For induction of mutations in crop plants, X-rays were first used by

For the induction of mutations in crop plants, X-rays were first used by H. J. Muller (1927). Mutation involves sudden changes in an organism's genetic code. Herman Muller studied the hereditary characteristics of fruit flies and, in 1927, discovered that the number of genetic mutations observed in fruit flies increased when they were exposed to x-rays.
Hermann Joseph Muller conducted three experiments in 1926 and 1927 that demonstrated that exposure to x-rays, a form of high-energy radiation, can cause genetic mutations, and changes to an organism's genome, particularly in egg and sperm cells.