Abstract
By using the protoplast fusion techniqlle we obtained rice-soybean hybrid calli having soybean nuclei and chloroplasts of both parents. In the brown hybrid calli sorting-out of chloroplasts occurred and green calli having soybean chloroplasts and white calli having rice chloroplasts were segregated (NIIZEKI et al. 1985). The heteroplasmic hybrid calli with both parent chloroplasts were extremely sensitive to streptomycin under both light and dark conditions, while the parent calli and the green and white calli produced by the sorting-out of chloroplasts were resistant to streptomycin under light conditions, but very sensitive under dark conditions. From this result it can be assumed that the responses of these calli to streptomycin may be related to the chloroplast for the follow-ing reasons : Firstly, the difference in the response of the parent calli or the calli with sorted-out chloroplasts to streptomycin under light and dark conditions suggests that the sensitivity to streptomycin may be related to the chloroplasts which require light for their functions and secondly, the recovery of streptomycin resistance in the calli with sorted-out chloroplasts indicates that the chloroplasts respond to streptomycin. However, the pcssibility that the sensitivity to streptomycin resides in the other organelles could not be excluded. Also, the reason for the heteroplasmic state of the calli being very sensitive even under light conditions remains unknown. After long term culture streptomycin resistant portions in the heteroplasmic hybrid calli increased in number under light conditions. This means that the sorting-out of chloroplasts progressed in the hybrid calli and the number of callus portions or cells with only one of the parent chloroplasts increased.
