E. Ann Clark, Plant Agriculture, University of Guelph (aclark@uoguelph.ca)
Presented to Is Your Food Safe?, sponsored by the Professional Institute of the Public Service of Canada, 7/8 May 99
To a surprising degree, the legitimacy of field crop genetic engineering is based upon assumptions, many of which can and should be challenged. Assumptions-based "science" permeates the risk assessment process, blinding assessors to environmental risks transparently evident to ientists. It will be argued that the historic exclusion of all but molecular biologists from the process of GE, while expeditious, has placed society, the environment, and indeed the industry itself at risk. No useful purpose is served by continuing to bypass, minimize, and dismiss the potential ecological harm from GE organisms. It is in the best interests of all of us to openly acknowledge potential risks and to fund research to quantify, predict, and deal with them.
Many of the most egregious shortcomings of commercial GE, such as "substantial equivalence" and familiarity, arise naturally from a foundation of faulty assumptions.
Faulty Assumptions (FA) and Reality Checks (RC)
FA-1. GE is just an extension of plant breeding - nothing to get excited about.
RC-1. At least three arguments can be made to dispute this reasoning.
a. Plant breeding is almost entirely a matter of reshuffling alleles to achieve desired traits. Alleles are particular variants (e.g. B and b) of a given gene, such as the classic BB or Bb for brown eyes versus bb for blue eyes. With few commercial exceptions, as triticale (wheat x rye), plant breeders work only with the alleles and genes they can find already existing within their chosen species or closely related species that are able to cross.
Now, compare this with GE, which moves genes and groups of genes across the barriers of species, genus, family, and even order of life. Genes from a fish can be moved into tomato. From a petunia into a soybean. From a human into a cow. Yes, really. It has been done.
b. In conventional breeding, the recombining of alleles occurs in an orderly fashion, without spatial changes to "where" in a chromosome or on "which" chromosome a given allele occurs. This is critical because the physical placement of a given gene on a chromosome has a powerful influence on its interactions with other genes, and hence, its effectiveness.
In contrast, because of the inexact methods used to insert the transgenes, the actual placement of the foreign transgenes within a chromosome is haphazard and unpredictable - causing all manner of confusion and difficulty.
c. And finally, the products of conventional plant breeding are generally "stable". Alleles that have been recombined generally do not moderate or lose their effectiveness over time through silencing and other natural chromosome "repair" processes - because the changed alleles are not recognized as abnormal or aberrant.
Conversely, one of the biggest challenges in GE is the stability of the new genetic constructs - they can lose their effectiveness after a generation or two simply because natural repair processes which maintain chromosome integrity detect the alien genes and "fix" them.
It is thus incorrect, except in the most simplistic terms, to consider GE as just another form of plant breeding. GE is to plant breeding as stitching a wound is to neurosurgery.
FA-2 GE crops are just conventional crops with an added trait or two - virtually identical
* Conventional crops are not weedy or pestiferous.
* GE crops are just like conventional crops with an extra gene or two,
none of which are intended to affect pestiferousness
* Therefore, if simple measurements and observations indicate that
the GE crop is similar to it conventional counterparts, it is assumed that
the GE crops will not be pestiferous.
RC-2. This assumption is used to justify the absence of actual field testing for potential weediness, pestiferousness, or anything else. However, this argument is flawed on several grounds.
a. Weed problems have been created by gene flow from conventionally bred crops (various references cited in deJong, 1992; Ellstrand, 1996; and Rissler and Mellon,1996). Furthermore, crops themselves can become weeds as volunteers in a subsequent crop - an agronomic problem which complicates and aggravates crop rotation and management decisions when the volunteer is herbicide-resistant.
b. The traits bred into GE crops (e.g. herbicide-resistance; frost tolerance; plant pesticides) are fundamentally different from those accessed through conventional plant breeding. The utility or degree to which the new GE traits enhance fitness, and hence, would be beneficial in promoting weediness, aggressiveness, and survival of weedy relatives is outside the experience of conventional plant breeding. Brown et al. (1996) surveyed 20 fields in Idaho and Washington, and reported finding escaped canola plants in both roadsides and ditches. They interpreted this finding as evidence that seed can move widely throughout a region. Thus, escaped crop plants may constitute a potential weed threat analogous to what has been claimed by Percy Schmeister - a Saskatchewan farmer currently being sued by Monsanto for allegedly retaining GE seed.
