GM Crop Database

Database Product Description

MON832

Host Organism: Zea mays (Maize)

Trait: Glyphosate herbicide tolerance.

Trait Introduction: Microparticle bombardment of plant cells or tissue

Proposed Use: Production for human consumption and livestock feed.

Product Developer: Monsanto Company

Summary of Regulatory Approvals

Country	Food	Feed	Environment	Notes
Canada	1997			View Application for environmental release and feed approval withdrawn by proponent
United States	1996

Introduction Expand

Maize line MON832 was developed to allow the use of glyphosate, the active ingredient in the herbicide Roundup®, as a weed control option for maize crops. Two novel genes were introduced into maize line MON832, which in combination provide field level tolerance to glyphosate. The novel plants express a glyphosate tolerant version of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoding gene isolated from Agrobacterium tumefaciens strain CP4 (CP4 EPSPS). Glyphosate specifically binds to and inactivates EPSPS, which is involved in the biosythesis of the aromatic amino acids tyrosine, phenylalanine and tryptophan. The EPSPS enzyme is present in all plants, bacteria and fungi, but not in animals, which do not synthesize their own aromatic amino acids. The modified enzyme (CP4 EPSPS) has a reduced binding affinity for glyphosate and allows the plant to function normally in the presence of the herbicide.

The second gene codes for glyphosate oxidase (gox gene), a bacterial enzyme from Ochrobactrum anthropi and is ubiquitous in nature. Glyphosate oxidase (GOX) accelerates the normal degradation of glyphosate into aminomethylphosphonic acid (AMPA) and glyoxylate. AMPA is the principal metabolite of glyphosate and is degraded by several microorganisms while glyoxylate is commonly found in plant cells and is broken down by the glyoxylic pathway for lipid metabolism.

These two enzymes, CP4 EPSPS and glyphosate oxidase, allow MON832 maize to be protected against herbicide damage when glyphosate is used for weed control in the cultivation of maize.

Summary of Introduced Genetic Elements Expand

Code	Name	Type	Promoter, other	Terminator	Copies	Form
goxv247	glyphosate oxidoreductase	HT	CaMV 35S chloroplast transit peptide from A. thaliana SSU1A gene (CTP1)		3
CP4 epsps	5-enolpyruvyl shikimate-3-phosphate synthase	HT	enhanced CaMV 35S, maize HSP70 intron chloroplast transit peptide from A. thaliana EPSPS gene (CTP2)	A. tumefaciens nopaline synthase (nos) 3'-untranslated region	1
nptII	neomycin phosphotransferase II	SM	bacterial promoter		1 complete, 1 rearranged	Not expressed in plant tissues because of bacterial promoter.

Characteristics of Zea mays (Maize) Expand

Center of Origin	Reproduction	Toxins	Allergenicity
Mesoamerican region, now Mexico and Central America	Cross-pollination via wind-borne pollen is limited, pollen viability is about 30 minutes. Hybridization reported with teosinte species and rarely with members of the genus Tripsacum.	No endogenous toxins or significant levels of antinutritional factors.	Although some reported cases of maize allergy, protein(s) responsible have not been identified.

Donor Organism Characteristics Expand

Latin Name	Gene	Pathogenicity
Agrobacterium tumefaciens strain CP4	CP4 epsps	Agrobacterium tumefaciens is a common soil bacterium that is responsible for causing crown gall disease in susceptible plants. There have been no reports of adverse effects on humans or animals.

Modification Method Expand

Maize line MON832 was produced by biolistic transformation of embryogenic maize cells with a mixture of DNA from two plasmids, PV-ZMBK07 and PV-ZMGT10. Plasmid PV-ZMBK07 contained the synthetic cr1Ab gene regulated by the enhanced duplicated cauliflower mosaic virus 35S promoter (CaMV E35S) and the maize hsp70 heat shock protein intron. The polyadenylation signal was from the Agrobacterium tumefaciens nopaline synthase (nos) gene.

