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6 Conclusions and Recommendations: Plants Numerous ways exist to modify plants genetically. We have grouped them into three broad categories: classical, cellular, and molecular. Classical methods include sexuad hybridization, embryo culture (rescue), undirected mutagenesis, and anther and ovule cul- ture. CeBular methods include cell fusion and tissue culture to produce somaclonal variation. Molecular techniques include several methods (such as recombinant DNA and electroporation) that result in specific insertions of defined DNA sequences. . Methods used for genetically modifying plants include cIassi- cal, cellular, and molecular techniques. The molecular tech- niques are the most powerful and precise for incorporating new traits. Plants genetically modified by classical techniques have been highly beneficial to society during this century. These benefits are expected to continue and grow In the years ahead through the ad- ditional applications of recently developed molecular and cellular techniques. Farmers and consumers wiD be the major beneficiaries of the Unproved econorn~c productivity that should keep farmers more competitive in the world markets, while improving food, feed, and new plant products through production practices that me compatible with the environment. 65

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66 . Society will continue to benefit greatly from genetically mod- ified plants. WHAT DOES PAST EXPERIENCE TEACH US? About Introductions Over the past hundred years, plant breeders and other agricul- tural scientists have accumulated vast experience and information about the introduction of genetically modified plants into the en- vironment. ~ fact, ahnost all of the major crops currently grown in the United States have been introduced from foreign sources and further bred ~ the United States for improved characteristics. New weed species also have been introduced, although most weeds were introduced in early colonial times, 200 to 300 years ago. Our past experience with these introductions leads to two conclusions: (1) Considerable success has been achieved in introducing and com- mercializing genetically modified crops and other plants, and (2) problems (economic or environmental), when they occur, are usually minor or manageable. Domesticated species, such as most field crops, pore little di- rect threat to the environment. Problems that have resulted from introductions have been indirect, such as increased soil erosion zl.nA associated with managed ecosystems, such as farms. These problems can be effectively controlled by altering such farming practices as crop rotation, cultivation, cultivar selection, or choice of herbicides. Extensive experience has been gained from routine field introduc- tions of plants modified by classical genetic methods. For example, an individual corn, soybean, wheat, or potato breeder may introduce into the field 50,000 genotypes per year on average or 2,000,000 in a career. Hundreds of million of field introductions of new plant genotypes have been made by American plant breeders in this cen- tury. There have been no unmanageable problems from these field introductions through the use of established practices. _ , _~ ~ . Plants modified by classical genetic methods meet the famil- iazity criterion on the basis of experience with hundreds of minions of safe introductions over decades. Current oversight practices of such field introductions are appropriate, and no additional oversight is required.

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67 About Genetic Modification The majority of genetic modifications that are being proposed for domesticated crops by molecular methods are similar to those already achieved by classical means. These include resistance to her- bicicles, pests, drought, and salt as well as compositional changes in the seed or other plant parts. The genes being used to obtain these traits may differ Tom those used in the past, but so far these genes have introduced traits with which we have considerable experi- ence. Therefore, our experience with the introduction of plants and genetic modifications by classical means is relevant to the mtroduc- tion of plants modified by newer methods such as recombinant DNA techniques. Molecular genetic methods differ from classical and cellular methods in that molecular genetic methods involve manipulation of not more than a few genes and their associated regulatory ele- ments. These genes and their elements are usually weD characterized, whereas classical and cellular methods may modify many genes but with limited characterization. Most plants modified by the molecular techniques proposed for field research have been modified only by the addition of one or a few characterized genes within the genome of a domesticated plant. In contrast, classical procedures such as sexual hybridization and some cellular procedures such as cell fusion result in the recombination of entire genomes of the two parental cells. Because the specific gene products added by molecular techniques are better characterized than those added by classical procedures, questions about the changes effected In plants modified by molecular techniques can be asked and answered more precisely. Experience gained so far from field research on molecularly mod- ified plants, as well as from extensive laboratory and greenhouse research, supports the following conclusions: Crops modified by molecular and cellular methods should pose risks no different from those modified by classical genetic methods for similar traits. As the molecular methods are specific In terms of what genes are being added, users of these methods will be more certain about the traits they introduce into plants. Dissimilar traits will require careful evaluation in small-scale field tests where plants exhibiting undesirable phenotypes can be destroyed.

