Ottawa, Canada
October 15, 2007Source:
Canadian Food Inspection
Agency
This Decision Document has been
prepared to explain the regulatory decision reached under
Directive 94-08 (Dir94-08), entitled "Assessment Criteria
for Determining Environmental Safety of Plants with Novel
Traits", its companion biology document BIO1994-11,
"The Biology of Zea mays
L. (Corn/Maize)", and Directive 95-03
(Dir95-03), entitled "Guidelines for the Assessment of Novel
Feeds: Plant Sources".
The Canadian Food Inspection
Agency (CFIA), specifically the specifically the Plant Biosafety
Office, of the Plants Products Directorate, the Biotechnology
Environmental Release Assessment Unit of the Science Strategies
Directorate and the Feed Section of the Animal Health and
Production Division have evaluated information submitted by
Syngenta Seeds Inc. This
information is in regard to the corn rootworm (Diabrotica
spp.) resistant corn event
MIR604. The
CFIA has determined that this plant with novel traits
(PNT) does not present altered environmental risk nor, as a
novel feed, does it present livestock feed safety concerns when
compared to currently commercialized corn varieties in Canada.
Unconfined release into
the environment and use as livestock feed of corn event MIR604
is therefore authorized by Plant Biosafety Office of the Plant
Products Directorate and the Feed Section of the Animal Health
and Production Division as of July 20, 2007. The authorization
is limited to three years. Renewal of the three year
authorization is conditional upon the submission of additional
research results related to rootworm resistance management. Any
corn lines derived from event MIR604 may also be released into
the environment and used as livestock feed, provided that (i)
no inter-specific crosses are performed, (ii)
the intended uses are similar, (iii) it
is known based on characterization, that these plants do not
display any additional novel traits and are substantially
equivalent to currently grown corn varieties in Canada, in terms
of their potential environmental impact and livestock feed
safety, (iv) the novel genes are
expressed at a level similar to that of the authorized line and
(v) the insect resistance management
requirements described in the present document are applied.
Corn event MIR604 is
subject to the same phytosanitary import requirements as its
unmodified counterpart.
Please note, that the livestock
feed and environmental safety of novel feeds and
Inc. are critical steps
in the potential commercialization of these plant types. Other
requirements, such as the evaluation of food safety by Health
Canada, have been addressed separately from this review.
Table of Contents
I.
Brief Identification of the Modified Plant
II.
Background Information
III. Description of the Novel Trait
- Corn Rootworm Resistance
- Expression of
Phosphomannose Isomerase
- Development Method
- Stable Integration into
the Plant Genome
IV.
Criteria for the Environmental Assessment
- Potential of Corn event
MIR604 to Become a Weed of Agriculture or be Invasive of
Natural Habitats
- Potential for Gene Flow
from Corn event MIR604 to Wild Relatives Whose Hybrid
Offspring May Become More Weedy or More Invasive
- Altered Plant Pest
Potential of Corn event MIR604
- Potential Impact of Corn
event MIR604 on Non-Target Organisms
- Potential Impact of Corn
event MIR604 on Biodiversity
- Potential for Development
of Rootworm Resistance to corn event MIR604
V.
Criteria for the Livestock Feed Assessment
- Potential Impact of Corn
event MIR604 on Livestock Nutrition
- Potential Impact of Corn
event MIR604 on Livestock and Workers/Bystanders
VI.
New Information Requirements
VII. Regulatory Decision
| Designation
of the Modified Plant: |
Corn Event
MIR604,
OECD Unique Identifier SYN-IR604-5 |
| Applicant: |
Syngenta
Seeds Canada Inc. |
| Plant
Species: |
Maize (Zea
mays L.) |
| Novel
Traits: |
Resistance
to Western and Northern Corn Rootworms. (Diabrotica
virgifera virgifera and
Diabrotica barberi) |
| Trait
Introduction Method: |
Agrobacterium-mediated
transformation |
| Proposed
Use of the Modified Plant: |
Production
of corn for human consumption (wet mill products, dry
mill products and seed oil) and oil, meal, grain, silage
and other byproducts for livestock feed. These plants
are not intended to be grown outside the normal
production area for corn in Canada. |
Syngenta Seeds
Inc. developed, through the
use of recombinant DNA
techniques, a corn event resistant to corn rootworm (Diabrotica
spp.), a pest of corn in
Canada. The corn event, designated as MIR604, was developed to
provide a method to control yield losses from insect feeding
damage caused by rootworm larvae.
