Figure 4 - uploaded by Antje Dietz-Pfeilstetter
Content may be subject to copyright.
Detection of the mutated clg1 gene in spiked DNA samples by PCR. C: 100 ng CLG seed DNA; M: 100 ng Marcant seed DNA; 0.11%: CLG seed DNA diluted in Marcant seed DNA; NTC: no template control; size standard: Generuler 100 bp plus Ladder (Fermentas).
Source publication
Canola (Brassica napus) varieties containing inherent restrictions on gene flow may address problems of seed- and pollenmediated gene flow. The aim of this study was to explore the effectiveness of 1) low-dormancy varieties in avoiding GM soil seedbanks and volunteers, and 2) cleistogamous (clg) genotypes to avoid outcrossing. GM and non-GM varieti...
Context in source publication
Context 1
... qualitative PCR method was shown to be specific at an annealing temperature of 62°C for the detection of mutated clg1 gene sequences of CLG seed DNA in a background of non-target canola DNA (Marcant). The primer set yielded in an amplification of a specific prod- uct of the expected size of 218 bp clg1 gene sequences were detected, even in samples with < 0.1% of CLG seed DNA in a background of Marcant seed DNA, while the negative control (100% Marcant seed DNA) showed no amplification (Figure 4). ...
Citations
... It should be mentioned that the percentage of hybrid seeds was even higher if the oilseed rape was the maternal plant. Considering the large losses accompanying the gathering of the crop (several thousands of seeds are lost per m 2 , while the germination could be maintained for up to 10 years) (Gruber et al., 2012) and the unpretentiousness of oilseed rape, the use of crop lines with male sterility should be additionally accompanied by technologies allowing the minimization of the seed loss during both crop collection and its transport. ...
The lack of knowledge about the impact on ecosystems has restricted the expansion of genetically modified plants. We review the potential gene flow into the environment due to the cultivation of transgenic oilseed rape. The problem is immediate for this crop as its allogamous weedy relatives are widespread. The main difficulty in assessing the risk is caused by the fluctuation in the hybridization frequencies depending on the transgenes used, the crop’s line and population features, and also the imperfection of current methods of molecular diagnostics. In order to minimize such risks, the preliminary investigation of crosspollination, inheritance, expression, and phenotypical effects of transgenes in hybrids with both their wild and domestic relatives is recommended in all regions where GM-crops are going to be grown. Based on this data, specific measures and recommendations to prevent gene flow can be developed. Domestic GM-crop lines, properly tested in local ecosystems can be grown without any environmental threat.
... There is clear evidence that the potential to develop secondary dormancy is affected by the OSR genotype (Gruber et al., , 2012Schatzki et al., 2013). Four QTL could be identified, which together explained 35% of the phenotypic dormancy (Schatzki et al., 2013). ...
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.
... External factors, however, such as temperature or soil moisture, which are crucial factors for dormancy induction, cannot be influenced and result from interaction of current weather conditions with soil texture. A regression analysis from a survey of farmers' fields in Germany revealed cropping frequency and region (soil/climate) as most relevant factors determining the numbers of OSR volunteers (Gruber et al. 2012). A more specific definition of the soils that offer a higher risk for volunteers would help farmers to better plan their agronomic measures beforehand. ...
The study should reveal the effects of soil texture and of seed characteristics of oilseed rape (Brassica napus L.) on seed survival in the soil by a burial experiment. Seeds of 58 conventional and new trait accessions (genetically modified and/or with altered seed ingredients) were buried for six months in sandy loam (SL), clay (C) or silty clay loam (SICL) in the seasons 2008/2009 and 2009/2010 in Germany. Between 84-93% (2008/2009) and 64-87% (2009/2010) of the conventional seeds survived in the soil, and so did 41-67% and 8-44% of the new trait seeds. Significantly more seeds were found in C and SICL compared to SL. Seed survival also significantly depended on the genotype, with high and low seed survival in both conventional and new trait accessions. Seed survival rates are probably linked with moisture and oxygen provided by different soils. As soils with good water storage condi- tions seem to have a higher probability for oilseed rape seeds from harvest losses to survive, other measures such as growing low dormancy varieties and proper soil tillage are especially relevant to avoid volunteers on these soils.
... External factors, however, such as temperature or soil moisture, which are crucial factors for dormancy induction, cannot be influenced and result from interaction of current weather conditions with soil texture. A regression analysis from a survey of farmers' fields in Germany revealed cropping frequency and region (soil/climate) as most relevant factors determining the numbers of OSR volunteers (Gruber et al. 2012). A more specific definition of the soils that offer a higher risk for volunteers would help farmers to better plan their agronomic measures beforehand. ...
... According to studies of Gruber et al. (2010) up to 17% of OSR seeds of the initial seed rain can be found in the soil seed bank one year after seed rain, and up to 1.6% of the seed rain can still exist four years after OSR harvesting, depending on OSR cultivar and the mode of soil tillage. There is clear evidence that the potential to develop secondary dormancy is affected by the OSR genotype ( Gruber et al., , 2012Schatzki et al., 2013). Four QTL could be identified, which together explained 35% of the phenotypic dormancy ( Schatzki et al., 2013). ...
... There is clear evidence that the potential to develop secondary dormancy is affected by the OSR genotype ( Gruber et al., , 2012Schatzki et al., 2013). Four QTL could be identified, which together explained 35% of the phenotypic dormancy ( Schatzki et al., 2013). ...
