Genotype Variations in Water Use Efficiency Correspond with Photosynthetic Traits in Tempranillo Grapevine Clones

Abstract

Mediterranean viticulture is highly dependent on soil water availability. Moreover, global warming is likely to increase average temperatures and the frequency of heat waves, thus leading to greater water scarcity. To cope with this situation, much research focused on the selection of genotypes with higher water use efficiency (WUE). Several previous studies indicated that WUE varies between genotypes of the Tempranillo cultivar with some showing interesting improvement in the leaf WUE. Here, we assessed the associations between the leaf WUE and physiological parameters in six selected Tempranillo clones. The plants were cultivated in pots and two water conditions were applied sequentially: a well-watered period followed by a moderate water stress and recovery phase. Growth parameters and intrinsic WUE were monitored during both periods. Pressure–volume and AN/Ci curves were measured after the plants were re-watered. At the end of the season, biomass accumulation and total irrigation water were used to calculate whole plant WUE (WUEWP). AN/Ci curves revealed significant differences in several photosynthetic parameters, including mesophyll conductance (gm), maximum velocity of carboxylation (Vcmax) and leaf respiration (R). Clones RJ51 and 1048 both exhibited high WUE, but presented distinct physiological traits: RJ51 had the highest gm, while genotype 1048, had the lowest R. This study confirms that physiological traits generally explain the intracultivar diversity in WUE observed in previous studies.

Unraveling the Physiological Mechanisms Underlying the Intracultivar Variability of Water Use Efficiency in Vitis vinifera “Grenache”

“…Notwithstanding, the environment has also been a relevant factor. These results are in agreement with those observed in “Tempranillo”, in which, despite the inter-seasonal variability, consistency in the WUE response of genotypes to water deficit has also been detected across environments [ 17 , 18 , 19 ].…”

“…In fact, Dayer et al [ 14 ] observed that the capacity of genotypes to increase water use under well-watered conditions was strongly associated with hydraulic traits. However, Tortosa et al [ 19 ] did not report differences in leaf hydraulic traits (osmotic potential at turgor loss point, cell wall elasticity, or cell capacitance) that would explain differences in gas exchange parameters (g s and WUE i ) among “Tempranillo” genotypes.…”

“…Other factors that can explain these differences could be the nitrogen content in the leaf, or higher mesophyll conductance [ 39 ]. Variability in mesophyll conductance was indeed associated with grapevine WUE i [ 40 ] and has recently been reported to be an important trait of differentiation within “Tempranillo” genotypes [ 19 ]. Nevertheless, mesophyll conductance in grapevines could not be explained by anatomical variability, suggesting that biochemical mechanisms play an important role in WUE i [ 40 ].…”

“…From a physiological perspective, it is the net photosynthesis (A N ) divided by stomatal conductance (g s ). To date, stomatal regulation and photosynthetic capacity have been shown to play a key role in WUE i improvement among genotypes [ 17 , 18 , 19 , 20 ]. Nevertheless, both physiological mechanisms depend on many physiological traits, such as leaf morphology, osmotic adjustment, ABA dynamics, and aquaporins, among many others, which have been poorly explored in an integrated approach [ 11 , 21 ].…”

“…Therefore, studies under controlled experimental conditions are needed to confirm these results, and especially to elucidate the factors underlying these differences in WUE [ 17 ]. In this sense, Tortosa et al [ 19 ] have recently reported that physiological traits explained the differences in WUE between genotypes within the cultivar “Tempranillo”. Specifically, they linked differences in WUE mainly to mesophyll conductance and respiration rates, but also to maximal carboxylation and maximal electron transport rates.…”