Spontaneous hybridizations between oilseed rape and wild radish

The occurence of spontaneous hybridization between Brassica napus (oilseed rape) and Raphanus raphanistrum (wild radish) was investigated under different density conditions in cages and open-field experiments. Hybrids with wild radish as the seed parent were identified by screening for herbicide resistance belonging to rape. Small seed size and intermediate morphology were used to screen for hybrids with rape as the seed parent. Leaf isozyme patterns and flow cytometry provided confirmation of hybrids. Wild radish in an oilseed rape field produced as many as three interspecific hybrids per 100 plants. This is the first report of such a spontaneous event. The frequency of hybrids is expected to range from 0.006 to 0.2% of the total seed produced, at P = 0.05. Male-sterile oilseed rape plants surrounded by wild radish can produce up to 37 hybrids per plant. Seed production of the F₁ hybrids and their F₂ descendants was up to 0.4% and 2%, respectively, of that of wild radish. Gene escape from transgenic oilseed rape to wild related species is discussed.     

Assessment of interspecific hybridization between transgenic oilseed rape and wild radish under normal agronomic conditions

In order to assess the hybridization rate between oilseed rape and wild radish under normal agronomic conditions, three 1-ha field experiments were performed. In each case, wild radish plants were transplanted at different densities in the middle, the border, or the margin of the herbicide-tolerant oilseed rape field. Among the 189084 seedlings obtained from seeds harvested on wild radish plants, only one herbicide-tolerant interspecific hybrid (RrRrAC, 2n = 37) was characterized from seeds harvested on an isolated plant growing in the margin of the field. Thus, for the wild radish total harvest, with a 95% confidence limit, the frequency of interspecific hybrids was assessed to range from 10^–7 to 3.10^–5. Interspecific hybrids were detected in all cases among the smallest seeds with a diameter less than 1.6 mm harvested on oilseed rape, but the highest frequency was obtained from oilseed rape close to wild radish plants growing as clusters in the border or the margin of the field. Most hybrids had the expected triploid genomic structure (ACRr, 2n = 28) except for four amphidiploids (AACCRrRr, 2n = 56) and one hybrid from a wild radish unreduced gamete (ACRrRr, 2n = 37). Among the 73847 seedlings observed on the oilseed rape total harvest, the frequency of interspecific hybrids was assessed to range from 2.10^–5to 5.10^–4, with a 95% confidence limit. The results are discussed with regard to the type of oilseed rape variety used and the characteristics of the interspecific hybrids. Received: 5 October 1999 / Accepted: 11 November 1999     

转基因油菜的基因流及生态风险

综合评述了转基因油菜的基因流及其生态风险.油菜作为最早的转基因作物之一目前已在加拿大和澳大利亚大面积商业化应用.(常)异花授粉作物油菜的天然异交率可达30%左右,也易与其它芸苔属作物杂交,因此转基因油菜的生态风险已引起各国科学家的高度重视.转基因油菜主要通过与其野生近缘种的花粉交换和与非转基因油菜的花粉交换两种方式进行花粉的输出.基因可能逃逸到相关野生近缘种,但在大田环境下能够得到杂种的可能性很小;由于基因的漂流在油菜田块间确实存在,因此在种植转基因油菜的过程中必须考虑其间隔距离.     

Development of crop-specific transposable element (SINE) markers for studying gene flow from oilseed rape to wild radish

The screening of wild populations for evidence of gene flow from a crop to a wild related species requires the unambiguous detection of crop genes within the genome of the wild species, taking into account the intraspecific variability of each species. If the crop and wild relatives share a common ancestor, as is the case for the Brassica crops and their wild relatives (subtribe Brassiceae), the species-specific markers needed to make this unambiguous detection are difficult to identify. In the model oilseed rape (Brassica napus, AACC, 2n=38)-wild radish (Raphanus raphanistrum, RrRr, 2n=18) system, we utilized the presence or absence of a short-interspersed element (SINE) at a given locus to develop oilseed rape-specific markers, as SINE insertions are irreversible. By means of sequence-specific amplified polymorphism (SINE-SSAP) reactions, we identified and cloned 67 bands specific to the oilseed rape genome and absent from that of wild radish. Forty-seven PCR-specific markers were developed from three combinations of primers anchored either in (1) the 5- and 3-genomic sequences flanking the SINE, (2) the 5-flanking and SINE internal sequences or (3) the SINE internal and flanking 3-sequences. Seventeen markers were monomorphic whatever the oilseed rape varieties tested, whereas 30 revealed polymorphism and behaved either as dominant (17) or co-dominant (13) markers. Polymorphic markers were mapped on 19 genomic regions assigned to ten linkage groups. The markers developed will be efficient tools to trace the occurrence and frequency of introgressions of oilseed rape genomic region within wild radish populations.     

