Doubling time of S. cerevisiae haploid in YPD liquid is 90 min. In SD it is less, about 5x107 per ml. They remain reasonably viable for a couple of months. Longer incubation above 4C toughens the diploid wall, requiring increased digestion for dissection. Asci of wild strains may be harder to digest than those of laboratory strains.
Haploids form homozygous diploids spontaneously at low frequency in cultures.
Spheroplast transformation sometimes also produces a high proportion of homozygous diploids. These are not easily distinguished from haploids. The differences in cell sizes is too slight to be a clear indicator of ploidy. Tetrads from triploids, when dissected, give extremely poor viability, in the range of 0 to 3 colonies from 10 dissected tetrads. Viability is somewhat better in the Sigma 1278b background, but growth is very slow.