Partial root zone drying exerts different physiological responses on field-grown grapevine (Vitis vinifera cv. Monastrell) in comparison to regulated deficit irrigation

Improving Peach Fruit Quality Traits Using Deficit Irrigation Strategies in Southern Tunisia Arid Area

The peach (Prunus persica L.) is one of Tunisia’s major commercial fruit crops and is considered one of the biggest water consumers of all crops. In warm and arid areas of southern Tunisia, irrigation is necessary to ensure orchard longevity and high yield and fruit quality. Nevertheless, under water-scarcity conditions and low water quality, water management should rely on efficient deficit irrigation strategies. In this study, sustained deficit irrigation (DI) and partial root-zone drying (PRD50) at 50% of crop evapotranspiration (ETc) were evaluated for their impact on the primary and secondary metabolites of the peach fruit of early cultivar Flordastar grown in the Tataouine region. A full irrigation (FI) treatment at 100%, etc., was used as a control treatment. Color, dry-matter content, firmness, organic acids, sugars, phenolic compounds, vitamin C, β-carotene and minerals were assessed on harvested mature fruits. Dry-matter content and firmness increased significantly under DI and PRD50 (13% and 15.5%). DI fruit had the highest soluble-solid content (SSC), reaching Brix values of 14.3°. Fruit sorbitol and sucrose contents were not affected by Di and PRD50. Higher glucose in fruit juice was observed in PRD50 (23%) and DI (21.5%) compared to FI, which had the highest malic acid content (33.5–37%). Quinic and citric acids decreased with DI and PRD50, while almost all individual phenolic compounds increased with deficit irrigation. Hydroxycinnamates and anthocyanins were significantly higher in fruits harvested from DI and PRD50 treatments. Proanthocyanidins (catechin and epicatechin) were only improved by DI, while flavone compounds and vitamin C were not affected by irrigation restrictions. β-carotene was higher in fruits yielded under FI (0.71 mg/100 g DM) than DI and PRD50 (0.21–0.43 mg/100 g DM). Macro- and micronutrients significantly increased in DI and PRD50 fruit. A significant difference between DI and PRD50 fruits was observed for Zn and Fe concentrations. This research highlights the positive impact of reduced irrigation on bioactive-fruit quality attributes and the suitability of PRD50 and DI as tools for irrigation management in arid areas of southern Tunisia, contributing to water-saving in orchards and the improvement of fruit commercial value.

Abscisic Acid Mediates Drought and Salt Stress Responses in Vitis vinifera-A Review

The foreseen increase in evaporative demand and reduction in rainfall occurrence are expected to stress the abiotic constrains of drought and salt concentration in soil. The intensification of abiotic stresses coupled with the progressive depletion in water pools is a major concern especially in viticulture, as most vineyards rely on water provided by rainfall. Because its economical relevance and its use as a model species for the study of abiotic stress effect on perennial plants, a significant amount of literature has focused on Vitis vinifera, assessing the physiological mechanisms occurring under stress. Despite the complexity of the stress-resistance strategy of grapevine, the ensemble of phenomena involved seems to be regulated by the key hormone abscisic acid (ABA). This review aims at summarizing our knowledge on the role of ABA in mediating mechanisms whereby grapevine copes with abiotic stresses and to highlight aspects that deserve more attention in future research.

Response of Clementine Mandarin to Water-Saving Strategies under Water Scarcity Conditions

Water scarcity is the most constraining factor for crop production, especially in arid and semi-arid areas of Mediterranean countries such as Morocco. Within these conditions, different water-saving strategies using deficit irrigation (DI) were tested on two six-years old clementine varieties (‘Sidi Aissa’ and ‘Orogrande’). These DI strategies were applied during the second part of fruit growth and during fruit maturation and included: the control treatment (Cntl), in which the trees received 100% of crop evapotranspiration (ETc) for the entire irrigation season; regulated deficit irrigation (RDI), with an application of 75% of ETc (RDI-1); partial rootzone drying (PRD), with an alternating irrigation between the two root system halves for 3–4 (PRD-3/4) and 7 (PRD-7) days, with an application of 50% crop water requirements; and RDI-2, with an application of 50% of crop water needs during fruit maturation. The results indicate that the trees preferably absorb the water from the upper 0–30 cm-depth soil profile and that fruit drop was increased by PRD for ‘Sidi Aissa’, whereas RDI-1 had no effect on this parameter. The DI strategies had no effect on fruit drop for ‘Orogrande’. The PRD reduced fruit size, yield and fruit juice content, with the effect being more pronounced on ‘Sidi Aissa’. The RDI-1 had no effect on fruit yield for ‘Orogrande’ but reduced it for ‘Sidi Aissa’. RDI-2 had no effect on yield, fruit size or fruit juice content. The DIs tested increased water use efficiency and enhanced fruit maturation as a result of increased juice sugar content and reduced acidity. The PRD tends to increase salt accumulation in the rootzone. Overall, ‘Orogrande’ was less sensitive to water stress and was more water-use efficient, and, under the semi-arid conditions of the experimental zone, PRD should not be used on clementine.

Transcriptomics integrated with metabolomics reveals the effect of regulated deficit irrigation on anthocyanin biosynthesis in Cabernet Sauvignon grape berries

Regulated deficit irrigation (RDI) is a new type of water-saving irrigation technology developed in recent years which was well suited to arid and semi-arid grape plant areas. The anthocyanin synthesis of grapes under RDI was revealed through omics in this study. RDI slightly decreased the hundred-grain weight and increased the soluble solid content, juice pH, reducing sugar content, and total anthocyanin content. Meanwhile, the total acid content decreased before ripening. Transcriptomics and metabolomics analyses revealed that large numbers of differentially expressed genes (DEGs) and significantly changed metabolites (SCMs) were filtered in the RDI groups. RDI1 with 30% ETc upregulated 7 related gene expression levels in the anthocyanin biosynthetic pathway and also increased some metabolites contents. Eventually, the contents of most monomeric anthocyanins in the RDI groups were increased, and the proportion of Mv increased in the ripe grapes of the RDI groups. In all, RDI is a useful water-saving irrigation method which could also increase anthocyanin content in grapes.