Abstract
Three groups of mutants with different rates of spontaneous reversion were identified at the homocysteine locus in Ustilago maydis. And it is suggested that the locus has the pseudoallelic nature. Studies of the reversion rates per unit time by the zero term of Poisson formulation in strain 4-24 have shown that limiting concentration of methionine in the minimal medium did not induce the reversion at least for 96 hours at the locus in question.
