medium yield, long fibre and resistance to beetle pests
high yield and production of toxic protein crystals which kill dipteran pests
high yield and resistance to bollworms
Solution
Bacillus thuringiensis forms crystals containing a toxic insecticidal protein. Bt toxin protein exists as inactive protein but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline $\mathrm{pH}$ of the gut, which solubulise the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause death of the insect. Specific Bt toxin genes were isolated from $B$. thuringiensis and incorporated into the several plants such as cotton. The toxin is coded by a gene named cry. There are a number of them, $\mathrm{eg}$, the proteins encoded by the genes cry IAc and cry II Ab control the cotton bollworms, that of cry IAb control corn borers.