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68 About Weeds The vast majority of introduced wild species are unsuccessful in their new habitats and therefore fad] to become established. How- ever, on occasion introduced wild, non-native species can give rise to problems. A better understanding of the process of species estate lishment would enhance predictability in determining the ultimate success or failure of an Introduced wild, non-native plant. If the newly introduced plant poses problems, standard control measures are usually available. A major issue is the potential ability of genetically modified plants to hybridize with weedy relatives to yield offspring with char- acteristics that enhance weediness. On the basis of evidence of gene movement between classically bred plants and weedy relatives, this process occurs infrequently, but varies widely among crops. When gene movement from crops to weeds occurs, the weeds become more croplike and compete for the same resources. This phenomenon is not believed to have caused problems In natural ecosystem, but has within managed ecosystems. The potential for enhanced weediness ~ the major environ- mental concern surrounding the introduction of genetically modified plants. The incidence of enhanced weediness has been extremely low ~ the past and has been controllable. CONTROL AND CONTlNEMl:NT OF GI:NETICAIlY MODIFIED PLANT VARIETIES An array of options exists for confining a plant to its test site. These options include male sterility, removal of reproductive organs, herbicides, insecticides, disinfectants, tilIage, water manipulation (flooding and irrigation), isolation from similar plants, photoperiod manipulation, dates of planting and restriction in the number of locations, and physical barriers such as cages. Titian field tests of cIassicaBy bred plants are normally carried out with different plants having many different gene combinations. Great care is taken to track modified properties in the plant and to retain properties of interest by avoiding contamination with sim- ilar plants grown in the same or nearby fields. The small scale of plots, such ~ 20 feet long by 3 rows wide, limits the disse}nination of a particular plant. Further, repeated and periodic observations help ensure that undesirable genotypes are not propagated further.

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69 Acreage of selected plants ~ increased over several years, and each year observations are made of both desirable and undesirable traits. Millions of individual plants are tested annually In the United States, and no environmental damage has been documented from their re- lease. Standard confinement practices have been effective in keeping in bounds both poorly domesticated and highly domesticated plants. Proven and routinely applied confinement methods include biological, chemical, physical, geographical, environmental, and temporal control, as well as limitation of the size of the field plot. The committee could document no case of escape of a plant introduction from a confined experimental field plot (1 acre or less) that has produced problems In natural ecosystems. Confinement of plants in small field tests is almost always suc- cessful. Particular traits may be transmitted by pollen to other related plants in the vicinity, but most available evidence shows this to be rare. Unless that trait confers a strong selective advantage to the progeny of the recipient, no adverse effects will occur. ~ nec- essary, such plants can be destroyed. Molecular genetic techniques neither enhance nor decrease the probability of occurrence of such genetic transfer relative to classical methods of genetic manipulation. Established confinement options are as applicable to field introductions of plants modified by molecular and cellular methods as they are for plants modified by classical genetic methods. . [ARG~SCA[E INTRODUCTIONS AND COMMI:RCIAIIZATION This report addresses small-scale experimental introduction, not large-scale introductions ~d commercialization. As experience with small-scale field research increases, the information gamed will per- rn~t large-scale introductions to be approached with greater confi- dence. A plant that exhibits desirable traits in small-scale tests will be graduaDy increased In number and either returned to a breeding program or released as a cultivar. Oversight mechanisms should re- ma~n flexible to accommodate the transition that wiD occur as testing of crops modified by molecular methods proceeds from isolated field plots to large-scale, multisite testing. This field research Is critical to the development of new crop varieties and hybrids.

