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Sent: 07 June 2002 11:58
Subject: 21: Natural gene flow - cherimoya fruit tree
This is from Dr Aisha, A. A. Badr in the Tropical fruit division of the Alexandria Horticultural Research Station, Alexandria, Egypt. I have worked for more than 33 years in breeding research and propagation using conventional methods and concerned and beginning biotechnological researches on papaya, loquat and, prefered, the cherimoya [a fruit tree, Annona cherimola, also called custard apple, chirimoya or chirimolla...Moderator].
In the case of fruit trees there is a great need to increase productivity. The gene flow from one cherimoya species to another was naturally done across open or chance pollination as a result of random plantation. Controlled self-pollination is important to preserve good cultivars. As we work long ago in breeding of cherimoyas we used conventional methods of pollination for improving the adapted species and cultivars. Such research revealed gene modification and gene flow as noticed by improving fruit performance, seed number, productivity and high acceptability. This was clear when pollination was done using introduced wild Annona cherimolia for pollinating indigenous Annona squamosa. The gene flow was pronounced in their hybrid A. atemoya, which showed great variation than parents and high number of clones distributed and adapted in the country.
Regarding the classification mentioned in the Background Document of this conference, Annona squamosa could be considered as a domesticated species. The high quality sqamosa selection in Egypt, namely "Abd El-Razik", is grown now in hot areas and desert. In Alexandria (mediterranian sea environment), the most adapted species are: A. Squamosa (special adapted cultivars with protuberances attached to the fruit after ripening, while protuberances of known squamosa were partially separated after ripening), A. cherimolia and A. senegalensis (the wild cherimoya, which is known in other countries as A. glabra). Both of the last species were introduced long ago and showed high adaptability, tolerancy and longevity, followed by A. atemoya. Researches was also conducted on papaya.
The breeding, selection and improvement was done long ago in Egypt (1935) and research were re-conducted again by me since 1989. So a background of evaluated species and selection of improved and tolerant long-survival trees and cultivars is found in published research. Conventional methods of propagation for spreading cultivars followed and other studies were continued.
I believe that all previous effort with such background must be followed by modern studies for improving populations, so trials are conducted on micropropagation as quick method for gene flow and for conservation of new and old selections. Inducing mutation, doubled haploid is also under study, besides other biotechnological research. The biggest problems facing such studies is the lack of trained people and facilities needed for conservation of natural and adapted species.
In my opinion, the human resources is one of the most important factors for success of research, including high desire to complete research with high soul, searching not only as a work, but for loving the research work. Trained responsible people are also needed.Comments:
- It was noticed that common or even highly educated people, always ask about safety of eating GM food. The fearful feeling increases when they find big-sized, highly-colored or unusual characteristics of fruits or vegetables in the markets. Juicy fruits such as grapes, plums, apricot; seedless fruits such as cherimoya; vegetables such as strawberry, cantaloupe are also fearful, so that people search for native cultivars with good smell and smaller size. The question is about how much risk during gene transfer operation and what are the carcinogenic used substances and their residual effect.
- In relation to the message of Niels Louwaars (message 19, 6 June): Of course the importance of native crops and cross pollination research must be considered. There is much valuable research in libraries that needs to be applied. Old research is not found on the world wide web. This will help if we need information about Africa. We can help each other for this great work
Dr Aisha, A. A. Badr
Tropical Fruit Division
Alexandria Horticultural Research Station
momidic (at) hotmail.com
Sent: 07 June 2002 13:46
Subject: 22: Gene flow in transgenic plants: challenges and opportunities
This is from Willy Valdivia-Granda and Edward Deckard in the Plant Pathology Department and the Plant Sciences Department respectively of the North Dakota State University, United States.
Despite the uncertainty and disagreements about the consequences of unintended effects of transgenic plants in least developed countries (LDCs), there has been a significant increase in the area dedicated to its growth. In 2000, the area of transgenic crops in LDCs grew by 51 % from 7.1 million hectares in 1999 to 10.7 million, compared with increase of only 2 % in industrialized countries where the area increased from 32.8 million in 1999 to 33.5 million in 2000 (James, 2000). Risks associated with the release of transgenic plants include their potential persistence as weeds, gene flow to wild relatives, contamination of genetic diversity centers and genetic erosion. In addition to the development of pest's resistance, undesired effects on non-target organisms including microorganisms, parasitoids and predators have been raised.