Potential gene flow of two herbicide-tolerant transgenes from oilseed rape to wild B. juncea var. gracilis

Four successive reciprocal backcrosses between F₁ (obtained from wild Brassica juncea as maternal plants and transgenic glyphosate- or glufosinate-tolerant oilseed rape, B. napus, as paternal plants) or subsequent herbicide-tolerant backcross progenies and wild B. juncea were achieved by hand pollination to assess potential transgene flow. The third and forth reciprocal backcrosses produced a number of seeds per silique similar to that of self-pollinated wild B. juncea, except in plants with glufosinate-tolerant backcross progeny used as maternal plants and wild B. juncea as paternal plants, which produced fewer seeds per silique than did self-pollinated wild B. juncea. Germination percentages of reciprocal backcross progenies were high and equivalent to those of wild B. juncea. The herbicide-tolerant first reciprocal backcross progenies produced fewer siliques per plant than did wild B. juncea, but the herbicide-tolerant second or third reciprocal backcross progenies did not differ from the wild B. juncea in siliques per plant. The herbicide-tolerant second and third reciprocal backcross progenies produced an amount of seeds per silique similar to that of wild B. juncea except for with the glufosinate-tolerant first and second backcross progeny used as maternal plants and wild B. juncea as paternal plants. In the presence of herbicide selection pressure, inheritance of the glyphosate-tolerant transgene was stable across the second and third backcross generation, whereas the glufosinate-tolerant transgene was maintained, despite a lack of stabilized introgression. The occurrence of fertile, transgenic weed-like plants after only three crosses (F₁, first backcross, second backcross) suggests a potential rapid spread of transgenes from oilseed rape into its wild relative wild B. juncea. Transgene flow from glyphosate-tolerant oilseed rape might be easier than that from glufosinate-tolerant oilseed rape to wild B. juncea. The original insertion site of the transgene could affect introgression.     

Polymorphism for interspecific hybridisation within a population of wild radish (Raphanus raphanistrum) pollinated by oilseed rape (Brassica napus)

The within-population polymorphism of wild radish (Raphanus raphanistrum) for interspecific hybridisation with two cultivars of oilseed rape (Brassica napus) was investigated by hand crossing experiments and fluorescence microscopy. Wide variability among plants was observed in the ability of oilseed rape pollen to germinate on the wild radish stigma; the frequency of pistils showing pollen tubes ranged from 0 to 1, depending on the female plant. The ratio of fertilised ovules to the total number of ovules in ovaries where pollen tubes arrived ranged from 0.02 to 0.51. Overall, the results provide evidence for the presence of different phenotypes. In 40% of the plants, pistils had no or very few pollen tubes and few fertilised ovules. In 23%, the foreign pollen tubes grew through the style towards the ovary, but had low ovule fertilisation efficiency. The remaining 37% showed a large number of pollen tubes in the style and frequent ovule fertilisation, and two plants showed no difference between foreign and conspecific pollen. With regard to post-zygotic barriers, pollen germination and ovule fertilisation represent minor barriers to interspecific hybridisation between oilseed rape and wild radish. It is suggested that the effectiveness of these barriers could be improved through plant breeding; this could reduce the risk of gene flow from transgenic oilseed rape to populations of wild relatives. Received: 15 April 2001 / Accepted: 24 May 2001     

Characterization of backcross generations obtained under field conditions from oilseed rape-wild radish F1 interspecific hybrids: an assessment of transgene dispersal

