Killer behaviour in wild wine yeasts associated with Merlot and Malbec type musts spontaneously fermented from Northwestern Patagonia (Argentina)

The occurrence of killer wine yeasts in Comahue Region (Patagonia, Argentin a) was studied. Wild wine yeasts were isolated from spontaneously fermentin g Merlot and Malbec type musts. Out of 135 isolates analyzed 37% were sensi tive to some well characterized killer toxins as K-1-K-10 and did not show killer activity (sensitive phenotype, S), 21% showed neutral phenotype (N) and 42% demonstrated killer activity (killer phenotype. K). All but two kil ler strains, identified as Candida pulcherrima and Kluyveromyces marxianus, were Saccharomyces cerevisiae. Additionally, all killer strains were sensi tive to some killer reference strains, showing a killer-sensitive phenotype (KS): neither Saccharomyces or non-Saccharomyces wild yeasts were phenotyp e killer-resistant (KR). The incidence of the killer character varied with respect to fermentation stage and grape variety. increasing throughout ferm entation (13-55% to 36-90%). Irrespective of grape must type. the neutral a nd sensitive yeasts were ever predominant at initial stages of fermentation . All but six neutral strains, identified as Saccharomyes cerevisiae, were Kloeckera apiculata.