Hybridisation and introgression between Brassica napus and B. rapa in the Netherlands

Introgression of Herbicide-Resistant Gene from Genetically Modified Brassica napus L. to Brassica rapa through Backcrossing

Interspecific hybridization between two different Brassicaceae species, namely Brassica rapa ssp. pekinensis (♀) (AA, 2n = 2x = 20) and genetically modified Brassica napus (♂) (AACC, 2n = 4x = 38), was performed to study the transmission of a herbicide resistance gene from a tetraploid to a diploid Brassica species. Initially, four different GM B. napus lines were used for hybridization with B. rapa via hand pollination. Among the F1 hybrids, the cross involving the B. rapa (♀) × GM B. napus (♂) TG#39 line exhibited the highest recorded crossability index of 14.7 ± 5.7. However, subsequent backcross progenies (BC1, BC2, and BC3) displayed notably lower crossability indices. The F1 plants displayed morphological characteristics more aligned with the male parent B. napus, with significant segregation observed in the BC1 generation upon backcrossing with the recurrent parent B. rapa. By the BC2 and BC3 generations, the progeny stabilized, manifesting traits from both parents to varying degrees. Cytogenetic analysis revealed a substantial reduction in chromosome numbers, particularly in backcrossing progenies. BC1 plants typically exhibited 21-25 chromosomes, while BC2 progenies showed 21-22 chromosomes, and by the BC3 generation, stability was achieved with an average of 20 chromosomes. SSR marker analysis confirmed the progressive reduction of C-genome regions, retaining minimal C-genome-specific bands throughout successive backcrossing. Despite the extensive elimination of C-genome-specific genomic regions, the glyphosate resistance gene from the male parent B. napus was introgressed into BC3 progenies, suggesting that the glyphosate resistance gene located and introgressed in A-chromosome/genome regions of the Brassica plants.

Persistence of genetically engineered canola populations in the U.S. and the adventitious presence of transgenes in the environment

Feralization of genetically engineered (GE) crops increases the risk that transgenes will become integrated into natural and naturalizing plant populations. A key assumption of the management of GE crops is that populations of escaped plants are short-lived and therefore the risks they pose are limited. However, few populations of escaped crop plants have been tracked over the long term so our understanding of their persistence in ruderal or natural landscapes is limited. We repeated a large-scale road survey of feral GE canola populations in North Dakota, USA, initially conducted in 2010. Our objectives in 2021 were to determine the current distribution of feral canola populations, and to establish the relative frequency of GE and non-GE phenotypes in populations of canola throughout North Dakota. Our results indicate that, although the incidence of feral canola was less in 2021 than 2010, escaped canola populations remain common throughout the state. The prevalence of alternate forms of GE herbicide resistance changed between surveys, and we found an overabundance of non-GE plants compared to the frequency of non-transgenic forms in cultivation. Indirect evidence of persistence includes sampling plants with multiple transgenic traits, and finding populations far from transportation routes. We conclude that feral canola populations expressing transgenic herbicide resistance are established outside of cultivation, that they may be under selection for loss of the transgene, but that they nonetheless pose long-term risks by harboring transgenes in the unmanaged landscape.

Interspecific Hybridization of Transgenic Brassica napus and Brassica rapa-An Overview

In nature, interspecific hybridization occurs frequently and can contribute to the production of new species or the introgression of beneficial adaptive features between species. It has great potential in agricultural systems to boost the process of targeted crop improvement. In the advent of genetically modified (GM) crops, it has a disadvantage that it involves the transgene escaping to unintended plants, which could result in non-specific weedy crops. Several crop species in the Brassica genus have close kinship: canola (Brassica napus) is an ancestral hybrid of B. rapa and B. oleracea and mustard species such as B. juncea, B. carinata, and B. nigra share common genomes. Hence, intraspecific hybridization among the Brassica species is most common, especially between B. napus and B. rapa. In general, interspecific hybrids cause numerous genetic and phenotypic changes in the parental lines. Consequently, their fitness and reproductive ability are also highly varied. In this review, we discuss the interspecific hybridization and reciprocal hybridization studies of B. napus and B. rapa and their potential in the controlled environment. Further, we address the fate of transgenes (herbicide resistance) and their ability to transfer to their progenies or generations. This could help us to understand the environmental influence of interspecific hybrids and how to effectively manage their transgene escape in the future.

