Genetically Modified Trees Research Articles

Advances and Perspectives of Transgenic Technology and Biotechnological Application in Forest Trees.

Transgenic technology is increasingly used in forest-tree breeding to overcome the disadvantages of traditional breeding methods, such as a long breeding cycle, complex cultivation environment, and complicated procedures. By introducing exogenous DNA, genes tightly related or contributed to ideal traits—including insect, disease, and herbicide resistance—were transferred into diverse forest trees, and genetically modified (GM) trees including poplars were cultivated. It is beneficial to develop new varieties of GM trees of high quality and promote the genetic improvement of forests. However, the low transformation efficiency has hampered the cultivation of GM trees and the identification of the molecular genetic mechanism in forest trees compared to annual herbaceous plants such as Oryza sativa. In this study, we reviewed advances in transgenic technology of forest trees, including the principles, advantages and disadvantages of diverse genetic transformation methods, and their application for trait improvement. The review provides insight into the establishment and improvement of genetic transformation systems for forest tree species. Challenges and perspectives pertaining to the genetic transformation of forest trees are also discussed.

Perceptions of land managers towards using hybrid and genetically modified trees

Hybridization and genetic modification are potential methods for incorporation of stress tolerance being explored to support some at-risk tree species. However, many concerns, both ecological and economic, have been identified in using these biotechnologies, such as potential for invasiveness or high cost. There is limited information on perceptions towards hybrid and genetically modified (GM) trees, particularly from individuals responsible for widescale tree management. An online survey was administered to land managers in Indiana, USA to gauge perceptions to hybrid and GM trees, and current hybrid tree use. Land managers had stronger concern for ecological, rather than economic, issues, with potential for invasiveness being strongest. Agreement was highest for using the tree types for conservation and restoration of at-risk species and production purposes. However, perceptions varied by characteristics such as concern type, age, and land type managed. Ecological concern and land type managed most strongly predicted hybrid use. Overall, the majority of land managers agreed, rather than disagreed, with a variety of potential hybrid and GM tree advantages and purposes. Thus, results indicate that if these biotechnologies are deemed appropriate for supporting at-risk species, the majority of land managers in Indiana might be agreeable to such recommendations from researchers. However, it was also clear that despite this, most respondents concurrently had strong ecological concerns about suitability as a native species replacement. To address this, it is essential that these tree types be thoroughly vetted, and land managers be actively engaged in the process, as this population would ultimately be responsible for any widescale implementation of hybrid and GM trees.

Realized pollen flow and wildling establishment from a genetically modified eucalypt field trial in Southeastern Brazil

Confined field trials of genetically modified (GM) trees are the essential step toward the identification of the most productive cultivars and the assessment of the likely environmental impacts of the GM trees including the potential for gene flow by pollen and distance dispersal by seeds. Our study investigated the potential for wildling establishment and realized pollen flow from a clonal GM eucalypt field trial in Southeastern Brazil. The GM eucalypt stand was established in 2009, surrounded by a 3m wide forest road and signal grass (Bracharia sp.) fields. No seedling regeneration was found between 2010 and 2014 in and around the stand, confirming the expectations of the unlikelihood of eucalypt seedling establishment based on its limited invasive potential in competitive tropical environments. In 2014, open-pollinated seeds were collected from 28 non-GM eucalypts located between three and 650m distance from the GM trial. A total of 420 seedlings were grown in a greenhouse and screened for the presence of the transgenic construct by a multiplexed PCR assay targeting two transgenes and an internal control. The highest average transgene pollen flow (16%) was seen at short distances (3–15m), rapidly diminishing to 3% by a 240m distance and continued at this low rate up to the furthest distance assessed (650m) from the GM trial. The negative exponential distribution of GM pollination success was similar to that observed in non-GM eucalypt pollen flow studies, indicating that low levels of effective pollination are expected over long distances. To the best of our knowledge, this is the first experimental assessments of realized pollen flow measured by the effective production of seedlings from a genetically modified tree in field conditions.

