TABLE 1.

Strains used in this study

Strain numbera	Species or strain	Mating type	Genotype or description	Reference or sourcec
Y169	S. cerevisiae	MATa	lys1	This laboratory
Y170	S. cerevisiae	MATα	lys1	This laboratory
Y184	S. cerevisiae	MATα	ade1 his1	This laboratory
Y185	S. cerevisiae	MATa	ade1 his1	This laboratory
Y266	S. cerevisiae	MATα	lys1 ρ−	Y170
Y267	S. cerevisiae	MATα	lys1 ρ−	Y170
Y166	S. bayanus	Diploid	Homothallic, ura3-1	MCYC 623-6C (R. Borts)
Y244	S. bayanus	MATα	ura3− G418R	Y166 transformed with P161
Y245	S. bayanus	MATa	ura3− G418R	Y166 transformed with P161
Y327	S. exiguus	MATα	Spontaneous ho−	CBS 2141
Y328	S. exiguus	MATa	Spontaneous ho−	CBS 2141
Y339	S. exiguus	MATα	his−	Y327
Y345	S. exiguus	MATa	arg−	Y328
Y188	S. castellii	Diploid	Homothallic	CBS 4310
Y239	S. castellii	MATa	Induced ho−	Y188
Y257	S. castellii	MATa	met−	Y239
Y323	CBS 6463b	MATa	Spontaneous ho−, ρ−	CBS 6463
Y344	CBS 6463	MATa	ura3− ρ−	Y323
Y280	Hybrid	Hybrid	Prototroph	Y244 × Y169
Y500	Hybrid	Hybrid	Prototroph	Y257 × Y245
Y507	Hybrid	Hybrid	Prototroph, ρ−	Y184 × Y344
MT502	S. cerevisiae	MATa	sst2-1 met1 leu2-3,112 his3 can1	M. T. Hansen
MT503	S. cerevisiae	MATα	sst2-1 met1 leu2-3,112 his3 can1	M. T. Hansen
MT504	S. cerevisiae	MATα	leu2-3,112 gal2 sst1	V. McKay
MT505	S. cerevisiae	MATa	leu2-3,112 gal2 sst1	V. McKay

^aY, J. Piskur collection; MT, T. Nilsson-Tillgren collection. 

^bCBS 6463 (Y323) was previously classified as S. dairenensis, but it actually represents a novel species (17b). 

^cMCYC, Microbiology Collection of Yeast Cultures, Madrid, Spain; CBS, Centraalbureau voor Schimmelculture, Delft, Holland.