FIG. 6.

Sexual reproduction of M. gypseum involves MAT1-1 and MAT1-2 heterothallic isolates. After incubation at room temperature in the dark for 1 month, cleistothecium formation and ascospore production were observed on Medium E plates when MAT1-1 and MAT1-2 M. gypseum strains were coincubated. (A) The cleistothecium is a small white structure formed on mating plates and visible with the naked eye. (B) Under light microscopy, the mature cleistothecium is yellowish. (E and F) The cleistothecium monitored with scanning electron microscopy (SEM) was enveloped by mature peridial hyphae, many of which are coiled and spiral. The ascospores are round cells with a diameter of ∼3 μm (as observed by light microscopy [C] and SEM [G]). (C) Asci containing eight ascospores were visible by light microscopy. Ascospores germinated to produce hyphae when spread on Sabouraud dextrose agar and were incubated for 5 days at room temperature (as observed by light microscopy [D] and SEM [H]).