Stewart et al. (1996), for example, documented the enhanced fitness of Bt canola vs. unmodified Bt escapes, when subjected to moderate to heavy insect attack.
c. A given GE event can have unexpected effects beyond the intended trait, many of which are entirely unpredictable and could enhance risks of weed creation (see FA-3).
d. Contrary to the perceptions of proponents and government regulators alike, it is not possible to predict weediness or other risks from simple morphological measurements. For example, proponents have attached unwarranted importance to the attributes associated with weediness by Baker (1965; Table 1) and others. Yet in a study of 49 British annuals, Williamson (1993) found only a weak correlation - of no predictive value - between Baker's list of traits and weediness. Some of the worst weeds had few of Baker's traits, while some with many of "weedy" traits were not, in fact, weedy (Table 1).
Yet even this
Table 1. Baker's List (adapted from Rissler and Mellon (1996)
| Characters Associated with Weediness | |
| 1 | Seeds germinate in many environments |
| 2 | Seeds remain viable a long time |
| 3 | Plants grow rapidly through the vegetative phase to flowering |
| 4 | Plants produce seeds continuously as long as growing conditions permit |
| 5 | Flowers are self-compatible, but not obligatorily self-pollinated |
| 6 | Pollen from flowers that are cross pollinated is carried by nonspecialized flower visitors (usually insects or by wind |
| 7 | Plants produce large numbers of seed in favorable environmental conditions |
| 8 | Plants produce seed in a wide range of environmental circunstances |
| 9 | Plants are adapted for both long- and short-distance dispersal |
| 10 | If perennials, the plants have vigorous vegetative reproduction or regeneration from fragments |
| 11 | If perennials, the plants are brittle near the soil line to prevent easy withdrawal from the soil |
| 12 | Plants compete by special means, such as forming rosettes, choking growth, producing toxic chemicals |
The potential for an GE entity - whether a cultivar, a microbe, or an insect - to become invasive cannot be predicted without targeted study, and even then, it is wise to recall that "Nature bats last". For example, the infamous Colorado potato beetle (CPB) originated in the eastern Rocky Mountains, from southern Mexico to Colorado, with Solonaceous species such as Solanum rostratum and S. angustifolium as its original, preferred hosts (van Lenteren, 1992). But potato (S. tuberosa) reportedly evolved in South America - outside of this zone. Domesticated potatoes eventually reached Colorado - the original host range of CPB - in 1859. Inexplicably, the CPB then switched preferred hosts, becoming a significant, worldwide pest of potatoes from the early 1900's onward, despite having evolved in the absence of potato in the first place (van Lenteren, 1992).
"Organisms with novel combinations
of traits are more likely to play novel ecological roles, on average, than
are organisms produced by recombining genetic information existing within
a single evolutionary lineage" (Tiedje
et al., 1989).
| Table 2. Critique of criteria used to assess environmental impact of GE crops in Canada | ||
| Assessment Criteria | How Addressed in Decision Documents | Critique |
| 1. potential...to become a weed of agriculture or be invasive of natural habitats | *unmodified plants of this species are not invasive, and the GE entity
exhibits reproductive and survival params within the norms for the unmodified
plants, therefore, the GE entity is deemed to be not different from an
unmodified plant
* novel traits have no intended effect on weediness or invasiveness; therefore, the new GE entity will have no altered weed or invasiveness potential compared to current cultivars (N.B. emphasis added) |
*little or no actual testing is reported; inferences are made from
measurements as plant height, stem count, and vigor
* no recognition of potential unintended interactions or side effects apart from the intended trait (see Stewart et al. (1997) on increased fitness of Bt oilseed rape |
| 2. potential for gene-flow to wild relatives | *no wild relatives; no sweat
* trait confers no ecological advantage, so won=t be retained in the wild |
*parochial perspective, ignoring global, downstream implications
* little or no testing reported; inferences are made *unaware of Tabashnik et al. (1997) showing that resistance to Bt was retained in target pests through >100 generations, in the absence of Bt; see also Stewart et al. (1997) showing Bt DOES confer ecological advantage |
| 3. potential ...to become a plant pest | * the GE entity is not substantively different from the unmodified plant, and the unmodified plant is not a pest, so the GE entity will not be a pest | *ignores potential for unintended side effects, apart from the intended trait |
| 4. potential impact...on non-target species, including humans | * the GE entity is not substantively different from the unmodified
plant, and the unmodified plant is not a harmful, so the GE entity will
not be harmful
* results of some type of monitoring is presented, including visual observations, of effects on beneficials - results almost invariably favorable to the GE entity (e.g. positive effect on beneficials, contrary to independent European reports) |
*ignores potential for unintended side effects, apart from the intended
trait (see below)
* little or no consideration of soil biota (see below) * no apparent testing of human impact * no consideration of horizontal gene transfer (see below) * no consideration of ramifying effects on enemies of target pests * no assessment of secondary pest creation |
| 5. potential impact on biodiversity | * no novel phenotypic characteristics which would extend current geographic
range
* plant pesticide could reduce insecticidal sprays and increase potential for IPM * therefore, net effect is always neutral or positive |
* ignores essentially all ecological interactions, and decades of evidence on cascading effects, secondary pest creation; see also Johnson and Gould, 1992. |
FA-3 There are no wild relatives of commercial crops in Canada - hence, no need to worry about outcrossing
Superweeds? It is common, but incorrect, to state that there are no weedy ancestors of crop plants in North America. True, they didn=t evolve here, but they are here now. Indeed, despite the fact that virtually all North American crops evolved elsewhere, wild or weedy relatives now exist in North America for many important crops (Table 2). Thus, contrary to some sources, weed generation or augmentation is a significant risk in North American agriculture.