Gene flow from glufosinate-resistant transgenic oilseed rape to wild radish was studied over two backcross generations. Under field conditions,?seed production from oilseed rape-wild radish F₁ hybrids due to pollination by wild radish was always low: on average 0.12 and 0.78 seeds per 100 flowers and per plant, respectively. The cytogenetics of the resulting «BC₁» plants can be explained in the main by three different genomic constitutions: either ACRrRr, 2n=37, ACRr, 2n=28 (the same chromosome number as the mother plant), or by the amphidiploid AACCRrRr, 2n=56. The probability of gene exchange through chromosome pairing was high only in plants with 2n=28 or 37 chromosomes. Due to the viability of unreduced or partially reduced female gametes, most of the «BC₁» plants (81.9%) were Basta resistant whereas the analysis of oilseed rape specific loci indicated that their transmission varied with the locus. In spite of low male fertility (8.7%), an improvement of the female fertility over the F₁ hybrids was observed with an average production of 1.4 and 11 seeds per 100 flowers and per plant, respectively. At the following «BC₂» generation, the bar gene transmission (57.2% of Basta-resistant plants) decreased as did the chromosome number, with a majority of plants having between 24 and 27 chromosomes, with 10.5% similar to wild radish (2n=18). The lower the chromosome number, the better the fertility of the «BC₂» plants. On average, 7.9 and 229.3 seeds per 100 flowers and per plant were produced. Gene-flow assessment is discussed based on these data.     

抗草丁膦和抗草甘膦转基因油菜的抗性基因向野芥菜的流动

通过人工去雄授粉和田间隔行种植试验,研究了抗草丁膦和抗草甘膦转基因油菜(Brassica napus)中的bar基因和EPSPS基因向野芥菜(B. juncea var. gracilis)流动的可能性。结果表明在人工授粉的情况下,以野芥菜为母本,分别以两种转基因油菜为父本,亲和性指数都很高,达13以上,与野芥菜自交或开放授粉条件下的亲和性指数没有明显差异,说明两种转基因油菜和野芥菜的亲和性较好。经两次除草剂筛选,人工杂交获得的所有F₁对相应的除草剂都表现出了明显的抗性,且经PCR检测扩增出了各自的特异性条带,说明人工杂交获得的所有F₁都携带了相应的抗性基因。F₁的适合度研究表明,两种F₁种子萌发率和母本都没有明显差异,营养生长明显好于母本。但花粉活力和结实率明显下降,携带抗草丁膦基因F₁的花粉活力和每角果粒数分别是32.4%和0.59粒,携带抗草甘膦基因F₁的花粉活力和每角果粒数分别是35.1%和0.58粒。经两次除草剂筛选和PCR检测,表明野芥菜和抗草丁膦油菜或与抗草甘膦油菜田间隔行种植分别能产生0.02%和0.014%的携带抗性基因的F₁杂种。以上结果表明抗除草剂转基因油菜的抗性基因具有向野芥菜流动的可能性,且bar和EPSPS基因向野芥菜流动的可能性类似,但对其可能引起的环境后果需要做进一步地深入研究。     

Competition affects gene flow from oilseed rape (female symbol) to Brassica rapa (male symbol)

Unlike most studies on hybridisation between oilseed rape and Brassica rapa, this study focused on hybridisation with oilseed rape as the maternal parent. This is a key cross because, assuming that plastids are inherited maternally, F(1)-hybrid production with maternal oilseed rape (B. napus) is the only transgene escape route from transplastomic oilseed rape. We investigated such F(1)-hybrid production in winter oilseed rape co-cultivated with weedy B. rapa at three plant densities each with two proportions of the different species. The paternity of the progeny produced on oilseed rape was assessed, and several fitness parameters were determined in oilseed rape mother plants in order to correlate hybridisation and plant competition. At higher density, the vegetative fitness per mother plant decreased significantly, but the density only affected the frequency of F(1)-hybrids significantly (a decrease) in the treatment with equal proportions of each species. As to the proportions, at higher B. napus frequencies, there were fewer F(1)-hybrids per mother plant and a significant increase in most biomass components. Thus, B. rapa was the stronger competitor in its effect on both the vegetative and reproductive fitness in B. napus, and the hybridisation frequency. In conclusion, the relative frequency of the two species was a more influential parameter than the density. Hybridisation with B. napus as the female will be most likely at current field densities of B. napus and when B. rapa is an abundant weed.     

Correction of chlorophyll-defective male-sterile winter oilseed rape (Brassica napus) through organelle exchange: Characterization of the chlorophyll deficiency

