FIG. 3.

The ascospores from Δnox-2 homozygous crosses are nonviable. Strains CNCKA-Z (Δnox-2 A) and CNCKA-AN1 (Δnox-2 a) were crossed and allowed to produce ascospores. Shot ascospores were collected as water suspensions, heat activated, plated on sorbose-containing medium, and incubated for 3 days (top panels) or incubated in liquid minimal medium and observed under the microscope (bottom panels; magnification, ×1,077). Only ascospores generated by the wild-type strains (WT) were able to germinate and generate colonies.