Role of Mutation Breeding in Crop Improvement with Special Reference to Indian Subcontinent

Abstract

The primary source of all genetic variations existing in any organism, including plants and animals, is mutation. Mutation provides the raw material for natural selection by creating variation 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 present on the earth, mutation can also be artificially induced by a number of physical mutagenic agents like gamma rays, X-rays and fast neutrons and several types of chemical mutagens like EMS, NMU and EI. 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. It is frequently practised by plant breeders all over the world for crop improvement. Nearly 3365 mutant varieties belonging to >240 plant species have been developed and officially released by the turn of the twenty-first century. The cumulative number 3365 of released mutant varieties in six continents of the world indicates that Asia tops the regional list with 2052, closely followed by Europe (960) and North America (209). With more than 100 mutant varieties each, China, India, Japan, Russia, the Netherlands, Germany and the USA are the leading countries among approximately more than 80 countries actively engaged in the development and release of mutant varieties. During the last five decades, several countries took up extensive crop improvement programmes through mutation breeding and made spectacular accomplishments in evolving several superior mutant varieties in a large number of important agricultural crop species including cereals, pulses, oilseeds, vegetables, fibres, medicinal plants and ornamentals. Large numbers of these mutant varieties, being cultivated by farmers in millions of acres in several countries, have made significant contribution worth billions of dollars in global food production. A wide range of characters including yield, maturity, quality and tolerance to biotic and abiotic stresses have been improved in the mutant varieties developed so far. Among the seven countries of the Indian subcontinent, India has made a significant contribution in crop improvement through mutation breeding by developing 542 mutant varieties in 85 crop species. The other two countries of the Indian subcontinent, Pakistan and Bangladesh, have also made major contributions through mutation breeding by releasing 79 and 76 mutant varieties of crop plants, respectively.