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70 An important consideration in the commercialization of plants produced by any of the available techniques is how to deploy resis- tance genes so that they remain effective in controlling pests. For example, if the Bacillus thuringiens's endotoxin gene is widely used without regard to the development of resistance, tolerance to this useful bioinsecticide might develop. The same is true for disease- resistance genes. Another concern associated with large-scale use is the potential genetic "cont~nination~ of populations of wild relatives of cultivated plants by genes from unrelated organisms that have been introduced into the cultivar. However, for this concern to be valid, gene ~ntro- gression would have to occur and the resulting progeny would have to have a selection advantage in their wild environment. . Experience gained through smaB-scale field research is crucial to the large-scale use of genetically modified plants. A FRAMEWORK FOR ASSESSING RISE Most of the extensive past experience on field research of plants that have been genetically modified by classical techniques is rele- vant to field research of plants modified by molecular and cellular techniques. Procedures of confinement, monitoring, and mitigation work equally well, regardless of how the plant was produced. The types of modifications that have been seen or anticipated with molecular techniques are similar to those that have been pro- duced with classical techniques. No new or inherently different haz- ards are associated with the molecular techniques. Therefore, any oversight of field tests should be based on the plant's phenotype and genotype and not on how it was produced. The power of the molec- ular methods, however, does present the possibility that plants with unfa~riiliar but desired phenotypes may be produced. In some cases, new genes sources may be used, but familiar phenotypes will result. Plants with unfamiliar phenotypes should be subject to oversight until their behavior Is predictable and shown to be nondetrimental to the environment. In this section, the committee proposes a decLsion-making framer work (Fig. ~1) that allows experimental field testing based on (1) famuliarity with the plant and genetic modification (Fig. 6-2), (2) the ability to confine the plant (Fig. ~3), and (3) the perceived environmental unp act if the plant should escape confinement (Fig. ~4~.

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74 Situations that are familiar and considered safe on the basis of past experience or experimentation should be cIassifiec] as manage- able by accepted standards (MAS). MAS plants would include, for example, classically produced plants and other plants with familiar phenotypes. These plants should be field-tested In a manner that is most appropriate based on past experience in traditional plant breeding. All plants can be confined, some more readily than others. The use of sterile plants is probably the best example of easy confinabil- ity, providing that attention is paid to the dissern~nation of vege- tative propagules. The other extreme would be to confine an open- pollinated plant in the presence of cross-hybridizing wild relatives. In this situation, confinement may be as strict as physical containment in a quarantine greenhouse. It Is clear that the appropriate level of confinement depends on the plant and the geographic area for the field test. If confinement is difficult or uncertain, attention needs to be given to the potential environmental ~rnpact of the introduction. If there is potential for considerable negative environmental impact, confinement procedures should be rigorous, ~ with screened cages. If potential impact is low, less stringent procedures should be called for. As data based on field tests accumulate, it may be desirable to lessen the confinement requirements so that a plant can be used in a cro~improvement program. Field-test results need to be assessed for potential negative environmental impact as a result of altered char- acter~stic~ of weediness, toxicity, or pest resistance. Data obtained through field testing provide the best way to assess the presence of undesirable characteristics accurately. The committee has also included a set of example questions (Figs. ~1 through ~4) that might need to be asked at each phase in the decision-making process. This is not a comprehensive list. The importance attached to each of these questions should be determined on a case-by-case basis. GEOGRAPHIC FAME OF REFE1tENCE Even though the issues discussed in this report are of interest worldwide, it is important to keep in mind that it is written to address the concerns of the United States. The occurrence of weedy or wild relatives for major crops depends on geographic area. In addition, some uses of genetically modified plants will be better

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76 suited for certain geographic areas than others. Therefore, each country and geographic area will need to determine the extent to which the introduction of a genetically modified plant wall have an impact on its environment. OVERSIGHT CONSIDERATIONS It Is reasonable to ask what type of oversight is needed to pro- tect the public welfare and environment, yet does not unnecessarily restrict biotechnological research and commercial development. In- stitutional or local review has a long history of success. For example, in some cases crop certification of plants for expanded field tests and commercialization uses established institutional review or no review. Similarly decentralized local oversight is also used for approval of animal, human, and other exper~rnental procedures including exper- iments utilizing recombinant DNA techniques. Therefore, local over- sight is seen as a suitable option for assessing the risk associated with most research. It is desirable to delegate low-risk introductions- probably 95 percent or more of all ongoing research to local over- sight, so that federal oversight can be used for those few cases where perceived risk exists because confinement Is questionable. We also note that organizations such as government and uni- versity research groups are underrepresented in field introductions of plants modified by molecular techniques. This absence probably arises from the complexity and cost of seeking regulatory approval. This research community has played a vital role not only in develop ing contemporary procedures and techniques, but also In most plant improvement. If the fuB benefit of molecular modifications Is to be realized, the academic and governmental research communities must have access to and be encouraged to apply the technologies of cellular and molecular genetic modification to plants and to evaluate them through field testing.