EFSA Panel on Genetically Modified Organisms (GMO), Mullins E, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Firbank LG, Guerche P, Hejatko J, Moreno FJ, Naegeli H, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Ardizzone M, De Sanctis G, Federici S, Fernandez Dumont A, Gennaro A, Gomez Ruiz JA, Goumperis T, Lanzoni A, Lenzi P, Neri FM, Papadopoulou N, Raffaello T, Streissl F. Assessment of genetically modified oilseed rape MON 94100 for food and feed uses, under regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2020-169)

Oilseed rape MON 94100 was developed to confer tolerance to dicamba herbicide. The molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic and compositional characteristics tested between oilseed rape MON 94100 and its conventional counterpart needs further assessment, except for the levels of carbohydrates, calcium and ADF in seeds, which do not raise nutritional and safety concerns. The GMO Panel does not identify safety concerns regarding the toxicity and allergenicity of the dicamba mono-oxygenase (DMO) protein as expressed in oilseed rape MON 94100. The GMO Panel finds no evidence that the genetic modification impacts the overall safety of oilseed rape MON 94100. In the context of this application, the consumption of food and feed from oilseed rape MON 94100 does not represent a nutritional concern in humans and animals. The GMO Panel concludes that oilseed rape MON 94100 is as safe as the conventional counterpart and non-GM oilseed rape reference varieties tested, and no post-market monitoring of food/feed is considered necessary. In the case of accidental release of viable oilseed rape MON 94100 seeds into the environment, this would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of oilseed rape MON 94100. The GMO Panel concludes that oilseed rape MON 94100 is as safe as its conventional counterpart and the tested non-GM oilseed rape reference varieties with respect to potential effects on human and animal health and the environment.

EFSA Panel on Genetically Modified Organisms (GMO), Naegeli H, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Firbank LG, Guerche P, Hejatko J, Moreno FJ, Mullins E, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Ardizzone M, Devos Y, Federici S, Dumont AF, Gennaro A, Gómez Ruiz JÁ, Neri FM, Papadopoulou N, Paraskevopoulos K, Lanzoni A. Assessment of genetically modified oilseed rape 73496 for food and feed uses, under Regulation (EC) No 1829/2003 (application EFSA-GMO-NL-2012-109)

Oilseed rape 73496 was developed to confer tolerance to the herbicidal active substance glyphosate through the expression of the glyphosate acetyltransferase protein GAT4621. The molecular characterisation data and bioinformatic analyses identify no issues requiring food/feed safety assessment. None of the identified differences between oilseed rape 73496 and its conventional counterpart in the agronomic/phenotypic endpoints tested needs further assessment. Differences identified in seed composition of oilseed rape 73496 as compared to its conventional counterpart raise no safety and nutritional concerns in the context of the scope of this application. No safety concerns are identified regarding toxicity and allergenicity of the GAT4621 protein as expressed in oilseed rape 73496. No evidence is found that the genetic modification would change the overall allergenicity of oilseed rape 73496. Based on the outcome of the comparative and nutritional assessments, the consumption of oilseed rape 73496 does not represent any nutritional concern, in the context of the scope of this application. The implementation of a post-market monitoring plan is recommended to confirm the predicted consumption data and to verify that the conditions of use are those considered during the pre-market risk assessment. In the case of accidental release of viable oilseed rape 73496 seeds into the environment, oilseed rape 73496 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the intended uses of oilseed rape 73496. The GMO Panel concludes that oilseed rape 73496, as described in this application, is as safe as its conventional counterpart and the non-genetically modified oilseed rape reference varieties tested with respect to potential effects on human and animal health and the environment.

