Abstract
A three-step culture method for rapid regeneration of plants derived from mesophyll protoplasts was previously reported. Since a large number of regenerated plants were produced from protoplasts by this method, the chromosome constitutions of the calli and the regenerated plants were examined throughout the period of culture. In the callus-growing phase of the first and second steps of culture, the number of tetraploid cells increased gradually, but anaphase abnormalities were not detected. In the organization phase of the third step of culture, the tetraploid cells were eliminated and a high frequency of diploid plants was obtained (99%). Furthermore, most of the regenerated plants were uniform in their quantiative characteristics such as plant height, Ieaf shape, flower shape and pollen fertility. On the basis of these results, it was concluded that the three-step culture method for rapid regeneration was effective for the purpose of reducing the occurrance of genetic instability in the plants regenerated from protoplasts.
