| Abstract: | One of the CMS systems presently investigated by rape breeders is the alloplasmic system derived from a male sterile radish and transferred to rape. However, these male sterile lines of rape with the radish cytoplasm exhibit yellow leaf colour at low temperatures. Moreover, no restorer genes for this system are known to occur in rape. The present investigation was, therefore, directed to the formation of new cross combinations between radish and rape in order to eliminate the above mentioned problems by additional transfer of corresponding radish genes into the rape recipient. After the initial intergeneric crosses, male sterile hybrids were received by in-vitro embryo culture and colchicine treatment. These hybrids were not backcrossed to rape as usual, but to one of the monogenomic ancestral species of rape, in order to increase the probability of allosyndesis between radish and rape chromosomes. After subsequent back-crossing with rape, the desired male sterile plants with 38 chromosomes were recorded, forming normal green leaves even at low temperatures. In a parallel backcross programme, restorer genes from male fertile radish were also transferred into rape by the same backcrossing procedure. The first alloplasmic male fertile plants were found in the BC: generation. They were cross pollinated to male sterile plants to prove their potential of fertility restoration. |