Many developing countries are the genetic centers of origin for cultivated plants modified by genetic engineering. Heterotic hybrids, resulting from the hybridization of transgenic crops with wild relatives, may rapidly accumulate fitness that can lead to non-intentioned problems in both agricultural and natural ecosystems. Hybridization between transgenic plants and their wild relatives can produce genetic pollution of natural gene pools. Insect or herbicide resistant plants may become weeds and their problem enhanced trough gene stacking. [Refers to the insertion of two or more genes into the genome of an organism. An example would be a plant carrying a Bt transgene giving insect resistance, and a bar transgene giving resistance to a specific herbicide...Moderator].
Selectively neutral genes in one background will not necessarily be so in another (Hails, 2000). For example, hybrids with herbicide resistant will have minor impact in an environment where no herbicide application is produced. However, risk is plausible if these hybrids contain a gene that confers insect resistance and imposes selective advantage over its natural relatives. The rate at which these biological interactions will overpass lineage barriers and exhibit novel combinations and ecological properties is dependent on other organisms, including animals and humans, and the closeness and number of wild relatives in both agricultural and non-agricultural ecosystems.
Most models assume that gene flow is due to variation in the frequency of pollen movement between species and locations. However, multiple mechanisms for the physical transfer of DNA from one species to another are known (Syvanen, 1994). Transgenic potato, papaya, and squash have been engineered with viral coat proteins. However, two safety issues have been raised: 1) gene flow from the transgene to an infecting virus by recombination could lead to new viral genomes 2) heteroencapsidation could allow non vectored virus to become vector trasmisible (Golsalves, 1998; NAS, 2000, Barton and Dracup, 2000; Wolfenbarger and Phifer, 2000). [heteroencapsidation is where transgenic plants expressing the coat protein gene of an aphid-transmissible virus may mediate the spread of a non-aphid transmissible isolate of the virus or other unrelated viruses...Moderator].
A distinguishing characteristic of many transgenic plants is the presence of antibiotic resistance genes that allow selection of transformed cells in selective growth media. Kanamycin is one of the most commonly used resistance markers for plant transformation and it still used for the treatment of human infections (NAS, 2000). [kanamycin is an antibiotic of the aminoglycoside family, important as a substrate for selection of plant transformants...Moderator]. Despite that resistance to antibiotics can arise from a mutation in the pathogen genome, the risks of acquisition of resistance genes for pathogens from transgenic plants have been raised. It has been argued that the development of new transformation systems does not solve the problem of antibiotic resistance genes in transgenic plants approved for commercialization (Syvanen, 1999). The investment of time and money in transgenic plants containing antibiotic resistance markers makes it difficult that these plants will be withdrawn from the market (Syvanen, 1999).
The risk assessment of gene flow in developing countries is complicated by the reduced research in their local environments and due to the fact that most studies on gene flow have concentrated on economically important crops for developed countries. In addition, many LDCs lack the resources and infrastructure to assess the risks related with innovations such as the introduction of transgenic plants and their cumulative effects on their environments.References:
Willy Valdivia Granda
Plant Stress Genomics and Bioinformatics Group
North Dakota State University
PO BOX 5130
701 231-8440 (Lab)
701 231 8255 (Fax)
willy.valdivia (at) ndsu.nodak.edu
Sent: 07 June 2002 14:08
Subject: 23: Frequency of gene-flow and gene-flow rates
My name is Franco Di-Giovanni and I am an air dispersal modeller with a private air quality consulting company in southern Ontario, Canada. My academic training has been in the physics and computer simulation of the airborne dispersal of plant pollen. For the last few years I have been working with the forestry industry in Ontario on defining appropriate genetic isolation zones for forest tree seed production with the aide of simulation models of pollen dispersal. We hope to begin work soon with the Canadian federal government on using these dispersal simulation models to aide risk assessments for "plants with novel traits," as defined in Canada, which includes GM crops.