Corn event MIR604 was developed
using recombinant DNA
technology, resulting in the introduction of the modified cry3A
(mcry3A) gene and the pmi marker gene. The
mcry3A gene is derived from the cry3A gene from
Bacillus thuringiensis
subsp.
tenebrionis and encodes a modified δ-endotoxin Cry3A
protein, with enhanced activity against corn rootworms. The
pmi gene from Escherichia coli
encodes the phosphomannose isomerase (PMI) enzyme. Expression of
the PMI
enzyme allows the plant to utilize mannose as a carbon source.
This trait is of no agronomical interest but was used to select
transformed from non-transformed plants during the development
phase of corn event MIR604.
Syngenta Seeds
Inc. has provided data on the
identity of corn event MIR604, a detailed description of the
transformation method, data and information on the gene
insertion site, gene copy number and levels of gene expression
in the plant and the role of the inserted genes and regulatory
sequences. The novel proteins were identified and characterized.
Data was provided for the evaluation of the potential toxicity
of the novel proteins to livestock and non-target organisms and
potential allergenicity of the novel proteins to humans and to
livestock.
Corn event MIR604 has been
field tested in the United States and the data for trial years
2002 and 2003 were submitted.
Agronomic characteristics of
corn event MIR604 such as seedling emergence, plant height, time
to reproduction, lodging, susceptibilities to various corn pests
and pathogens, and yield parameters were compared to those of
unmodified corn counterparts.
Nutritional components of corn
event MIR604, such as proximates, amino acids and fatty acids
were compared with those of unmodified corn counterparts.
The Biotechnology Environmental
Release Assessment (BERA) Unit of the Science Strategies
Directorate,
CFIA, has reviewed the above information, in light of
the assessment criteria for determining environmental safety of
PNTs, as
described in the Directive 94-08 (Dir94-08), entitled
"Assessment Criteria for Determining Environmental Safety of
Plants With Novel Traits". The
BERA Unit has considered:
- potential of corn event
MIR604 to become a weed of agriculture or be invasive of
natural habitats;
- potential for gene flow
from corn event MIR604 to wild relatives whose hybrid
offspring may become more weedy or more invasive;
- potential for corn event
MIR604 to become a plant pest;
- potential impact of corn
event MIR604 or its gene products on non-target species,
including humans; and
- potential impact of corn
event MIR604 on biodiversity.
The Feed Section of the Animal
Health and Production Division,
CFIA,
has also reviewed the above information with respect to the
assessment criteria for determining the safety and efficacy of
livestock feed, as described in Directive 95-03 (Dir95-03),
entitled "Guidelines for the Assessment of Novel Feeds:
Plant Sources". The Feed Section has considered:
- potential impact of corn
event MIR604 on livestock nutrition; and
- potential impact of corn
event MIR604 on livestock and workers/bystanders
Syngenta Seeds
Inc. has provided the
CFIA
with a method for the detection and identification of corn
products containing the corn event MIR604.
| 1.
Resistance to Corn Rootworms (Diabrotica
spp.) |
| |
Bacillus thuringiensis
subsp.
tenebrionis is a common
gram-positive soil-borne bacterium. In the spore forming
stage, it produces several insecticidal protein
crystals, including the δ-endotoxin Cry3A protein which
is active against certain coleopteran insects, such as
the Colorado potato beetle. The protein is insecticidal
to susceptible coleopterans after cleavage by proteases
in the insect's gut, forming a protease-resistant active
fragment that is the bio-active form of the protein.
Insecticidal activity is believed to depend on the
binding of the active fragment to specific receptors
present in susceptible insects on midgut epithelial
cells, forming pores which disrupt osmotic balance and
eventually result in cell lysis and insect death.
However, the native Cry3A does not have significant
activity against corn rootworms due to its insensitivity
to corn rootworm protease. Syngenta modified the native
cry3A gene to introduce a corn rootworm protease
recognition site into the Cry3A protein. In addition,
the cry3A coding sequence was optimized to accommodate
the preferred codon usage for maize. Except for the
introduction of the protease recognition site, the amino
acid sequence of the mCry3A protein is identical to that
of the native Cry3A protein expressed in Colorado potato
beetle resistant potatoes which have been authorized by
the
CFIA for unconfined release and livestock
feed. This protein has been shown to be non-toxic to
humans, other vertebrates and invertebrates.
The mcry3A
gene is expressed in event MIR604 using a promoter which
confers preferential expression of the mCry3A protein in
the roots of corn. Tissue samples were collected at
various growth stages from two event MIR604 hybrids
grown at a representative
US field trial site. Levels of mCry3A protein
were evaluated by enzyme-linked immunosorbent assays.
