# A Smart and Sustainable Future for Viticulture Is Rooted in Soil: How to Face Cu Toxicity
### Current Situation in Vineyards (Including Toxicity in Plants and Effects)  
Several studies have reported an accumulation of metals in agricultural soils due to common agricultural practices, such as manure fertilization and spraying for pest control [33, 34, 35]. For instance, Cu in apple orchards can have an average annual total increase ranging from 2.5 to 9 mg kg\({}^{-1}\) year\({}^{-1}\) deriving from the application of Cu-containing agrochemicals [36]. The accumulation of Cu through time can be influenced not only by the age, but also by other factors, such as soil organic matter content and pH [33]. As shown in Figure 1, vineyard soils are prone to Cu accumulation, since the practice of spraying Cu salts as fungicides dates back at least as far as 1761 [37]. After the introduction in 1885 of the mixture of Cu sulfate and lime, called \"Bordeaux mixture\" [38], its use became generalized on wine-producing farms. Because of this, the concentration of Cu in vineyards can be many times higher than the background values of forest soils in the same region, reaching up to 3000 mg kg\({}^{-1}\)[39, 40]. Next, high Cu concentration differences can also be found inter-row and intra-row within the same vineyard [41]. Although much research is currently taking place to find alternatives to Cu, this element is still crucial to fighting fungal diseases in vines, especially in organic farming, limiting the supply of pure Cu to 28 kg ha\({}^{-1}\) over a period of 7 years [43; 44; 45]. For these reasons, the global trends of vine-cultivated areas and the use of Cu should be monitored, particularly in newly planted vineyards. Indeed, the shallow root system of newly planted vine plants might be more affected by high Cu levels than older plants, since Cu mainly accumulates in the upper soil layers (where the concentration of organic matter is higher). In fact, the first effects of Cu phytotoxicity are evident at the root level, with a clear decrease of root elongation, abnormal root branching, thickening and dark coloration [46]. As a consequence of this altered root development, the roots' ability to take up water and other nutrients is clearly impaired [32; 47]. In this regard, it is worth mention the negative effect of Cu toxicity on P acquisition by roots [48; 49], highlighting the interactions occurring between the different nutrient acquisition mechanisms. Critical Cu concentrations in roots range from 100 to 400 mg kg\({}^{-1}\) dry weight [10; 46]. Like other heavy metals, an excess of Cu may also cause the generation of toxic reactive oxygen species (ROS), which, in turn, can damage several important biomolecules like DNA, proteins and lipids [50]. Usually,  
Figure 1: Cu concentration distribution (**a**) compared to the distribution of vineyards (**b**) in Europe [42]. Several high Cu concentration areas perfectly match viticulture areas. plants exhibit an excellent translocation barrier of excessive Cu between roots and shoots. This limits the risk of Cu accumulation in edible plant tissues that exceeds toxic levels to livestock and humans. However, toxic concentration levels, as well as symptoms of Cu toxicity, have also been well described for the aerial part of plants [30, 31, 32]. Typical cases of Cu toxicity at the root and shoot levels of vine plants (_Vitis vinifera_ L., _cv Gera_) are presented in Figure 2.  
Considering the soil surface dedicated to viticulture, in 2019, worldwide vine cultivation covered 7.4 million hectares [51], and it has been considered stable in recent years, with a global balance given by heterogeneous evolution in different regions of the world [52]. In Europe (Figure 1), the vine-cultivated area is stable, being balanced between the European Union \"grubbing up\" program (i.e., the replacement of vine plants with other agricultural crops, [53]) on the one hand, and the possibility of Member States authorizing the planting of up to 1% of the vineyard surface already planted each year [54], on the other hand.