I would like to address the items of gene-flow and gene-flow rates in this discussion.
The points I wished to raise were as follows: Where information is required on plant gene-flow distances and rates, it would be unwise to base decisions upon a few field trails. Isolation standards set for the production of seed seem, as far as I can tell, to have been based upon "representative" gene-flow distances established through a limited number of field trials. In some cases (at least in the Canadian case) isolation distances for GM crop field trials have also been based upon distances used for seed production isolation.
Field trials are essentially "snap-shots" in time of gene- or pollen-flow, under specific and generally non-repeatable conditions. Pollen- and gene-flow are inherently variable phenomena and I am generally uncomfortable with isolation distances promulgated without knowledge of the variability's involved. For example, what would a worst-case pollen- or gene-flow distance be? For wind pollinated crops, such factors as wind speed, atmospheric stability and turbulence, pollen and plant characteristics contribute to this variation. Think about the variability of smoke emanating from industrial smoke stakes, for example. Further, gene-flow is affected by pollen viability and other biological factors which themselves are influenced by (variable) environmental conditions. This type of information should be available to those assessing the risks of introduction of plants with novel traits.
We are developing a modelling system that is essentially a field trial "simulator," allowing the user to examine the long-term patterns of pollen- and gene-flow, thus providing information on variability and, ultimately, probabilities for pollen and gene-flow at various distances. We believe this to be a sounder basis for assessing the probabilities of pollen dispersal and, ultimately, gene-flow for wind pollinated outcrossing plants. However, as others have mentioned in this conference [e.g. Niels Louwaars, message 19, 6 June...Moderator], scientific information on pollination mechanisms of many tropical plants is not as well developed as we would like, and for certain plant-types pre-requisite pollination ecology studies may be required.
Others have raised the issue of the liability of the negative consequences of gene-flow, and this provides an interesting twist to discussions. In the environmental field, the concept of "polluter pays" is well established. However, in agriculture, the onus has generally been on the producer of the crop (products) to sufficiently isolate their fields so as to produce a "pure" product. These issues are being raised by a potential class-action law suit being initiated by organic farmers in western Canada against biotech companies: these farmers feel that because of the widespread use of GM canola, that they can no longer produce organic crops in the region.
Franco Di-Giovanni, PhD
Senior Air Quality Modeller
2240 Speakman Drive
Canada N1C 1B6
Tel: 905-822-0946 ext.168
email: fdi-giovanni (at) airzoneone.com
Sent: 07 June 2002 15:43
Subject: 24: gene flow risk assessment - plants
[Both this message and the next one (by Dr. Wozniak) that we received exceed the normal length limits. Participants are reminded that messages should not exceed 600 words...Moderator]
I am Tom Nickson, a scientist with Monsanto Company and team leader for a group of about 20 scientists who are responsible for the design of our science based approach to assessing the ecological risks for our biotech crops. I would like to share with this group some information concerning the approach that we take when assessing risks associated with gene flow from transgenic crops. Because our focus is plant biotechnology, this note is not intended to address the broader topics of transgenic fish or other organisms.
It is first important to understand that this evaluation is grounded in the scientific principles of risk assessment as outlined in several sources (US Environmental Protection Agency (EPA), 1998 and Suter, 1993). The fundamental principles of the risk assessment framework we use for GM plants are, 1) risk assessment has a scientific basis, 2) it is conducted case-by-case, 3) risk assessment is iterative and new information requires a re-examination of the risk characterization and previous risk decision, and 4) inclusive of all available information. Regarding the last point, available information is not necessarily limited to scientific fact because expert opinions and personal beliefs are also considered in a well-conducted risk assessment. Clearly, the more objective, quantified information available, the less uncertainty will result; and hence a more certain decision can be made. However, in complex matters of plant ecology many parameters are not available quantitatively, and they must be described in qualitative terms. This is particularly evident in the hazard assessment which I will mention later.
