MUTATIONS IN PLANT EVOLUTION, CROP DOMESTICATION AND BREEDING

Abstract

Mutations and natural selection have been the cornerstone of plant evolution. Mutations have also played a significant role in crop domestication and plant breeding. Defined as sudden heritable changes in the DNA in living cells, not caused by genetic segregation or genetic recombination, mutations can be intragenic (point mutations), structural (chromosome rearrangements) or genome mutations (changes in chromosome number). Extranuclear or plasmone mutations such as those leading to cytoplasmic male sterility are also of significance in crop breeding. Using mutation techniques, defects in elite cultivars such as susceptibility to a new pathogen can be fixed faster than backcrossing. If a gene of interest is not available in the germplasm, mutation induction could be the only non-GM pathway to introduce a new trait. Mutation breeding is the only straightforward alternative for improving seedless crops and cultivars. Since the first publications of induced mutagenesis using x-rays almost a century ago, many more potent physical and chemical mutagens have been introduced, and methodologies for using those in seed (both self- and cross- pollinated) and vegetatively propagated crops have been established. This review first looks at the role of mutations in plant and crop evolution and then describes the choices available for mutation breeding programmes in terms of available mutagenic agents, treatment methods from cell cultures to whole plants, and some of the achievements. There are exciting opportunities available for modern plant breeding through integration of mutation techniques with plant molecular approaches. More than 3400 registered mutants in over 170 species in the largest mutant database managed by FAO/IAEA is a testament to the success of practical application of the technology.