“Mutations” In Aspergillus Niger Bombarded by Low Voltage Cathode Rays

SUMMARY

Irradiation of spores of Aspergillus niger has produced several variant strains of this fungus. These strains differed markedly from the parent, most commonly in the color of the fruiting mycelium. One showed an evident increase in size. They have been continued through several asexual generations without showing any appreciable change. Calculations indicate that at the voltage used (ca. 12 electron kilovolts) the electrons penetrate the spores far enough to release most of their energy in the zone in which the nucleus is located. This suggests that the observed effects are a result of changes in the nucleus and that they may therefore be considered mutations. A cytological examination of the different variants showed only one evident nuclear change; in the large variant the number of chromosomes was twice that of the normal form. Otherwise the cytology of all the variants and of the species was alike. Several repetitions of the work gave comparable results, producing variant forms of apparently identical nature.