[Formation of diploids by Aspergillus niger and their biosynthesis of citric acid].

Diploid organisms appeared spontaneously in heterokaryons of Aspergillus niger produced by crossing a beige mutant, which was adenine-deficient, and a green mutant requiring the addition of yeast autolysate. The frequency of diploidization increased two-fold under the action of colchicine (0.5%). The diploids became prototrophous, the colour of their conidia increased 1.5--2.4 times. The rate of production of citric acid by the diploid strains which had originated under the action of colchinine was 1.5 times higher than that of the parent haploid mutants.