Abstract
Since 1964 the author has endeavored to obtain useful novel mutants in flower plants by gamma-ray irradiation. Plenty of annual, perennial and bulbous plants were grown several times under different dosages of chronic gamma-ray irradiation in the gamma-field of the Institute of Radiation Breeding, Ohmiya. Among many mutants obtained in the series of experiments, especially two mutated strains, semi-double flowering wallflower and white-flowering moss verbena, are described in this report due to their apparent available characteristics and genetical stability of the recessive nature.
Firstly, in the wallflower, Cheiranthus cheiri, many slightly-double or semi-double flowered plants were detected in the γ1-group which was raised from seeds produced by the single-flowered plants grown and irradiated in the gamma-field for about three months (ca. 4Kr) in 1972. The degree of their doubling of flowerlets was very variable, both between plant and plant and between flowerlets on the same inflorescence. These double flowers were possibly induced by a recessive gene and consisted of a few small spoon-like petallets mixed with pistils and stamens. In appearance, however, their inflorescences seemed to be inferior to those of the commercial cultivars, such as Double Early Wonder, due to somewhat tiny, poor flower stalks and lowered seed fertility.
Next, in the moss verbena, Verbena erinoides, a pure-white flowered seedling was found in the Spring of 1973 among several purple-red ones spontaneously germinated around the parental plants which were irradiated in the gamma-field in 1972. General characteristics of the mutated plant were similar to those of nonirradiated plants, except for flower color. In detail, however, the size of the white flowerlet was a little smaller than the latter. Then, the mutant produced a few seeds under open pollination and raised five γ2 seedlings in 1975 and, furthermore, eight γ3 plants in 1976. All the plants showed pure-white flowers exactly like those of γ1 plant, without any genetic segregation. So, it was supposed that white-flowering was simple recessive against the colored. The white-flowering moss verbena might be available for carpet plants in the garden, even though the white-flowered V. erinoides var. alba Hort. had been described formerly by Dermen which, however, has not been found in any gardens in our country.