The second plasmid, PV-AMGT10, contained genes encoding the CP4 EPSPS enzyme from the common soil bacterium, A. tumefaciens sp. CP4, and glyphosate oxidoreductase (goxv247) from Ochrobactrum anthropi. Constitutive expression of these genes in plant cells was under the control of the CaMV E35S promoter, the hsp70 intron, and nos 3' terminator. Post-translational targeting of the CP4 EPSPS and glyphosate oxidoreductase enzymes to the chloroplast was accomplished by fusion of the 5'-terminal coding sequences with the chloroplast transit peptide DNA sequences from the Arabidopsis thaliana EPSPS gene (CTP2) and from A. thaliana SSU1A gene (CTP1), respectively. Plasmid PV-ZMGT10 also contained sequences from the lacZ operon, ori-pUC and the neo gene. The neo gene on both plasmids was included as a selectable marker to identify bacteria transformed with recombinant plasmid DNAs. Expression of the neo gene was regulated by a bacterial promoter and therefore is not functional in plants.

Characteristics of the Modification Expand

The Introduced DNA

Southern blot analysis of genomic DNA from MON832 confirmed that sequences from plasmid PV-ZMBK07, containing the cry1Ab gene, were not incorporated but that the CP4 EPSPS encoding sequences along with three copies of the gox gene and two NPTII/ori-pUC sequences (one complete and one rearranged) were integrated as a single 16 kb insert.

Genetic Stability of the Introduced Trait

Segregation and stability data were consistent with a single site of insertion into the genomic DNA of line MON832.

Expressed Material

The CP4 EPSPS and GOX enzymes were constitutively expressed in tissues throughout the plant and at all plant growth stages. Enzyme linked immunosorben assay (ELISA) was used to quantitate the expression levels of CP4 EPSPS and GOX in the leaves, forage, and kernels of plants grown in field trials. Average amounts were as follows: in leaves 49.61 EPSPS µg/g fresh weight (fwt) and 4.92 GOX µg/g fwt; in forage 21.32 EPSPS µg/g fwt and 3.32 GOX µg/g fwt; and in kernels 5.83 EPSPS µg/g fwt and 1.97 GOX µg/g fwt.

Western immunoblot analysis was used to confirm that NPT II was not detectable in MON832, which was predicted since expression of the neo gene was regulated by a bacterial promoter known not to be active in plants.

Food and/or Feed Safety Considerations Expand

Dietary Exposure

Grain from maize line MON832 was intended mainly for use in animal feed. The major human food uses for maize are extensively processed starch and oil fractions prepared by wet or dry milling procedures and products include corn syrup and corn oil, neither containing protein. Human exposure to the modified protein from whole grain corn in the diet was considered to be very low due both to its low abundance in the protein fraction of the grain and to the proportionately low percentage of protein in the kernel, compared with the major starch component. Overall, the dietary exposure of consumers in the United States and Canada to grain from MON832 maize was anticipated to be the same as for other lines of commercially available field corn.

Nutritional Data

The major components of maize grain and forage from MON832 were analysed on plant material harvested from field trials. Compositional data for protein, fat, ash, carbohydrates, calories, moisture, amino acids, and fatty acids for line MON832 grain were comparable to the data from the control line and within published ranges for commercial hybrids. Similar promximate analysis, including acid detergent fibre and neutral detergent fibre analyses, were performed on forage for line MON832 and an appropriate control. Based on these compositional data, it was concluded that there were no significant differences between the forage from line MON832 and the control line.

Toxicity

The low potential for toxicity of transgenic maize line MON832 was demonstrated by examining the amino aid sequence homology, protein characterization, digestive fate studies in simulated gastric and intestinal fluids and acute oral toxicity in mice. Using sophisticated computerized search capabilities, the evidence showed that the CP4 EPSPS and GOX proteins did not show meaningful amino acid sequence homology when compared to known allergens or protein toxins. These studies support the safety of the proteins and are consistent with the history of safe presence and ubiquitous distribution of Agrobacterium and Achromobacter spp. in the soil. An acute mouse toxicity study further indicated that there were no toxic effects caused by CP4 EPSPS or GOX proteins administered by oral gavage, as measured by the absence of treatment related adverse effects in mice.

