Sporulation

Abstract

Diploid hybrids (or hybrids of higher ploidy) having been obtained, sporula­tion can then be induced in a number of ways, mostly involving growth of the culture on a medium containing potassium acetate, glycerol or other non-fermentable substrate. Sporulation may also be induced in raffinose-acetate solutions. The presence of K ions improves sporulation. For most yeast strains, McClary’s medium (Fowell 1969) gives adequate sporulation. Growth on a relatively rich pre-sporulation medium such as yeast extract-peptone glucose medium is desirable. Sporulation may be induced in liquid or on solid medium, or in protoplasts as well as in intact cells. Induction of sporula­tion in protoplasts has the advantage that the unsporulated protoplasts may be burst by addition of water to the osmotically stabilized sporulation medi­um which must be used in this method, and the spores can either be isolated by micromanipulation of the naked tetrads or harvested, free of unsporulated vegetative cells, and subjected to random spore analysis.