Comparative analysis of students’ attitudes toward implementation of genetically modified trees in Serbia

Genetically-modified (GM) trees represent a new frontier in biotechnology, though many environmental concerns associated to the commercial use of GM trees and their products have been recently raised. In general, GM trees involve no safety issues related to human health, therefore public attitudes toward their commercial use should depend on environmental concerns or personal philosophical viewpoints, but also on educational level and background. To assess the relevance of the educational level and background on attitudes toward acceptance of commercial GM tree cultivation, a survey was conducted in January 2014 among 400 students from the Faculty of Forestry of the University of Belgrade and from the Faculty of Applied Ecology “Futura” at the University Singidunum (Belgrade). The aim was to determine whether different educational profiles and educational level significantly affect students’ attitudes toward GM trees. Results showed no significant differences in the responses among students from both faculties. All students showed a good knowledge of GM trees and agreed that different genetic modifications of forest trees would be very important for their country. Also, more than a half of students from both faculties would agree with commercial planting of GM trees and would purchase their final products. However, 70 to 90% of students from both faculties considered the hazards associated with the commercial use of GM trees as “serious hazard” or “slight hazard”. The implication of the above results are discussed.

GM trees with increased resistance to herbivores: trait efficiency and their potential to promote tree growth.

Climate change, as well as a more intensive forestry, is expected to increase the risk of damage by pests and pathogens on trees, which can already be a severe problem in tree plantations. Recent development of biotechnology theoretically allows for resistance enhancement that could help reduce these risks but we still lack a comprehensive understanding of benefits and tradeoffs with pest resistant GM (genetically modified) trees. We synthesized the current knowledge on the effectiveness of GM forest trees with increased resistance to herbivores. There is ample evidence that induction of exogenous Bacillus thuringiensis genes reduce performance of target pests whereas upregulation of endogenous resistance traits e.g., phenolics, generates variable results. Our review identified very few studies estimating the realized benefits in tree growth of GM trees in the field. This is concerning as the realized benefit with insect resistant GM plants seems to be context-dependent and likely manifested only if herbivore pressure is sufficiently high. Future studies of secondary pest species and resistance evolution in pest to GM trees should be prioritized. But most importantly we need more long-term field tests to evaluate the benefits and risks with pest resistant GM trees.

Ecological interactions between herbivores and silver birch and aspen trees genetically modified for fungal disease resistance

Many risks and environmental concerns have been linked with the cultivation of genetically modified (GM) trees. Among the most frequently mentioned risks are the unintentional/pleiotropic effects of transgenes on organisms or plant properties that are not the targets of genetic modification. Risks in forest ecosystems are difficult to predict, due to the long life cycles of trees and their complex ecological interactions. This thesis is focused on the interactions between insect and mammal herbivores and transgenic trees. The studied silver birch (Betula pendula Roth) carried a sugar beet chitinase IV gene and the aspen and hybrid aspen (Populus sp.) carried a pine pinosylvin synthase gene, both aiming to improve the trees’ resistance to fungal diseases, but also potentially affecting insect and mammal herbivores. Tree growth and quality, and insect density and composition were studied during the field trial. The palatability of transgenic trees was studied in the feeding experiments using the lepidopteran herbivores rusty tussock moth and buff-tip (Orgyia antiqua L., Phalera bucephala L.) and the mammalian herbivores mountain hare and roe deer (Lepus timidus L., Capreolus capreolus L.). The studies revealed that sugar beet chitinase IV caused unintentional effects on silver birch: the transgenic trees were smaller and their red leaf colour indicated stress. There were differences in herbivore pressure between transgenic and wild-type birches: GM trees had a higher aphid density but a lower diversity of insect species and visible leaf damages. The relative growth rate of O. antiqua on transgenic birches was lower in comparison to wild-type birches. No difference in the palatability to mammals was found between transgenic and wild-type trees. The results suggest that the impact on herbivores is speciesdependent. The pleiotropic effects of the transgenes affecting plant-herbivore interaction can explain these impacts. These results should be taken into account when considering the biosafety of GM trees.

Fifteen years of forest tree biosafety research in Germany

Since beginning of 1990, several projects on biosafety research were initiated in Germany with genetically modified plants. Germany was also one of the first countries active on biosafety research with genetically modified trees (GMTs). An EU-funded project coordinated by the Institute of Forest Genetics (Johann Heinrich von Thuenen Institute, Grosshansdorf), from 1994 to 1997, was the first project of this kind in Germany. In the frame of this project, transgene stability was studied under greenhouse conditions in different transgenic aspen clones. A high degree of transgene expression stability was found in transgenic lines, however, gene silencing was detected in some transgenic plants. In Germany, the jump of the GMTs from the greenhouse to the field was initiated in 1996 by the Institute of Forest Genetics (Grosshansdorf), when the first field trial with genetically modified (GM) poplar was approved for five years. In the year 2000 and in cooperation with the University of Tuebingen, the same institute established a second field trial with GM poplar to study possible horizontal gene transfer (HGT) from the transgenic poplar into mycorrhizal fungi. No HGT was detected in those studies. Two further national funded projects on phytoremediation and status of mycorrhizal fungi in GMTs under field conditions were run by the University of Freiburg on 2002 - 2004 and 2003 - 2005. Topics of national funded biosafety research projects on GMTs released to the field but as well on greenhouse grown plants were transgene stability, genetic containment, transgene influence on mycorrhizal and phytopathogenic fungi, generative and vegetative propagation capacity, and horizontal gene transfer.

