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, Argentina) was studied. Wild wine yeasts were isolated from spontaneously fermenting Merlot and Malbec type musts. Out of 135 isolates analyzed 37% were sensitive to some well characterized killer toxins as K1-K10 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 killer strains, identified as Candida pulcherrima and Kluyveromyces marxianus, were Saccharomyces cerevisiae. Additionally, all killer strains were sensitive to some killer reference strains, showing a killer-sensitive phenotype (KS); neither Saccharomyces or non-Saccharomyces wild yeasts were phenotype killer-resistant (KR). The incidence of the killer character varied with respect to fermentation stage and grape variety, increasing throughout fermentation (13-55% to 36-90%). Irrespective of grape must type, the neutral and sensitive yeasts were ever predominant at initial stages of fermentation. All but six neutral strains, identified as Saccharomyces cerevisiae, were Kloeckera apiculata.