Pollen-mediated gene flow from transgenic cotton is constrained by physical isolation measures

Pollen-mediated gene flow in the cultivation of transgenic cotton under experimental field conditions in Spain

There is an increasing concern about the coexistence between GM (genetically modified) and non-GM (non-genetically modified) crops. Maize (Zea mays L.) is a cross-pollinated crop, so pollen dispersion is an important way of gene flow (pollen-mediated gene flow, PMGF) in maize. Cross-pollination can occur between non-GM maize planted in open environments next to GM maize field. Therefore, the combination of isolation distance and border rows could keep the gene flow less than labeling threshold. The field experiments were conducted at Taiwan (R.O.C) Agricultural Research Institute in Wufeng District, Taichung City in 2009 and 2010. There were two crop seasons in each year. In our study, the Black Pearl (source plot: purple kernel) was planted in the center while the White Pearl (receptor plot: white kernel) was planted in the surroundings in 2009. In 2010, using four varieties (Honey 236, Black Pearl, Tainung 1, Tainung 4) to simulate GM maize as pollen source and using Snow Jean to simulate non-GM maize as receptor. Our objectives was to confirm the isolation of maize from gene flow by distance (2009 experiment) and time (2010 experiment). Overall, when the isolation distance was 18.75 m (pollen source and pollen receptor synchrony in flowering times), the mean of outcrossing rate can decrease to 0.64%. We provide a security distance between GM and non-GM fields of about 20 m should be sufficient to maintain the adventitious presence of GM maize from gene flow below the 0.9% threshold (labelling threshold in the European Union). Increasing temporal separation reduced the distance required to achieve gene flow isolation. Outcrossing rate was <0.9% at 0.75m when 1 week of temporal separation was used. In previous researches, atmospheric dispersion model was used to simulate the pollen spread of maize. However, in this study, the simplified Gaussian plume model was fitted well (R2=0.845) for the outcrossing rate data. In our study, a model based on Gaussian plume model was used to calculate the pollen concentration and pollution rate of non-GM maize by GM maize in down wind. The modified model of Gaussian plume model can simulate the outcrossing rate of serious cases by simple parameters (data from 2009-1 and 2009-2), which also could provide an useful tool to control coexistence of GM and non-GM maize in the future.

Genetically modified organisms (GMOs) have been developed and commercialized in many countries for the past decade. The regulations on these GMOs in Korea have been established through the labeling and safety evaluation systems for management of genetically modified (GM) foods under the Food Sanitation Act enacted by the Korea Food and Drug Administration (KFDA). To manage these regulations effectively, several methods for GMO detection, including polymerase chain reaction (PCR) methods and immunoassay, are applied. For detection of GMOs at the level of DNA, primers from the promoter, terminator, other marker genes, and expressed proteins used in a wide range of GMOs were designed for single, multiplex, real-time PCR, and microarray applications. In Korea, multiplex PCR methods specific to GM soybean, maize, canola, and cotton were designed. The limit of detection (LOD) value was determined to be 1 % of GM mixtures, which is a significant value for the PCR method used for the labeling threshold in Korea. A DNA microarray chip was also developed for the detection of 24 GMOs, including GM soybeans, 13 GM maizes, 3 GM canolas, 5 GM cottons, and 1 GM rice. This DNA chip was proven to successfully detect GMOs from raw and processed foods. In the near future, more powerful screening and detection methods are needed for handling many kinds of GMOs and unauthorized GMOs.

Modeling and estimation of pollen-mediated gene flow at the landscape scale

Persistence of seeds, seedlings and plants, performance of transgenic wheat in weed communities in the field and effects on fallow weed diversity

ISAAA has estimated that genetically modified (GM) crops, mainly soybean, maize, cotton and canola, are cultivated worldwide in an area that has increased from 1.7 million hectares in 1996 to 134 million hectares in 2009, of which more than 80% have an herbicide-tolerant trait (ISAAA 2010). This work reviews the agricultural and environmental concerns about the likelihood for gene flow from GM wheat (Triticum aestivum L.). Wheat is the world’s most important crop species, grown on over 210 million hectares. There are no GM wheat varieties commercially available but transgenic wheat varieties are being successfully developed and field-tested. That makes wheat in the pipeline of genetically engineered crops to be cultivated. Although wheat is predominantly a self-pollinating crop, pollen from one plant can travel via wind to other receptive plant, being outcrossing between wheat cultivars possible at variable rates. Coexistence problems in wheat could thus arise if no measures are taken before releasing and marketing any transgenic cultivar, as has occurred with other GM crops such as oilseed rape or maize, where measures were implemented after commercial transgenic introduction. Besides this, wild Aegilops species like Ae. geniculata Roth., Ae. cylindrica Host., Ae. biuncialis Vis. or Ae. triuncialis L. can form natural interspecific hybrids with wheat where they grow in sympatry. These natural hybrids are highly sterile, although seeds may occasionally be found. Data presented aim to contribute to the determination of the extent of this phenomena. These data are necessary to manage the possible impact of transgenic wheat hybrids before the transgenic crop can be grown under field conditions. Herbicide-tolerant wheat parental varieties can be used to obtain resistant progeny detectable by herbicide selection, providing a high approach to the potential occurrence of intra and interspecific pollen mediated gene flow.

