In which ways genetically modified plants are useful?

Explanation

Since the genes introduced into the plants can produce the pest killing toxins in the plants itself the farmers need not spray pesticides
. Bt toxin : Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt).Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm,armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
B. thuringiensis forms protein crystals during a particular phase of their growth and these crystals contain a toxic insecticidal protein. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and whale. eventually cause death of the insect.
Bt cotton :
Bt cotton is a transgenic cotton variety that contains a gene from a bacterium Bacillus thuringiensis.The product of the gene can kill the insect.
Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the cotton plants the choice of genes depents up on the crop and the largeted post,as most Bt toxin are insect group specific. The Toxin is coded by a gene named cry. There are a number of them, for example the proteins encoded by the genes cryIAC and cryIIAb control the cotton bollworms.