence of a partial reproductive barrier between wild and cultivated pearl millets (Pennisetum glaucum)

Summary The occurrence of seed malformation in association with reduced thousand grain weight and germination ability has been observed in crosses between cultivated female plants and wild male plants. A survey of 16 cultivated accessions (P. glaucum subsp. glaucum) and 11 wild accessions (P. glaucum subsp. monodii) ranging over the whole species diversity showed this postzygotic incompatibility was general, but its intensity varied greatly with the cultivated female accession used and very little with the wild male parent origin. About 15% of the 123 cultivated x wild crosses observed gave normal seeds. Seed malformation has never been observed in crosses between cultivated accessions and appeared independent of genetic distances between the parents. The reciprocal crosses between wild female plants and cultivated male plants gave normal-looking seeds with good germination but consistently reduced thousand grain weight. Both seed malformation and seed small size are an expression of a genetic imbalance. These slight reproductive barriers seem to have been built during the domestication process.Abbreviation ICRISAT International Crop Research Institute for the Semi-Arid Tropics     

Prediction of indirect selection for seed and forage yield of lucerne based on evaluation under spaced planting

Phenotypic selection under spaced planting is frequently used in forage species. This study aimed to compare the predicted efficiency of direct selection for lucerne seed or forage yield under dense planting with indirect selection based on the same traits or seed yield components evaluated under spaced planting. Sixteen genotypes randomly chosen from a representative sample of locally adapted germplasm were grown for two years as individual clones spaced at 75 cm (density =1.78 plants/m²) and in dense plots formed by one row of four clones spaced at 10 cm (density = 50 plants/m²) using a randomized complete block design with three replications. Indirect selection based on seed yield under spaced planting was just 19% less efficient than direct selection, owing to moderate genetic correlation between plant densities (r_g = 0.66) and somewhat higher broad‐sense heritability under spaced planting than under dense planting. The relative efficiency of indirect selection for seed yield in density based on individual seed yield components under spaced planting ranged from modest to very low and was always below 45%. The efficiency of indirect selection for dry matter yield based on yield response under spaced planting was moderate for total yield (64%) and very low for second‐year yield (32%) relative to direct selection.     

Influence of Water Stress on the Chemical Composition of Seeds of Two Lupins (Lupinus albus and Lupinus mutabilis)

We have performed chemical proximate analysis and determined the carbohydrate profile of mature seeds of Lupinus albus, cv. Rio Maior and Lupinus mutabilis, cv. Potosi plants, either well watered (ww) or subjected to a water-stress period (imposed from the 15th to 35th day after anthesis). Protein content from lupin seeds was 450 and 320 g kg⁻¹ of seed on dry weight basis, for ww plants, respectively, of L. albus and L. mutabilis. Water stress did not affect protein content. The oil content of ww plants was about 120 g kg⁻¹ of seed dry weight for L. albus and 180 g kg⁻¹ of seed dry weight for L. mutabilis. Water stress reduced those values of half. The sugar content was about 90 g kg⁻¹ for L. albus and 50 g kg⁻¹ of seed dry weight for L. mutabilis, in ww plants. Water stress led to an increase in sugar content to 200 and 130 g kg⁻¹ of seed dry weight, respectively, for L. albus and L. mutabilis. The α-galactosides amounted to 70 % of the total sugars (raffinose being 30 % and stachyose, 40 %) and sucrose was about 20 % of the total sugars. Water stress increased total carbohydrates and increased the sucrose/α-galactoside ratio, although reducing raffinose content and increasing sucrose content.     

Selection for Seed Yield in Lolium perenne L.*

Components of seed yield were estimated for each set of 100 plants derived from six varieties of Lolium perenne. Significant differences between the varieties were found for all components of seed yield, but the range was broader within each variety. An indirect selection of seed yield using the character seeds per spike produced a selection response similar to that obtained by direct selection on high seed yield per plant. A direct and indirect selection of characters estimated in small, drilled plots of topcross off-springs (F₁) was less successful than the selection based on the single plants. Spearman rank correlation coefficients between the single plants and their offsprings did not show significant agreement for seed yield. But altogether the results indicated that the increase of seed yield/area was about 6 % when 10 % of the best plants were selected.     

Outcrossing frequencies from multiple high erucic acid oilseed rape fields to a central receptor field

Genetically modified oilseed rape is currently grown on about 23 % of the global oilseed rape acreage. In order to separate transgenic and non-transgenic oilseed rape production and to ensure co-existence of different agricultural cultivation schemes, as is specified by the European legislation, confinement measures have to be defined. Pollen-mediated gene flow is the most important means by which transgenes are dispersed between fields. In contrast to the majority of the previous investigations the objective of this study was to assess the extent of gene flow in the case of multiple pollen-donor fields. A high erucic acid rape genotype was used as biochemical marker for the quantification of outcrossing into a low erucic acid oilseed rape variety. Outcrossing data were obtained from two experimental locations. As expected, multiple pollen sources in a fragmented landscape can result in high gene transfer frequencies, thus requiring larger isolation distances than a field design with a single pollen donor source. The results of the study are transferable to homozygous transgenic oilseed rape varieties.