DNA sequence polymorphisms in the genus Saccharomyces IV. Homoeologous chromosomes III of Saccharomyces bayanus, S. carlsbergensis, and S. uvarum

Abstract

Single chromosome III transfers have been accomplished from the two species S. bayanus and S. uvarum into genetically marked S. cerevisiae strains. Incompabilities between S. bayanus or S. uvarum, and S. cerevisiae strains may account for the very few chromosome addition lines obtained. The preliminary genetic map for S. bayanus chromosome III is similar to the genetic map for a S. carlsbergensis chromosome III from Danish lager strain BK2208. Recombination is absent between the transferred chromosomes and the auxotrophically marked chromosome from S. cerevisiae in the interval HIS4 to LEU2 but recombination does occur in the interval LEU2 to THR4. The mapped S. bayanus chromosome III carries HIS4 pattern III while the mapped chromosome III from the lager strain contains HIS4 pattern II. Transfer of a chromosome III from S. uvarum to S. cerevisiae has been recognised by restriction endonuclease fragment patterns, OFAGE chromosome separations and molecular hybridization, but a genetic map could not be constructed for an S. uvarum chromosome due to instability of the chromosome addition lines. The hypothesis is put forward that the S. carlsbergensis type strain and the lager strains are sibling species and species hybrids both produced by hybridization of an S. cerevisiae top fermenting strain and the bottom fermenting strain S. monacensis. The lager strains and the authentic type strain are designated S. carlsbergensis. From the electrophoretic karyotypes of type strains of Saccharomyces and molecular hybridization patterns it is deduced that S. bayanus, S. inusitatus, S. pastorianus and S. uvarum are closely related but distinet from the bottom fermenting strains. © 1986 Carlsberg Laboratory.