Evolution of copper tolerance in Hanseniaspora uvarum under climate-driven selective pressures : analysis of strains isolated over twenty years

Overview & Synopsis

Climate change is reshaping viticultural ecosystems through rising temperatures, altered rainfall patterns and adjustments in plant protection strategies. The ClimHans project investigates the evolution and adaptation of different species of the genus Hanseniaspora in response to these environmental shifts. Among this genus, Hanseniaspora uvarum species plays a dual role in fermented beverages: it is described as a spoilage yeast in winemaking due to acetic acid and ethyl acetate production (Ciani and Picciotti, 1995; Ciani and Maccarelli, 1997), while certain strains are technologically valued (Aponte and Blaiotta, 2016; Testa et al., 2021). Environmental changes may therefore influence diversity of this species as well as tolerance to technological stresses, like the copper widely applied as a vineyard fungicide and present also during the winemaking process (Wand et al., 2023). This work tests the hypothesis that environmental and climatic changes may affect copper stress tolerance within H. uvarum populations. This study evaluated intra-specific variability in copper tolerance within a collection of H. uvarum strains originating from diverse French viticultural regions and spanning several decades. Two complementary experimental approaches were implemented based on the study of Grangeteau et al. (2017). Solid medium assays were conducted using copper concentrations mimicking those encountered on grape berries following phytosanitary treatments. Growth was monitored through colony development on solid plates by colony diameter estimation. In parallel, liquid culture assays were done with different copper concentrations representative of those potentially present in must during vinification. Growth-related fitness parameters were calculated. Finally, tolerance was defined relative to copper-free controls, allowing determination of maximum tolerated concentration. Preliminary results reveal intra-specific heterogeneity in copper sensitivity, suggesting that environmental pressures contribute to functional diversification and may ultimately impact wine quality in future production systems.