Combining rootstocks and deficit irrigation techniques to maintain vineyard sustainability under semiarid and water limiting conditions

By Pascual Romero

The threat of climate change (CC) will make it necessary to combine different adaptation measures, especially those related to irrigation and water management and availability, in order to maintain the sustainability of vineyards (Iglesias y Garrote et al., 2015) - especially in the semiarid, warm, and more vulnerable winegrowing regions of Southern Europe (such as SE Spain). In a recent study, we combined the use of different rootstocks and deficit irrigation (DI) techniques (RDI and PRI) with a low amount of water (Table 1), to increase WUE and improve vine performance and sustainability, as a long-term adaptation to CC in semiarid and water limiting areas. The results show that the rootstock had a significant impact on the ability to extract water from the soil and, in consequence, on the vine water status, leaf photosynthesis, vigor, productivity, WUE, and berry quality of Monastrell vines (Romero et al., 2018).

Table 1. Deficit irrigation strategy and water volume applied for each irrigation method (PRI and RDI) in each phenological period and the total for every year of the experiment (2012-2016).

Table 2. Berry technological quality index (QI technological berry), berry phenolic quality index (QI phenolic berry), and overall berry quality index (QI overall berry) calculated for Monastrell grapes at harvest, for five different rootstocks (140Ru, 1103P, 41B, 110R, and 161-49C) and two different irrigation methods (PRI and RDI), from 2012 to 2016.

Our study showed, that vines grafted on invigorating rootstocks - such as 1103P or 140Ru, both classified as rootstocks with high or very high drought tolerance, maintained greater water uptake capacity during the growing season and were able to exploit soil water resources more efficiently, increasing the irrigation efficiency under DI. This greater soil water uptake was also reflected in higher leaf nutrient content and vigor, superior accumulation of water and dry matter in plant organs, higher yield and WUE response (especially in 140Ru: yield: > 16,000 kg/ha, WUE: 18 kg grape/m3). But this was offset by poorer final berry quality and color, lower polyphenolic and nutraceutical concentrations in the must, and lower QI scores (Table 2), compared to rootstocks of medium-low vigor due, among other factors, to a greater dilution effect (bigger berry size and greater water content in the pulp and in the whole berry). In addition, vines grafted on either of the invigorating rootstocks had sink-source ratios such as yield/pruning weight and leaf area/yield, that were well outside the optimal agronomic ranges proposed for improving polyphenolic berry quality in DI Monastrell grapevines (Romero et al., 2016), suggesting that these vines were unbalanced. Besides, these vines had more closed canopies (higher proportion of shaded and internal leaves within the canopy) and decreased PAR in the cluster zone, which can also negatively affect berry quality.

Interestingly, the results revealed that Monastrell vines grafted on the least productive and least vigorous rootstocks - 161-49C, followed by 110R showed a significant improvement in long-term vine performance and berry quality under DI. Low yield/vigor rootstocks (especially 161-49C) stimulated the accumulation of polyphenolics (stilbenes, anthocyanins) and amino acids and some improvements in technological parameters (higher tartaric/malic ratio and TSS, lower pH), giving the highest berry QI scores (Table 2). Besides, they showed several other positive features, which may also have contributed to higher berry quality: lower berry weight, lower cluster compactness, lower % of big clusters, higher % of small clusters and a higher degree of homogeneity in the clusters. These vines were also better balanced, with significantly lower yield/pruning weight ratios, a higher leaf area/yield ratio, a high exposed leaf area/total leaf area ratio (more open canopies and exposed clusters), and had a greater water stress level during ripening (around -1.3 MPa, Figure 1) as maintained in vines grafted on 161-49C, close to or within the optimum physiological and agronomic thresholds and ranges proposed for Monastrell grapevines (Romero et al., 2010). All these features improved Monastrell berry quality (phenolic and technological) and nutraceutical potential.

