Genotoxic activity of plant growth-regulating hormones in Aspergillus nidulans

Three plant growth-regulating hormones, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and kinetin (6-furfuryl-aminopurine), were tested for their genetic activity in Aspergillus nidulans in a plate test. The first two hormones were found to greatly increase somatic segregation in the fungus whereas kinetin was not effective. Several concentrations of the plant hormones were used and it was found that increasing concentrations of IAA and IBA increased mitotic segregation of the fungus with most of the segregants being produced by mitotic crossing-over, together with non-disjunctional segregants at a lower level. The metabolic activation technique was also used and it was shown that when S9 mixture was added to IAA and IBA a further 3- to 5-fold increase in the number of segregants was obtained. In the case of kinetin the S9 had no effect.