Moderate Water Stress Impact on Yield Components of Greenhouse Tomatoes in Relation to Plant Water Status.

The scarcity of water resources affects tomato production. Deficit irrigation may optimize water management with only a low reduction in yield. Deficit irrigation scheduling based on applied water presented no clear conclusions. Water stress management based on plant water status, such as water potential, could improve the scheduling. The aim of this work was to evaluate the physiological and yield responses of different tomato cultivars to deficit irrigation. Three experiments were carried out in 2020 and 2022 at the University of Seville (Spain). "Cherry" and "chocolate Marmande" cultivars with an indeterminate growth pattern were grown in a greenhouse. Treatments were: Control (full irrigated) and Deficit. Deficit plants were irrigated based on water potential measurements. Moderate water stress did not significantly reduce the yield, although it affected other processes. Fruit size and total soluble solids were the most sensitive parameters to water stress. The latter increased only when persistent water stress was applied. However, truss development and fruit number were not affected by the level of water stress imposed. Such results suggest that moderate water stress, even in sensitive phenological stages such as flowering, would not reduce yield. Deficit irrigation scheduling based on plant water status will allow accurate management of water stress.

Endocarp Development Study in Full Irrigated Olive Orchards and Impact on Fruit Features at Harvest.

Endocarp development in olive trees includes three periods: growth (Period I), massive sclerification (Period II) and maximum hardening (Period III). The two first are strongly related to yield and irrigation management. Period I was reported to coincide with mesocarp cell division and thus with final fruit size. Period II was considered to be the most drought-resistant phenological stage. However, little is known in olive trees about the length of these periods and their capacity for predicting fruit size at harvest. The aim of this work was to evaluate the length of both periods in different cultivars and different location of full irrigated orchards. We also aimed to study the fruit feature impact on harvest at the end of Period I. Data from full irrigated olive orchards of cv Cornicabra, Arbequina and Manzanilla in two different locations (Ciudad Real, Central Spain, and Seville, South Spain) were used. The pattern of pit-breaking pressure throughout the season was measured with fruit samples for several years (2006 to 2022). These data and climatic data were used to compare different estimation methods for the length of Period I and II of endocarp development. Then, fruit volume and dry weight at the end of Period I were used to estimate fruit features at harvest. Results suggest that the Period I length was less temperature- and cultivar-dependent than expected. The duration of this period was almost constant at around 49 days after full bloom. Thermal time was negatively correlated with fruit size at the end of Period I. On the contrary, a lineal thermal model presented the lowest variability when estimating the Period II length, which was also affected by the cultivar. The best fit between fruit dry weight and volume at Period I vs. harvest was unique for oil cultivars (Cornicabra and Arbequina), while cv Manzanilla presented a different relationship. A temperature increase in the future would not affect the Period I length but would reduce the fruit size at the end of this period and at harvest.

Establishing a Reference Baseline for Midday Stem Water Potential in Olive and Its Use for Plant-Based Irrigation Management.

Midday stem water potential (SWP) is rapidly becoming adopted as a standard tool for plant-based irrigation management in many woody perennial crops. A reference or "baseline" SWP has been used in some crops (almond, prune, grape, and walnut) to account for the climatic influence of air vapor pressure deficit (VPD) on SWP under non-limiting soil moisture conditions. The baseline can be determined empirically for field trees maintained under such non-limiting conditions, but such conditions are difficult to achieve for an entire season. We present the results of an alternative survey-based approach, using a large set of SWP and VPD data collected over multiple years, from irrigation experiments in olive orchards located in multiple countries [Spain, United States (California), Italy, and Argentina]. The relation of SWP to midday VPD across the entire data set was consistent with an upper limit SWP which declined with VPD, with the upper limit being similar to that found in Prunus. A best fit linear regression estimate for this upper limit (baseline) was found by selecting the maximum R 2 and minimum probability for various upper fractions of the SWP/VPD relation. In addition to being surprisingly similar to the Prunus baseline, the olive baseline was also similar (within 0.1 MPa) to a recently published mechanistic olive soil-plant-atmosphere-continuum (SPAC) model for "super high density" orchard systems. Despite similarities in the baseline, the overall physiological range of SWP exhibited by olive extends to about -8 MPa, compared to about -4 MPa for economically producing almond. This may indicate that, despite species differences in physiological responses to low water availability (drought), there may be convergent adaptations/acclimations across species to high levels of water availability. Similar to its use in other crops, the olive baseline will enable more accurate and reproducible plant-based irrigation management for both full and deficit irrigation practices, and we present tentative SWP guidelines for this purpose.

Correlation between water stress and phenolic compounds of hydroSOStainable almonds.

BACKGROUND: Water scarcity is currently affecting many areas of the world, reaching worrying levels in drought areas such as southern Spain. To cope with this issue, researchers in the agricultural sector have implemented deficit irrigation strategies intended to reduce water consumption by increasing fruit quality. Almond is among the most popular tree nuts worldwide and also the most nut cultivated in Spain. Almond consumption, together with other nuts, has been widely associated with improvements in cardiovascular health, metabolic syndrome and diabetes owing to their bioactive compounds such as polyphenols. Water deficit strategies generate hydroSOStainable almonds, raised under water stress conditions, with high content of bioactive compounds. The aim of this work was to study the relationship between water stress, color and polyphenols in hydroSOStainable almonds. For this, instrumental color, total phenolic content and phenolic compounds were measured and correlated using Pearson's correlation. RESULTS: The results showed a strong relationship between water stress, color and polyphenols of almonds, showing that increasing water stress in plants up to ~100 MPa × day values of stress integral increase the polyphenols in almonds, leading to a reddish color. CONCLUSION: Finally, this research demonstrated that implementing water-saving strategies help to improve the phenolic content and color of hydroSOStainable almonds and also that isorhamnetin-3-O-rutinoside, isorhamnetin-3-O-glucoside and kaempferol-3-O-glucoside could be important markers of hydroSOStainable almonds (cv. Vairo). Besides, hydroSOStainable almonds could be an important source of phenols, providing 25% of the estimated total polyphenolic daily intake. © 2020 Society of Chemical Industry.