Allergenicity

The CP4 and GOX proteins are not likely to be toxic or allergenic. The amino acid sequences of both proteins were compared with known toxins and allergens did not show meaningful amino acid sequence homology. In addition, the potential for allergenicity was assessed based upon the characteristics of known food allergens (stability to digestion, stability to processing). Unlike known protein allergens, studies have shown that the CP4 and GOX proteins are rapidly degraded and their enzymatic activity lost under conditions that simulate mammalian digestion.

Abstract Collapse

Maize (Zea mays L.), or corn, is grown primarily for its kernel, which is largely refined into products used in a wide range of food, medical, and industrial goods.

Only a small amount of whole maize kernel is consumed by humans. Maize oil is extracted from the germ of the maize kernel and maize is also a raw material in the manufacture of starch. A complex refining process converts the majority of this starch into sweeteners, syrups and fermentation products, including ethanol. Refined maize products, sweeteners, starch, and oil are abundant in processed foods such as breakfast cereals, dairy goods, and chewing gum.
In the United States and Canada maize is typically used as animal feed, with roughly 70% of the crop fed to livestock, although an increasing amount is being used for ethanol production. The entire maize plant, the kernels, and several refined products such as glutens and steep liquor, are used in animal feeds. Silage made from the whole maize plant makes up 10-12% of the annual corn acreage, and is a major ruminant feedstuff. Livestock that feed on maize include cattle, pigs, poultry, sheep, goats, fish and companion animals.

Industrial uses for maize products include recycled paper, paints, cosmetics, pharmaceuticals and car parts.
The MON832 line of maize was developed to allow the use of glyphosate, the active ingredient in the herbicide Roundup®, as a weed control option. In order to obtain field tolerance to glyphosate herbicide, two novel genes, EPSPS and goxv247, were introduced maize by particle acceleration (biolistic) transformation.

The EPSPS gene codes for the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) that is present in all plants, bacteria and fungi. The EPSPS gene put into MON832 was isolated from strain CP4 of the common soil bacterium Agrobacterium tumefaciens and is a glyphosate tolerant form of EPSPS. The EPSPS enzyme is part of an important biochemical pathway in plants called the shikimate pathway that is involved in the production of aromatic amino acids and other aromatic compounds. When conventional maize plants are treated with glyphosate, they cannot produce the aromatic amino acids needed to grow and survive. EPSPS is not present in mammals, birds or aquatic life forms, which do not synthesize their own aromatic amino acids. For this reason, glyphosate has little toxicity to these organisms. The EPSPS enzyme is naturally present in foods derived from plant and microbial sources.

MON832 contains a second gene that codes for a modified version of glyphosate oxidase (GOX) enzyme that is ubiquitous in nature. The goxv247 gene inserted into MON832 was isolated from strain LBAA of the bacterium Ochrobactrum anthropi. The GOX enzyme accelerates the normal breakdown of the herbicide glyphosate into two non-toxic compounds, aminomethylphosphonic acid (AMPA) and glyoxylate. AMPA is the principal breakdown product of glyphosate and is degraded by several microorganisms, while glyoxylate is commonly found in plant cells and is broken down by the glyoxylic pathway for lipid metabolism.

The major components of grain and forage from MON832 maize were analyzed in order to determine their safety for use as food and as livestock feed. Proximate analysis determined that MON832 grain was comparable to that of the non-transgenic control line in its protein, fat, ash, carbohydrate, fibre, moisture and caloric content. Additionally, the amino acid and fatty acid composition of MON832 grain was comparable to that of a non-transgenic line. Based on this data, it was concluded that there was no significant difference between the forage from MON832 maize and the control line.