Another key point concerning the broad ecological risk assessment for GM crops (not specific to gene flow) is the concept of comparative risk assessment. For many of the GM crops currently marketed in the world (herbicide tolerant, insect and virus protected), the final form of the risk assessment is comparative - where the risks associated with the GM plant are characterized and compared to those associated with the conventional system in which the GM crop will be introduced. As such, an appropriate comparative context should be determined at the outset of the risk assessment research. For example, the ecological risks associated with a crop protected against specific targeted insects by Bt (e.g., Bt cotton) should be compared to the conventionally grown crop. A complete assessment would consider non-target impacts of Bt from constitutive plant expression versus exogenous pesticide applications, yields obtained from Bt compared to conventionally produced product, risk of human toxicity of Bt compared to exogenously applied pesticides, and the potential impacts associated with resistance developed to Bt and the alternative pesticides that would be used.
Critical to conducting an appropriate risk assessment for gene flow is having clearly defined and operational terms (sometimes referred to as Terms of Reference). These should begin with the most important terms in risk assessment: hazard and exposure or likelihood. (Note: Risk = Hazard X Exposure). Hazard, as defined by Suter (1993) is "a state that may result in an undesired event, the cause of risk". Likewise, a recent report from the EU (Van den Eede, no date) defined hazard as: "a property of a substance, a property of an act, a property of phenomenon or a property of process that could cause harm" where they defined harm as "the realization of hazard: it is any form of physical or mental injury". The second component of risk is "exposure", which in the context of gene flow is synonomous with likelihood or frequency. The literature on gene flow from GM crops is repleat with many scientific works that measure the frequency of gene flow (the phenomenon), and inaccurately characterize their results using the broader term "risk".
The challenge that faces scientific risk assessors studying gene flow is having an accurate and testable definition for hazard. Given that hazard is a property that has undesired or injurious consequences, the challenge for scientists is to develop risk assessment experiments that can quantitatively or qualitatively assess the nature and magnitude of an injurious event associated with gene flow. This is made more complicated by the fact that gene flow has been occurring within domesticated crops and between these crops and their wild relatives in areas of sympatry for millenia. Prior to the development of transgenes, the undesired properties associated with gene flow have typically been in the direction from the weed to the crop (e.g., wild beet to sugarbeet). I am unaware of hazards associated with gene flow from a crop to a wild relative being of such significant magnitude as to merit the need for mitigation practices. In these cases, whole genomes have been involved. The situation that existed in agriculture prior to the introduction of GM crops provides little insight into the potential hazards and their magnitude that might be present from the introduction of a few transgenes into the system.
This lack of knowledge has resulted in broad characterizations of the hazards associated with gene flow from GM crops such as: impacts on biodiversity, impacts on population dynamics, genetic swamping, and alterations of gene pools; all of which are inoperative in terms of science based hypothesis testing. Furthermore, these "hazards" are rarely placed within the context of the experience with agricultural practices that have been used for centuries.
We have focused our scientific assessment of hazard on the potential for the transgene to confer increased weediness to the crop or its sexually compatible wild relative since there are valid methods to assess the growth, reproductive potential, persistance and dormancy of plants. For example, a modified maize plant that exhibits the same weediness characteristics as its conventional counterpart in field tests conducted at multiple sites over multiple years can be concluded to be unaltered in its weediness potential. In addition, we assess the potential for wild relatives to be growing near the area of intended release, as well as the frequency that our modified corn plant crosses with its conventional counterpart to determine if this property has been meaningfully altered. In the case where the properties measured for the modified corn plant compared to its control are similar, our characterization for the risk associated with gene flow is that it is not different from the risk associated with the conventional corn.
As a personal observation, the current biotech products have shown no measureable risks compared to the risks already present from their traditionally grown counterparts. However, the lack of detectable effects and measurable hazards seems to have left some of the scientific community with a sense of uncertainty, possibly due to dissatisfaction with negative results. As such, some have requested test systems to be designed to be more sensitive. However, the keen focus on detecting effects can result in a loss of perspective on relevence of the effect to safety and what is biologically meaningful within the entire system. Clearly, this is a balance where scientific discussion and dialogue can help to develop better test systems and means to obtain new knowledge and ensure that appropriate decisions can be made. Lastly, we must also balance our concerns resulting from a perceived lack of knowledge on how one or two transgenes will impact biodiversity with our need to prudently introduce new technologies that could help the overall sustainability of agriculture around the world?References:
Thomas E. Nickson, Ph.D.
