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Decision Document DD2002-40
Determination of the Safety of BASF's
Imazethapyr Tolerant (CLEARFIELDTM) Rice
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| This Decision Document has been prepared to explain the regulatory decision
reached under the guidelines Dir95-03 Guidelines for the
Assessment of Livestock Feed from Plants with Novel Traits and Dir94-08 Assessment Criteria
for Determining Environmental Safety of Plants with Novel Traits.
The Canadian Food Inspection Agency (CFIA), specifically the Feed Section of
the CFIA, with advice from the Plant Biosafety Office of the CFIA has evaluated
information submitted by BASF regarding the Imazethapyr tolerant
CLEARFIELDTM rice lines CL121, CL141 and CFX51. CFIA has determined
that feed derived from these plant with novel traits does not present a concern
to environmental or livestock feed safety, when compared to currently
commercialized rice varieties in Canada.
Livestock feed use of the CLEARFIELDTM rice lines CL121, CL141
and CFX51 is therefore authorized as of February 5, 2002. Lines CL121, CL141
and CFX51 and any rice lines derived from them may be imported and/or released,
provided no inter-specific crosses are performed, provided the intended use is
similar and provided it is known following thorough characterization that these
plants do not display any additional novel traits and are substantially
equivalent to currently commercialized rice, in terms of their potential
environmental impact and livestock feed safety.
The CLEARFIELDTM rice lines are subject to the same
phytosanitary import requirements as their unmodified counterparts.
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Table of Contents
- Brief Identification of Plant with Novel Traits
(PNT)
- Background Information
- Description and Assessment of the Novel Trait
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- Imazethapyr Tolerance
- Development Method
- Stable Expression
- Criteria for Safety Assessment
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- Potential of lines CL121, CL141 and CFX51 to Become Weeds of
Agriculture
or Invasive of Natural Habitats
- Potential for Gene Flow to from lines CL121, CL141 and CFX51
to Wild Relatives
Whose Offspring May Become More Weedy or More Invasive
- Altered Plant Pest Potential of lines CL212, CL141 and
CFX51
- Potential Impact on Non-Target Organisms of lines CL121,
CL141 and CFX51
- Potential Impact on Biodiversity of lines CL121, CL141 and
CFX51
- Nutritional Criteria Assessment as Livestock Feed
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- Anti-Nutritional Factors
- Nutritional Composition
- New Information Requirements
- Regulatory Decision
Designation of the PNTs:
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CLEARFIELDTM rice lines CL121, CL141 and CFX51
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Applicant:
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BASF
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Species:
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Rice (Oryza sativa)
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Novel Traits:
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Tolerance to imazethapyr, an imidazolinone herbicide
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Trait introduction method: |
Chemically induced seed mutagenesis
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Intended use of the PNT:
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Production of rice for livestock feed, human food and industrial uses. These
materials will be grown outside of Canada, in the usual production areas for
rice. |
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BASF has developed three rice lines tolerant to imazethapyr, an
imidazolinone herbicides. These rice lines, referred to as
CLEARFIELDTM rice (lines CL121, CL141 and CFX51 all of which were
derived from crosses with the 93AS3510 mutant), were developed to provide an
alternative strategy for weed control.
The development of the CLEARFIELDTM rice was accomplished using
chemically induced seed mutagenesis. The herbicide tolerance results from a
single point mutation modification of the acetohydroxyacid synthase (AHAS) gene
such that this enzyme, the target of imidazolinone herbicides, is no longer
affected by imazethapyr.
93AS3510 was field tested in the United States in 2000.
BASF has provided data on the identity of CLEARFIELDTM rice
lines, a detailed description of the modification method and breeding history,
information on the modified gene, the resulting protein and its mode of action
and the stability of trait expression. Relevant scientific publications were
also supplied.
Agronomic characteristics of rice lines CL121, CL141 and CFX51 derived from
93AS3510 such as grain yield, days to 50% head, plant height and milling were
compared to those of unmodified rice counterparts.
