抗蟲基因轉殖植物之類別與其對環境中昆蟲類之影響

Abstract

Insecticidal substances produced in transgenic crops for insect resistance can generally be divided into 4 groups, δ-endotoxin of Bacillus thuringiensis (Bt), lectins, enzyme inhibitors and enzymes. The δ-endotoxin major toxic substance of Bt. The gene for the endotoxin from Bt is inserted into plants to produce insect-resistant crops. The most common modifications of crops are to insert the cry1 gene for the control of lepidopterans and to insert the cry3 gene for coleopterans. Since 1995, the main lectin studied has been the snowdrop lectin (Galanthus nivalis agglutinin, GNA). The gene is inserted to produce proteins in tobacco, potato, rice, and wheat which inhibit the growth of insect pests such as moths, aphids, and hoppers. Enzyme inhibitors include protease inhibitors and α-amylase inhibitors. Genetically modified rice, wheat, tobacco, and potatoes with protease inhibitors show various degrees of resistance to leaf hoppers and lepidopteran larvae. Research has mainly been conductedα-Amylase inhibitors on beans for resistance to bean weevils. Enzymes include chitinase and cholesterol oxidase. Transgenic crops with a chitinase-producing gene which is found in microorganisms to insects show resistance to their pest insects. Such food injures the peritropic membrane of the midgut of the target insect and hence normal food consumption and nutrition absorption are disturbed. Cholesterol oxidase isolated from bacteria reduces the growth rates of insects by destroying cell membranes in the digestive tract. Among the transgenic crops with the above insecticidal substances, Bt crops such as Bt cotton, Bt corn, and Bt potatoes have been commercially cultivated in large areas.