The low potential for toxicity of the transgenic maize line MON832 was demonstrated by examining the amino acid sequence homology and protein characterization of the line. The CP4 EPSPS and GOX proteins did not show meaningful amino acid sequence homology with known allergens or protein toxins. Further assessment of the allergenic potential of these proteins consisted of digestibility studies and an acute oral toxicity study involving mice. Results of the digestibility studies indicated that, unlike known protein allergens, the CP4 EPSPS and GOX proteins are rapidly degraded and their enzymatic activity lost under conditions that simulate mammalian digestion. The mouse toxicity study indicated that there were no toxic effects caused by consumption of the CP4 EPSPS or GOX proteins, as measured by the absence of treatment-related adverse effects in the mice. It was therefore concluded that the CP4 EPSPS and GOX proteins are not likely to pose any toxicity or allergenicity concerns.

Links to Further Information Expand

Office of Food Biotechnology, Health Canada

Novel Food Information: Roundup Ready Maize Line, MON832
[PDF Size: 21.47K bytes]

US FDA

Biotechnology Consultation Agency Response Letter BNF No. 000035
[PDF Size: 178.76K bytes]

This record was last modified on Monday, March 28, 2016

Product Related Info

Biology Documents

Maize biology document
Biology of Maize L.
General Description

Maize is a tall, monoecious, annual grass varying in height from 1 to 4 meters (Watson & Dallwitz 1992). The main stem is made up of clearly defined nodes and internodes. Internodes are wide at the base and gradually taper to the terminal inflorescence at the top of the plant. Leaf blades are found in an alternating pattern along the stem. Maize is a unique grass as both male and female flowers are borne on the same plant but are located separately. The tassels or staminate (male) inflorescence form large spreading terminal panicles that resemble spike-like racemes. Pollen is shed from the tassel and is viable for approximately 10 to 30 minutes as it is rapidly desiccated in the air (Kiesselbach 1980). Maize plants shed pollen for up to 14 days. The reproductive phase begins when one or two auxiliary buds, present in the leaf axils, develop and form the pistillate inflorescence or female flower (Purseglove 1972). The auxiliary bud starts the transformation to form a long ‘cob’ on which the flowers will be borne. From each flower a style begins to elongate towards the tip of the cob in preparation for fertilization. These styles form long threads, known as silks. The base of the silk is unique, as it elongates continuously until fertilization occurs (Purseglove 1972). Styles may reach a length of 30 cm, the longest known in the plant kingdom. Individual maize kernels, or fruit, are unique in that mature seed is not covered by floral bracts (glumes, lemmas, and paleas) as in most other grasses, but rather the entire structure is enclosed and protected by large modified leaf bracts, collectively referred to as the ear (Hitchcock and Chase 1951). The mature female flowers will remain ready for fertilization for up to two weeks, at which point if fertilization has not occurred, the nucleus will de-organize and fertilization will no longer be possible (Hitchcock & Chase 1951). The pollen of maize, a protandrous plant, matures before the female flower is receptive (Purseglove 1972). This may have been an ancient mechanism to ensure cross-pollination, but is no longer considered conducive to modern agricultural practices. However, decades of conventional selection and improvement have produced many maize varieties with similar maturities for both male and female flowers, to ensure seed set for agricultural proposes.

Reproduction

Under natural conditions, maize reproduces only by seed production. Pollination occurs with the transfer of pollen from the tassels to the silks of the ear. About 95% of the ovules are cross-pollinated and about 5% are self-pollinated (Poehlman 1959), although plants are completely self-compatible. Maize, as a thoroughly domesticated plant, has lost all ability to disseminate its seeds and relies entirely on the aid of man for its distribution (Stoskopf 1985). The kernels are tightly held on the cobs and if ears fall to the ground, so many competing seedlings emerge that the likelihood that any will grow to maturity is extremely low. Maize cannot reproduce asexually by natural means. It is possible to reproduce maize using tissue culture techniques, however, it has proven extremely difficult with a low rate of success (Hoisington et al. 1998).

