Ploidy of serotype AD strains of Cryptococcus neoformans.

Twenty-four serotype AD strains of Cryptococcus neoformans were tested for ploidy and mating type. These included 13 natural isolates (1 from a patient, 1 from peach juice, 11 from pigeon droppings), 2 single clones from one of these natural isolates, 7 F1 progeny from a self-fertile strain and 2 F1 progeny of a cross between a strain from a patient (serotype A, alfa-mating type: MATalfa) and a tester strain (serotype D, a-mating type: MATa). Six strains (2 of natural isolates, 1 of single clone and 3 of F1 progeny) were MATalfa, 1 of F1 progeny was MATa, 4 (1 of natural isolate, 1 of single clone and 2 of F1 progeny) were a-alfa-mating type (MATa-alfa) and 13 (10 of natural isolates and 3 of F1 progeny) were untypable. Most strains, regardless of mating type, were diploid.