Spontaneous and induced mitotic recombination in Ustilago violacea detected at the cellular level.

Spontaneous and induced mitotic recombination in the heterobasidiomycete Ustilago violacea was detected at the cellular level using a sporidial morphology mutation. Mitotic recombination was induced by ultraviolet light (UV), nitrogen mustard (NM) and metabolically nonactivated cyclophosphamide (CP). The effects of low (14 °C) and high (30 °C) temperature and culture age on induced mitotic recombination are reported. Low temperature after inductive treatment uniformly reduced mitotic recombination. High temperature increased UV induced recombination, had no effect on NM-induced recombination and reduced CP-induced recombination to the spontaneous level. Temperature alone had no effect on mitotic recombination. Ultraviolet light-induced recombination was correlated with the rate of cell division and cell survival as cells passed from log to stationary phase growth. Detection of mitotic recombination at the cellular level is discussed as a method to assay postreplication repair of genetic damage and as a screen for agents which induce genetic damage in eukaryotic cells.