Average mCry3A levels in both hybrids across all stages,
expressed in micro-grams mCry3A protein per gram dry
weight tissue (µg/g),
ranged from ca. 5-26
µg/g
in leaves, 7-25
µg/g
in roots and 7-24
µg/g
in whole plants. Average levels measured in kernels from
both hybrids at senescence were ca. 0.85
µg/g.
No mCry3A protein was detected in pollen from the MIR604
hybrids.
The mCry3A protein was
shown to degrade readily in the soil. In soil
degradation experiments, the average time to degrade 50%
of the initial soil concentration of mCry3A protein was
7.6 days.
The mCry3A protein
expressed in corn event MIR604 kernels was purified from
leaves and characterized. The identity of the purified
protein was confirmed by Western immunoblot analysis and
insecticidal activity.
The levels of mCry3A
protein in corn MIR604 tissues were too low to extract
sufficient amounts for evaluation of environmental and
feed safety. To obtain sufficient quantities of mCry3A
protein for safety studies, it was necessary to express
the mcry3A gene in an
E. coli
production system. The equivalency of the plant-produced
protein to the
E. coli-
produced protein was evaluated by comparing their
molecular weight, immunological reactivity, insecticidal
activity and glycosylation status. Based on the results,
both proteins were found to be equivalent.
The potential mammalian
toxicity and allergenicity of the mCry3A protein was
evaluated. The mCry3A protein lacks sequence similarity
to known allergens and toxins. No adverse effects were
observed when mCry3A protein was ingested by mice at a
dose of 2,377 mg/kg
body weight. In vitro digestive fate studies
have shown that the protein is rapidly degraded in
simulated gastric fluid, unlike protein allergens which
are normally resistant to digestion. The mCry3A protein
expressed in event MIR604 is not glycosylated.
Incubation for 30 minutes at 95ºC
or 65ºC resulted in
complete or partial inactivation of mCry3A protein,
respectively. |
| 2.
Expression of Phosphomannose Isomerase |
| |
The pmi gene
from Escherichia coli,
which encodes the enzyme phosphomannose isomerase (PMI)
was introduced in corn event MIR604. Expression of
PMI
was used as a selectable marker during the process of
developing corn event MIR604. Maize cells producing
PMI
can utilize mannose as a primary carbon source, whereas
cells lacking the pmi gene fail to proliferate
in a mannose-based culture medium. Expression of the
PMI
protein is of no agronomic or industrial interest and
was only used during the process of regenerating plant
material following transformation. Insert sequencing
showed that two base-pair changes occurred in the
PMI
encoding sequence, resulting in two amino-acid changes
in the protein sequence. These two amino-acid
substitutions have no apparent effect on the
functionality of the
PMI
protein. The
pmi gene expressed in corn event MIR604 is linked
to a constitutive promoter. Tissue samples were
collected at various growth stages from two MIR604
hybrids grown at a representative
US field trial
site. PMI
protein was detected at low levels in most plant tissues
analyzed. The highest levels were detected in silk
tissue at anthesis (< 0.3-6.8
µg/g)
and pollen (3.9 - 5.2
µg/g).
Due to low expression
of PMI
protein in corn event MIR604, it was not feasible to
extract sufficient amounts of
PMI
protein from plant tissues for safety studies. It was
necessary to express the pmi gene in an
E.
coli production system to obtain sufficient
quantities of
PMI protein. The
PMI
protein produced in
E. coli
contains 16 additional amino-acids at the N-terminus of
the protein (derived from the expression vector) and
differs by two amino-acids from the
PMI
protein expressed in MIR604 corn. The equivalency of the
MIR604 corn-produced
PMI
protein to the E.
coli-produced
PMI
was evaluated by comparing their immunoreactivity,
glycosylation status and enzymatic activity. Based on
the results, both proteins were found to be nearly
equivalent, with no significant differences.
The potential toxicity
and allergenicity of the
PMI
protein was evaluated. It is likely that small amounts
of PMI
proteins from various sources have always been present
in the food and feed supply due to the ubiquitous
occurrence of
PMI proteins in nature, including bacteria,
yeast, food plants and animals.
PMI
proteins are present in many mammalian tissues and in
humans. Syngenta Seeds Inc.
investigated amino acid sequence homology of
PMI
protein produced in corn event MIR604 with known protein
allergens. There is one region of sequence homology of 8
contiguous identical amino acids between the
PMI
protein and a known allergen, alpha-parvalbumin from
Rana species. Further
investigation using sensitive serum screening technology
demonstrated that this sequence identity is not
biologically relevant and has no implication for the
potential allergenicity of the
PMI
protein. The
PMI protein does not possess significant amino
acid sequence similarities to other allergens. In
vitro digestive fate studies have shown that the
PMI
protein is rapidly degraded in simulated gastric and
intestinal fluids unlike protein allergens which are
normally resistant to digestion. The
PMI
protein is inactivated following incubation at 65ºC for
30 minutes and the
PMI
protein produced in corn event MIR604 is not
glycosylated, unlike many known allergens, providing
additional evidence that
PMI
protein does not have the properties of known allergens.
