Die unterschiedliche empfindlichkeit der genome von oenothera berteriana gegenüber äthylmethansulfonat

Abstract

The different sensitivity of the genomes of Oenothera barteriana against ethyl methanesulfonate Oenothera berteriana is a complex heterozygote species with genome complexes named B and 1. Egg and sperm cells were treated with ethyl methanesulfonate. Thereafter self-pollination was carried out. Because both genomes may be mutated by the mutagen, the genetic constitution of the M 1-mutants was termed B′ and l′, respectively. These mutants were crossed to plants which carry in the pollen either the B or 1 complex. Because there are no homozygous forms, crossing of B′.l′ × B yields B.1′ plants, crossing of B′.1′ × 1 only B′.1 plants. Thus it was possible to compare the EMS sensitivity of the genomes. It was found that the genome complex 1 is considerably more sensitive to EMS than is the genome complex B. This agrees with the findings after X-irradiation. It could be shown by the experiments with X-rays that the different sensitivity of the two genomes is caused by a different chromosome mutation rate; aberrations are more often induced in chromosomes of the l-complex than in chromosomes of the B-complex. This higher sensitivity of the 1-genome for X-rays and ethyl methanesulfonate is presumably caused by small, scarcely visible, deficiencies. Translocations cannot account for this phenomenon, since they do not appear after ethyl methanesulfonate treatment in Oenothera berteriana. The translocations which often can be found after X-irradiation are, however, important for the appearance of trisomic plants in the X 2-generation. For the frequency of non-disjunction is raised by these translocated chromosomes. Since ethyl methanesulfonate does not cause translocations, there are no trisomic plants in the M 2-generation.