Nutritional components of rice lines CL121, CL141 and CFX51 derived from
93AS3510 such as proximates, amino acids and fatty acids were compared with
unmodified rice counterparts. Anti-nutritional factors were also
determined.
The Feed Section of the Animal Health and Production Division, CFIA, with
input from the Plant Biosafety Office of the Plant and Health Production
Division, CFIA, has reviewed the above information. The following assessment
criteria as described in regulatory directives Dir95-03 and Dir94-08 were used
to determine the suitability as livestock feed and the environmental safety of
feed from these plant with novel traits:
- potential impact of CLEARFIELDTM rice on the safety of
livestock;
- potential impact of CLEARFIELDTM rice on livestock
nutrition;
- potential of CLEARFIELDTM rice to become weeds of agriculture or
be invasive of natural habitats;
- potential for gene flow from CLEARFIELDTM rice to wild relatives
whose hybrid offspring may
become more weedy or more invasive;
- potential of CLEARFIELDTM rice to become a plant pest;
- potential impact of CLEARFIELDTM rice or their gene products on
non-target species, including humans, and
- potential impact of CLEARFIELDTM rice on biodiversity.
- Imazethapyr Tolerance
- Imidazolinone herbicides are active against the enzyme acetohydroxyacid
synthase (AHAS), also known as acetolactate synthase (ALS).
- AHAS is an enzyme found in bacteria, certain other micro-organisms and
plants. This enzyme catalyses the first step in the biosynthesis of the
essential branched chain amino acids isoleucine and valine. Herbicide induced
AHAS inhibition results in a lethal decrease in protein synthesis. Unmodified
rice is not tolerant to imidazolinone herbicides.
- A single amino acid substitution in the AHAS gene, sufficient to alter the
binding site for imidazolinones such that the herbicide imazetapyr no longer
inhibits the AHAS enzyme, resulted in a herbicide tolerant phenotype.
- The novel imazethapyr tolerance is under the control of the native AHAS
promoter and is believed to be constitutively expressed. Sequence information
from the modified AHAS gene was submitted for 93AS3510.
- The tolerance to imidazolinone herbicides was demonstrated by comparison of
the activity of the AHAS enzyme extracted from 93AS3510 rice plants to that of
wild type rice plants.
- The levels of valine, leucine and isoleucine produced in rice are regulated
by feedback inhibition. BASF provided data to support the claim that modified
AHAS does not affect feedback inhibition and hence, the regulation and levels
of these amino acids.
- Unlike known food allergens, AHAS is a minor protein in plant tissue
(~0.001% of total protein in rice seed), it is heat sensitive and protease
susceptible. The AHAS protein from 93AS3510 was shown to be heat sensitive,
with no detectable activity of AHAS after 1 min of heating at 100
oC. AHAS was completely degraded within 5 minutes of trypsin
treatment. The unmodified form of the AHAS protein shows no amino acid
similarity to known allergens. The amino acid sequence of mutated AHAS differs
by one amino acid from that of unmodified rice.
- The major endogenous allergens of rice are the 14-16kDa group of proteins
that show homology to the alpha-amylase/trypsin inhibitor family from wheat and
barley. It was demonstrated that 93AS3510 had comparable levels of trypsin
inhibitor activity to that of unmodified comparators. Rice also contains
endogenous allergens reported as 33 kDa and 56-60 kDa proteins and a
lipid-transfer protein. BASF provided evidence to show that the protein
components of 93AS3510 are not altered in comparison with an unmodified
comparator. SDS-PAGE electrophoresis and HPLC were run on protein extracts from
unmodified and modified rice to indicate that no new major proteins or
increased protein expression occurred as a result of the mutagenic event.