Now, the presence of potentially crossable relatives does not necessarily mean that they are sexually compatible or that crossing does indeed occur, or that the trait would persist in the wild community.
Ellstrand (1996) reported, however, that of the 30 most important crops (in terms of acreage grown) in the United States, over half co-occur with at least one wild weedy relative somewhere in North America, and of these, some degree of sexual compatibility with the sown crops was common. He noted further that in some cases, as rye, sorghum, rice, and beets, hybridization with weedy relatives had already led to more aggressive weeds.
FA-6 - Will affect one and only one trait, and will do it consistently.
It should be further recognized that processes relating to making transgenic plants may, in fact, enhance the potential for outcrossing to wild ancestors. Bergelson et al. (1998) compared the ability of transgenic vs. mutant Arabidopsis thaliana plants to cross with wild-type plants. A. thaliana is a highly selfing species, for which risk of outcrossing is considered negligible. Both the transgenic and mutant Afather@ plants expressed the same mutant allele - Csr1-1 - conferring resistance to the herbicide chlorosulphuron. Per-plant outcrossing rate was 0.3% for mutant fathers compared to 6% for transgenic fathers - a roughly 20-fold enhancement. Further studies revealed that two transgenic lines differed in their ability to outcross, with rates differing from 1.2% to 10.8%.
While A. thaliana is not itself a weed, this study reveals two quite critical dimensions of GE technology:
that transgenically inserting the Csr1-1 allele - which has already been introduced into dozens of crops and is intended as a selectable marker for plant transformation vectors - could enhance the potential for outcrossing even in strongly selfing plants.
b. that transgenic manipulations can affect the expression of traits completely unrelated to the target trait.
Traits which are most likely to be retained in crop:weed hybrids are those which confer fitness, as by altering invasiveness, conferring winterhardiness, insect, or disease tolerance, or herbicide resistance. However, as noted by Rissler and Mellon (1996 p.50), neutral transgenes may also persist due to swamping (repeated flow caused by large scale repeated plantings), or by linkage to other valued transgenes. And many current transgenes can indeed be valuable to both volunteers and crop:weed hybrids. Stewart et al. (1996), for example, documented the enhanced fitness of Bt canola vs. unmodified Bt escapes, when subjected to moderate to heavy insect attack. Snow et al. (1996) observed the unintentional movement of rust resistance from cultivated to weedy sunflower, resulting in enhanced fecundity in the crop:weed hybrid where rust was problematic.
One of the ten worst weeds in the world, johnsongrass, hybridizes freely with cultivated sorghum and is likely to retain either neutral or positive transgenes in an agricultural setting (Arriola and Ellstrand, 1997). Paterson and Chandler (1996) emphasized that johnsongrass is problematic not simply in sorghum, but also in maize, soybean, cotton, and other crops. They consider that the exposure of transgenic sorghum to johnsongrass on 8 million acres in the US Apresents an enormous opportunity for gene exchange, even if such events are relatively rare.@
A few of the many examples of studies into crop:weed hybridization are presented in Table 3.