Syngenta Seeds
Inc. investigated
amino acid sequence homology of
PMI
protein produced in corn event MIR604 with known protein
toxins and found that the
PMI
protein does not possess significant amino acid sequence
similarities to known toxins. Furthermore, no adverse
effects were observed when the
E. coli-produced
PMI
protein was ingested by mice at a dose of 3,080
mg/kg body
weight.
Based on the above, the
PMI
protein is unlikely to be a toxin or an allergen. |
| 3.
Development Method |
| |
The mcry3A
and pmi genes were introduced in corn event
MIR604 via Agrobacterium-mediated
transformation of immature maize embryos derived from a
proprietary maize line. Embryos producing embryogenic
callus were transferred to cell culture medium
containing mannose. Event MIR604 was identified as a
successful transformant and was chosen for further
development. |
| 4.
Stable Integration into the Plant Genome |
| |
Molecular
characterization by Southern blot analysis demonstrated
that corn event MIR604 contains one intact copy of the
mcry3A and pmi gene cassettes inserted
at a single site in the corn genome. No additional
elements, including intact or partial
DNA
fragments of the mcry3A or pmi
cassette or backbone sequences from the plasmid vector,
linked or unlinked to the intact insert, were detected
in corn event MIR604. Sequencing of the introduced
DNA
confirmed the organization of the genetic elements and
revealed that some truncation occurred at the right
border and left border of the insert. These deletions
have no effect on the functionality of the
DNA
insert and this phenomenon has been previously observed
with Agrobacterium
transformation. In addition, three single nucleotide
changes were also identified in the insert. One of the
changes occurred within the promoter driving the
expression of the mcry3A gene. The remaining
two changes occurred with the
PMI
coding sequence, resulting in two amino acid
substitutions. However, these nucleotide changes had no
effect on the functionality of the insert.
The inheritance pattern
of the mcry3A and pmi genes within a
segregating generation of event MIR604 showed that both
genes segregate according to Mendelian rules of
inheritance for a single genetic locus. Concentrations
of mCry3A and
PMI proteins in event MIR604 tissues were
measured across four generations and the results
indicate stability of mCry3A and
PMI
protein expression across generations. |
| 1.
Potential of Corn event MIR604 to Become a Weed of
Agriculture or be Invasive of Natural Habitats
|
| |
The biology of corn,
described in the
CFIA
Biology Document BIO1994-11, shows that unmodified
plants of this species are not invasive of unmanaged
habitats in Canada. Corn does not possess the potential
to become weedy due to the lack of seed dormancy, the
non-shattering nature of corn cobs and the poor
competitive ability of seedlings. According to the
information provided by Syngenta Seeds
Inc., corn event
MIR604 was determined to be similar to unmodified corn
in this respect.
MIR604 corn hybrids were tested at 13 locations in 2002
and 15 locations in 2003 in the United States corn belt.
A total of 16 agronomic traits were evaluated. These
agronomic traits covered a broad range of
characteristics that encompass the entire life cycle of
the maize plant and included data assessing seedling
emergence, plant height, time to reproduction, lodging,
susceptibility to various corn pests and pathogens, and
yield characteristics. For the majority of agronomic
traits, no statistically significant differences between
MIR604 hybrids and their non-transformed isogenic
counterparts were observed. Although instances of
statistically significant differences between MIR604 and
control hybrids were observed for some traits, there
were no consistent trends in the data across locations,
MIR604 hybrids or years that would indicate that any of
these differences were due to the genetic modification.
As MIR604 hybrids experience less root feeding damage
than controls, some significant agronomic and
morphological differences were to be expected depending
upon the trait being assessed and combination of pest
pressure and environmental conditions experienced at
each trial location.
Additionally, specific
disease trials conducted in 2002 and 2003 indicated that
MIR604 hybrids had no altered susceptibility to corn
pathogens compared to control hybrids. No altered
susceptibility to non-rootworm insect pests was recorded
over the course of the agronomic trials.
The results showed no
biologically meaningful differences between corn MIR604
hybrids and their isogenic non-transgenic counterparts,
other than resistance to corn rootworm feeding damage.
No competitive advantage was conferred to corn event
MIR604 by the expression of the mCry3A and
PMI
proteins, other than that conferred by resistance to
rootworms. The introduction of these novel traits did
not make corn MIR604 weedy or invasive of natural
habitats since none of the corn reproductive or growth
characteristics were modified, and MIR604's tolerance to
abiotic and biotic stresses was unchanged except for the
introduced trait.
