Insect resistance – Bt Crops:
i. Bt Cotton
Bt cotton is a genetically modified organism (GMO) or genetically modified pest resistant plant cotton variety, which produces an insecticide activity to bollworm. Strains of the bacterium Bacillus thuringiensis produce over 200 different Bt toxins, each harmful to different insects. Most Bt toxins are insecticidal to the larvae of moths and butterflies, beetles, cotton bollworms and gatflies but are harmless to other forms of life.The genes are encoded for toxic crystals in the Cry group of endotoxin. When insects attack and eat the cotton plant the Cry toxins are dissolved in the insect’s stomach.The epithelial membranes of the gut block certain vital nutrients thereby sufficient regulation of potassium ions are lost in the insects and results in the death of epithelial cells in the intestine membrane which leads to the death of the larvae.
The advantages of Bt cotton are:• Yield of cotton is increased due to effective control of bollworms.• Reduction in insecticide use in the cultivation of Bt cotton• Potential reduction in the cost of cultivation.
Bt cotton has some limitations:• Cost of Bt cotton seed is high.• Effectiveness up to 120 days after that efficiency is reduced• Ineffective against sucking pests like jassids, aphids and whitefly.• Affects pollinating insects and thus yield.
ii. Bt Brinjal
The Bt brinjal is another transgenic plant created by inserting a crystal protein gene (Cry1Ac) from the soil bacterium Bacillus thuringiensis Bt Brinjal into the genome of various brinjal cultivars. The insertion of the gene, along with other genetic elements such as promoters, terminators and an antibiotic resistance marker gene into the brinjal plant is accomplished using Agrobacterium- mediated genetic transformation.The Bt brinjal has been developed to give resistance against Lepidopberan insects, in particular the Brinjal Fruit and Shoot Borer (Leucinodes orbonalis).
iii. Dhara Mustard Hybrid (DMH)
DMH -11 is transgenic mustard developed by a team of scientists at the Centre for Genetic Manipulation of Crop Plants Delhi University under Government sponsored project. It is genetically modified variety of Herbicide Tolerant (HT) mustard. It was created by using “barnase/barstar” technology for genetic modification by adding genes from soil bacterium that makes mustard, a self-pollinating plant. DMH -11 contains three genes viz. Bar gene, Barnase and Barstar sourced from soil bacterium. The bar gene had made plant resistant to herbicide named Basta.