Genetic segregation of natural Saccharomyces cerevisiae strains derived from spontaneous fermentation of Aglianico wine M. Sipiczki 1,2 , P. Romano 3 , A. Capece 3 and M. Paraggio 3 1 Department of Genetics, University of Debrecen, Debrecen, Hungary, 2 Research Group of Microbial Developmental Genetics, Hungarian Academy of Sciences, Debrecen, Hungary, and 3 Dipartimento di Biologia, Difesa e Biotecnologie Agro-Forestali, Universita della Basilicata, Campus Macchia Romana, Potenza, Italy 2003/0826: received 17 September 2003, revised 28 January 2004 and accepted 30 January 2004 ABSTRACT M. SIPICZKI, P. ROMANO, A. CAPECE AND M. PARAGGIO. 2004. Aims: Investigation of the meiotic segregation of karyotypes and physiological traits in indigenous Saccharomyces strains isolated from Aglianico (South Italy) red wine. Methods and Results: Segregation was studied in F1 and F2 descendants. Tetrads were isolated from sporulating cultures by micromanipulation. The spore clones were subjected to karyotype analysis by pulse-field gel electrophoresis (Bio-Rad model CHEF-DR II) and to various physiological tests. Certain chromosomes of the isolates showed 2 : 2 segregation patterns in F1 but proved to be stable in F2. The ability of cells to utilize maltose also segregated in a 2 : 2 manner in F1 and did not segregate in F2. Resistance to CuSO 4 , SO 2 tolerance, the fermentative power and the production of certain metabolites segregated in both F1 and F2 generations and showed patterns indicating the involvement of polygenic regulation. Conclusions: The analysis revealed a high degree of genetic instability and demonstrated that meiosis can improve chromosomal and genetic stability. Significance and Impact of the Study: Winemaking is critically dependent on the physiological properties and genetic stability of the fermenting Saccharomyces yeasts. Selection of clones from F2 or later generations can be a method of reduction of genetic instability. Keywords: Cu resistance, ethanol tolerance, fermentation, karyotype, metabolites, Saccharomyces, segregation, wine. INTRODUCTION Since the 1970s the inoculation of pure cultures into the grape must have been used to reduce fermentation time, improve wine quality and its homogeneity over successive vintages. Pure cultures for inoculation have been obtained from natural isolates in many vine-growing regions of the world. When yeasts are being selected for inoculated winemaking, one of the criteria to be considered is the sta- bility of the physiological and technological characteristics. Their stability is thought to be determined by genetic factors such as the stability of chromosomes (karyotype) and the allele combinations of genes involved in the production of metabolites or in the adaptation of the yeast cells to changes of the environment during fermentation. Natural yeast strains frequently segregate and produce meiotic or mitotic progeny of diverse chromosomal com- plements (e.g. Bakalinsky and Snow 1990; Longo and Vezinhet 1993; Miklos et al. 1997; Nadal et al. 1999; Puig et al. 2000; Carro and Pina 2001; Carro et al. 2003). Segregation can also adversely affect the stability of physiological traits including the production of metabolites important for wine quality (e.g. Mortimer et al. 1994; Correspondence to: Matthias Sipiczki, Department of Genetics, University of Debrecen, PO Box 56, H-4010 Debrecen, Hungary (e-mail: lipovy@tigris.klte.hu). ª 2004 The Society for Applied Microbiology Journal of Applied Microbiology 2004, 96, 1169–1175 doi:10.1111/j.1365-2672.2004.02254.x