Attempted pollen-transmission of cytoplasmic male sterility and the spontaneous occurrence of male sterility in O-type lines of sugar beet (Beta vulgaris L.).

Several instances of the occurrence of male-sterile individuals in progenies of O-type sugar beet lines are described, and the theoretical explanations considered. An attempt was made to transmit cytoplasmic male sterility through massive pollination by plants carrying S-plasm and fertility-restoring genes. No male sterility was demonstrated in the F1 generation, nor in the backcross to the O-type line used as the original recipient. It was concluded that pollen-transmission did not provide an acceptable explanation of the observed degree of contamination of the 0-types, and that N-plasm may have changed into S-plasm in these cases. Segregation of the monogerm character in the same material could not be satisfactorily explained in terms of simple genetic control.