Genetically Modified Herbicide-tolerant Research Articles

Relations between the oilseed rape volunteer seedbank, and soil factors, weed functional groups and geographical location in the UK

Data mining techniques were applied to model the presence and abundance of volunteer oilseed rape (OSR) ( Brasica napus L.) in the seedbank at 257 arable fields used for baseline sampling in the UK's Farm Scale Evaluations of genetically modified herbicide tolerant (GMHT) crops. Constructed models were supported by statistical tests. Volunteer OSR was most likely present if a previous OSR crop had been grown in the same field, but it was also present at sites where it had not been grown in the previous 8 years (24% of all fields). In 136 fields where it was found, it showed a slow decline in abundance since the last crop. However, data mining indicated previously unfound correlations between oilseed rape abundance, total seedbank and several other factors, notably percent of nitrogen and percent of carbon in the soil, all of which were smallest in the centre of arable production in southern England and greatest in the surrounding south-west, west and north. In a separate analysis, its abundance was also associated with particular plant life history groups, which include broadleaf weeds such as Capsella and Matricaria species, having a similar phenology to oilseed rape, between rapidly developing annuals and the biennials and perennials. The findings are a reference point in the evolution of oilseed rape as a weed and potential GM impurity. Data mining approaches provide models that may be used to assess the status of volunteer OSR in other countries or at a later time in the UK.

Statistical models to evaluate invertebrate–plant trophic interactions in arable systems

Over the past 40 years there have been marked shifts in arable farmland management that are widely believed to have had a considerable impact on flowering plants and invertebrates and the small mammals and birds that rely upon them. It is not yet possible to predict the dynamics of plants and invertebrates either with past or future changes in farmland management. This study investigates whether a basic invertebrate classification, formed of broad trophic groups, can be used to describe interactions between invertebrates and their resource plants and evaluate management impacts for genetically modified, herbicide-tolerant (GMHT) and conventional herbicide management in both spring- and winter-sown oilseed rape. It is argued that the analyses validate trophic-based approaches for describing the dynamics of invertebrates in farmland and that linear models might be used to describe the changes in invertebrate trophic group abundance in farmland when driven by primary producer abundance or biomass and interactions between invertebrates themselves. The analyses indicate that invertebrate dynamics under GMHT management are not unique, but similar to conventional management occurring over different resource ranges, and that dynamics differed considerably between spring- and winter-sown oilseed rape. Thus, herbicide management was of much lower impact on trophic relationships than sowing date. Results indicate that invertebrate dynamics in oilseed rape are regulated by a combination of top-down and bottom-up trophic processes.

Mitigation of indirect environmental effects of GM crops

Currently, the UK has no procedure for the approval of novel agricultural practices that is based on environmental risk management principles. Here, we make a first application of the 'bow-tie' risk management approach in agriculture, for assessment of land use changes, in a case study of the introduction of genetically modified herbicide tolerant (GMHT) sugar beet. There are agronomic and economic benefits, but indirect environmental harm from increased weed control is a hazard. The Farm Scale Evaluation (FSE) trials demonstrated reduced broad-leaved weed biomass and seed production at the field scale. The simplest mitigation measure is to leave a proportion of rows unsprayed in each GMHT crop field. Our calculations, based on FSE data, show that a maximum of 2% of field area left unsprayed is required to mitigate weed seed production and 4% to mitigate weed biomass production. Tilled margin effects could simply be mitigated by increasing the margin width from 0.5 to 1.5 m. Such changes are cheap and simple to implement in farming practices. This case study demonstrates the usefulness of the bow-tie risk management approach and the transparency with which hazards can be addressed. If adopted generally, it would help to enable agriculture to adopt new practices with due environmental precaution.

Effects of successive seasons of genetically modified herbicide-tolerant maize cropping on weeds and invertebrates

The use of genetically modified herbicide-tolerant (GMHT) crops influences the abundance of weeds and some invertebrate groups because the associated herbicide regime contrasts with that of conventional systems. However, it is not clear to what extent these effects might be cumulative; should GMHT crops be grown continuously. In northern Europe, in the near future, this situation is most likely to apply to maize crops. Here, we consider the effects of continuous GMHT maize cropping on plant and invertebrate taxa using a split-field experiment. Half of each field was managed using GMHT and the other half with a conventional variety, with the treatments retained for two seasons. The treatment effects were broadly consistent with those found in the larger sample of non-continuous maize sites within the Farm Scale Evaluations. There was little evidence of effects being significantly more pronounced in the second year; any cumulative differences in above-ground biodiversity between GMHT and conventional cropping were too variable to be readily detected.

