Looking for a more efficient genotypes in water use. A key for a sustainable viticulture

Aim: Grapevine has traditionally been widely cultivated in drylands. However, in recent decades, a significant part of the viticulture all over the word and specifically in Mediterranean basin, is being irrigated. In recent years, due to climate change, among other reasons, the available natural water resources have been reduced substantially compromising the sustainability of viticulture, especially in the most arid areas. Therefore, it is necessary to search for genotypes with greater water use efficiency (WUE not only among varieties but also, between clones of the same variety). 

Methods and Results: In this work, 23 clones of cv. Tempranillo were evaluated during five consecutive years in two experiments. First, a three-year field experiment determining the variability in WUE by measuring gas exchange parameters. Second, a two-year experiment in pots, analyzing the response of those Tempranillo clones to different degrees of soil water availability. Different growth parameters, leaf gas exchange rates, and biomass production were measured. Field data of leaf exchange rates and derived parameters showed a wide variability among clones in WUE up to 80% to that previously achieved comparing different cultivars.  These differences appear to be due to differences in photosynthesis capacity rather than to a more efficient control of water loss. Pot experiments reveal differences among clones in biomass production and gas exchange parameters as indicators of plant water use efficiency. A joint analysis of pot and field data showed a consistency in higher and lower WUE genotypes, although significant environmental condition effects were present. 

Conclusions: 

The whole analysis of WUE indicators quantified the degree of variability in WUE among clones, and identified the best and worst water use efficient clones in both well-watered and water deficit conditions.

Significance and Impact of the Study: These findings open new ways for future research focused on the physiological basis of the variations in WUE, and can also be extended to other reputed drought-tolerant cultivars.