obsolete formation of azygotic ascus upon sporulation true abnormal sporulation resulting in formation of azygotic asci formation of azygotic asci upon sporulation FYPO:0000279 2011-04-19T04:37:01Z midori OBSOLETE. A sporulation phenotype in which azygotic asci form following conjugation and subsequent sporulation. Azygotic ascus formation occurs when meiosis takes place within a diploid cell rather than in a zygote produced by sporulation. Zygotes can resume vegetative growth and form colonies of diploid cells if returned to rich media before commitment to meiosis; under nitrogen starvation, diploid cells heterozygous for mating type will undergo azygotic meiosis. Azygotic asci have a characteristic linear morphology resembling that of a single vegetatively growing cell. This term was made obsolete because it was incorrectly defined. Although the description in the text definition is accurate, azygotic sporulation is not necessarily an abnormal occurrence. The term was also used incorrectly in annotations. sporulation defects, azygotic asci