Out-crossing between genetically modified herbicide-tolerant and other winter oilseed rape cultivars

Out-crossing between genetically modified herbicide-tolerant (GMHT) and non-GM rape cultivars was studied using GMHT source field plots of approximately 0.8 ha. Levels of cross-pollination between adjacent fully fertile rape varieties declined rapidly with increasing distance from the interface between plots. A varietal association with low levels of male sterility showed higher levels of out-crossing than other varieties. Out-crossing data were used to compare negative exponential and inverse power-law models for their fit to describe the observed relationship between cross-pollination and distance from source. Results showed that the inverse power-law model provided a better fit of the data.

The effects of GMHT crops on bird abundance in arable fields in the UK

Abstract Bird surveys were carried out in summer 2000 and winter 2000/2001 on 24 sugar beet fields, 11 maize fields, 10 spring rape fields and (for winter-only) 23 winter rape fields divided into conventional and genetically modified herbicide tolerant (GMHT) treatments. These fields were a sub-sample of those used in the farm scale evaluation (FSE [Firbank, L.G, Heard, M.S., Woiwod, I.P., Hawes, C., Haughton, A.J., Champion, G.T., Scott, R.J., Hill, M.O., Dewar, A.M., Squire, G.R., May, M.J., Brooks, D.R., Bohan, D.A., Daniels, R.E., Osborne, J.L., Roy, D.B., Black, H.I.J., Rothery, P., Perry, J.N., 2003. An introduction to the farm-scale evaluations of genetically modified herbicide tolerant crops. J. Appl. Ecol. 40, 2–16.]). The study aimed to compare bird abundance between GMHT and conventional crop treatments. In the summer, the abundance of yellowhammers Emberiza citrinella and of granivores collectively was significantly greater on conventional than GMHT sugar beet. Abundance of granivores and species richness was significantly greater on conventional than GMHT maize, but only after the application of herbicides to the GMHT treatment. No significant differences were detected in spring oilseed rape. No significant differences were detected prior to herbicide application in any crop. In winter, granivores were more abundant on bare plough following conventional sugar beet treatment than following GMHT treatment. Woodpigeon Columba palumbus , blackbird Turdus merula and corvids were more abundant on maize stubbles following GMHT treatment. These differences were in accord with likely differences in food availability ascertained from previous research carried out under the FSE.

Weed seed resources for birds in fields with contrasting conventional and genetically modified herbicide-tolerant crops

The UK Farm Scale Evaluations (FSEs) have shown that the use of broad spectrum herbicides on genetically modified herbicide-tolerant (GMHT) crops can have dramatic effects on weed seed production compared to management of conventional varieties. Here, we use FSE data and information on bird diets to determine how GMHT cropping might change the food resources available to farmland birds. More than 60 fields of each of four crops, spring- and winter-sown oilseed rape, beet and maize, were split, one half being sown with a conventional variety, the other with a GMHT variety. Seed rain from weeds known to be important in the diets of 17 granivorous farmland bird species was measured under the two treatments. In beet and spring oilseed rape, rain of weed seeds important in the diets of 16 bird species was significantly reduced in GMHT compared to conventional halves; for no species did it increase. In winter oilseed rape, rain of weed seeds important in the diets of 10 species was significantly reduced in GMHT halves; for only one species did it increase significantly. By contrast, in maize, rain of weed seeds important in the diets of seven species was significantly greater in GMHT halves; for no species was it reduced. Treatment effects for the total weed seed energy available to each bird species were very similar to those for seed rain alone. Measuring the effects on individual bird species was outside the scope of this study. Despite this, these results suggest that should beet, spring and winter rape crops in the UK be largely replaced by GMHT varieties and managed as in the FSEs, this would markedly reduce important food resources for farmland birds, many of which declined during the last quarter of the twentieth century. By contrast, GMHT maize would be beneficial to farmland birds.

Using a spatial and stage-structured invasion model to assess the spread of feral populations of transgenic oilseed rape

