Hybridization studies involving Saccharomyces fragilis and Zygosaccharomyces dobzhanskii.

In a preceding paper (1956) the writers reported that pigmentation occurs in varyinig degree among strains of most species of the proposed but as yet undescribed new genus, Dekkeromyces. Hybrids may yield more pigment than either parent, thereby permitting easy selection of hybrids from a population consisting of both hybrids and parent species. This method of isolating hybrids requires one or both of the parents to produce a small or moderate amount of pigment, but neither parent should be strongly chromogenic. Another procedure has been devised for separating hybrids from their parents. The parent strains may be selected without regard to the amount of pigment they produce, but they must differ from each other in the assimilation of two carbon sources. Because this study has resulted in the first ascosporogenous yeasts known to ferment both maltose and lactose, and because the hybrids reported here may be of particular interest to geneticists, the results of this study will be presented in greater detail than was done in the previous study.