Figure 1. Seasonal evolution of midday stem water potential, Ψs in 2012, 2013, and 2015 for each rootstock. The green dashed lines indicate the optimum range of Ψs (-1.25/-1.35 MPa, moderate water stress) that improves Monastrell berry quality. The red dashed line represents the dangerous threshold of Ψs and severe water stress.

Our results also show that, berry quality parameters and nutraceutical potential were significantly improved by the PRI method, relative to RDI. Depending on the specific rootstock-scion interaction, PRI can also be beneficial for Monastrell yield or berry quality, even with low irrigation water volumes, decreased θv availability in the wet root zone and lower root water uptake compared to RDI. Thus, compared to RDI, the application of PRI with low water volumes improved substantially Monastrell yield response (110R) and berry quality (polyphenols, amino acids) and nutraceutical potential - especially for low vigor rootstocks (161-49C, 110R) and two invigorating rootstocks (140Ru, 1103P). Our results also reflected intrinsic changes in vine physiology and berry metabolism caused specifically by PRI and altered endogenous hormonal status of the berries (e.g. abscisic acid, ABA).

The effects of PRI differed clearly between the two low vigor rootstocks, 110R and 161-49C. Thus, PRI vines grafted on 110R showed enhanced pruning weight, yield (+ 1400 kg ha-1), total amino acids, and resveratrol and a similar QI score compared to RDI vines grafted on 110R. In contrast, 161-49C vines under PRI maintained similar vigor and lower berry weight, yield (-1700 kg ha-1), and WUEyield, compared to RDI vines, but had the highest QItecnological berry, QIphenolic berry, and QIoverall berry scores and nutraceutical potential of all the combinations (Table 2). This rootstock-scion-irrigation method combination, under DI with low water volumes, would give low yields of berries of highest quality and nutraceutical potential for the production of premium red wine with a high added value.

 

Figure 2. Application of conventional regulated deficit irrigation (RDI) and partial root zone drying irrigation (PRI) techniques in field–grown Monastrell grapevines grafted onto different rootstocks in SE Spain.

In conclusion, the application of low irrigation volumes (85-90 mm year-1), in combination with low fertilizer inputs, low vigor rootstocks (161-49C and 110R), and well-designed DI strategies (PRI and RDI, Table 1) it could be an adaptation to CC in order to guarantee the sustainability of the Monastrell vineyards under semiarid conditions of SE Spain. Besides, for the invigorating, drought tolerant rootstocks (especially 140Ru), our results show that irrigation could be reduced even more under optimized DI strategies in order to control the excess vigor and yield.

 

Pascual Romero

Grupo de Riego y Fisiología del Estrés. Departamento de Bioeconomía, agua y medio ambiente. Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), c/ Mayor s/n, 30150, La Alberca, Murcia, Spain.

Pascual Romero
Telephone: +34 968 366739
Fax: +34 968 366792
e-mail: pascual.romero@carm.es

Biologist, PhD. Agrarian researcher at the Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), Ministry of Water and Agriculture, Region of Murcia, Spain. Main head of several national search projects focused in topics related to the physiology of water stress, plant-soil water relations, water use efficiency and the application of different deficit irrigation techniques and new irrigation technologies in different species such as: almond, peach, citrus and vine.

 

References:

Iglesias, A., Garrote, L. 2015. Adaptation strategies for agricultural water management under climate change in Europe. Agr. Water Manag. 155, 113-124.
Romero, P., Fernández-Fernández, JI, Martínez-Cutillas, A. 2010. Physiological thresholds for efficient regulated deficit irrigation management in winegrapes grown under semiarid conditions. Am. J. Enol. Vitic. 61 (3), 300-310.
Romero, P., Fernández-Fernández, J.I., Gil-Muñoz, R., Botía, P. 2016. Vigour-yield-quality relationships in long-term deficit-irrigated wine grapes grown under semiarid conditions. Theor. Exp. Plant Physiol. 28, 23-51.
Romero, P., Botía, P., Navarro, J.M. 2018. Selecting rootstocks to improve vine performance and vineyard sustainability in deficit irrigated Monastrell grapevines under semiarid conditions. Agr. Water Manag. 209, 73-93.