Bt corn

Saturnina C Halos, Ph.D.Chair, Biotechnology Advisory TeamDepartment of Agriculture

Topics:What is Bt corn?What are the basic features of Bt corn MON810?

What is Bt corn?

Bt corn is corn genetically engineered to resist corn borers by producing its own insect control protein, Cry1AbBt corn was developed by transferring the gene for Cry1Ab from Bt or Bacillus thuringiensis, a bacterium

abundant in Philippine soils

Bacillus thuringiensis Bt gene

Bt gene

AgrobacteriumParticle Acceleration

Genetically engineering Bt corn

Transferring genes by hybridization

Bt corn MON810 - genetically engineered to resist corn borers by producing its own insect control agent Bt corn MON810 - developed by inserting the cry1Ab gene from Bacillus thuringiensis (Bt), into corn cultivar Hi-II by gene gun transformation cry1Ab gene produces the insect control protein Cry1Ab Field trials of Bt corn MON810 shows: Asiatic corn borer damage effectively controlled in Bt corn MON810

The insecticidally active portion of the Cry1Ab protein produced by the Bt corn is identical to that found in nature and in commercial Bt spray formulations

Safety of Cry1Ab

Cry proteins act by selectively binding to specific sites localized on the lining of the midgut of susceptible insect species

Following binding, holes are formed that disrupt midgut ion flow causing gut paralysis and eventual death due to bacterial sepsis

Safety of Cry1Ab

Cry1Ab is insecticidal only when eaten by the larvae of lepidopteran insects (moths and butterflies), and its specificity of action is directly attributable to the presence of specific binding sites in the target insects. There are no binding sites for Cry1Abon the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to Cry1Ab

MON810 = conventional corn as shown inin more than 20 field trials in the Phil & hundreds more in other countries

MON810 grew normally and exhibited the expected morphology, reproductive and physiological characteristics of corn

MON810 had no unexpected pest or disease susceptibility compared to conventional corn

MON810 has no potential to transfer the cry1Ab gene to wild relatives

Corn has no closely related hybridizing species growing in the wild in the Philippines Its closest relative, katigbi does not naturally hybridize with corn

Reproductive characteristics such as pollen production, viability & dispersal were unchanged in MON810

The cry1Ab gene in MON810 has no potential for transfer to wild species in the Philippines

MON810 corn has no adverse effect on beneficial arthropodsMON810 hybrids were compared to their non-transformed counterpart for relative abundance of beneficial arthropods

Cry1Ab had no direct nor indirect effect on the beneficial arthropod populations

When compared with currently planted corn varieties, MON810 corn did not present an increased risk to or impact on interacting organisms, including people except specific lepidopteran insect species

The food and livestock feed safety of MON810 corn was established based on several standard criteria. The nutritional equivalence of MON810 grain & silage to conventional corn was shown by analyses of key nutrients including proximates ( e.g moisture, fat, protein, fibre, ash and carbohydrate) amino acid composition, fatty acid profiles, and minerals (calcium and phosphorus).

Bt corn Non-Bt corn Less mycotoxin

Less antifungal in feeds

More mycotoxinMore antifungal in feeds

Bt corn MON810 safer than insect damaged corn

The nutritional equivalence of Bt corn MON810 and conventional maize was confirmed in feeding trials: quail, chickens

MON810 corn has low potential for toxicity of plant-expressed Cry1Ab

protein Lack of amino acid sequence homology

with known protein toxins Lab studies show Cry1Ab protein rapidly degraded in simulated gastric

fluids Cry1Ab protein displayed no acute toxicity when administered to lab mice

Safety of Bt corn as food/feed

No adverse effect seen on mice fed with high doses of Cry1Ab protein that were 200-1000 fold greater than humans would be exposed to based on consumption of MON810 grain

The insect control protein, Cry1Ab has no potential for allergenicityThe potential allergenicity of Cry1Ab was assessed by examining: physiochemical characteristics; amino acid sequence homology to known protein allergens; and digestibility

Cry1Ab lacks amino acid sequence homology with known allergens

Cry1Ab is rapidly degraded in acidic gastric fluids

The Cry1Ab protein has about 40 years history of safe use, demonstrated by its use in microbial Bt spray formulations in agriculture and forestry with no evidence of adverse effects.

This fact, combined with the lack of amino acid sequence homology between Cry1Ab protein and known allergens, and the rapid degradation of Cry1Ab protein in acidic gastric fluids, were sufficient to provide with reasonable certainty that Cry1Ab has no allergenic potential

Global production of Bt corn In 2000 growing season ~ 6.8 million hectares, representing 15% of all transgenic crops grown that year

This area of Bt corn planted in the USA, Canada, Argentina, South Africa, Spain and FranceIn the Philippines, 2002-2003 season ~ 120 has last season ~ 12,000 has target this year > 50,000 has

Regulatory authorities in the Philippines Canada & USA requires Bt corn developers to implement specific Insect Resistant Management (IRM) Programs.

Potential exists for Bt-resistant corn borer populations to develop as areas planted with Bt corn expand. IRM programs are designed to reduce this potential and prolong the effectiveness of Bt proteins against target insects

Bt corn flowers

Thank you for your kind attention