What would not be regulated by the U.S. Environmental Protection Agency as a biopesticide?

A. A bacterial mutant strain that protects crops from frost damage by a pathogenic bacterial strain
B. The cry toxin genes that are engineered in agronomically important crops
C. The pesticide, Rotenone, which is extracted from the seeds of some legumes
D. The synthetic agricultural insecticide, DDT
E. The papaya ringspot virus gene engineered in papaya to make it resistant to the virus

DDT is the substance not regulated as a biopesticide because it is synthetic, whereas Bt toxin and related genetic modifications are biopesticides, with Bt being an organic insecticide safe for the environment and non-toxic to humans.

Explanation:

The substance that would not be regulated by the U.S. Environmental Protection Agency (EPA) as a biopesticide is "The synthetic agricultural insecticide, DDT." This is because DDT is a synthetic chemical and does not fall under the categories of biopesticides that the EPA regulates, such as naturally occurring substances, microbial pesticides, or plant-incorporated protectants (PIPs). In contrast, bacterial mutants, the cry toxin genes used in engineered crops (e.g., Bt toxin), and genes engineered in crops for virus resistance (e.g., papaya ringspot virus gene) are all examples of biopesticides or are related to biotechnological methods used for pest control that would typically fall under EPA regulation.

For instance, Bacillus thuringiensis (Bt) is a bacterium producing protein crystals with insecticidal properties, approved for use by organic farmers and safe for the environment and non-toxic to humans. Meanwhile, Rotenone, derived from legumes, is a naturally occurring substance that the EPA would regulate as a biopesticide because it fits the category of a biochemical pesticide.