Ecological Technology Center
Monsanto Company, V2B
800 N. Lindbergh Blvd.
St. Louis, MO 63141
thomas.nickson (at) monsanto.com
Sent: 07 June 2002 16:38
Subject: 25: gene flow; Plant-Incorporated Protectants; USA
This posting is from Dr. Chris A. Wozniak, a scientific reviewer with the Biopesticides and Pollution Prevention Division (BPPD) at the U.S. Environmental Protection Agency (EPA) in Washington, D.C. My position as a biologist in BPPD includes review of mammalian toxicology issues, gene flow potential from Plant-Incorporated Protectants (PIP; plants engineered with pesticidal traits), molecular characterization of transgenes, and the assessment of degradation rates of Bt delta-endotoxin in soil following culture of Bt crops. My training is primarily in plant pathology and plant molecular biology with research experience in plant transformation and biocontrol of insect pests through the use of pathogenic microbes and genetically modified (rDNA) plants. My comments, like those of my colleague Dr. Suzanne Wuerthele from region 8 (Denver, CO) of the U.S. EPA, are to be taken as personal scientific opinion and not to be construed as representing the policy or views of the Agency. [As mentioned in message 2, the Rules of the Forum state explicitly that participants are assumed to be speaking on their own behalf, unless they state otherwise...Moderator].
With regard to message 5, June 3 from Dr. Wuerthele and to provide background on what is examined in the U.S. review of PIPs by the EPA:
The scientific review of the genetically modified plants which express pesticidal traits (e.g., insect or disease resistance) is performed in the U.S. by BPPD staff scientists who examine the product characterization (transgene sequence and function, plant compositional analysis, genetic stability / heritability, protein sequence and function, expression levels, comparison of sequence to toxin and allergen databases, protein thermostability), acute mammalian toxicity (oral dosing of rats), acute avian toxicity (oral dosing of chickens or quail), non-target organism effects (fish, aquatic invertebrates, earthworms, insects....), gene flow potential, environmental fate, insect resistance management for Bt crops, and potential for weediness. A more thorough discussion of our risk assessments can be found at http://www.ostp.gov/html/012201.html as represented in the analysis of case studies (MON 810 maize).
In the examination of gene flow potential, the U.S. EPA/BPPD has looked at the three species which are engineered to express pesticidal traits (i.e., potato, maize, cotton). Since cotton and potato contain extant sexually compatible relatives within the U.S., its possessions and territories, these were examined in more detail (see http://www.epa.gov/oppbppd1/biopesticides/otherdocs/bt_brad2/3%20ecological.pdf).
While we recognize that cultivated, commercial varieties selected over centuries by indigenous peoples and breeders are capable of hybridizing with sexually compatible wild or feral relatives and thereby transferring their 'exotic' traits, the case of PIP gene flow is under closer scrutiny because of the novel aspects of the transgenic traits and legal mandate. While the phenotype present in the PIPs registered to date (i.e., viral resistance, insect resistance) are within the normal realm of the genome of the PIPs registered (i.e., Bt maize, Bt cotton, Bt potato, virus resistant potato), the sequence of the gene construct may differ from endogenous genes. The functionally analogous phenotype (e.g., disease resistance, insect resistance) and gene are the keys to interaction with the environment (e.g, with related plant species through gene flow, introgression, non-target organism effects), not the process which created it.
The cautious route was chosen with regard to gene flow to native species (e.g., Hawaiian cotton (Gossypium tomentosum)) from a PIP until which time we can properly assess any hazard (e.g., enhanced or decreased fitness, loss of biodiversity through 'swamping' of populations...) associated with transfer of a pesticidal trait to this declining species. Note, however, that we do not assess the potential for gene flow to conventional or organic crops as part of our risk assessment as long as there is a food tolerance (defined below) in place as mandated by the Federal, Food, Drug and Cosmetic Act.