Table 2. Examples of crops cultivated in the US which /have wild/weedy relatives (same species or genus) in the US (adapted from Rissler and Mellon, 1996)
| Fiber | Fruit/Nut | Grass/Cereal | Legume | Oil Crop | Vegetable/Herb | Misc. | |
| Cotton | Berries(1) | alternative grains(2) | alfalfa | Canola | artichoke | herbs(3) | mustard |
| flax | Cherry | forages(4) | peas | Peanut | asparagus | lettuce | sugarbeet |
| Peach | millet | Sunflower | brassicas(5) | pepper | tobacco | ||
| Pecan | rice | carrot | potato | ||||
| Plum | small grains(6) | celery | radish | ||||
| Walnut | sorghum | cucurbits(7) | spinach | ||||
| sugarcane | eggplant | tomato | |||||
Table 3. Examples of gene flow, hybridization, and enhanced weediness attributable to transgenic crops cultivated in the US
| Crop | Weedy Relative or Recipient | Distance of Pollen Travel | Evidence of Crossing | Fitness/Persistence of Hybrid | Reference |
| canola
(Brassica napus) |
wild radish (Raphanus raphanistrum L.) | Male-sterile transgenic plants pollinated by weedy relative - transgenic transmission was maternal | F1 hybrids had poor fertility, but became more fertile with successive generations and resembled wild radish | Chevre et al., 1997 | |
| birdsrape mustard (B. rapa L.)(8) | At least 26 m, but varied with weather and windspeed | a few (1:1000 seedlings tested) were herbicide-resistant hybrids | 2 F1 plants produced viable seed; weak F1 hybrids but when backcrossed to either parent, were as vigorous and high-yielding as either parent species | Brown et al., 1996 | |
| B. rapa | hybrid superior to wild parent during establishment phase | Linder and Schmitt (1995) | |||
| oilseed rape (B. rapa) | B. campestris | transgenes for herbicide resistance expressed in F1 and BC1 | Mikkleson et al., 1996 | ||
| radish (Raphanus sativa) | wild radish | hybrid showed superior total seed set, compared to wild parent | fitness correlates of hybrid exceeded those of wild parent | Klinger and Ellstrand, 1994 | |
| sorghum
(Sorghum bicolor) (2n) |
johnsongrass (S. halepense)(4n) | At least 100 m in both years and at two separate research stations | declined with distance, but as high as 2% at 100 m; frequency varied over test statio ns and years | hybrids showed no significant increase or decrease in time to flowering; tiller, panicle, or seed production; pollen viability; or biomass - fitness unchanged from johnson grass | Arriola and Ellstrand, 1996 and 1997 |
| strawberry (Fragaria x ananassa) | F. virginiana | species co-exist, are interfertile, have overlapping flowering times, and share common pollinators | Spira et al., 1996 | ||
| alfalfa (Medica-go sativa) | alfalfa | Greater than 400 m | Skinner and Peaden, 1993 | ||
| potato (Solanum tuberosum) | various wild relatives | cites reference for pollen movement on bumblebees up to 5 km | crossability increased from Rotata to Tuberosa (wild) and Tuberosa (cultivated) | Jackson and Hanneman, 1996 | |
| commercial potatoes | at least 1100 m | transgenic traits transferred to nontransgenic potatoes | Skogsmyr, 1994. | ||
| sunflower (Helian-thus annuus) | wild sunflower (Helianthus annuus) | At least 1000 m | spontaneous hybridization common (a 6.4 km isolation zone recommended for sunflower seed nurseries (Smith, 1978) | regional differences in comparing wild to crop/wild hybrid fitness; hybrids marginally less vigorous in some traits; however, hybridization inadvertantly transferred rust resistance which gave a 24% advantage in seed production to the hybrids when rust present | Arias and Rieseberg, 1994; Snow et al., 1996 |
| rice (Oryza sativa) | wild weed rice (same species) | readily hybridizes | progeny show marked morphological convergence to the weedy parent | Langevin et al., 1990 |
| Table 1 Canadian decisions authorizing commercial release of genetically engineered field crop cultivars | ||
|
Determination of the Safety of NatureMark Potatoes= Colorado Potato Beetle (CPB) Resistant Potato (Solanum Tuberosum L.) Lines ATBT04-6) |
Decision Document DD96-09: Determination of Environmental Safety of Event 176 Bt Corn (Zeamays L.) Developed by Ciba Seeds and Mycogen Corporation | Decision Document DD95-05: Determination of Environmental Safety of Monsanto Canada Inc.=s Glyphosate Tolerant Soybean (Glycine max L.) Line GTS 40-3-2, |
| The biology of potato... shows that there are no wild relatives in Canada that can naturally hybridize with S. tuberosum. AAFC therefore concludes that gene flow from NewLeafm Atlantic lines to potato relatives is not possible in Canada.@ | The biology of corn...indicates that there are no wild relatives in Canada that can freely hybridize with Zea mays L. ...AAFC therefore concludes that gene flow from Event 176 to corn relatives is not possible in Canada@. | The description of the biology of G. max...shows that it is not naturalized in Canada...AAFC therefore concludes that, in Canada, ....there is no potential for transfer to wild species@. |
FA-4 Containment
FA-5 Outcrossing did not originate with GE.