The above
considerations led the
CFIA
to conclude that corn event MIR604 has no increased
weediness or invasiveness potential compared to
currently commercialized corn varieties. |
| 2.
Potential for Gene Flow from Corn event MIR604 to Wild
Relatives Whose Hybrid Offspring May Become More Weedy
or More Invasive |
| |
The biology of corn,
as described in
CFIA
Biology Document BIO1994-11, indicates that there are no
wild relatives in Canada that can hybridize with corn.
None of the data submitted by Syngenta Seeds
Inc. on corn MIR604
indicated any change in sexual compatibility as a result
of the genetic modification.
The
CFIA
has therefore concluded that gene flow from corn event
MIR604 to wild relatives is not possible in Canada. |
| 3.
Altered Plant Pest Potential of Corn event MIR604
|
| |
The expression of the
mCry3A δ-endotoxin and
PMI
phosphomannose isomerase is unrelated to plant pest
potential, and corn is not considered a plant pest in
Canada. Field evaluation of MIR604 corn hybrids did not
show any increase or decrease in susceptibility to
disease or insect stressors, other than to rootworms,
compared to unmodified corn counterparts. Rootworm
damage is not known to be a principal factor restricting
the establishment or distribution of corn in Canada.
The
CFIA
has, therefore, determined that the corn event MIR604
does not display any altered pest potential compared to
currently commercialized corn varieties. |
| 4.
Potential Impact of Corn event MIR604 on Non-Target
Organisms |
| |
Literature reports and
studies to support the safety of potatoes expressing
Cry3A proteins indicate that Cry3A
Bacillus thuringiensis δ-endotoxins are
active only against specific coleopteran insects, and
are not toxic to humans, other vertebrates, and
non-coleopteran invertebrates. The mCry3A protein has a
similar spectrum of activity to the native Cry3A, but
with enhanced toxicity to Northern and Western corn
rootworms, both major coleopteran pests of corn. There
are no coleopteran species currently listed by the
Committee on the Status of Endangered Wildlife in Canada
as being a threatened or endangered species. (Please
refer to http://www.cosewic.gc.ca/index.htm for more
information). As mCry3A is not detectable in pollen of
MIR604 corn, MIR604 corn poses minimal risk to
pollinators and non-target pollen consumers.
Syngenta Seeds
Inc. has submitted
data from dietary toxicity studies on the effect of the
bacterial mCry3A protein on non-target invertebrates,
including the honeybee (Apis
mellifera), insidious flower bug (Orius
insidiosus), seven spot ladybird (Coccinella
septempunctata), ground beetle (Poecilus
cupreus), rove beetle (Aleochara
bilineata) and earthworm (Eisenia
foetida). In all cases, the mCry3A protein
was demonstrated to be safe to these indicator species
at doses exceeding 5 times the estimated environmental
concentration of mCry3A in the diet of non-target
invertebrates feeding on MIR604 tissues or exposed to
MIR604 corn via their preys.
Monarch butterfly (Danaus
plexippus) larvae feeding on milkweed plants
may be exposed to corn pollen drifting from adjacent
corn plants. As the activity of mCry3A protein is
restricted to some Coleopteran species (D.
plexippus is a Lepidopteran) and mCry3A is
not detectable in pollen of MIR604 corn, MIR604 corn
poses no risk to the monarch butterfly.
Data was also submitted
on non-target vertebrates including the mouse, the
bobwhite quail and the rainbow trout. No harmful effects
were detected when mice and quails were exposed to a
single oral dose of 2,377 mg
mCry3A/kg body weight and
652 mg mCry3A/kg
body weight, respectively. These doses represent 2,600
times and 1,400 times the worst-case daily dose of
mCry3A to mammals and birds feeding on MIR604 grain,
respectively. No harmful effects were detected when
juvenile rainbow trout were fed a fish diet containing
50% MIR604 corn grain for 28 days.
Phosphomannose
isomerase is a ubiquitous enzyme involved in
carbohydrate metabolism. Phosphomannose isomerases of
varying degrees of amino acid homology to
PMI
expressed in corn event MIR604 occur widely in nature.
Phosphomannose isomerases have been detected in some
crop species, mammals, humans, yeast, fungi and
bacteria. Species that will be exposed to
PMI
from MIR604 corn tissues are highly likely to have prior
exposure to similar
PMI
proteins. No harmful effects of such exposure are known
or expected. The
PMI
protein expressed in corn event MIR604 is not homologous
to any known toxins. Additionally, the
bacterially-expressed
PMI
protein showed lack of acute toxicity to the mouse at a
single oral dose of 3,080 mg
PMI
kg body weight.