Pollen competition as a reproductive isolation barrier represses transgene flow between compatible and co-flowering citrus genotypes.

Background/ObjectiveDespite potential benefits granted by genetically modified (GM) fruit trees, their release and commercialization raises concerns about their potential environmental impact, and the transfer via pollen of transgenes to cross-compatible cultivars is deemed to be the greatest source for environmental exposure. Information compiled from field trials on GM trees is essential to propose measures to minimize the transgene dispersal. We have conducted a field trial of seven consecutive years to investigate the maximum frequency of pollen-mediated crop-to-crop transgene flow in a citrus orchard, and its relation to the genetic, phenological and environmental factors involved.Methodology/Principal FindingsThree different citrus genotypes carrying the uidA (GUS) tracer marker gene (pollen donors) and a non-GM self-incompatible contiguous citrus genotype (recipient) were used in conditions allowing natural entomophilous pollination to occur. The examination of 603 to 2990 seeds per year showed unexpectedly low frequencies (0.17–2.86%) of transgene flow. Paternity analyses of the progeny of subsets of recipient plants using 10 microsatellite (SSR) loci demonstrated a higher mating competence of trees from another non-GM pollen source population that greatly limited the mating chance of the contiguous cross-compatible and flowering-synchronized transgenic pollen source. This mating superiority could be explained by a much higher pollen competition capacity of the non-GM genotypes, as was confirmed through mixed-hand pollinations.Conclusions/SignificancePollen competition strongly contributed to transgene confinement. Based on this finding, suitable isolation measures are proposed for the first time to prevent transgene outflow between contiguous plantings of citrus types that may be extendible to other entomophilous transgenic fruit tree species.

COST Action FP0905: Biosafety of forest transgenic trees: improving the scientific basis for safe tree development and implementation of EU policy directives

Background The potential for unintended consequences of the spread of foreign genes (either via vertical or horizontal transfer) and of pleiotropic effects following transgene expression may be enhanced in long-lived forest trees. The COST Action FP0905 will focus on four key aspects related to the biosafety of genetically modified trees (GMTs): (a) analyses of the efficiency of existing gene containment strategies to avoid or if not possible to minimize gene flow; (b) facilitate efforts to develop sitespecific integration of transgenes in tree genomes to minimize variability of transgene expression and pleiotropic effects, (c) evaluate possible methods to monitor GMTs in the whole production chain, and (d) conduct socio-economic and cost/benefit analyses in relation to the use of GMTs in plantations. This Action combines multidisciplinary knowledge generated with transgenic lines of different forest genera (such as, Populus spp., Pinus spp., Eucalyptus spp., Betula spp., Castanea spp., Picea spp., etc.) as well as extensive expertise in correlated topics. The information gained should contribute to strengthen the scientific basis for the execution of the EU policy directives related to transgenic trees intended for cultivation in Europe. The main objective of the COST Action is to evaluate and substantiate the scientific knowledge relevant for GMT biosafety protocols by putting together already existing information generated in various European and Non-EU countries as basis for future EU policy and regulation for the environmental impact assessment and the safe development and practical use of GMTs.

Biological characterization of genetically modified trees (GMTs)

