Abstract
Varietal difference in culture response of 14 days old immature embryos was examined by culturing on 2, 4-D medium, using 102 local wheat cultivars collected from varlous parts of the world. Callus induction ancl green spot formation occurred in all of the cultivars tested, indicating that culture method of immature embryo could be applicable to most of wheat cultivars. However, culture response showed wide varietal variation, being ranged from 25% to 100% in callus induction rate, from 18% to 94% in regeneration capacity of callus and from 10% to 85% in culture efficiency. The estimated correlation coefficient between the former two characters was r=0.09, indicating that callus induction rate and regeneration capacity of callus were controlled by independent systems. Though varietal variation in culture response was observed within each cultivated area, statistically significant difference existed also among the cultivated areas. Callus induction rate showed wide varietal variation and was lower in the Central region of wheat evolution. The negative correlation observed between callus induction rate and the first inoculation date suggested that low rate of callus induction in this region might be partly ascribable to the existence of late heading cultivars. On the other hand, regeneration capacity of callus was lower in the northern part of Japan and the northeastern part of China than in the other parts of both countries, and such difference seemed to be caused by genetic factors. In this case, culture method should be improved to increase the culture efficiency of these cultivars. For further improvement of tissue and cell culture systems of wheat, the suitable cultivars detected in this study would be useful as novel genetic materials.