Field evaluations
showed that MIR604 corn is more resistant to corn
rootworm than unmodified corn, but not more resistant to
other pest insects or pathogens.
Composition analyses
showed that the levels of key nutrients and
anti-nutrients in corn MIR604 grain and forage are
comparable to those in commercial corn varieties.
Based on the above, the
CFIA
has determined that, compared to current commercial corn
varieties, the unconfined release of corn event MIR604
will not result in altered impacts on non-target
organisms, including humans. |
| 5.
Potential Impact of Corn event MIR604 on Biodiversity |
| |
Corn event MIR604 has
no novel phenotypic characteristics that would extend
its range beyond the current geographic range of corn
production in Canada. Since corn has no wild relatives
with which it can outcross in Canada, there will be no
transfer of the novel traits to other species in
unmanaged environments. In addition the novel traits
were determined to pose minimal risks to non-target
organisms.
At present, the use of
chemical insecticides to control rootworm is permitted
in Canada. Currently, crop rotation represents the
principal method of rootworm control in Canada. MIR604
corn provides an alternative method to existing methods
of control of corn rootworm. Therefore, the reduction in
local pest species as a result of the release of MIR604
corn does not present a significant change from existing
agricultural practices.
The
CFIA
has therefore concluded that the potential impact on
biodiversity of corn event MIR604 is equivalent to that
of currently commercialized corn varieties. |
| 6.
Potential for Development of Rootworm Resistance to Corn
event MIR604 |
| |
In order to
significantly minimize the likelihood of the development
of insect pest resistance to
PNTs
expressing novel insect resistance, the
CFIA
requires that an insect resistance management (IRM) plan
be implemented for these products. Coleopteran insects
have a significant ability to develop resistance to
conventional chemical insecticides. Therefore it is
reasonable to expect that resistance to the insecticidal
properties of corn event MIR604 may develop. The
following
IRM design is intended to reduce or delay corn
root worm (CRW) resistance to the mCry3A protein. A
component of the
IRM
strategy that will be used with MIR604 corn is the
establishment of a refuge of
CRW-susceptible
corn within or adjacent to the MIR604 corn field. Should
resistant insects occur, they would then be able to mate
with susceptible insects to keep the frequency of
resistance genes diluted in the insect population.
CFIA
believes that sound management practices and
IRM
strategies can significantly reduce and delay the
development of mCry3A protein resistant
CRW
populations. However the
CRW populations must be monitored for the
development of resistance in a regular and consistent
manner.
CFIA
understands that Syngenta Seeds Canada
Inc. has developed,
and will implement, an
IRM
plan that includes the following key components:
- The use of
structured refugia to provide a population of corn
rootworms that have not been exposed to the mCry3A
protein and are available to reproduce with
potentially resistant rootworms which may emerge
from the MIR604 crop.
- The early
detection of rootworm populations resistant to the
corn-expressed insecticidal protein is extremely
important. Close monitoring for the presence of such
populations, in rootworm-resistant corn fields and
surrounding areas, is therefore warranted.
Monitoring includes the development of appropriate
detection tools such as visual field observations
and laboratory bioassays, education of growers,
reporting schedules, and mitigation procedures in
case of resistance development.
- Education tools
will be developed and provided to all growers,
district managers and field managers. These will
include information on product performance,
resistance management, monitoring procedures and
timetables, detection protocols for resistant
rootworm individuals, instructions to contact
Syngenta Seeds Inc.
and strategies to be followed if unexpected levels
of rootworm damage occur.
- Syngenta Seeds
Canada Inc. will
have documented procedures in place for responding
to these reported instances of unexpected rootworm
damage. These procedures will include, where
warranted, the collection of plant tissue and
rootworms and use of appropriate bioassays to
evaluate suspected mCry3A resistant individuals, and
a protocol for immediate action to control resistant
individuals.
- Detection of
confirmed resistant rootworm populations and
mitigation measures will be immediately reported to
CFIA.
- Integrated Pest
Management practices will be promoted, such as
prediction of infestation problems from field
histories.
Research
related to the proposed
IRM
plan is ongoing, and as research progresses, the new
information will be used to determine if the present
IRM
plan should be maintained in its present form, or if it
will be modified. Therefore, the renewal of the present
three year authorization will be contingent upon
Syngenta Seeds Canada Inc.
demonstrating significant progress in research related
to rootworm resistance management.
Note: The Plant
Biosafety Office periodically audits compliance with the
IRM
requirements. |
| 1.