Jarl, C. I., Ljungberg, U. K. and Bornman, C. H. 1988. Correction of chlorophyll-defective male-sterile winter oilseed rape ( Brassica napus ) through organelle exchange: Characterization of the chlorophyll deficiency. - Physiol. Plant. 72: 505–510.
As is known, the introduction of male-sterile Raphanus sativus L. cytoplasm into Brassica napus L. results in male-sterile oilseed rape plants, which display a temperature-related chlorophyll defect. The influences of temperature and irradiance on this defect were investigated. Compared to a line of normal (green phenotype) male-fertile oilseed rape, the male-sterile line had reduced chlorophyll content, fewer chloroplasts per cell, an altered ultrastructure of the chloroplasts and reduced activities of both photosystems, although the relative amounts of the photosystems and the chlorophyll a/b ratio were similar. The lower activity of the photosystems is explained by a decreased functional antennae size and a reduced efficiency in the interactions between the nuclear-encoded light-harvesting proteins and the reaction centres coded for by the plastome. Some thylakoid polypeptides differed in proportion between the male-fertile line with green phenotype and the male-sterile line with chlorotic phenotype. Characters, in which the two lines exhibited differences, are ascribed to difficulties in molecular communication between the oilseed rape nucleus and the radish cytoplasm, which are combined in the deficient male-sterile line.     

Inheritance of oilseed rape (Brassica napus) RAPD markers in a backcross progeny with Brassica campestris

Different cultivars/transgenic lines of oilseed rape (Brassica napus) were crossed (as females) with different cultivars/populations of Brassica campestris. All cross combinations produced seed, with an average seed set per pollination of 9.8. Backcrossing of selected interspecific hybrids (as females) to B. campestris resulted in a much lower seed set, average 0.7 seed per pollination. In the single backcross progeny where a large enough population (92 plants) was obtained for analysis, 33 B. napus specific RAPD markers were investigated to determine the extent of transfer of oilseed rape genetic material into this population. Markers were transferred to the backcross generation with frequencies ranging from 26% to 91%. Almost all of the markers (30/33) were transferred in a frequency not significantly different from 50%. Analysis of the pairwise segregation of markers revealed that 23 markers could be assigned to six linkage groups, most probably reflecting six B. napus C-chromosomes. The presence of backcross plants with recombinant genotypes suggests that complex genetic processes can take place during interspecific hybridisation and backcrossing in these Brassica species. The implications of our results for the possible choice of integration sites of transgenes in oilseed rape are discussed.     

Frequency-dependent fitness of hybrids between oilseed rape (Brassica napus) and weedy B. rapa (Brassicaceae)

Fitness of interspecific hybrids is sometimes high relative to their parents, despite the conventional belief that they are mostly unfit. F(1) hybrids between oilseed rape (Brassica napus) and weedy B. rapa can be significantly more fit than their weedy parents under some conditions; however, under other conditions they are less fit. To understand the reasons, we measured the seed production of B. napus, B. rapa, and different generations of hybrid plants at three different densities and in mixtures of different frequencies (including pure stands). Brassica napus, B. rapa, and backcross plants (F(1) ♀ × B. rapa) produced many more seeds per plant in pure plots than in mixtures and more seeds in plots when each was present at high frequency. The opposite was true for F(1) plants that produced many more seeds than B. rapa in mixtures, but fewer in pure stands. Both vegetative and reproductive interactions may be responsible for these effects. Our results show that the fitness of both parents and hybrids is strongly frequency-dependent and that the likelihood of introgression of genes between the species thus may depend on the numbers and densities of parents and their various hybrid offspring in the population.     

Stress and domestication traits increase the relative fitness of crop-wild hybrids in sunflower

After a decade of transgenic crop production, the dynamics of gene introgression into wild relatives remain unclear. Taking an ecological genetics approach to investigating fitness in crop-wild hybrid zones, we uncovered both conditions and characteristics that may promote introgression. We compared diverse crop-wild hybrid genotypes relative to wild Helianthus annuus under one benign and three stressful agricultural environments. Whereas relative fitness of crop-wild hybrids averaged 0.25 under benign conditions, with herbicide application or competition it reached 0.45 and was more variable. In some instances, hybrid fitness matched wild fitness (approximately 1). Thus, wild populations under agronomic stress may be more susceptible to introgression. Although 'domestication' traits are typically considered unlikely to persist in wild populations, we found some (e.g. rapid growth and early flowering) that may enhance hybrid fitness, especially in stressful environments. Rigorous assessment of how particular genotypes, phenotypes, and environments affect introgression will improve risk assessment for transgenic crops.     

