Abstract
Fertility and morphological characteristics of interspecific and intergeneric hybrids between radish, cabbage, and Chinese cabbage were compared with those of the parents. Because some hybrid progenies were sterile, they were propagated vegetatively through in vitro culture. Hypocotyl segments were imbedded on MS medium containing combinations of two phytohormones: 2, 4-D plus BA or kinetin, or NAA plus BA or kinetin. The synthetic auxin and cytokinin concentrations were 0.1 and 1.0 mg/liter, respectively. For plant regeneration, callus obtained from the hypocotyl was subcultured at monthly interval on a callus initiation or MS media with or without cytokinins.
1. Reciprocal hybrids showed considerable variations in their morphological characters.
2. Both parents and hybrid progenies formed callus on the MS medium supplemented with auxins and BA and the subculture medium containing BA.
3. About 6% of the interspecific radish explants regenerated shoots on the initial medium; none was obtained in the first and second subculture media. From 5067% of the calli from intergeneric hybrids between cabbage and radish yielded shoots on the initial medium; 1666% and 1020% of the calli formed shoots on the first and second subculture, respectively. As much as 70% of the calli from interspecific hybrids between cabbage and Chinese cabbage formed shoots on the initial medium; 3060% of the calli regenerated shoots when subcultured. Variations in callus size and weight obtained from parents and their progenies as a result of reciprocal crosses indicated that the ability to form callus and to regenerate shoots from calli was controlled by different genetic factors.