The risk of roadside verge invasion by transgenic plants is favoured when a cultivated species can persist outside fields as feral populations. We chose oilseed rape as a model species to evaluate the spread of genetically modified herbicide tolerant (GMHT) feral populations under selection pressure (herbicide spraying) in the medium term. We developed a stepwise invasion model that combines stage-structured dynamics (via a leslie matrix) and seed dispersal (via a mixture of two kernels) within an integro-differential equation. Modelling choices were made to conform to our intention to obtain methodological insight about the necessity to integrate long-distance seed dispersal in models of gene flow among oilseed rape. We thus assumed that roadside verges are a one-dimensional and uniformly suitable habitat and that events of dispersal and demography are deterministic. We performed elasticity analyses of population growth rate and invasion speed to highlight the determinants of population demography and spread. Rare events of long-distance dispersal controlled population spread. The risk of road verge invasion by feral populations of GMHT oilseed rape under selection pressure is thus real and does exist, since it was proved experimentally that oilseed rape can be dispersed by vehicles. Models of oilseed rape should then include long-distance seed dispersal otherwise they would underestimate feral population spread. Population growth rate and invasion speed depended on the same demographic transitions, i.e. those including local recruitment (local production of new individuals), but not on the persistence of seeds in the seed bank. Therefore, plant sterilisation would be more efficient to limit feral population spread than selection of cultivars without seed dormancy. The assumptions made about habitat continuity and homogeneity were consistent in the framework of this stepwise approach. However, integrating habitat heterogeneity and stochasticity would improve this invasion model.

Effects of genetically modified herbicide-tolerant cropping systems on weed seedbanks in two years of following crops

The Farm Scale Evaluations (FSEs) showed that genetically modified herbicide-tolerant (GMHT) cropping systems could influence farmland biodiversity because of their effects on weed biomass and seed production. Recently published results for winter oilseed rape showed that a switch to GMHT crops significantly affected weed seedbanks for at least 2 years after the crops were sown, potentially causing longer-term effects on other taxa. Here, we seek evidence for similar medium-term effects on weed seedbanks following spring-sown GMHT crops, using newly available data from the FSEs. Weed seedbanks following GMHT maize were significantly higher than following conventional varieties for both the first and second years, while by contrast, seedbanks following GMHT spring oilseed rape were significantly lower over this period. Seedbanks following GMHT beet were smaller than following conventional crops in the first year after the crops had been sown, but this difference was much reduced by the second year for reasons that are not clear. These new data provide important empirical evidence for longer-term effects of GMHT cropping on farmland biodiversity.

Predicting longer‐term changes in weed populations under GMHT crop management

SummaryThe UK Farm Scale Evaluations (FSE) compared the effects on biodiversity of management of genetically modified herbicide‐tolerant (GMHT) crops and conventional crops over the shorter term. We simulated population changes over seven 4‐year rotations (28 years) for weeds in crop rotations that included cereals and spring‐sown GMHT and conventional oilseed rape and beet, using FSE data and assuming the continuation of the weed management systems practised in the FSE. The weed density dependence that was modelled integrated change caused by population dynamics and farmers’ responses to changes in weed density. Predicted weed seed populations decreased under conventional management and at a greater rate under GMHT. Total seed densities were lower for GMHT cropping by a factor of 0.7–0.8. The predicted distributions of weeds had more fields with lower weed densities under GMHT cropping. Such changes could affect animal populations on farmland, depending on the scale of uptake of GMHT crop cultivars.

Invertebrate biodiversity in maize following withdrawal of triazine herbicides

Responses of key invertebrates within Farm Scale Evaluations (FSEs) of maize reflected advantageous effects for weeds under genetically modified herbicide-tolerant (GMHT) management. Triazine herbicides constitute the main weed control in current conventional systems, but will be withdrawn under future EU guidelines. Here, we reappraise FSE data to predict effects of this withdrawal on invertebrate biodiversity under alternative management scenarios. Invertebrate indicators showed remarkably consistent and sensitive responses to weed abundance. Their numbers were consistently reduced by atrazine used prior to seedling emergence, but at reduced levels compared to similar observations for weeds. Large treatment effects were, therefore, maintained for invertebrates when comparing other conventional herbicide treatments with GMHT, despite reduced differences in weed abundance. In particular, benefits of GMHT remained under comparisons with best estimates of future conventional management without triazines. Pitfall trapped Collembola, seed-feeding carabids and a linyphiid spider followed closely trends for weeds and may, therefore, prove useful for modelling wider biodiversity effects of herbicides. Weaker responses to triazines applied later in the season, at times closer to the activity and capture of invertebrates, suggest an absence of substantial direct effects. Contrary responses for some suction-sampled Collembola and the carabid Loricera pilicornis were probably caused by a direct deleterious effect of triazines.