Classification and Phylogeny of Maize

Zea is a genus belonging to the grass family, Poaceae, in the Andropogoneae tribe, but is commonly cited in literature to belong to the tribe Maydeae. Zea (zeia) was derived from an old Greek name for a food grass. The genus Zea consists of four species of which only Zea mays ssp. mays L. is economically important. The other Zea species, referred to as teosintes, are largely wild grasses native to Mexico and Central America (Doebley 1990). The number of chromosomes in Zea mays is 2n=20, 21, 22, 24 (FAO 2000c). The tribe Maydeae consists of seven genera: two of American origin, Zea and Tripsacum; and five of Eastern origin which extend from India through Southeastern Asia to Australia and include Coix, Sclerachne, Polytoca, Chionachne and Trilobachne (Watson & Dallwitz 1992). It is generally agreed that maize phylogeny was largely determined by the American genera Zea and Tripsacum, however it is accepted that the genus Coix contributed to the phylogenetic development of the species Z. mays (Radu et al. 1997). The genus Manisuris, from the tribe Andropogoneae, may also have contributed to the evolution of Zea mays (Eubanks 1997a; Radu et al. 1997).

Center of Origin and Progenitors of Maize

The center of origin for Zea mays ssp. mays has been established as the Mesoamerican region, now Mexico and Central America (Watson & Dallwitz 1992). The exact period of domestication and the ancestors from which maize arose are unclear. Archaeological records suggest that domestication of maize began at least 6000 years ago, occurring independently in regions of the southwestern United States, Mexico, and Central America (Mangelsdorf 1974). The origins of domesticated maize have been difficult to trace as hybridization events in its evolution are thought to have involved a now extinct wild maize ancestor of which little evidence has been found (Eubanks 1997a).

Germplasm Diversity

A study in 1992 concluded that maize landraces occupied 42% of the land under production in less developed countries (México 1994). Mexico and Central America are the only regions where ancient maize lines, such as pod corn, are found (Mink & Dorosh 1985). The survival of maize landraces has been attributed to the integral role maize sustains in small communities where it has very specific uses for food and other special functions. These landraces have been well characterized in Latin America, and germplasm not yet evaluated is known to be present in the region. There is a growing trend in developing countries to adopt improved maize varieties, primarily to meet market demand. In Mexico, only 20% of the corn varieties grown 50 years ago remain in cultivation (World Watch Institute 2000). The narrowing of genetic diversity in modern maize varieties emphasizes the importance of conserving genetic traits for future plant breeding. Leading the way in preserving maize germplasm is CIMMYT (International Maize and Wheat Improvement Centre), which has the world’s largest collection of maize accessions, with over 17,000 lines (CIMMYT 2000). Collections of distant maize relatives native to Asia have been recommended by conservation experts to ensure their preservation for future research (Sharma 1998).

Relatives of Maize

The closest wild relatives of maize are the teosintes which all belong to the genus Zea. The teosintes are wild grasses native to Mexico and Central America and have limited distribution (Mangelsdorf et al. 1981). Teosinte species show little tendency to spread beyond their natural range and distribution is restricted to North, Central and South America (Watson & Dallwitz 1992). The nearest teosinte relative to Z. mays ssp. mays is Z. mays ssp. mexicana (Schrader) Iltis (previously classified as Euchlaena mexicana, Zea mexicana) (2n = 20). This Central Mexican annual teosinte is a large flowered, mostly weedy grass with a broad distribution across the central highlands of Mexico. It does not spread readily. It has limited use as a forage and green fodder crop, but can be problematic due to weedy tendencies (Doebley 1990, Watson & Dallwitz 1992). The closest wild relatives to maize outside the Zea genus are from the genus Tripsacum. The genus Tripsacum is comprised of about 12 species that are mostly native to Mexico and Guatemala but are widely distributed throughout warm regions in the USA and South America, with some species present in Asia and Southeast Asia (Watson & Dallwitz 1992). All species are perennial, warm season grasses.

