Table 1. Yeast isolates analyzed in this study.
| Lab, standard, and isolate identifier | Origin | Ploidy | SNPs (singletons) | Spore formation (%) (n) | Three or four spores (%) | Two spores (%) | Viable spores (tetrads) (%) |
|---|---|---|---|---|---|---|---|
| YJS5845, CIC, Ponton 11 | Human, mouth, Spain | 2 | 68,564 (825) | 93 (147) | 53 | 39 | 20 (40) |
| YJS5845 + CHR XIV | 96 (174) | 60 | 35 | 19 (39) | |||
| YJS5885, CKN, CLI_19 | Human, feces, France | 2 | 76,104 (955) | 57 (139) | 31 | 24 | 30 (28) |
| YJM521 | Human clinical, CA | 2 | 53,947 (22) | 78 (221) | 69 | 5.9 | 94 (10) |
| YJS4806, CFI, WLP013 | Beer, UK | 4* | nt | 15 (10) | |||
| YJS4810, CFN, WLP006 | Beer, unknown | 4* | nt | 5.0 (10) | |||
| YJS5882, CKK, CLI_16 | Human clinical, France | 4 | nt | 72 (8) | |||
| YJS5678, CBF, SD-15 | Bakery, Italy | 4* | nt | 70 (10) | |||
| YJS5512, BML, NCYC_2780 | Human clinical, Belgium | 4* | nt | nt | |||
| YJS4970, CGC, UCD_06-645 | Fruit, Davis, CA | 4 | no spores |
Nineteen of 1011 baker’s yeast isolates contain the incompatible MLH1-PMS1 genotype in heterozygous (18 isolates) or homozygous (YJM523) combinations (Bui et al. 2017). One isolate is triploid and 12 are tetraploid (six are shown here), two of which cannot sporulate. The remaining six are diploid, and the four diploid isolates that sporulate, YJS5845, YJS5885, YJM521, and YJM523, all belong to the MR3 mosaic clade (113 members) that are admixed with ancestry from two or more populations. In the MR3 clade, the mean number of singletons was 721 (± 1150 SD, ± 108 SE, and median = 163). The diploid isolates YJM521 (Clemons et al. 1997) and YJS5845 are homothallic, and YJS5885 appears to be functionally heterothallic (see text). The percentage of cells forming at least one spore (n is the cells examined) is shown under spore formation, and the distribution of these cells into 3, 4, or 2 spore asci is shown, along with the % spore viability seen in dissected tetrads (n = number dissected). Our original stock of YJS5845 contained euploid and aneuploid (additional copy of chromosome XIV) cells. The euploid and aneuploid isolates were analyzed for spore formation and viability separately. *, contains chromosomal aneuploidy (Peter et al. 2018); nt, not tested.