Mutation, a heritable change in a genetic characteristic of an organism, is a natural process that creates new variants (alleles) of genes. Mutation is the primary source of all genetic variations existing in any organism, including plants. Variation so created by mutation provides the raw material for natural selection and is a driving force in evolution.
Natural selection operates to bring about evolution of new races and species through the variability created by natural mutations and amplified by subsequent recombination of genes during sexual reproduction. Besides natural mutations that occur spontaneously due to various kinds of radiations and cosmic rays received from the sun and also emitted by several radioactive elements, mutation can also be artificially induced by a number of physical agents like gamma rays and X-rays and several types of chemical agents belonging to few specified groups known as chemical mutagens. The standard technique of creating variability by means of altering genes through induction of mutations by physical or chemical mutagens and using the same effectively through elaborate methods of selection techniques in various generations for improvement of a particular crop species for desired objectives is called mutation breeding. This is frequently practiced by plant breeders all over the world for crop improvement.