How can grapevine genetics contribute to the adaptation to climate change?

摘要

Climate change is modifying the environmental conditions in all the vineyards across the world. The expected effects on grape and wine production can be positive in some grape growing regions, but under warmer or dryer conditions the volume and quality of the wines produced can be impaired. Adaptation to new climatic conditions includes changes in the cultivation areas, changes in the vineyard or cellar practices, and use of new rootstock?×?scion combinations. In this article, we provide an overview of the possible effects of climate change on grapevine physiology and berry quality and we describe the more important traits and the genetic variability that can be used in the adaptation process. We also present the modern techniques that can be used by researchers to identify the links between genomic information and behaviors in the field. Finally, we discuss the existing opportunities in the present grapevine collections and the strategies that can be used by breeders to create new varieties. Introduction?There is no doubt that climatic conditions have changed all around the world during the past decades, and simulations with different scenarios of greenhouse gas emissions (GHG) show that the observed tendencies will continue during the present century (IPCC, 2013). Agricultural production in general is very responsive to environmental conditions, and destabilization of grape and wine production due to climate change can have not only significant direct impacts on farmers' incomes (Moriondo et al., 2011; Webb et al., 2008) and employment in the wine industry, but also indirect impacts on land use, landscapes, tourism activities and rural life in numerous regions.Because CO2 is the elementary molecule at the origin of plant biomass, the expected increase in atmospheric CO2 concentration can have direct effects on the physiology of the plants. However, the most studied effects of this increase are the possible impacts on climatic conditions. The Intergovernmental Panel on Climate Change (IPCC) forecasts an increase of temperatures across the globe (IPCC, 2013) and changes in precipitations, with more contrasts between wet and dry areas and wet and dry seasons, and more extreme precipitation events (IPCC, 2013). The last IPCC report predicts specific regional changes but does not confirm a general tendency of increased drought risks.Adaptation of the grape and wine industry to climatic changes can be envisaged by moving cultivation areas (Malheiro et al., 2010) and by changing the profiles of the wines produced. Here, we will consider that a successful adaptation to climate change will be for a present grape growing area to produce the same type of wine, with the same volumes, in the future.This goal can be achieved by changes in the vineyard or cellar practices (Duchêne et al., 2014b; Keller, 2010) or by local changes in the location of the vineyards using the existing small-scale variability (Bonnefoy et al., 2013). Here, we will focus on how can grapevine genetics help in the adaptation process.Before describing the genetic variability and how it can be used, an overview of the expected effects of climatic changes on grapevine is necessary.Expected effects of climate change1. A shift in developmental stages?The first effect of climate change is an advance of developmental stages, observed worldwide (Duchêne and Schneider, 2005; Jones and Davis, 2000; Petrie and Sadras, 2008; Ramos et al., 2008). The link between grapevine phenology and temperatures is so close that it has been used, on the one hand, to assess temperatures from the past centuries (Chuine et al., 2004) and, on the other hand, to propose models for predicting developmental stages in the future (Duchêne et al., 2010; Fila et al., 2014; Webb et al., 2007). These models forecast an advance of two to three weeks by 2050 when compared to the last 30 years (Duchêne et al., 2010; Moriondo et al., 2011; Webb et al., 2007). With empirical models, Barnuud et al. (2014b) show that the shift in the dates when sugar content reaches 22°Brix will be greater in cool than in warm regions in Australia.As a consequence of earlier véraison dates, berry ripening will occur earlier in summer, under higher temperatures, and this can have a significant impact on berry quality.2. Effects on grape and wine quality?High temperatures accelerate the decrease of grape acidity, mainly because of a faster degradation of malic acid (Buttrose et al., 1971; Kliewer, 1971; Sweetman et al., 2014). The comparison between different grape growing regions (Barnuud et al., 2014b) or vintages (Duchêne et al., 2014a; Neethling et al., 2012) confirms this result. Varieties whose berries contain high quantities of tartaric acid should be less sensitive to climate change (Shiraishi, 1995) because the quantity of tartaric acid per berry is stable during berry ripening (DeBolt et al., 2008).An increase of sugar content in berries or alcohol content in wines during the past decades was frequ