- The original mutant line was isolated from a population derived by
chemical-induced mutagenesis of seed of rice line AS3510 with ethyl
methanesulfonate (EMS). Whole plant selection procedures for herbicide
tolerance were used. One herbicide tolerant mutant was selected and was
designated 93AS3510. 93AS3510 was crossed with commercial varieties using
conventional plant breeding techniques to create the imazethapyr tolerant
CLEARFIELDTM rice lines CL121, CL141 and CFX51.
- CL121 was derived from an initial cross of 93AS3510 to the rice variety
Cocodrie. Selections in the F3, F4, F5 and F6 progeny rows were made to isolate
CL121.
- CL141 was derived from an initial cross of 93AS3510 to the rice variety
Maybelle. Two additional backcrosses were made to Maybelle. Selections in the
F4, F5 and F6 progeny rows were made to isolate CL141.
- CFX51 was derived from an initial cross of 93AS3510 to the rice variety
Cypress. Selections in the F3, F4, F5 and F6 progeny rows were made to isolate
CFX51.
- The four lines (93AS3510, CL121, CL141 and CFX51) are diploids belonging to
genus and species Oryza sativa.
- The segregation of herbicide tolerance in crosses with 93AS3510 is
consistent with the inheritance of a single semi- or co-dominant allele.
Backcrossed F2 progeny of 93AS3510 consistently showed imazethapyr
tolerance.
Note: Rice lines CL121, CL141 and CFX51 will not be grown in
Canada and will only be imported as human food or livestock feed. The majority
of rice imported to Canada does not have an intact hull, which results in the
seed being incapable of germination and growth. Due to the unfavorable climatic
conditions for rice in Canada, it is unlikely that grain from rice lines CL121,
CL141 and CFX51 would be capable of persisting in the Canadian environment.
- The centre of origin of rice is considered to be in the subtropics of
Southeast Asia. Rice is not grown in Canada and is not adapted to the
environmental conditions encountered in Canadian agricultural environments.
- The CFIA evaluated data submitted by BASF on the biology of rice lines
CL121, CL141 and CFX51, and determined that vegetative vigour, time to maturity
and seed production were within the normal range of expression of these traits
currently displayed by commercial rice varieties.
- No competitive advantage was conferred to these plants, other than that
conferred by tolerance to an imidazolinone herbicide. Tolerance to an
imidazolinone herbicide will not, in itself, render rice weedy or invasive of
natural habitats since none of the reproductive or growth characteristics were
modified.
Rice lines CL121, CL141 and CFX51 are not intended for cultivation in Canada
and the novel traits have no intended effects on weediness or invasiveness. The
CFIA has therefore concluded that these rice lines have no altered weed or
invasiveness potential in Canada when compared to conventional rice
varieties.
- Species sexually compatible with rice do not occur in Canada. The wild
'rice' which occurs in Canada (Zizania aquatica) belongs to a
species that is not sexually compatible with domesticated rice (Oryza
sativa). Rice lines CL121, CL141 and CFX51 will not be cultivated in the
Canada and if released, would not persist.
The CFIA has therefore determined that gene flow to sexually compatible
species in Canada is not possible.
- Oryza sativa is not a plant pest in Canada, additionally the
agronomic characteristics of rice lines CL121, CL141 and CFX51 were shown to be
within the normal range of conventional rice varieties.
The CFIA has therefore determined that rice lines CL121, CL141 and CFX51 do
not present a plant pest concern.
- The detailed characterization of the modified gene containing a single base
pair change and the resulting enzyme, has led to the conclusion that the
expression of the novel protein does not result in altered toxic or allergenic
properties. The AHAS enzyme is not a known toxin, does not confer resistance to
agricultural pests and is commonly found in a wide variety of plants and
micro-organisms with a history of safe use.
Based on the above, the CFIA has determined that rice lines CL121, CL141 and
CFX51 will not result in altered impacts on non-target organisms, including
humans, compared to current rice varieties.