In the last 20 years, a large number of GMTs have been generated, characterized and field tested to evaluate their agronomic behaviour and their potential performance for technological applications. Therefore, important knowledge has been gained from these studies on the potential of GMTs whereas biosafety concerns have been raised on the plantation of transgenic trees in the field. The European Cooperation in Science and Technology (COST) action FP0905 on the biosafety of forest transgenic trees aims to help forthe building and implementation of EU policy directives to ensure a safe development and practical use of GMTs in the future. This Action is expected to generate important benefits thanks to the experience gained by the research community, to provide general information on these studies as well as to address public concerns about biosafety issues raised by transgenic tree plantations, and finally to help for the establishment and implementation of EU policy directives in the view of a future deployment of GMTs cultivation in Europe. Within this action, the objective of the working group 1 (WG1) is to gather the existing knowledge on genetically modified forest trees (GMTs) including both field trials and greenhouse experiments. More specifically, the action of WG1 is focused on the compilation of: - Data from literature and methods developed on gene flow and containment strategies - Data available on the traits targeted and the function of the gene introduced, on their intended and eventually unintended effects - Data on host species characteristics especially related to biosafety issues such as their biological cycle, their way of pollination and the characteristics of pollen and seed dispersal. This information will be collected from published papers in books and reviews as well as from reports from different agencies available on the web. Moreover, additional data will hopefully be gained through the responses of expert scientists from public or private institutions to an ongoing survey accessible at the website of the COST Action FP0905: [http://www.cost-action-fp0905.eu/index.php?option=com_kunena&Itemid=74&func=view&catid=4&id=11] The information collected will be used to: - 1) establish a list of protocols for the control of transgene flow and gene containment. - 2) establish the present state of the art in gene targeting strategies for site specific integration of transgenes. - 3) get an appraisal on the types of construct and genes inserted in GMTs in the past; in the present and in the future. This information will be compiled in a database that will be made available to the scientific community as well as to the European policy makers. The results of this work will enable the participants and end-users to get a clear factual overview of the global status of GMTs and especially the status of Europe compared to non-European countries. Furthermore, the information gathered will also be useful for assessment of environmental impacts of GMTs that is the object addressed in the WG2 of the COST Action FP0905.

Field trials of GM trees in the USA: activity and regulatory developments

Field trials are extremely important for all facets of research, breeding, and biotechnology. Tree physiology is distinctively different in greenhouses or growth chambers vs. field environments. Thus, results from non-field environments can be very misleading with respect to identification of promising biotechnologies and elite varieties. Large regulatory impediments to conduct of field tests of genetically modified (GM) trees will therefore tend to stifle scientific and technological development. This appears to be the case for genetically modified trees, where regulatory burdens to conducting field tests have grown in stringency in the USA and elsewhere in recent years [1,2]. Here, we present the record of recent field trials and some new regulatory developments in the USA.

Research in tree genetic engineering; the Canadian context for field trial of GM trees

Canada is in a unique position for the regulation of GM (genetically modified) plants since it is based on the novelty of the resulting traits and not on the process to obtain it. For this reasons the term “plant with novel traits” (or PNTs) is used and these traits can be introduced into plants using biotechnology, mutagenesis or conventional breeding techniques. In Canada, less than a handful of GE tree field trials have been conducted. In all cases, poplars or spruces were used. Consistent with international guidance provided for living modified organisms, particular attention is given to a specific trait by considering both its novelty for the Canadian environment and its potential effect on human health and the environment. Our research is in line with the development of a consolidated research approach and knowledge needed for international guidance (e.g. Cartagena Protocol on Biosafety under the Convention on Biological Diversity) developed for genetically modified organisms. Important losses due to insects and fungal pathogens result in a considerable reduction of yield in Canadian forest productivity. Compounding these problems is the increased movement of pests that has been facilitated by increased international trade of agricultural and forest products as well as global climate change. More recently the increased need for biomass production and specific bioproducts to sustain crop-based biofuel production has emerged. Forest biotechnology has the potential to maintain forest sustainability by contributing to the transformation of our forest industry so as to improve productivity in the context of tree plantation. In this presentation, we will show how genetic engineering of forest trees has been used in improving tree adaptation and pest protection. We will also describe the work being done on environmental assessment of field-grown trees and results on long-term expression of engineered genes.

Leaf litter from insect‐resistant transgenic trees causes changes in aquatic insect community composition

