Use of Gamma Rays in Crop Improvement

Induced mutation mimics the natural process of spontaneous mutation, which is the main working force behind the evolution of living beings. Among various mutagens, the gamma ray emitted from the ‘⁶⁰CO’ source is the most potent mutagen exploited for crop improvement, with the development of more than 50% of mutant varieties. The beauty of mutation breeding lies in its ability to improve one or a few traits while keeping the genetic makeup of the original variety intact. Most of the economic traits of important crops, right from yield, quality, and biotic and abiotic stresses to some novel variability which does not exist in the germplasm were successfully targeted for genetic improvement through gamma-ray-induced mutation. A large number of mutants were reported to have been induced through gamma rays in various crops and were either used directly as new varieties or as donor parents in hybridization program to develop improved varieties and hybrids. Among 3402 mutant varieties released worldwide for commercial cultivation in various crops including horticultural crops, gamma ray has contributed 1716 mutant varieties (50.44%). In the era of molecular biology, induced mutation is gaining more importance as mutants are the ideal genetic material for identification, isolation of genes, and study of the structure and functions of mutated genes. The recent advances in molecular biology, like next-generation sequencing (NGS), changed the scenario of mutant screening with MutMap (mapping-by-sequencing) and MutChromSeq (assorting the desired genes in the shortest time), thereby making the induced mutation relevant even in the genomic era. The present book chapter discusses the use of gamma rays in crop improvement through the creation of invaluable genetic variability to combat the challenges posed by climate change and population explosion and its contribution to food and nutritional security by developing mutant varieties throughout the world.