EFSA Panel on Genetically Modified Organisms (GMO), Naegeli H, Bresson J, Dalmay T, Dewhurst IC, Epstein MM, Firbank LG, Guerche P, Hejatko J, Moreno FJ, Mullins E, Nogué F, Rostoks N, Sánchez Serrano JJ, Savoini G, Veromann E, Veronesi F, Álvarez F, Ardizzone M, De Sanctis G, Devos Y, Fernandez‐Dumont A, Gennaro A, Gómez Ruiz JÁ, Lanzoni A, Neri FM, Papadopoulou N, Paraskevopoulos K. Assessment of genetically modified oilseed rape MS11 for food and feed uses, import and processing, under Regulation (EC) No 1829/2003 (application EFSA-GMO-BE-2016-138)

Oilseed rape MS11 has been developed to confer male sterility and tolerance to glufosinate-ammonium-containing herbicides. Based on the information provided in the application and in line with the scope of application EFSA-GMO-BE-2016-138, the genetically modified organism (GMO) Panel concludes that the molecular characterisation data and bioinformatic analyses do not identify issues requiring food/feed safety assessment. None of the identified differences in the agronomic/phenotypic characteristics tested between oilseed rape MS11 and its conventional counterpart needs further assessment. No conclusions can be drawn for the compositional analysis due to the lack of an appropriate compositional data set. No toxicological or allergenicity concerns are identified for the Barnase, Barstar and PAT/bar proteins expressed in oilseed rape MS11. Owing to the incompleteness of the compositional analysis, the toxicological, allergenicity and nutritional assessment of oilseed rape MS11 cannot be completed. In the case of accidental release of viable oilseed rape MS11 seeds into the environment, oilseed rape MS11 would not raise environmental safety concerns. The post-market environmental monitoring plan and reporting intervals are in line with the scope of the application. Since oilseed rape MS11 is designed to be used only for the production of hybrid seed, it is not expected to be commercialised as a stand-alone product for food/feed uses. Thus, seeds harvested from oilseed rape MS11 are not expected to enter the food/feed chain, except accidentally. In this context, the GMO Panel notes that, oilseed rape MS11 would not pose risk to humans and animals, while the scale of environmental exposure will be substantially reduced compared to a stand-alone product.

Morphological and genetic characteristics of F1 hybrids introgressed from Brassica napus to B. rapa in Taiwan

BACKGROUND

Unintentional introgression from genetically modified (GM) oilseed rape (Brassica napus) to a relative is inevitable in the open field. A feasible and practical strategy for restricting the spread of GM offspring is to set a reasonable isolated distance between GM B. napus and the relatives. To define the isolated distance, a pollen donor/recipient pair is a prerequisite to conducting the field trial of pollen flow. However, because the cultivation of GM B. napus is prohibited in Taiwan, it is difficult to obtain relevant information. Thus, this study explored the morphological and genetic characteristics of five varieties of B. napus (donor), three varieties of B. rapa (recipient), and the 15 corresponding F₁ hybrids, aiming to construct phenotypic data and genetic variation data and to select the most appropriate pollen donor/recipient for future field trials of pollen flow.

RESULTS

The genome size of all F₁ hybrids estimated using flow cytometry showed intermediate DNA content between B. napus and B. rapa varieties. Most of the F₁ hybrids had intermediate plant height and blooming period, and the rosette leaves type and colors resembled those of B. napus varieties. The results of sequence-related amplified polymorphism (SRAP) showed an average of 9.52 bands per primer combination and 67.87 polymorphic bands among the F₁ hybrid population. Similarity and cluster analyses revealed higher similarity between F₁ hybrids and B. napus varieties than between F₁ hybrids and B. rapa varieties. Furthermore, we identified a specific 1100-bp band (LOC106302894) in F₁ hybrids and B. napus varieties but not in B. rapa varieties.

CONCLUSIONS

The rosette leaves and the DNA marker LOC106302894 observed in F₁ hybrids are consistent phenotypic and genetic characteristics that can be used to identify the presence of unintentional hybridization from B. napus to B. rapa in Taiwan. Due to the prohibition of GM crop cultivation, the hybridization system of non-GM Brassica species in this study can be utilized as a mimic scheme to conduct pollen flow trials, thus facilitating the determination of the proper isolated distance.