Outcrossing

Gene flow from maize can occur by two means: pollen transfer and seed dispersal. Seed dispersal can be readily controlled in maize as domestication has all but eliminated any seed dispersal mechanisms that ancestral maize may have previously used (Purseglove 1972). The kernels are held tightly on the cobs and if the ear falls to the ground, competing seedlings limit growth to maturity (Gould 1968). Pollen movement is the only effective means of gene escape from maize plants. Pollen is released from the tassels at the top of the plant and transported by wind to the female flowers located on the stalk. Pollen shed occurs over a 14 day period, with a peak during the first 5 days of shed (Sears 2000). The stigmas are receptive for a large part of this two week interval (Kiesselbach 1980). Insects, such as bees, have been observed to collect pollen from maize tassels, but they do not play a significant role in cross-pollination as there is no incentive to visit the female flowers (Rayor et al. 1972).

Wind speed and direction affect pollen distribution

Differences in flowering dates among commercial maize varieties are small. Cross-pollination between varieties may occur if grown in adjacent fields. The limited viability of maize pollen reduces the risk of cross-pollination, as a receptive host must be found within the 30 minutes that the pollen remains biologically active. Cross-pollination is also affected by the concentration of maize pollen released; pollen produced by a maize crop will successfully compete with foreign pollen sources when present in higher concentrations (Rayor et al. 1972). The isolation of crops using separation distances and physical barriers are common techniques for restricting gene flow and ensuring seed purity for maize seed production. Cross-pollination is controlled in seed lots by separating different lines. The OECD standards require a minimum 200 m (660 ft) isolation distance for maize seed production. This distance has been estimated to maintain inbred lines at 99.9% purity. Physical barriers, such as trees or barrier rows, are also effective in reducing cross-pollination. Detasseling or bagging the tassel effectively prevents pollen movement and limits gene flow.

Intraspecific hybidization

All forms of Zea mays spp mays, such as dent, sweet, and pop corn, freely cross pollinate forming fertile hybrids (Pursglove 1972).

Interspecific hybridization

All teosintes can be crossed to maize and form fertile hybrids, except for the tetraploid Z. perennis. Maize-teosinte hybrids exhibit low fitness and have little impact on gene introgression in subsequent generations (Galinat 1988). The tendency to form natural hybrids differs among teosintes: Z. luxurians rarely hybridizes with maize, whereas Z. mays ssp. mexicana frequently forms hybrids (Wilkes 1977). Molecular data confirms that there is gene flow between maize and teosinte and suggests that introgression of maize and teosinte occurs in both directions but at low levels (Doebley 1990).

Intergeneric hybridization Tripsacum species (T. dactyloides, T. floridanum, T. lanceolatum, and T. pilosum) have been successfully hand crossed with maize to form hybrids. The hybrids generally have 28 chromosomes, 10 from maize and 18 from Tripsacum, and are pollen sterile with limited female fertility (Mangelsdorf & Reeves 1939, Mangelsdorf 1974). This infertility is common in such wide crosses because of differences in chromosome number and lack of pairing between chromosomes (Eubanks 1997b). Maize readily crosses with hexaploid wheat (Triticum aestivum) with high frequencies of fertilization and embryo formation (plant breeders use maize pollen to develop double haploids of hexaploid wheat). However, maize chromosomes are eliminated from the genome during the initial stages of meiosis and result in haploid embryos. There is little evidence to suggest fertile hybrids between maize and hexaploid wheat could be produced in nature. There have been unsubstantiated reports of hybridization between maize and sugar cane (Saccaharum sp.).

