Applied since the 1930s to accelerate the process of developing and selecting new valuable agronomic traits, mutation breeding uses a plant’s own genetic make-up, mimicking the natural process of spontaneous mutation. The mutation process generates random genetic variations, resulting in mutant plants with new and useful traits.
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Mutation breeding
Classical breeding in its most simple form involves the selective propagation of plants with desirable characteristics and the elimination or "culling" of those with less desirable characteristics. Another technique, often referred to as cross breeding, is the deliberate interbreeding (crossing) of closely or distantly related but sexually compatible parental lines to produce new crop varieties or lines with desirable properties. Both techniques involve a multi-generational process that often requires five or more years to eliminate unwanted characteristics and develop the sought-after traits.
Jointly with the FAO, the IAEA assists its Member States in developing and implementing technologies that, through the use of gamma irradiation and X-rays, can induce the mutation of plants and thereby considerably speed up the breeding process. This can also involve the use of related biotechnologies to identify and select the required mutations.
A faster tool, yet environmentally friendly
Mutation breeding, in the case of self-pollinated crops that are disseminated by seed, is based on the self-fertilization – or selfing – of mutants until the induced desired character is stably expressed in advanced mutant generations. Often backcrossing to the original non-mutated genotype (part of the DNA sequence of a cell that determines its specific characteristic) is necessary to retain its favourable characteristics.
Mutation breeding is built on mutation induction and mutation detection. It has many comparative advantages: it is cost effective, quick, proven and robust. It is also transferrable, ubiquitously applicable, non-hazardous and environmentally friendly. More than 3,200 mutant varieties – including numerous crops, ornamentals and trees – have officially been released for commercial use in more than 210 plant species from over 70 countries (Source: FAO/IAEA Mutant Varieties Database).
Plant biotechnologies play an important role in mutation breeding. Plant tissue culture techniques are powerful tools in shortening the time needed to generate breeding mutant lines (those that always pass down certain traits to their offspring). This is a bottleneck for the exploitation of induced crop mutations that are recessive (in genetics, when one characteristic of a gene is not expressed because a more dominant one is displayed).
One such plant breeding tool is the doubled haploid technique, which refers to the doubling of chromosomes of a haploid – an organism or a cell that has only one member of each chromosome pair.
Another method is to identify molecular markers closely linked to the desired traits that can then be used to rapidly identify these traits. The development and dissemination of such molecular markers has the potential to further strengthen plant mutation breeding programmes, in particular for main food crops such as rice.
