Abstract
Seeds of 18 strains of 12 different species of Avena were irradiated with gamma-rays to evaluate the relationship between radiosensitivity and ploidy level. Germination, seedling growth and root growth were used as indices of radiosensitivity. Chromosome aberrations at anaphase of the first root-tip mitosis were also analyzed. There were little or no differences in radiosensitivity between diploids and tetraploids, while hexaploids exhibited higher resistance particularly in terms of germination and seedling growth. Within each ploidy group, marked variations in sensitivity were revealed between strains. Interphase chromosome volume (ICV) covered a rather narrow range among the strains used, and could not account for the within-ploidy variations or the high resistance of hexaploids. Judging from chromosome sensitivity expressed by the frequency of fragments per cell per genome, it seems that the within-ploidy variations are due to genetic differences modifying radiosensitivity and that there are no prominent differences on average in genetically determined sensitivity between different ploidy level. The main part of the observed high resistance of hexaploids can be best explained by genetic redundancy rather than by ICV and genetic differences.
