Which plant breeding technique was used to produce NP 836 variety of wheat (rust resistant), Indore-2 variety of cotton (resistant to boll worm), Regina-II variety of cabbage (resistant to bacterial rot), etc.?

Step-by-step solution

NP 836 is a variety of wheat that is resistant to rust and was developed through mutation breeding using X-rays. Similarly, Indore-2 variety of cotton (resistant to bollworm) and Regina-II variety of cabbage (resistant to bacterial rot) were also developed using mutation breeding. Mutation breeding involves exposing seeds or plants to radiation (like X-rays or gamma rays) or chemicals to induce mutations, followed by selecting the plants with desirable traits. Answer: Mutation breeding.