Summary1. Recent research has addressed how transgenic residues from arable crops may influence adjacent waterways, aquatic consumers and important ecosystem processes such as litter breakdown rates. With future applications of transgenic plants in forestry, such concerns may apply to forest stream ecosystems. Before any large‐scale release of genetically modified (GM) trees, it is therefore imperative to evaluate the effects of genetic modifications in trees on such ecosystems.2. We conducted decomposition experiments under natural stream conditions using leaf litter from greenhouse grown GM trees (Populus tremula × Populus tremuloides) that express Bacillus thuringiensis (Bt) toxins (cry3Aa; targeting coleopteran leaf‐feeding beetles) to examine the hypothesis that GM trees would affect litter decomposition rates and/or the aquatic arthropod community that colonizes and feeds on leaf litter in streams.3. We show that two independent transformations of isogenic Populus trees to express Bt toxins caused similar changes to the composition of aquatic insects colonizing the leaf litter, ultimately manifested in a 25% and 33% increases in average insect abundance.4. Measurements of 24 phenolic compounds as well as nitrogen (N) and carbon (C) in the litter did not significantly differ among modified and wild‐type trees and were thus not sufficient to explain these differences in the insect assemblage.5. Decomposition rates were comparable among litter treatments suggesting that the normal suite of leaf traits influencing decomposition was similar among litter treatments and that the shredding functions of the community were maintained despite the changes in insect community composition.6. Synthesis and applications. We report that leaf litter from GM trees affected the composition of aquatic insect communities that colonized litter under natural stream conditions. This suggests that forest management using GM trees may affect adjacent waterways in unanticipated ways, which should be considered in future commercial applications of GM trees. We also argue that studies at different scales (e.g. species, communities and ecosystems) will be needed for a full understanding of the environmental effects of Bt plants.

Current state of genetically modified plant impact on target and non-target fungi

For two decades, genetic engineering has made it possible to develop crops and trees designed for yield improvement and simplified culture management. This, combined with field deployment of monocultures over large areas, can result in environmental stress and unwanted potential side effects. The commercial production of genetically modified (GM) crops and the recent development of GM trees raise concerns about their potential impact on the environment, in general, and on the biodiversity of non-target organisms, in particular. Fungi are spread worldwide and play key roles in ecosystems. They have been closely associated with plants since they emerged from the oceans. This review critically examines research monitoring the potential effects of GM crops and GM trees on target and non-target fungi. Parsing public databases for peer-reviewed publications about GM plant impacts on fungi yielded 149 studies, a relatively modest number considering the diversity of crops and ecosystems studied. Analysis of these publications showed that the effects of GM plants expressing herbicide and insect tolerance on fungi are understudied while they dominate the GM area worldwide. Experiments monitoring the impact of GM crops and GM trees with enhanced antifungal activity towards target fungi showed, for the most part, significant decreases in disease severity caused by fungal pathogens. Significant changes, expressed as an increase or decrease in fungal development, abundance, and diversity of non-target fungi, were observed in 18 out of 60 studies and all of them involved GM plants expressing traits that were unexpected to affect fungi. The remaining 42 studies did not identify a significant impact on fungal populations. Therefore, in spite of the fact that GM plants have been commercialized since 1996, no clear generalized trend can be identified and it appears that a case-by-case approach is the safest.

Can Leaf Litter from Genetically Modified Trees Affect Aquatic Ecosystems?

In addition to potential benefits, biotechnology in silviculture may also be associated with environmental considerations, including effects on organisms associated with the living tree and on ecosystems and processes dependent on tree residue. We examined whether genetic modification of lignin characteristics (CAD and COMT) in Populus sp. affected leaf litter quality, the decomposition of leaf litter, and the assemblages of aquatic insects colonizing the litter in three natural streams. The decomposition of leaf litter from one of the genetically modified (GM) lines (CAD) was affected in ways that were comparable over streams and harvest dates. After 84 days in streams, CAD-litter had lost approximately 6.1% less mass than the non-GM litter. Genetic modification also affected the concentration of phenolics and carbon in the litter but this only partially explained the decomposition differences, suggesting that other factors were also involved. Insect community analyses comparing GM and non-GM litter showed no significant differences, and the two GM litters showed differences only in the 84-day litterbags. The total abundance and species richness of insects were also similar on GM and non-GM litter. The results presented here suggest that genetic modifications in trees can influence litter quality and thus have a potential to generate effects that can cross ecosystem boundaries and influence ecosystem processes not directly associated with the tree. Overall, the realized ecological effects of the GM tree varieties used here were nevertheless shown to be relatively small.

Bacterial and fungal communities in the rhizosphere of field-grown genetically modified pine trees (Pinus radiataD.)

