Concerns over pesticidal traits include the enhanced evolution of resistant pest strains, the toxicity or allergenicity of the gene products to humans, the hybridization of transgenic pest-protected plants with neighboring wild relatives, and adverse effects on nontarget organisms.
Many self-pollinated crops are released as inbred lines for example, soybeans, Glycine max, and barley, Hordeum vulgare.
Along with a herbicide resistance gene, the three Bt versions were " shot" by a biolistic gene gun into immature corn embryos taken from developing seeds about 15 days after pollination.
Somaclonal variation is variation that occurs during the tissue-culture process, and its phenotypic outcomes are often similar to other forms of mutagenesis.
The possible interference on food webs and on non-target organisms is another issue for careful consideration in tropical areas, especially if the varieties were developed aimed at the control of insects that are mainly pests in temperate regions.
Research to transfer insect resistance genes from Bt to crop plants is well under way. For example, crop plants with different life cycles annual versus perennial will differ in their associated arthropod communities.
These breeders use the natural plant genetic variation and induced mutations to select desirable traits and introduce them into cultivated plants, using a combination of classical and modern plant breeding methods.
Picard-Nizou et al. Ecological impact of Bt-transgenic plants: 1.
These studies show that, while Bt pollen does have some toxic effects when fed to butterfly larvae, the pollen densities likely to be encountered in the field are too low to pose a risk to monarch larvae.
Even so, studies show that farmers value the greater flexibility in pesticide spraying that GE crops provide and the increased safety for workers from less exposure to harmful pesticides.