Subsampling reveals that unbalanced sampling affects STRUCTURE results in a multi-species dataset

Studying the genetic population structure of species can reveal important insights into several key evolutionary, historical, demographic, and anthropogenic processes. One of the most important statistical tools for inferring genetic clusters is the program STRUCTURE. Recently, several papers have pointed out that STRUCTURE may show a bias when the sampling design is unbalanced, resulting in spurious joining of underrepresented populations and spurious separation of overrepresented populations. Suggestions to overcome this bias include subsampling and changing the ancestry model, but the performance of these two methods has not yet been tested on actual data. Here, I use a data set of 12 high-alpine plant species to test whether unbalanced sampling affects the STRUCTURE inference of population differentiation between the European Alps and the Carpathians. For four of the 12 species, subsampling of the Alpine populations-to match the sample size between the Alps and the Carpathians-resulted in a drastically different clustering than the full data set. On the other hand, STRUCTURE results with the alternative ancestry model were indistinguishable from the results with the default model. Based on these results, the subsampling strategy seems a more viable approach to overcome the bias than the alternative ancestry model. However, subsampling is only possible when there is an a priori expectation of what constitute the main clusters. Though these results do not mean that the use of STRUCTURE should be discarded, it does indicate that users of the software should be cautious about the interpretation of the results when sampling is unbalanced.

Performance of aneuploid backcross hybrids between the crop Brassica napus and its wild relative B. rapa

Crossings between the diploid wild Brassica rapa (AA, 2n = 20) and the tetraploid cultivar B. napus (AACC, 2n = 38) can readily be made. Backcrosses to the wild B. rapa (BC₁ ) produce aneuploids with variable chromosome numbers between 20 and 29. How does survival and performance relate to DNA content of plants? Growth of the BC₁ plants was measured in the lab. One plant in the F₁ self-pollinated spontaneously and produced abundant F₂ seeds that were also examined. The number of C-chromosomes was estimated from DNA values obtained with flow cytometry. Average DNA value of the BC₁ was similar to that of the parents, which shows that C-chromosomes do not reduce success of pollen or embryos. The average DNA value in the F₂ was 13% higher than in the F₁ , suggesting that extra C-chromosomes facilitated gamete success and/or embryo survival. Under both optimal and drought stress conditions growth and survival of BC₁ hybrids was similar to that of B. rapa. No significant correlations existed between growth or survival and DNA value. Aneuploid plants were not inferior under the conditions of the growth room and may persist in nature. We discuss other factors, such as herbivory, that could prevent hybrid establishment in the field.

Naegeli H, Birch AN, Casacuberta J, De Schrijver A, Gralak MA, Guerche P, Jones H, Manachini B, Messéan A, Nielsen EE, Nogué F, Robaglia C, Rostoks N, Sweet J, Tebbe C, Visioli F, Wal JM, Devos Y, Lanzoni A, Olaru I. Scientific Opinion on application EFSA-GMO-NL-2013-119 for authorisation of genetically modified glufosinate-ammonium- and glyphosate-tolerant oilseed rape MON 88302 × MS8 × RF3 and subcombinations independently of their origin, for food and feed uses, import and processing submitted in accordance with Regulation (EC) No 1829/2003 by Monsanto Company and Bayer CropScience

In this opinion, the GMO Panel assessed the three‐event stack oilseed rape (OSR) MON 88302 × MS8 × RF3 and its three subcombinations, independently of their origin. The GMO Panel has previously assessed the single events combined to produce this three‐event stack OSR and did not identify safety concerns; no new information that would modify the original conclusions was identified. The combination of the single OSR events and of the newly expressed proteins in the three‐event stack OSR does not give rise to food and feed safety and nutrition issues – based on the molecular, agronomic/phenotypic and compositional characteristics. In the case of accidental release of viable OSR MON 88302 × MS8 × RF3 seeds into the environment, the three‐event stack OSR would not raise environmental safety concerns. The GMO Panel therefore concluded that the three‐event stack OSR is as safe and as nutritious as its conventional counterpart and the tested non‐GM reference varieties in the context of the scope of this application. Since no new safety concerns were identified for the previously assessed two‐event stack OSR MS8 × RF3, the GMO Panel considered that its previous conclusions on this subcombination remain valid. For the two subcombinations MON 88302 × MS8 and MON 88302 × RF3 for which no experimental data were provided, the GMO Panel assessed the likelihood of interactions among the single events, and concluded that their different combinations would not raise safety concerns. These two subcombinations are therefore expected to be as safe as the single events, the previously assessed OSR MS8 × RF3, and OSR MON 88302 × MS8 × RF3. Since the post‐market environmental monitoring plan for the three‐event stack OSR does not include any provisions for two subcombinations not previously assessed, the GMO Panel recommended the applicant to revise the plan accordingly.