- Rice lines CL121, CL141 and CFX51, are safe to non-target organisms, do not
present altered weediness or plant pest potential and will not be grown in
Canada. In addition the novel trait has not altered the ability of these lines
to persist in the Canadian environment.
The CFIA has therefore concluded that the potential impact on biodiversity
of rice lines CL121, CL141 and CFX51 does not present any adverse impacts on
biodiversity in Canada.
The nutritional assessment was based on nutrient and anti-nutrient
composition of rice grain from the three lines derived from 93AS3510, compared
with five representative commercial lines (Cocodrie, Cypress, Drew, Wells,
Bengal) grown in three locations in the rice growing area of the United
States.
- Phytic acid, trypsin inhibitor and lectin concentrations were determined in
rice grain samples from each of CL121, CL141 and CFX51 and five commercial rice
varieties. Trypsin inhibitor and lectin concentrations were both below the
limit of detection in all of the varieties. Phytic acid levels in CL121, CL141
and CFX51 were equivalent to the levels observed in the five commercial
varieties.
- Nutritional components were measured in grain from rice lines CL121, CL141
and CFX51, and from five commercial control varieties grown in three US
locations. Components included crude fat, crude protein, crude fibre, amino
acid content and fatty acid content. The concentration of these components in
the three lines was within the range observed in the five control unmodified
lines.
If at any time, BASF becomes aware of any information regarding risk to the
environment, including risk to human or animal health that could result from
release of these materials in Canada, or elsewhere BASF will immediately
provide such information to CFIA. On the basis of such new information, CFIA
will re-evaluate the potential impact of the proposed use, and will re-evaluate
its decision with respect to the livestock feed use authorization of these rice
lines.
Based on the review of data and information submitted by BASF, including
comparisons of rice hybrids derived from 93AS3510 with unmodified rice
counterparts, the Feed Section of the Animal Health and Production Division,
CFIA, has concluded that the modified gene and its corresponding novel trait
will not confer to these plants any characteristic that would raise any
concerns regarding the safety or nutritional composition of
CLEARFIELDTM rice lines CL121, CL141 and CFX51. Rice grain, groats,
hulls, bran and rice bran oil are currently listed in Schedule IV of the
Feeds Regulations and are, therefore approved for use in livestock feeds
in Canada. Rice lines CL121, CL141 and CFX51 derived from 93AS3510 have been
assessed and found to be substantially equivalent to traditional rice
varieties, with respect to safety and nutritional quality. CL121, CL141 and
CFX51 and their products are considered to meet the present ingredient
definitions and are approved for use as livestock feed ingredients in Canada.
None of the rice lines will be grown in Canada nor can the seed overwinter,
therefore the release of the feed into the environment would result in no
intended or unintended environmental effects.
Livestock feed use of the CLEARFIELDTM rice lines CL121, CL141
and CFX51 derived from 93AS3510 is therefore authorized as of February 5, 2002.
CL121, CL141 and CFX51 and any other rice lines derived from them may be
imported and/or released, provided no inter-specific crosses are performed,
provided the intended use is similar, and provided it is known, following
thorough characterization that these plants do not display any additional novel
traits and are substantially equivalent to currently grown rice, in terms of
their livestock feed safety and environmental impact.
The CLEARFIELDTM rice lines are subject to the same
phytosanitary import requirements as their unmodified counterparts.
Please refer to Health Canada’s Decisions on Novel Foods for a
description of the food safety assessment of CLEARFIELDTM rice
lines. The food safety decisions are available at the following Health Canada
web site:
http://www.hc-sc.gc.ca/food-aliment/mh-dm/ofb-bba/nfi-ani/e_novel_foods_and_ingredient.html
This bulletin is published by the Animal Health and Production Division. For
further information, please contact the Feed Section at:
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Feed Section
Animal Health and Production Division
Animal Products Directorate
59 Camelot Drive, Nepean
Ontario, K1A 0Y9
Tel: (613) 225-2342
Fax: (613) 228-6614
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