Selection method of induced mutations

In autogamous crop plants, generally, the induction of mutation is preferably done by giving mutagen to the seeds, but this method leads to the formation of chimeras. For obtaining non-chimeric mutants, the mutagenic treatment at the initial stage of developing embryo is considered to be effective. The selection of macromutation in autogamous plants should be performed on a group of plants in the M2 generation, but that of micromutation on M3. For macromutation, when the mutants are easily detectable types, the use of one plant-one grain method is recommended, but when the mutants are not of the easily detectable types, the use of the ear progeny method is recommended. It is very difficult to apply the method of mutation breeding to allogamous crops, but this difficulty can be overcome by open-pollinating of M1 plants followed by sib-mating of M2 plants. To obtain mutation in vegetatively growing crops, chronic irradiation is given to growing plants, therefore chimeric mutants are obtained. To obtain a high percentage of non-chimeric mutants, the repeated cutting back method would be efficient. The effects of cutting back varies largely with the time and position of the cutting back. (Kaihara, S.)