Mutagenesis and Selection: Reflections on the In Vivo and In Vitro Approaches for Mutant Development

Abstract

Plant mutation breeding has become a major tool for the improvement of crop plants. Mutation breeding of crop plants is achieved by using physical and/or chemical mutagens in plants propagated via vegetative and sexual modes of propagation. Optimized protocols for the isolation of mutants, their screening and handling of mutant population are now fairly established in several crop plants. Plant improvement has become feasible for desirable traits like plant type, flowering, higher yield, disease, pest resistance, abiotic stress tolerance, nutritional quality including traits of industrial importance. Plant type, propagation method, ploidy and genetics of traits are some of the critical factors to be considered before undertaking mutagenesis as the sole method to isolate desired mutants. Despite the feasibility of undertaking mutation induction by using a wide variety of mutagens, isolation of desired mutant using irradiation techniques, in a given time will depend on the radiation facilities and treatment regime, besides the plant species. Methods of in vitro mutagenesis and in vitro selection have added another dimension for the development of mutants, especially in the case of vegetatively propagated crops using in vitro shoot cultures, embryogenic callus, cell suspensions and protoplast cultures. In vitro cultures offer potential benefits to select for biotic and abiotic tolerance besides nutritional quality. Success is often achieved based on optimization of appropriate in vitro culture system(s), high frequency plant regeneration, post-mutagenesis handling of mutant population and evaluation of mutants. Extensive research input is required to create and characterize mutation-induced genetic diversity followed by large-scale evaluation of the induced mutants for various agronomic, yield and nutritional quality characters for use in crop improvement.