Whilst looking at the fermentation characteristics of "lager" yeast with a view to selecting one for high (1.053-1.074/13-18°P)/very-high (>1.074/18°P, they used 1.101/24°P in their tests) gravity brewing, this group from Jiangnan University in China found that some of them were hybrids of
Saccharomyces kudriavzevii and
S. cerevisiae - so similar hybrids to Wyeast 1214/WLP500/Abbaye.
The classical idea is that Group I(Saaz) lager yeasts are triploids with 2
eubayanus genomes and one
cerevisiae whereas Group II (Frohberg) have two of each, but they found one ("BL25" from Germany) that was tetraploid despite appearing to belong to Group I by the Pham et al. PCR test. Likewise they had 42 strains that looked like Group II by the Pham et al PCR test, but 14 of the 42 were triploid.
"BL23" from China looked like a Saaz but had 37.44 % of its genome from
S. kudriavzevii, "BL42" looked like a Frohberg but had 32.42 % from
S. eubayanus and 12.8 % from
S. uvarum; they had previously found that the Frohberg BL52 was a hybrid of
S. cerevisiae and
S. uvarum. They then used supposedly species-specific primers and had no hits for eubayanus on 3 of their 12 Saaz strains and 1 and an iffy one for
kudriavzevii. Among their 42 Frohbergs they had 32 hits for
S. kudriavzevii and 31 for
S. eubayanus. Obviously the immediate question is how good are their PCR primers at only recognising one species, but one has to assume good faith by the previous workers who created them, in the absence of contrary evidence.
They were trying to breed yeast for very-high gravity brewing; they reckon that 1.101/24°P wort was equivalent in stress terms to 0.5M NaCl for lager yeast, . and 1.159/36°P was equivalent to 1.2M NaCl or 12 % ethanol. Although Frohberg strains are meant to be more robust than Saaz, they found that if anything the reverse was true for their high gravity fermentations as judged by cell growth but their attenuation was less and they produced more esters and fusel alcohols.
https://www.sciencedirect.com/science/article/pii/S0740002024000170