Modelling gene flow between oilseed rape and wild radish. I. Evolution of chromosome structure

The assessment of gene flow from crop species to weeds has found a new emphasis over the last years because of the marketing of transgenic crops and the possible selective advantage that crop (trans)gene may confer to the weeds. Several studies focused on the F1 interspecific hybrid production but few data are available on the factors affecting the genetic structure of advanced generations. It depends on the genomic structure of the species concerned as well as on the degree of their genome homology that affect the occurrence of intergenomic recombination. Oilseed rape (Brassica napus, AACC, 2n = 38)-wild radish (Raphanus raphanistrum, RrRr, 2n = 18), a distantly related weed, is a good model to address such questions. From seven male sterile oilseed rape lines carrying an herbicide tolerance transgene, F1 interspecific hybrids and four advanced generations were produced under field conditions with wild radish as pollinator. Observation of hybrid chromosome numbers across four generations revealed a high variability, especially in the “BC1” generation. A regression model was fitted in order to describe the relationship between parent and offspring chromosome numbers. The effects of generation, transgenic line and selection pressure on the mean relationship were investigated. The first two factors had an influence on the rate of decrease of chromosome numbers, whereas selection pressure resulted in the presence of an additional chromosome in the herbicide treated plants. The model provided a convenient framework for analysing how chromosome numbers evolve over successive hybridization events and it may prove useful as a basis for simulation-based approaches.     

Spontaneous hybridization between oilseed rape (Brassica napus) and weedy B. campestris (Brassicaceae): a risk of growing genetically modified oilseed rape

Frequencies of spontaneous hybridization between oilseed rape (Brassica napus L.) and weedy Brassica campesíris ssp. campestris L. were measured in agricultural fields. Hybrids were identified by enzyme electrophoresis, random amplified polymorphic DNA (RAPD) analysis, chromosome counting, morphology, and pollen fertility. When the two species were mixed 1:1, B. campestris produced 13% hybrid seeds and oilseed rape 9%. In two experiments with single plants of the self-incompatible B. campestris widely spaced within fields of oilseed rape, 56% and 93% hybrid seeds were produced. Analysis of a weedy population of B. campestris in oilseed rape revealed 60% hybrid seeds. Backcrossing of the hybrids to the weedy species seems to occur as supported by the finding in a natural population of two B. campestris-like plants with a marker specific to oilseed rape. The results suggest that transgenes could be dispersed from oilseed rape to B. campestris.     

Mitigation using a tandem construct containing a selectively unfit gene precludes establishment of Brassica napus transgenes in hybrids and backcrosses with weedy Brassica rapa

Transgenic oilseed rape ( Brassica napus ) plants can interbreed with nearby weedy Brassica rapa , potentially enhancing the weediness and/or invasiveness of subsequent hybrid offspring. We have previously demonstrated that transgenic mitigation effectively reduces the fitness of the transgenic dwarf and herbicide-resistant B. napus volunteers. We now report the efficacy of such a tandem construct, including a primary herbicide-resistant gene and a dwarfing mitigator gene, to preclude the risks of gene establishment in the related weed B. rapa and its backcross progeny. The transgenically mitigated and non-transgenic B. rapa  ×  B. napus interspecific hybrids and the backcrosses (BC₁) with B. rapa were grown alone and in competition with B. rapa weed. The reproductive fitness of hybrid offspring progressively decreased with increased B. rapa genes in the offspring, illustrating the efficacy of the concept. The fitness of F₂ interspecific non-transgenic hybrids was between 50% and 80% of the competing weedy B. rapa , whereas the fitness of the comparable T₂ interspecific transgenic hybrids was never more than 2%. The reproductive fitness of the transgenic T₂ BC₁ mixed with B. rapa was further severely suppressed to 0.9% of that of the competing weed due to dwarfism. Clearly, the mitigation technology works efficiently in a rapeseed crop–weed system under biocontainment-controlled environments, but field studies should further validate its utility for minimizing the risks of gene flow.     

Impact of ecological factors on the initial invasion of Bt transgenes into wild populations of birdseed rape (Brassica rapa)

The inevitable escape of transgenic pollen from cultivated fields will lead to the emergence of transgenic crop-wild plant hybrids in natural patches of wild plants. The fate of these hybrids and that of the transgene depend on their ability to compete with their wild relatives. Here we study ecological factors that may enhance the fitness of genetically modified hybrids relative to wild plants for a Bacillus thuringiensis (Bt) transgene conferring resistance to insects. Mixed stands of wild plants and first-generation hybrids were grown under different conditions of herbivore pressure and density, with Bt oilseed rape (Brassica napus) as the crop and B. rapa as the wild recipient. Biomass and fitness components were measured from plant germination to the germination of their offspring. The frequency of transgenic seedlings in the offspring generation was estimated using the green fluorescent protein marker. The biomass of F₁ Bt-transgenic hybrids relative to that of wild-type plants was found to be sensitive to both plant density and herbivore pressure, but herbivore pressure appeared as the major factor enhancing their relative fitnesses. In the absence of herbivore pressure, Bt hybrids produced 6.2-fold fewer seeds than their wild neighbors, and Bt plant frequency fell from 50% to 16% within a single generation. Under high herbivore pressure, Bt hybrids produced 1.4-fold more seeds, and Bt plant frequency was 42% in the offspring generation. We conclude that high-density patches of highly damaged wild plants are the most vulnerable to Bt-transgene invasion. They should be monitored early to detect potential transgene spread.     