Potential Impact of Corn event MIR604 on Livestock
Nutrition |
| |
Nutritional
Composition and Anti-Nutritional Factors
Nutritional
Composition:
Nutritional data was obtained from four corn hybrid
pairs containing event MIR604 hybrids (D, F, E3 and E4)
and their respective parental controls (C, E, E1, and
E2). Forage and grain samples were collected from
replicated plots at 12 locations over the 2002 and 2003
growing seasons (two hybrid pairs each). Samples in each
year were analyzed for proximate, amino acids, fatty
acids, minerals, vitamins, phytosterols and secondary
metabolites (ferulic acid, p-coumaric acid and
furfural). No statistically significant differences were
observed between MIR604 forage and its controls for
proximate, Acid Detergent Fibre (ADF), Neutral Detergent
Fibre (NDF), Ca and
P, except for ash in
2002 (one hybrid pair) and protein in 2003 (one hybrid
pair). All means were within ranges of literature
values. No statistically significant differences were
observed between MIR604 grain and its controls for
proximate and fibre in 2002. Fat (one hybrid pair),
protein, moisture, and
ADF (one
hybrid pair), were statistically significantly higher in
MIR604 grain than controls in 2003, but these analytes
were within literature ranges. Statistically significant
differences were observed in MIR604 hybrids and controls
for oleic (one hybrid pair) and stearic (both hybrid
pairs) in 2002. In 2003, statistically significant
differences were observed between MIR604 grain and
controls for stearic, oleic, linoleic and linolenic (one
hybrid pair), however fatty acids were within ranges of
literature values. No statistically significant
differences were observed for amino acids analyzed in
2002, except for tyrosine which was lower in MIR604 (F)
than control (E), and methionine which was higher in
MIR604(D) than control (C ). Statistically significant
differences were observed between MIR604 grain and their
controls for aspartic acid, threonine, serine, glutamic
acid, alanine, tyrosine (one hybrid pair), valine,
isoleucine, leucine, cystine (one hybrid pair) and
phenylalanine in 2003, however all means were within
literature values. Statistically significant differences
were observed between MIR604 and controls for
Zn (both hybrid pairs) in 2002
and for Cu,
Fe, Mg,
Mn,
P (one hybrid pair)
Ca, (both hybrids pairs) in
2003. Statistically significant differences were
observed for Vitamins B1, B2, E, niacin (one hybrid
pair), pyridoxine, β-carotene, cryptoxanthin and
γ-tocopherol between MIR604 grain and controls. All
minerals and vitamins analyzed were within literature
ranges. Campesterol and stigmasterol were significantly
higher in MIR604 hybrids than controls, while there were
no statistically significant differences in β-sitosterol
between MIR604 and controls for β-sitosterol. Ferulic
acid and p-coumaric acid were statistically
significantly lower in MIR604 compared to their
controls, however the ranges were within literature
values.
Anti-nutritional factors:
Phytic acid, raffinose and trypsin inhibitor were
analyzed in MIR604 corn (four hybrids) and compared to
parental controls. The trypsin inhibitor was not
significantly different between MIR604 and their
controls. Phytic acid and raffinose had some values
below the limits of quantification for the assay and
therefore were not subjected to statistical analyses.
Nutrient
Bioavailability:
Syngenta conducted a 49-day broiler chicken study to
evaluate whether transgenic MIR604(+ve)
corn grain had any adverse dietary effects on broiler
chickens when compared with those fed non-transgenic
corn (MIR604(-ve)). 900
birds were distributed into 36 pens (25 birds/pen),
assigned in a randomized complete block design. No
statistically significant differences were observed in %
survival of birds on MIR604(+ve
and MIR604(-ve) diets.
Body weights and feed conversion efficiencies of birds
were similar between test and control diets. Carcass
analyses showed no statistically significant differences
between test and control except for thigh meat weight
among female birds. In conclusion, the trial supports
the lack of deleterious effects on animal performance
and health associated with the diets from MIR604 grain
when compared to the non-transgenic corn.
The evidence provided
by Syngenta supports the conclusion that the nutritional
composition of MIR604 corn is substantially equivalent
to conventional corn varieties. |
| 2.
Potential Impact of Corn event MIR604 on Livestock and
Workers/Bystanders |
| |
Corn is not known for
the production of endogenous allergens and the
transformation event which produced Event MIR604 would
not be expected to induce their synthesis.
The mode of action and its
structural similarity to Bacillus
thuringiensis proteins, including Cry3A, for
which human and animal safety have been previously
established support the prediction that no adverse
health effects will result from exposure to the modified
Cry3A (mCry3A) protein encoded by the mcry3A
synthetic gene derived from Bacillus
thuringiensis
subsp. tenebrionis.