This study assessed the impact of Pinus radiata (D. Don) genetically modified (GM) by biolistic insertion of the LEAFY and nptII genes on rhizosphere microbial communities of field grown trees. Rhizosphere soil was sampled quarterly for two consecutive years. A culture-independent approach was used to characterise the microbial communities based on PCR and denaturing gradient gel electrophoresis (DGGE) of 16S/18S rDNA gene fragments, and internal transcribed spacer (ITS) fragments amplified from total rhizosphere DNA. Trees from two independent transformation events were sampled, together with non-modified control trees of the same parental genotype. DGGE profiles of rhizosphere general Bacteria did not differ between GM and control trees with one exception (summer 2006 sample). For Alphaproteo- and Actinobacteria, significant differences between treatments were detected in one out of eight samplings. Small seasonal shifts could be detected in all bacterial communities. General fungal and ectomycorrhizal communities did not differ significantly between GM and control trees with the exception of summer 2006, when ectomycorrhizal communities associated with GM trees from one transformation event differed from those associated with control trees. Small seasonal shifts of general fungal and ectomycorrhizal communities were seen over the two-year sampling period. More detailed analysis of microbial communities at one sampling date (using amplified rDNA restriction analysis (ARDRA) and 16S/18S rDNA sequencing) revealed significant differences in four ARDRA groups between one GM treatment and the control (bacteria), and significant differences in one ARDRA group between the two GM treatments (fungi). When data from all sampling dates are considered together, the low incidence of statistical differences in the microbial communities associated with the genetically modified and control trees suggests that there was no significant impact of this genetic modification on rhizosphere microbial communities.

Transgene stability and dispersal in forest trees

Transgenics from several forest tree species, carrying a number of commercially important recombinant genes, have been produced, and are undergoing confined field trials in a number of countries. However, there are questions and issues regarding stability of transgene expression and transgene dispersal that need to be addressed in long-lived forest trees. Variation in transgene expression is not uncommon in the primary transformants in plants, and is undesirable as it requires screening a large number of transformants in order to select transgenic lines with acceptable levels of transgene expression. Therefore, the current focus of plant transformation is toward fine tuning of transgene expression and stability in the transgenic forest trees. Although a number of studies have reported a relatively stable transgene expression for several target traits, including herbicide resistance, insect resistance, and lignin modification, there was also some unintended transgene instability in the genetically modified (GM) forest trees. Transgene dispersal from GM trees to feral forest populations and their containment remain important biological and regulatory issues facing commercial release of GM trees. Containment of transgenes must be in place to effectively prevent escape of transgenic pollen, seed, and vegetative propagules in economically important GM forest trees before their commercialization. Therefore, it is important to devise innovative technologies in genetic engineering that lead to genetically stable transgenic trees not only for qualitative traits (herbicide resistance, insect resistance), but also for quantitative traits (accelerated growth, increased height, increased wood density), and also prevent escape of transgenes in the forest trees.

Assessing the risk of gene flow from genetically modified trees carrying mitigation transgenes

The increasing use of genetically modified (GM) plants has raised concerns about the escape of transgenes to conventional populations. To counteract possible fitness advantages of GM plants, an advantageous ‘primary transgene’ may be linked to a ‘mitigation’ transgene that is selectively disfavored. A risk related to this technique is the possible break-up of the transgenes. This may lead to the establishment of genotypes that only express the primary transgenic trait and are therefore selectively favored over both conventional and GM genotypes. We study here how the establishment of break-up genotypes in tree populations depends on life history, pollen dispersal kernels, and the linkage between transgenes. To this end, we model the dynamics of an initially homozygous GM population and a conventional population growing next to each other. The simulations are based on a spatially explicit simulation model for population-genotype dynamics. Pollen and seed dispersal are described by fat-tailed dispersal kernels. Break-up of transgenes is due subsequent crossing of GM and conventional genotypes. The spatial pattern of pollen and seed dispersal causes break-up and establishment of new invasive genotypes to occur mostly in the conventional population. The amount of individuals of these genotypes established in the conventional population depends on the interaction between life-history traits, pollen dispersal distances and the linkage of the transgenes. Thus, risk assessment of transgene break-up requires information on the genetics, local dynamics, and dispersal of GM and conventional varieties. The approach presented here provides a tool for combining these different sources of information, and it contributes to the formulation of general rules for the management of GM tree populations.

GM technology in forestry: lessons from the GM food 'debate'

This paper aims to demonstrate the important lessons to be learnt from the Genetically Modified (GM) food 'debate', by examining the similarities of, and differences between, it and GM technology in forestry. Through consideration of a range of issues, such as technological applications, public concerns and the role of protest groups, it is concluded that the commercialisation of GM trees is likely to be as problematic as the commercialisation of GM crops has been in certain parts of the world. Therefore, it is recommended that public concerns be investigated, that attempts be made to value the wider potential costs and benefits of the technology to forestry, and that protest groups be listened to. Only through attempting to address these issues might it be possible to avoid the development of a 'debate' surrounding GM forestry that is as polarised and entrenched as that relating to GM food.