Volunteer oilseed rape (Brassica napus L.) can contribute to gene dispersal by pollen flow or by seed admixtures. The study should analyse the competition capacity of different crops towards oilseed rape volunteers. A field with a large soil seed bank of oilseed rape was planted with three winter crops (winter turnip rape (replacing oilseed rape, similar performance of turnip and oilseed rape presumed), winter barley, winter wheat) and three spring crops (faba beans, spring barley, maize). The crops were managed according best management practice and compared with "fallow" plots where all operations were similar to the crop plots, except sowing. The fallows should allow assessing the competition of crops and volunteers. The crop with the lowest competition capacity and highest risk for gene dispersal by oilseed rape volunteers was turnip rape (30 volunteers m-2), most of which flowered and set seeds (475 seeds plant-1), and thus exceeded the labelling threshold for transgenic admixture. Half as much volunteers established in faba beans (14 plants m-2), flowered and set seed (13 plants m-2). Though flowering volunteers were observed in spring barley, no seeds were produced. Volunteers emerged in all other crops as well, but reached neither flowering nor seed maturity. The comparison of crop and fallow showed that turnip rape, winter wheat and spring barley had the highest competition capacity towards oilseed rape volunteers. If the management practise (use of herbicides) is additionally taken into account, the crops with the lowest risk of gene dispersal by volunteer oilseed rape were maize, winter wheat and winter barley. The fallow plots were useful to assess the potential of emerging volunteers from the soil seed bank, and of gene dispersal. Plots like these (10-20 m 2) could be routinely established in commercial fields as control measurement for model calculations and predictions in terms of risk assessment.
Herbicide-tolerant winter oilseed rape (OSR) varieties offer the opportunity of using imazamox for weed control, an active ingredient belonging to the chemical group of acetolactate synthase (ALS-) inhibitors. However, ALS inhibitors are used in many different crops and are the most resistance-prone herbicide mode of action. Their frequent application in a crop rotation increases the selection pressure for ALS herbicide resistance in weeds, which has to be considered when designing resistance management strategies. Alopecurus myosuroides Huds. is a frequent and economically important grass weed in Northwestern Europe, which has evolved resistance to several herbicide modes of action. For the sustainable use of herbicide-tolerant OSR varieties, studies on the effects of the different intensities of ALS inhibitor use on A. myosuroides population dynamics and resistance development are required. Two field trials were conducted including susceptible and multiple resistant A. myosuroides individuals and four weed control strategies varying in their intensity of ALS inhibitor use over a three-year trial period. A. myosuroides head numbers, the presence of target-site mutations in surviving plants, and crop yields were assessed annually, and the amount of A. myosuroides seeds in the soil seed bank was determined at the end of the trial period. The results show that the intensity of ALS inhibitor use significantly influenced the density of A. myosuroides and the development of resistance. Under weed control strategy IV (no ALS inhibitors), an increase in A. myosuroides head number was observed due to multiple resistance in the A. myosuroides population employed in the field trial. None of the four weed control strategies was able to control A. myosuroides infestation to an acceptable level. The results on A. myosuroides densities in the soil seed bank were highly variable and inconsistent. Molecular analysis of surviving plants showed a selection of ALS-resistant biotypes depending on the ALS inhibitor selection pressure. This study did not reveal any specific deterioration of A. myosuroides infestation associated with the use of imidazolinone-tolerant OSR in a short-term crop rotation. However, this OSR production system should not be employed if ALS-resistant A. myosuroides plants are present in the field.
A joint assessment of two separate approaches investigated the occurrence of volunteer oilseed rape (Brassica napus L.; OSR) as affected by cultivar, field history and environment. Approach I comprised surveys for volunteers on >100 farmers’ fields in Germany in the years 2009 and 2010. Volunteers were assigned to the cultivars grown in previous years by inter-simple sequence repeat-PCR and cluster analysis. High-dormancy cultivars resulted in 0–7 and low-dormancy cultivars in 0–1.3 volunteers m⁻². Highest numbers originated from the most recent harvests 2007 and 2006. Approach II was a meta-analysis based on 116 data sets from field trials and farmers’ fields in Germany to evaluate and to rank the impact of management factors on the soil seedbank and volunteers in following crops. Varietal disposition to seed dormancy turned out to be the significantly most relevant factor. The contribution of varietal dormancy to variation in the soil seedbank and of volunteers in the 1st and 2nd following crop was 1.2–2.3 times as great as the contribution of post-harvest tillage. Up to 45% of the variation in the observations originated from factors that can be controlled by human actions on a given location in a given year. The overall analysis confirmed the results from independent short-term trials and showed that both agronomists and breeders need to contribute to reducing OSR volunteers.
The lack of knowledge about the impact on ecosystems restricts the expansion of genetically modified plants. We review the potential gene flow into the environment due to the cultivation of transgenic oilseed rape. The problem is immediate for this crop on the ground of the widespread of its allogamous weedy relatives. The main difficulty in risk assessment is caused by fluctuation in hybridization frequencies depending on the transgenes used, crop’s line and population features and also the imperfection of current methods of molecular diagnostics. For minimization of such risks, preliminary investigation of cross-pollination, inheritance, expression and phenotypical effects of transgenes in hybrids with both wild and domestic relatives is recommended in all regions where GM-crops are going to be grown. On the basis of this data, specific measures and recommendations to prevent gene flow can be developed. Domestic GM-crop lines, properly tested in local ecosystems, can be grown without any environmental threat.
Introduction Pathways of Gene Flow in Oilseed Rape Managing Gene Flow in Oilseed Rape Combining Biological Measures Package for Gene Containment Conclusion Acknowledgments References
For developers and regulators of genetically modified plants, an evaluation of gene flow is an essential part of the risk assessment required prior to a decision on whether a transgenic crop variety may enter the marketplace. Assessments of the probability of gene flow relative to non-GM varieties and the potential impact of the establishment of a transgene in populations outside of cultivation are used to determine a level of risk. We provide here an overview of the principles and methodologies which have been used in gene flow studies in transgenic crops. © 2014 Springer Science+Business Media New York. All rights are reserved.