For more than 20 years cotton has been the most widely sown genetically modified (GM) crop in Mexico. Its cultivation has fulfilled all requirements and has gone through the different regulatory stages. During the last 20 years, both research-institutions and biotech-companies have generated scientific and technical information regarding GM cotton cultivation in Mexico. In this work, we collected data in order to analyze the environmental and agronomic effects of the use of GM cotton in Mexico. In 1996, the introduction of Bt cotton made it possible to reactivate this crop, which in previous years was greatly reduced due to pest problems, production costs and environmental concerns. Bt cotton is a widely accepted tool for cotton producers and has proven to be efficient for the control of lepidopteran pests. The economic benefits of its use are variable, and depend on factors such as the international cotton-prices and other costs associated with its inputs. So far, the management strategies used to prevent development of insect resistance to GM cotton has been successful, and there are no reports of insect resistance development to Bt cotton in Mexico. In addition, no effects have been observed on non-target organisms. For herbicide tolerant cotton, the prevention of herbicide resistance has also been successful since unlike other countries, the onset of resistance weeds is still slow, apparently due to cultural practices and rotation of different herbicides. Environmental benefits have been achieved with a reduction in chemical insecticide applications and the subsequent decrease in primary pest populations, so that the inclusion of other technologies—e.g., use of non-Bt cotton- can be explored. Nevertheless, control measures need to be implemented during transport of the bolls and fiber to prevent dispersal of volunteer plants and subsequent gene flow to wild relatives distributed outside the GM cotton growing areas. It is still necessary to implement national research programs, so that biotechnology and plant breeding advances can be used in the development of cotton varieties adapted to the Mexican particular environmental conditions and to control insect pests of regional importance.

In recent years, the influence of genetically modified (GM) cotton expressing different types of Bt and EPSPS genes has been attested in term of reduced application of pesticides and insecticides coupled with improved cotton production. Although the cultivation of GM cotton has been authorized by the regulatory authorities of various countries in the world, based on the biosafety studies reported by most of the GM cotton producers, yet the information on its safe use are inadequate. In order to support the issues on food safety, it is therefore mandatory to conduct further safety assessment studies on GM cotton for each independent transgenic event on the basis of case assessment rule. In the present study, the effects of different doses of dietary GM cotton seed expressing Bt and EPSPS genes were studied on the level of serum biochemical in albino rabbits (Oryctolagus cuniculus). The rabbits were fed a diet containing different levels of GM cotton seeds (i.e., 20, 30, and 40% w/w) respectively mixed with standard diet for 180 days. During the course of the study, various serum enzymes, electrolytes, proteins, glucose and serum total cholesterol were examined at specific time intervals (0, 45, 90, 135, and 180) days. The results showed non-significant (P > 0.05) dose dependent effects in most of the evaluated serum biochemical parameters. Although, the results in some of the serum biochemistry were significantly different (P < 0.05) among the groups, however, they were not biologically significant, since all the differences were within the normal physiological range. These results thus, suggested that the GM cotton seed meal could be considered as safe as other conventional feed ingredients. The experimental evidence for the safe usage of GM cotton was highlighted in this study.

http://www3.interscience.wiley.com/cgi-bin/fulltext/120696197/HTMLSTART

Pollen migration in Pinus roxburghii has been estimated under two different conditions, viz. isolated single trees and at the fringe of natural forest. Trapping of pollen grains was conducted at geometrically increasing distances, i.e., 0, 5, 10, 20, 40, 80, 160, 320, 640, 1280 and 2560 m from the source. The observations revealed that the scattering of pollen grains was not uniform in all directions and that they travelled up to 2.5 km towards the downhill direction, while in the uphill direction dispersion of pollen grains was restricted to 320 m from the source. Pollen frequency declined rapidly as the distance from the source increased, with the highest densities within 50–100 m.