In sum, risk of outcrossing to produce new or more problematic weeds is a real issue even in North America - to say nothing of the enormous risk of intentionally targeting the Third World - home of most crop plants - for GE release (see Clark, 1999). Reproductively compatible close relatives exist, and often co-occur, with many important North American crops. Weeds have likely been created or worsened by introgression of crop genes, and many of the genes targeted in GE crops will confer a selective advantage to weeds growing in an agricultural setting. Furthermore, the very process of genetic engineering itself may well exacerbate this problem by promoting outcrossing.
Ecological Disruption
To a very large extent, agriculturalists - including agricultural scientists - are unaware of our enormous dependence upon Anature@ to make things work in the world, including in agriculture. For a good general review on this, see Spedding et al. (1981). More recently, a group of 13 ecologists, economists, and geographers headed by Costanza (1997) calculated the dollar value of all the Aservices@ supplied by the natural environment to humankind. They came up with a figure of $33 trillion, in the form of 17 distinct service areas such as N-fixation, erosion control, pollination, and biological control of pests. They argue that it is essential to give due weight to the natural Acapital@ that supports and sustains so much of human endeavor, to avoid making potentially disastrous policy decisions.
Such matters need to be front-and-center in Arisk assessment@ discussions, because recent research is showing the potential of GE interventions to disrupt ecological processes, with potentially adverse outcomes. Too often, papers published by GE advocates clearly do not see these risks (Feitelson et al., 1992; Lambert and Peferoen, 1992; CFIA, 1997). A few brief examples will suffice to make the point:
Soil Processes: Genetically engineered Klebsiella planticola , a common soil bacteria, was modified to transform plant residues into ethanol. However, it not only competed well with parental strains, but also with beneficial soil mycorrhizae and actually killed the test wheat plants (Holmes et al., 1998). Unmodified parental strains did not have these effects..
Doyle et al. (1995) reported that Pseudomonas putida which was genetically engineered to break down 2,4-D not only broke down the herbicide but also killed soil fungi which are an essential component of both soil fertility and plant disease protection.
Tapp and Stotzky (1995) demonstrated that active BT-endotoxins (as are synthesized by Bt-plants) can persist for extended periods in the soil, bound to clay particles where they are resistant to breakdown by soil microbes. The accumulation of active BT endotoxins in the soil will have unknown long-term effects on soil processes specifically because the endotoxins in Bt-plant residues are active. Much of the specificity of Bt endotoxins in their natural form arises because they reside in inactive forms which require host-specific solubilization and enzymatic cleavage as well as host-specific intestinal receptors to become an effective and selective toxin. Because of this critical difference, Crecchio and Stotzky (1998) speculated that transgenic Bt crop residues may be much less selective than Bt sprays, indiscriminantly affecting a range of insects. Many species could be at risk which would otherwise have been shielded by the very specific relationship which has evolved between the original Bt organism and and target insect hosts. Unbalancing the soil biotic community could have unacceptable effects on such "natural" services as nutrient cycling and disease suppression which we take for granted(9).
Extracellular recombinant DNA was found to persist for at least 24 weeks in soil, in a study reported by England et al. (1996) at Guelph. Similar findings were reported by Widmer et al. (1995), who compared stability of naked, linear plasmid DNA with that of DNA in plant tissues following introduction into non-sterile soil. They found that after an initial rapid rate of decay, a small fraction of recombinant DNA remained detectable in the soil for several months. The concern here is the ability of other organisms to take up extracellular, soil-bound DNA, including genes coding for antibiotic resistance and Bt, with unknown adverse effects on soil processes (Haack et al., 1996).