Management of genetically modified herbicide–tolerant sugar beet for spring and autumn environmental benefit

When used in genetically modified herbicide-tolerant (GMHT) crops, glyphosate provides great flexibility to manipulate weed populations with consequences for invertebrates and higher trophic levels, for example birds. A range of timings of band and overall spray treatments of glyphosate to GMHT sugar beet were compared with a conventional weed control programme in four field trials over 2 years. Single overall sprays applied between 200 and 250 accumulated day degrees (above a base air temperature of 3 degrees C; degrees Cd) and band applied treatments applied at 10% or 20% ground cover within the crop rows generally gave significantly greater weed biomass and seed rain than conventional treatments, while later band sprays (more than 650 degrees Cd) reduced seed return. Two overall sprays of glyphosate produced low weed biomass and generally lowest seed return of all treatments but tended to give some of the highest yields. However, the early overall sprays (200-250 degrees Cd) and band sprays gave as good or better yields than the conventional and were generally equivalent to the two overall-spray programme. Viable seeds in the soil after the experiment were generally higher following the early overall (200-250 degrees Cd) and the band spray treatments than following the conventional. The results show that altered management of GMHT sugar beet can provide alternative scenarios to those of the recent Farm Scale Evaluation trials. Without yield loss they can enhance weed seed banks and autumn bird food availability compared with conventional management, or provide early season benefits to invertebrates and nesting birds, depending on the system chosen. Conventional weed control does not have the flexibility to enable these scenarios that benefit both agriculture and environment, although there may be some options for increasing weed seed return in autumn.

Weed and arthropod populations in conventional and genetically modified herbicide tolerant fodder beet fields

The introduction of genetically modified herbicide tolerant (GMHT) crops has raised concerns from both scientists and non-governmental organisations about possible effects on arable flora and fauna due to the changes in herbicide application and management that such crops involve. Three consecutive studies were performed, covering flora and fauna in fields of GMHT and conventional fodder beets over the season, at different locations and under different spraying regimes. At all locations and in the 3 years, a denser and more diverse weed flora and arthropod fauna were found in GMHT beets in early and mid-summer than in conventional beets when glyphosate-treatment occurred at or after label recommendation. Following the herbicide applications the GMHT fields had fewer weed species and seeds and lower weed densities and biomass than conventional fields. However, application of glyphosate earlier than recommended resulted in an extremely low weed diversity, density and biomass during the entire season. Timing of the first glyphosate applications, i.e. the duration of the herbicide free period, was essential in terms of biodiversity improvements. In the long term reduced production of weed seeds in GMHT fields may deplete the weed flora if the GMHT strategy becomes widely adopted.

Genetically Modified Herbicide-tolerant Chile Pepper Does Not Differ From Non-GM Chile Pepper (Capsicum annuum L. cv. `Subicho') For Horticultural Characteristics.

Genetically modified herbicide-tolerant (GMHT) and non-GM chile pepper plants (Capsicum annuum L. cv. `Subicho') were grown in an isolated GMO field to evaluate horticultural characteristics. Phosphinotricin acetyltransferase (bar gene), which has a function of herbicide-resistance in plant, was introduced into chile pepper plants using the protocol of Agrobacterium-mediated transformation. Thirty nine characteristics were evaluated, consisting of 14 qualitative, 18 quantitative and 7 other characters. The evaluations were achieved by visual assessment for qualitative characteristics and numerical measurement for quantitative ones. The GMHT and non-GM plants did not differ in the 39 characteristics tested. Pollen viability and germination rate were not significant different between the GMHT plants and the non-GM plants. These results indicated that genetic transformation of bar gene into the chile pepper did not affect those horticultural characteristics and pollen viability.

Management of herbicide-tolerant oilseed rape in Europe: a case study on minimizing vertical gene flow

The potential commercialization of genetically modified herbicide-tolerant (GMHT) oilseed rape in Europe raises various concerns about their potential environmental and agronomic impacts, especially those associated with the escape of transgenes. Pollen of oilseed rape can be dispersed in space, resulting in the fertilization of sympatric compatible wild relatives (e.g. Brassica rapa) and oilseed rape cultivars grown nearby (GM and/or non-GM Brassica napus). The spatial and temporal dispersal of seeds of oilseed rape may lead to feral oilseed rape populations outside the cropped areas and oilseed rape volunteers in subsequent crops in the rotation. The incorporation of a HT trait(s) may increase the fitness of the recipient plants, making them more abundant and persistent, and may result in weeds that are difficult to control by the herbicide(s) to which they are tolerant. Vertical gene flow from transgenic oilseed rape to non-GM counterparts may also have an impact on farming and supply chain management, depending on labelling thresholds for the adventitious presence of GM material in non-GM products. Given the extent of pollen and seed dispersal in oilseed rape, it is obvious that the safe and sound integration of GMHT oilseed rape in Europe may require significant on-farm and off-farm management efforts. Crucial practical measures that can reduce vertical gene flow include (1) isolating seed production of Brassica napus, (2) the use of certified seed, (3) isolating fields of GM oilseed rape, (4) harvesting at the correct crop development stage with properly adjusted combine settings, (5) ensuring maximum germination of shed seeds after harvest, (6) controlling volunteers in subsequent crops, and (7) keeping on-farm records. The implementation of the recommended practices may, however, be difficult, entailing various challenges.