Acute oral toxicity studies demonstrated
non-observed-effect-level (NOEL) values of 2377
mg/kg-bw/day for mCry3A and 3080
mg/kg-bw/day for the bacterial
PMI
protein which are much higher values than the predicted
worst case exposure of 1.76
mg/kg-bw/day for mCry3A and 0.086
mg/kg-bw/day for
PMI
in starter weaner pigs. The proteins mCry3A and
PMI
have been demonstrated to be heat labile and rapidly
digested under conditions present in the
gastrointestinal tract. Toxicity findings indicate that
MIR604 which produces mCry3A and
PMI
proteins is not expected to result in adverse
toxicological effects in livestock fed MIR604 corn.
These proteins have shown no sequence similarities with
known allergens or toxins which would indicate potential
allergenicity or toxicity issues.
The history of use and
literature suggest that the bacterial
Bacillus thuringiensis Cry
proteins are not toxic to humans and other vertebrates.
The low mammalian toxicity of
Bacillus thuringiensis microbial insecticide
mixtures containing Cry proteins has been demonstrated
over the last 40 years.
Based on the predicted
exposure levels and the results of the above tests, no
significant risk to livestock and workers/bystanders is
expected from exposure to the modified Cry3A (mCry3A)
protein. |
If at any time, Syngenta Seeds
Canada Inc. becomes aware of
any information regarding risk to the environment, including
risk to human or animal health, which could result from release
of corn event MIR604 materials in Canada or elsewhere, Syngenta
Seeds Canada Inc. will
immediately provide such information to the
CFIA.
On the basis of such new information, the
CFIA
will re-evaluate the potential impact of event MIR604 on the
environment, livestock and human health, and may re-evaluate its
decision with respect to the livestock feed use and
environmental release authorizations of corn event MIR604.
Based on the review of the data
and information submitted by Syngenta Seeds,
Inc., and through comparisons
of corn event MIR604 with unmodified corn counterparts, the
Biotechnology Environmental Release Assessment Unit,
CFIA,
has concluded that the novel genes and their corresponding
traits do not confer to corn event MIR604 any characteristic
that would result in unintended environmental effects following
unconfined release.
Based on the review of
submitted data and information by Syngenta Seeds
Inc., including comparisons of
corn event MIR604 with it's unmodified corn counterparts, the
Feed Section of the Animal Health and Production Division has
concluded that the introduced genes and their corresponding
traits will not confer to corn event MIR604 any characteristic
that would raise any concerns regarding the safety or
nutritional composition of corn event MIR604. Grain corn, its
byproducts and corn oil are currently listed in Schedule
IV of the Feeds Regulations and
are, therefore, approved for use in livestock feeds in Canada.
Corn event MIR604 has been assessed and found to be as safe as
and as nutritious as traditional corn varieties. Corn event
MIR604 and its products are considered to meet present
ingredient definitions and are approved for use as livestock
feed ingredients in Canada.
Unconfined release into
the environment and use as livestock feed of corn event MIR604
is therefore authorized by Plant Biosafety Office of the Plant
Products Directorate and the Feed Section of the Animal Health
and Production Division as of July 20, 2007. The authorization
is limited to three years. Renewal of the three year
authorization is conditional upon the submission of additional
research results related to rootworm resistance management. Any
corn lines derived from event MIR604 may also be released into
the environment and used as livestock feed, provided no
inter-specific crosses are performed, provided the intended uses
are similar, provided it is known based on characterization that
these plants do not display any additional novel traits and are
substantially equivalent to currently grown corn varieties in
Canada in terms of their potential environmental impact and
livestock feed safety, provided the novel genes are expressed at
a level similar to that of the authorized line and provided the
insect resistance management requirements described in the
present document are applied.
Corn event MIR604 is subject to
the same phytosanitary import requirements as its unmodified
counterpart.
Please refer to Health Canada's
Decisions on Novel Foods for a description of the food safety
assessment of corn event MIR604. The food safety decisions are
available at the following
Health Canada web site:
http://www.hc-sc.gc.ca/fn-an/gmf-agm/appro/index_e.html
This bulletin is published by
the Canadian Food Inspection Agency. For further information,
please contact the Plant Biosafety Office or the Feed Section
at:
Plant
Biosafety Office
Plant Products Directorate
59 Camelot Drive
Ottawa, Ontario K1A 0Y9
Telephone: 613-225-2342 |
Feed
Section
Animal Health and Production Division
Animal Products Directorate
59 Camelot Drive
Ottawa, Ontario K1A 0Y9
Telephone: 613-225-2342 |
|
|