Gene Flow,Risk Assessment and the Environmental Release of Transgenic Plants

The release of genetically modified plants is governed by regulations that aim to provide an assessment of potential impact on the environment. One of the most important components of this risk assessment is an evaluation of the probability of gene flow. In this review, we provide an overview of the current literature on gene flow from transgenic plants, providing a framework of issues for those considering the release of a transgenic plant into the environment. For some plants gene flow from transgenic crops is well documented, and this information is discussed in detail in this review. Mechanisms of gene flow vary from plant species to plant species and range from the possibility of asexual propagation, short- or long-distance pollen dispersal mediated by insects or wind and seed dispersal. Volunteer populations of transgenic plants may occur where seed is inadvertently spread during harvest or commercial distribution. If there are wild populations related to the transgenic crop then hybridization and eventually introgression in the wild may occur, as it has for herbicide resistant transgenic oilseed rape (Brassica napus). Tools to measure the amount of gene flow, experimental data measuring the distance of pollen dispersal, and experiments measuring hybridization and seed survivability are discussed in this review. The various methods that have been proposed to prevent gene flow from genetically modified plants are also described. The current “transgenic traits” in the major crops confer resistance to herbicides and certain insects. Such traits could confer a selective advantage (an increase in fitness) in wild plant populations in some circumstances, were gene flow to occur. However, there is ample evidence that gene flow from crops to related wild species occurred before the development of transgenic crops and this should be taken into account in the risk assessment process.     

Evolution of enhanced reproduction in the hybrid-derived invasive, California wild radish (Raphanus sativus)

Evolution is receiving increased attention as a potentially important factor in invasions. For example, hybridization may have stimulated the evolution of invasiveness in several well-known plant pests. However, the mechanism for success of such hybrid-derived lineages remains unknown in the majority of the cases studied. Here we ask whether increased reproductive success (in terms of maternal fitness) has evolved in an invasive lineage with confirmed hybrid ancestry. We compare the relative fitness of the non-native, hybrid-derived California wild radish (Raphanus sativus) to that of its two progenitor species in field experiments at different sites and in different years. We found that California wild radish has high survivorship and produces more fruits per plant and more seeds per plant than either of its progenitors in several environments. Furthermore, populations of California wild radish display a strong genotype-by-environment interaction, indicating that maintenance of genetic and phenotypic diversity between populations may be responsible for the weed’s ability to invade a wide breadth of California habitats. Our results suggest that hybridization may contribute the evolution of enhanced invasiveness and, also, that by limiting the introduction and subsequent hybridization of congeners, we may be able to prevent the evolution of new invasive lineages.     

Dynamic expression of green fluorescent protein and Bacillus thuringiensis Cry1Ac endotaxin in interspecific hybrids and successive backcross generations (BC1 and BC2) between transgenic Brassica napus crop and wild Brassica juncea

The persistence and stability of a transgene encoding a Bacillus thuringiensis (Bt) Cry1Ac insecticidal protein was investigated in hybrids between crop Brassica napus and a recurrent wild Brassica juncea population. Interspecific hybrids (F₁) and backcross progenies (BC₁, BC₂) containing green fluorescent protein (GFP) and Bt genes were successfully produced in the greenhouse. Stable Bt toxin levels were found in hybrid and advanced backcross progenies formed in wild B. juncea. Bt Cry1Ac concentration was significantly lower in BC₂ plants than in transgenic B. napus, F₁, BC₁, while no significant differences were detected among the latter three plant genotypes. A GFP marker gene was used as a scorable marker and indicator of Bt transgene expression. GFP fluorescence intensity was significantly correlated with Bt Cry1Ac concentration at the flowering stage and the pod formation stage in both transgenic oilseed rape hybrids and backcrossed progenies (BC₁, BC₂). It was demonstrated that GFP was a suitable marker for Bt protein in the backcross of B. juncea, which could facilitate the detection of gene flow and is useful in biosafety management.