Hybrids between species can harbor a combination of beneficial traits from each parent and may exhibit hybrid vigor, more readily adapting to new harsher environments. Interspecies hybrids are also sterile and therefore an evolutionary dead end unless fertility is restored, usually via auto-polyploidisation events. In the Saccharomyces genus, hybrids are readily found in nature and in industrial settings, where they have adapted to severe fermentative conditions. Due to their hybrid sterility, the development of new commercial yeast strains has so far been primarily conducted via selection methods rather than via further breeding. In this study, we overcame infertility by creating tetraploid intermediates of Saccharomyces interspecies hybrids to allow continuous multigenerational breeding. We incorporated nuclear and mitochondrial genetic diversity within each parental species, allowing for quantitative genetic analysis of traits exhibited by the hybrids and for nuclear–mitochondrial interactions to be assessed. Using pooled F12 generation segregants of different hybrids with extreme phenotype distributions, we identified quantitative trait loci (QTLs) for tolerance to high and low temperatures, high sugar concentration, high ethanol concentration, and acetic acid levels. We identified QTLs that are species specific, that are shared between species, as well as hybrid specific, in which the variants do not exhibit phenotypic differences in the original parental species. Moreover, we could distinguish between mitochondria-type–dependent and –independent traits. This study tackles the complexity of the genetic interactions and traits in hybrid species, bringing hybrids into the realm of full genetic analysis of diploid species, and paves the road for the biotechnological exploitation of yeast biodiversity.

物种之间的杂交可以拥有来自每个亲本的有益特性的组合，并可能表现出杂交活力，更容易适应新的更恶劣的环境。种间杂种也是不育的，因此除非通过自身多倍化事件恢复生育力，否则进化将陷入死胡同。在Saccharomyces属中，在自然界和工业环境中很容易找到杂交种，它们已经适应了严酷的发酵条件。由于它们的杂交不育性，迄今为止，新商业酵母菌株的开发主要通过选择方法而不是通过进一步育种进行。在这项研究中，我们通过创建酵母菌的四倍体中间体来克服不育症种间杂交，以允许连续的多代育种。我们在每个亲本物种中纳入了核和线粒体遗传多样性，允许对杂种表现出的性状进行定量遗传分析，并评估核 - 线粒体相互作用。使用具有极端表型分布的不同杂种的合并 F12 代分离子，我们确定了对高温和低温、高糖浓度、高乙醇浓度和乙酸水平的耐受性的数量性状基因座 (QTL)。我们确定了物种特异性、物种之间共享的 QTL，以及杂种特异性的 QTL，其中变体在原始亲本物种中不表现出表型差异。此外，我们可以区分线粒体类型依赖性和独立性状。