Ecology. Deciding the future of GM crops in Europe.

To address concerns about genetically modified (GM) crops in the United Kingdom, a series of Farm Scale Evaluations were set up throughout England and Scotland to determine the effects of herbicide-tolerant GM crops versus conventional crops on farmland biodiversity. The results of this group of studies have now been published by the Philosophical Transactions of the Royal Society of London. In a thoughtful and balanced Perspective, [Freckleton, Sutherland and Watkinson][1] explain the findings of the Farm Scale Evaluation papers and discuss their implications for lifting the moratorium on growing GM crops in the United Kingdom. [1]: http://www.sciencemag.org/cgi/content/full/302/5647/994

Invertebrate responses to the management of genetically modified herbicide–tolerant and conventional spring crops. II. Within-field epigeal and aerial arthropods

The effects of the management of genetically modified herbicide-tolerant (GMHT) crops on the abundances of aerial and epigeal arthropods were assessed in 66 beet, 68 maize and 67 spring oilseed rape sites as part of the Farm Scale Evaluations of GMHT crops. Most higher taxa were insensitive to differences between GMHT and conventional weed management, but significant effects were found on the abundance of at least one group within each taxon studied. Numbers of butterflies in beet and spring oilseed rape and of Heteroptera and bees in beet were smaller under the relevant GMHT crop management, whereas the abundance of Collembola was consistently greater in all GMHT crops. Generally, these effects were specific to each crop type, reflected the phenology and ecology of the arthropod taxa, were indirect and related to herbicide management. These results apply generally to agriculture across Britain, and could be used in mathematical models to predict the possible long-term effects of the widespread adoption of GMHT technology. The results for bees and butterflies relate to foraging preferences and might or might not translate into effects on population densities, depending on whether adoption leads to forage reductions over large areas. These species, and the detritivore Collembola, may be useful indicator species for future studies of GMHT management.

Weeds in fields with contrasting conventional and genetically modified herbicide–tolerant crops. II. Effects on individual species

We compared the effects of the management of genetically modified herbicide-tolerant (GMHT) and conventional beet, maize and spring oilseed rape on 12 weed species. We sampled the seedbank before and after cropping. During the season we counted plants and measured seed rain and biomass. Ratios of densities were used to calculate emergence, survival, reproduction and seedbank change. Treatments significantly affected the biomass of six species in beet, eight in maize and five in spring oilseed rape. The effects were generally consistent, with biomass lower in GMHT beet and spring oilseed rape and higher in GMHT maize. With few exceptions, emergence was higher in GMHT crops. Subsequent survival was significantly lowered for eight species in beet and six in spring oilseed rape in the GMHT treatments. It was increased for five species in maize and one in spring oilseed rape. Significant effects on seedbank change were found for four species. However, for many species in beet and spring oilseed rape (19 out of 24 cases), seed densities were lower in the seedbank after GMHT cropping. These differences compounded over time would result in large decreases in population densities of arable weeds. In maize, populations may increase.

Design of the farm‐scale evaluations of genetically modified herbicide‐tolerant crops

AbstractThe Farm‐Scale Evaluations (FSE) is a three‐year experiment to study the effects on farmland wildlife of the commercial management of four genetically modified herbicide‐tolerant (GMHT) crops—beet, maize, spring oil‐seed rape and winter oil‐seed rape. The experiment records abundance of a wide range of weed and invertebrates in the arable system. The FSE is a paired comparison arranged as a randomized block design with two treatments (GMHT and conventional crop management) and fields as blocks. The choice of the half‐field as the experimental unit is based on field availability, the primary focus on the vegetation, the need to reduce variability and gains in sampling effort. Farms and fields are selected to reflect the range of geographical variation and farming intensity for each crop. A power analysis shows that using about 60 fields per crop over the three years will be sufficient to detect differences of ecological significance. Copyright © 2003 John Wiley & Sons, Ltd.

Herbicide-Tolerant Crops – Good or Bad for Europe?

Genetically modified herbicide-tolerant (GMHT) crops are being grown in many parts of the world. The EU will soon make a decision on their commercialization in Europe. It is not easy for legislators to reach conclusions as to the risks and benefits. This paper looks at the information emerging from countries where these GMHT crops are already commercialized, and identifies the benefits and problems. It then looks at issues especially relevant to the UK and not fully covered by the field experiences elsewhere, and where specific European research projects have endeavoured to find answers. It seeks to identify the benefits and the real problems for the UK that need to be resolved prior to commercialization.