Abstract: The invention provides method and compositions for yeast cultures with a predetermined desirably improved trait, such an enhanced or reduced ability to produce particular fermentation products. In one embodiment, the breeding scheme involves assembling and surveying a large population of natural wine yeast for a chosen trait; select appropriate individuals from this population and repeatedly back-crossing to well-established commercial strain by selecting HO/HO spores from the selected and commercial parental strains, treating asci with zymolase and carrying out spore-spore pairings, observing the spore pairs at intervals to detect formation of primary zygotes, and selecting and sporulating primary zygote clones; analyzing segregants of primary zygote clones and scoring for the trait; selecting the best segregants; and repeating the back-crossing procedure using a different HO/HO spore clone from the commercial parent in each cross.