Biology References
1. CIMMYT (International Maize and Wheat Improvement Centre) (2000). CGIAR Research, Areas of Research: Maize (Zea mays L.) http://www.cgiar.org/areas/maize.htm
2. Doebley, J. F. (1990). Molecular Evidence for Gene Flow among Zea species. BioScience 40, 443- 448.
3. Eubanks, M.W. (1997a). Further evidence for two progenitors in the origin of maize. Maize Newsletter 71, 35-35.
4. FAO (2000c). Species Description. Zea mays L. http://www.fao.org/WAICENT/faoinfo/agricult/agp/agpc/doc/gbase/data/pf000342.htm
5. Galinat, W.C. (1988). The origin of corn. In: Corn and Corn Improvement. Agronomy Monographs No.18. American Society of Agronomy, G.F Sprague and J.W. Dudley, (eds.). Madison, Wisconsin, pp. 1-31.
6. Gould, F.W. (1968). Grass Systematics. McGraw Hill, N.Y., USA.
7. Hitchcock, A.S. & A. Chase. (1951). Manual of the Grasses of the United States (Volume 2). Dover Publications: N.Y. p. 790-796.
8. Hoisington, D., Listman, G.M. & Morris, M.L. (1998). Varietal development: applied biotechnology. In: Maize Seed Industries in Developing Countries. M. L. Morris (ed). Lynne Rienner Publishers, Inc. pp. 77-102.
9. Kiesselbach, T.A. (1980). The structure and reproduction of corn. Reprint of: Research Bulletin No. 161. 1949. Agricultural Experiment Station, Lincoln, Nebraska. University of Nebraska Press. p. 93.
10. Laurie, D.A. & Bennett, M.D. (1986). Wheat x maize hybridization. Can. J. Genet. Cytol. 28, 313-316.
11. Mangelsdorf, P. C. & Reeves, R.G. (1939). The origin of Indian corn and its relatives. Texas Agric. Expt. Sta. Bull. 574.
12. Mangelsdorf, P. C. (1974). Corn: its Origin, Evolution and Improvement. Harvard Univ. Press, Cambridge, Mass.
13. Mangelsdorf, P. C., Roberts, L.M. & Rogers, J.S. (1981). The probable origin of annual teosintes. Bussey Inst., Harvard Univ. Publ. 10, 1- 69.
14. México, D.F. (1994). Maize seed industries revisited: emerging roles of the public and private sectors. World Maize Facts and Trends1993/94. CIMMYT.
15. Mink, S. D. & Dorosh, P.A. (1987). An overview of corn production. In: The Corn Economy of Indonesia. Cornell University Press, London.
16. Poehlman, J.M. (1959). Breeding Field Crops. Holt, New York, USA.
17. Purseglove, J.W. (1972). Tropical Crops: Monocotyledons 1. Longman Group Limited., London.
18. Radu, A, Urechean, V., Naidin, C. & Motorga, V. (1997). The theoretical significance of a mutant in the phylogeny of the species Zea mays L. Maize Newsletter 71, 77-78.
19. Rayor, G.S., Ogden, E.C. & Hayes, J.V. (1972). Dispersion and deposition of corn pollen from experimental sources. Agronomy Journal 64, 420-427.
20. Sears, M.K., Stanley-Horn, D.E. & Matilla, H.R. (2000). Ecological impact of Bt corn pollen on Monarch butterfly in Ontario. Canadian Food Inspection Agency (http://www.cfia-acia.agr.ca/english/ plaveg/pbo/btmone.shtml)
21. Sharma, A.B. (1998). Experts for conservation of wild crop varieties. The Financial Express. Indian Express Group.
22. Stoskopf, N.C. (1985). Cereal Grain Crops. Reston, Virginia: Reston Publishing Company, Inc., Prentice-Hall Company.
23. Watson, L. & Dallwitz, M.J. (1992). Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References. Version:18th August 1999. http://biodiversity.uno.edu/delta
24. World Watch Institute (2000). Crop gene diversity declining. Trends in Plant Science 5, 7.
25. Wilkes, H.G. (1977). Hybridization of maize and teosinte, in Mexico and Guatemala and the improvement of maize. Economic Botany 31, 254-293.
LAST UPDATED: SEPTEMBER 2002

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Characteristics of Zea mays (Maize) Expand

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Modification Method Expand

Characteristics of the Modification Expand

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Summary of Regulatory Approvals

Introduction Expand

Summary of Introduced Genetic Elements Expand

Characteristics of Zea mays (Maize) Expand

Donor Organism Characteristics Expand

Modification Method Expand

Characteristics of the Modification Expand

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Biology of Maize L.

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