Donegan et al. (1997) studied the post-harvest effects of proteinase inhibitor I - another insecticidal protein - in buried GE tobacco residues. Compared to unmodified (parent plant) tobacco residues, transgenic residues altered the species composition of the soil biota responsible for organic matter decomposition and nutrient cycling. Species composition and balance in fungal feeding nematodes, which has been shown to influence N mineralization and plant growth, was altered by the transgenic residues.
In the aggregate, then, the potential is clear for GE entitities, both microbial and crop, to affect biological processes in ways which could compromise the ability of the soil to perform the Aservices@ we demand of it.
Biological Control. A key concern with both GE as well as chemical approaches to pest control is unintentional and adverse effects on non-target organisms (see Clark, 1998). Indeed, target-specificity is reportedly one of the chief advantages of the Bt-approach to pest control. But does it work?
Chapman and Hoy (1991) showed that Bt var. tenebrionis wettable powder, which is specific to Coleoptera, was shown to affect not simply two-spotted spider mite (Tetranychus urticae Koch), but also western predatory mites (Metaseiulus occidentalis (Nesbitt). This was a powdered spray, and hence, would have been more selective than a transgenic application. The capacity of Bt-crops to affect beneficial as well as harmful insects would influence its compatibility with IPM and other biocontrol efforts.
In Scotland, Birch et al. (1997) found that ladybugs (Adalia bipunctata) which fed on peach potato aphids ((Myzus persicae) which had in turn fed on GE potatoes(10) produced up to 30% fewer progeny and lived only half as long as ladybugs feeding on aphids which had fed on conventional potatoes. Similar evidence of ecological ramification was reported from Hilbeck and colleagues at the Swiss Federal Research Station for Agroecology and Agriculture. They found that the BT endotoxin from transgenic corn killed most cornborers, but the green lacewings which fed on the cornborers were also killed. In subsequent studies, they found that 50% more lacewings died after consuming catepillers fed on Bt than consuming the purified Bt directly.
In an Internet communication, Altieri (1998) commented that the aphids in the Birch et al. (1997) study had apparently sequestered the BT endotoxin and succeeded in transferring it to predators, in this case, the ladybug. He cited further evidence that the phenomenon of toxin sequestration followed by transfer from herbivore to parasite was not uncommon in nature. Movement of the debilitating impact of BT endotoxins through soil invertebrate communities, with consequent impacts on soil organic matter and nutrient cycling, could have far reaching effects on ecosystem function.
Many other examples exist, particularly in regard to the loss of elegant selectivity of natural Bt when inserted transgenically. As a whole, the speed with which GE entities are being commercialized - without meaningful consideration of risk factors - bears striking parallels to the development and commercialization of biocides. The risks of biocides are being elucidated after the fact in part, tragically, using epidemiological studies on afflicted people (various in Benbrook, 1996; Colborn et al., 1996; Garry et al., 1996; Steingraber, 1996). It might have been hoped that contemporary GE decision-making would have benefitted from the lessons of biocide-based agriculture.
Conclusions
The historical record of scientific and societal scrutiny of the risks posed by genetically organisms gives little comfort to GE advocates and regulators. Risks identified and concerns expressed at the highest levels of the scientific community in the mid 70's have still not been addressed and resolved. Far from it. Despite the virtual absence of government funding toward this end, a very wide range of research reports cited from the last 10-15 years not only support but amplify these historic environmental concerns.
The issues raised should not be pigeonholed as Aethical@ or Asocial@ or Aconsumer@ based. Proponents of this technology need to acknowledge the biological and ecological basis for these concerns, and the strength of the scientific evidence which underlies them. Painting the opposition as hysterical greenies does you a disservice.
You are encouraged to take a pro-active stance on these issues. Fund the growing population of researchers who are willing and able to contribute to addressing these risks. Do this in an open and above-board fashion that unites, rather than polarizes, the scientific community and consuming public. Do this in your own best interest. It is time.
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1. 1Blackberries, blueberries, cranberries, raspberries, strawberries
4. 4Bluegrass, fescue, ryegrass
5. 5Broccoli, cabbage, cauliflower, turnip
7. 7Cucumber, melon, pumpkin, squash
8. 8 Under natural field conditions, black mustard, wild mustard, and birdsrape mustard were found to hybridize and produce seed more readily than canola x weed species
9. 9 Should agriculturalists and others worry about unbalancing an ecosystem? See Clark, 1998 for explicit examples of the dire implications that have evolved from just such a situation.
10. 10Engineered to contain lectin from snowdrops, which is known to interfere with insect digestion