For the sake of brevity I will respond to only a few comments contained in Dr. Wuerthele's response [message 13, June 5...Moderator] to Dr. Toby Bradshaw (message 5, June 3). I would have liked to respond to message 1 of May 31, however, ironically I was away from the office at a gene flow workshop.
Paragraph 4.) As far as I know, there is no evidence existing to demonstrate that rDNA techniques produce inherently unstable or unpredictable plants (or bacteria or fungi...). If there are such studies in the literature, they should be cited in full. Instability in the genome (e.g., Ds/Ac in maize, natural mutation rates, translocations, rearrangements) is the fodder of classical/conventional breeders and allows for new plant varieties (and new species). Experience with a variety of different transgenes and crops has led to some unintended effects (e.g., cotton boll drop, altered Petunia flower color and Sugarbeet leaf morphology...). However, unintended effects do not necessarily mean they should have been unexpected. With each experiment, our knowledge grows relative to fine tuning the production and selection procedures. This is the same for conventional breeding - rogue out the bad ones and select those with desirable characteristics. The studies I have reviewed regarding stability of transgene inheritance, based upon Mendelian inheritance and Chi square analysis, have been carried through the fourth or further backcross generation with no suggestion whatsoever that the inserted gene construct was unstable or in anyway altered following insertion. Similarly, the expression levels of the transgenes were within the range of variation as typical for protein levels of traits in near isogenic lines of the cultivar in question when grown under field conditions.
Paragraphs 5 and 2.) Conventional breeding includes embryo rescue techniques, pistil/style modifications, colchicine mediated chromosome doubling, bridging and wide hybrid crosses, phytohormone treatments to alter post-fertilization events, and chemical or irradiation induced mutations. This includes transfer from species through bridging crosses that bring gene combinations together that would otherwise not occur naturally. Tomato, wheat, triticale (rye/wheat), barley, potato, Tripsacum and sugarbeet are just a few examples where this has worked. The majority of tomato varieties produced in Italy (where they revere the 'love apple') and in some other countries are the result of chemical or radiation induced DNA damage (mutation). The alleles present in many key traits are not natural in the sense that they may have never evolved on their own without man's intervention. While they may seem like inefficient methods to produce novel tomato fruits, they are obviously worth the effort (i.e., feasible) and have produced some great tasting, nutritious and safe produce. There is no a priori reason to expect genetically modified plants to produce anything less, as long as careful screening and selection are practiced.
(Food tolerance - all pesticides associated with application in or on crops, intended for food or feed, require a tolerance or exemption from the requirement of a tolerance in order to be legally applied. A simple way to think of this is the amount of residue allowed on a finished crop or commodity. All PIPs to date have been granted an exemption from the requirement of a food tolerance. PIP -Plant-incorporated protectant - a pesticidal substance expressed within a plant and the genetic material necessary for its production. Common examples of these are cotton, corn and potato engineered to express the endotoxin from Bacillus thuringiensis (Bt) to provide insect resistance. The trait is the PIP, not the plant itself.)
Chris A. Wozniak, Ph.D.
U.S. Environmental Protection Agency
Biopesticides and Pollution Prevention Division
1200 Pennsylvania Ave., NW, 7511C
Washington, DC 20460
703-308-7026 - fax
wozniak.chris (at) epa.gov
Sent: 07 June 2002 17:00
Subject: 26: Liabilities and economics of transgenic crops
I am Stuart Smyth, a Ph.D. Candidate in Biotechnology at the University of Saskatchewan, Canada. I am researching the social science impacts of GM crops.
Many of you may be interested in this months Nature Biotechnology that has a section on the environmental impact of GM crops. The commentary that I have co-authored discussed some of the economic costs that have arisen from gene flow. We posit that a seed sterility mechanism may play an important role in the further development of GM crops. [This article was published in Nature Biotechnology, Volume 20, pages 537-541...Moderator]
Ph.D. Candidate in Biotechnology
University of Saskatchewan
sjs064 (at) mail.usask.ca