In this paper, we consider the pollen-mediated gene flow of purple-colored maize lines during co-cultivation with yellow-grain pollen-recipient maize lines. We analyze the factors influencing pollen dispersion: wind (speed and direction), distance, the synchrony of the pollen donor and receptor flowering. It was established that the maximum percentage of crosses in maize lines with the same flowering dates was recorded at the distance of 1–4 m from the donor plant. The percentage of crosses decreased by a factor of 5 with an increase in the distance to 10 m. At a distance of 40 m from the donor plant, the percentage of hybrid grains among the freely pollinated grains of the recipient plant fell by a factor of 12.5. At close distances (1–4 m), hybrid grains on the cobs of the recipient lines were observed 4 times longer in the line with earlier flowering periods or in the line with the same flowering times, but with a sharper angle of leaves. According to our experimental data, at a distance of 10 m from the maize of a pollen donor, the guaranteed does not exceed the Russian threshold of 0.9% of the presence of GMO products in food (yield). The analysis of experiments on maize spreading with pollen in Volga region of Russia provides evidence-based recommendations for safe co-cultivation of non-GM and GM varieties and maize lines at the distance 10 m.

The potential impact of genetically modified (GM) crops on biodiversity is one of the main concerns in an environmental risk assessment (ERA). The likelihood of outcrossing and pollen-mediated gene flow from GM crops and non-GM crops are explained by the same principles and depend primarily on the biology of the species. We conducted a national-scale study of the likelihood of outcrossing between 11 GM crops and vascular plants in Chile by use of a systematized database that included cultivated, introduced and native plant species in Chile. The database included geographical distributions and key biological and agronomical characteristics for 3505 introduced, 4993 native and 257 cultivated (of which 11 were native and 246 were introduced) plant species. Out of the considered GM crops (cotton, soya bean, maize, grape, wheat, rice, sugar beet, alfalfa, canola, tomato and potato), only potato and tomato presented native relatives (66 species total). Introduced relative species showed that three GM groups were formed having: a) up to one introduced relative (cotton and soya bean), b) up to two (rice, grape, maize and wheat) and c) from two to seven (sugar beet, alfalfa, canola, tomato and potato). In particular, GM crops presenting introduced noncultivated relative species were canola (1 relative species), alfalfa (up to 4), rice (1), tomato (up to 2) and potato (up to 2). The outcrossing potential between species [OP; scaled from 'very low' (1) to 'very high' (5)] was developed, showing medium OPs (3) for GM-native relative interactions when they occurred, low (2) for GMs and introduced noncultivated and high (4) for the grape-Vitis vinifera GM-introduced cultivated interaction. This analytical tool might be useful for future ERA for unconfined GM crop release in Chile.

Black M, Bewley JD, eds. 2000. Seed technology and its biological basis. 419 pp. Sheffield: Sheffield Academic Press. £89 (hardback).

Extent of pollen-mediated gene flow and seed longevity in switchgrass (Panicum virgatum L.): Implications for biosafety procedures

Transgenic wheat (Triticum aestivum L.) varieties are being developed and field-tested in various countries. Concerns regarding gene flow from genetically modified (GM) crops to non-GM crops have stimulated research to estimate outcrossing in wheat prior to the release and commercialization of any transgenic cultivars. The aim is to ensure that coexistence of all types of wheat with GM wheat is feasible in accordance with current regulations. The present study describes the result of a field experiment under the semi-arid climate conditions of Madrid, Spain, at two locations ("La Canaleja" and "El Encin" experimental stations) in Madrid over a 3-year period, from 2005 to 2007. The experimental design consisted of a 50 × 50 m wheat pollen source sown with wheat cultivars resistant to the herbicide chlortoluron ('Deganit' and 'Castan' respectively) and three susceptible receptor cultivars ('Abental', 'Altria' and 'Recital') sown in replicated 1 × 1 m plots at different distances (0, 1, 3, 5, 10, 20, 40, 80 and 100 m) and four directions. Outcrossing rates were measured as a percentage of herbicide-resistant hybrids using an herbicide-screening assay. Outcrossing was greatest near the pollen source, averaging 0.029% at 0 m distance at "La Canaleja" and 0.337% at "El Encin", both below the 0.9% European Union regulated threshold, although a maximum outcrossing rate of 3.5% was detected in one recipient plot. These percentages declined rapidly as the distance increased, but hybrids were detected at different rates at distances of up to 100 m, the maximum distance of the experiment. Environmental conditions, as drought in 2004-2005 and 2005-2006, may have influenced the extent of outcrossing. These assays carried out in wheat under semi-arid conditions in Europe provide a more complete assessment of pollen-mediated gene flow in this crop.