Reconstruction of the Evolutionary History of Saccharomyces cerevisiae x S. kudriavzevii Hybrids Based on Multilocus Sequence Analysis

In recent years, interspecific hybridization and introgression are increasingly recognized as significant events in the evolution of Saccharomyces yeasts. These mechanisms have probably been involved in the origin of novel yeast genotypes and phenotypes, which in due course were to colonize and predominate in the new fermentative environments created by human manipulation. The particular conditions in which hybrids arose are still unknown, as well as the number of possible hybridization events that generated the whole set of natural hybrids described in the literature during recent years. In this study, we could infer at least six different hybridization events that originated a set of 26 S. cerevisiae x S. kudriavzevii hybrids isolated from both fermentative and non-fermentative environments. Different wine S. cerevisiae strains and European S. kudriavzevii strains were probably involved in the hybridization events according to gene sequence information, as well as from previous data on their genome composition and ploidy. Finally, we postulate that these hybrids may have originated after the introduction of vine growing and winemaking practices by the Romans to the present Northern vine-growing limits and spread during the expansion of improved viticulture and enology practices that occurred during the Late Middle Ages.

近年来，种间杂交与基因渐渗（introgression）被越来越多地认为是酿酒酵母属（Saccharomyces）酵母菌演化过程中的关键事件。此类机制可能参与了新型酵母基因型与表型的形成，这些新兴类群随后得以定植并主导人类活动构建的新型发酵环境。目前，杂交种形成的具体条件仍不明确，近年来文献中报道的全部天然杂交种所对应的独立杂交事件数量也尚未可知。
本研究通过分析推断，至少存在6次独立的杂交事件，由此产生了26株酿酒酵母（Saccharomyces cerevisiae，缩写S. cerevisiae）×库德里阿兹威氏酵母（Saccharomyces kudriavzevii，缩写S. kudriavzevii）杂交种，这些杂交种分别分离自发酵与非发酵两类环境。结合基因序列信息，以及此前关于其基因组组成与倍性的研究数据，可推测参与本次杂交事件的亲本菌株分别为不同的葡萄酒酿酒酵母菌株与欧洲来源的库德里阿兹威氏酵母菌株。
最后，本研究提出假说：此类杂交种可能形成于古罗马将葡萄种植与葡萄酒酿造技术推广至现今北方葡萄种植带之后，并在中世纪晚期改良葡萄栽培学（viticulture）与酿酒学（enology）技术的扩张进程中得以传播扩散。