How does water stress affect the low molecular weight phenolics of hydroSOStainable almonds?

Water scarcity is a threat for food production because, water, is more and more limited and force farmers to use new deficit irrigation (DI) strategies without affecting fruit yield and quality. No information exists on almond polyphenols and proanthocyanidins (PAs) produced under DI. The present work studied the effect of 2 regulated DI (RDI) and one sustained (SDI) on the low molecular weight phenolics together with the antioxidant activity (AA) in almonds. Fifteen phenolic compounds were identified (13 flavonoids and 2 non-flavonoids) and 10 PAs. Kaempferol-3-O-galactoside was the predominant compound in almond skin and whole kernel but it was not found in deskinned kernels. The use of moderate RDI significantly increased the total phenolic content in skin (∼9.8%), PAs, and the AA. Consequently, after one season the application of DI positively affected the almond cv. Vairo phenols, however, several seasons must be evaluated in order to corroborate the present results.

Optimization of roasting conditions in hydroSOStainable almonds using volatile and descriptive sensory profiles and consumer acceptance.

HydroSOStainable almonds are harvested from trees cultivated under controlled water stress by using a regulated deficit irrigation (RDI) strategy. The aim of this study was to investigate consumers' perception to select the best roasting temperature for the hydroSOStainable almonds and its correlation with volatile compounds, descriptive sensory attributes, instrumental color, and texture. Thirty-five volatile compounds were identified and the key compounds for the roasting process were 2,5-dimethylpyrazine, furfural, and trimethyl pyrazine. Pyrazines, furans and, in general, volatiles were higher in hydroSOStainable almonds than in control. Instrumental color and trained panel showed that almonds roasted at 190 °C presented intense color and burnt notes in both irrigation treatments, while almonds roasted at 150 °C were under-roasted. Principal component analysis (PCA) grouped together the samples of the same irrigation treatment, but separated samples roasted at different temperatures. Partial least square regression (PLS) results indicated that consumers overall liking was positively linked to specific volatiles (alkanes, alcohols, aldehydes, and furans) and sensory attributes (sweetness, roasted, almond ID, nutty, hardness, and crispiness), but, negatively correlated with pyrazines, bitterness, astringency, woody, and burnt flavor notes. Penalty analysis showed that almonds roasted at 150 and 190 °C were penalized due to low roasted aroma and soft almonds, and over-roasted samples with too intense color and burn notes, respectively. While no penalization being found for almonds roasted at 170 °C. Overall, roasting at 170 °C for 10 min in a convective oven were the optimum conditions for roasting Vairo almonds. PRACTICAL APPLICATION: This research describes the link between physicochemical and sensory analysis of roasted almonds giving evidence about possible sensory quality markers. Besides, it provides valuable information for the food industry to produce roasted almonds that meet consumer demands and for the agricultural sector by encouraging reduction of irrigation water consumption by almond trees.

Nutrition Quality Parameters of Almonds as Affected by Deficit Irrigation Strategies.

The influence of full irrigation, double-regulated (RDI) and sustained deficit irrigation (SDI) treatments on almond quality was assessed by analyzing different parameters: sugars, organic acids, antioxidant activity, total phenolic content (TPC), and volatile compounds. Almond quality studies for plants submitted to water stress are scarce, and it is essential to understand the biochemical responses of plants to water stress in maintaining fruit yield and quality. Citric acid, sucrose, antioxidant activity, and TPC were not affected by the application of studied deficit irrigation strategies (DI). An increase in malic acid and a decrease in glucose was observed for stressed samples (T3 and T4), while a higher number of total volatiles compounds was found for moderate RDI (T2). Using deficit irrigation strategies, the almond yield and quality was not changed, and in fact, some parameters, such as glucose and key volatile compounds, slightly increased under moderate RDI. This finding might encourage farmers to implement these strategies and contribute to sustainable agriculture.

Quality Attributes and Fatty Acid, Volatile and Sensory Profiles of "Arbequina" hydroSOStainable Olive Oil.

The use of deficit irrigation techniques on olive orchards is the main trend aiming to optimize water savings while improving functional and sensory characteristics of oils from trees under deficit irrigation techniques. The brand hydroSOStainable has been defined for crops produced under water restriction conditions. HydroSOStainable olive oils obtained under two new regulated deficit irrigation and one sustained deficit irrigation treatments in "Arbequina" olive trees were evaluated by analyzing quality parameters, antioxidant activity, total phenol content, fatty acid profile, volatile compounds, and sensory descriptors. Results showed that some of these irrigation strategies improved the phenol content at "moderate" stress levels, slightly enriched the fatty acid profile (~3.5% increased oleic acid and simultaneously decreased saturated fatty acids), and increased some key volatile compounds and also several key sensory attributes. Therefore, hydroSOStainable olive oil may be more attractive to consumers as it is environmentally friendly, has a higher content of several bioactive compounds, and has improved sensory characteristics as compared to control (fully irrigated) oils.

Effect of Spanish-style processing on the quality attributes of HydroSOStainable green olives.

BACKGROUND: Three treatments of regulated deficit irrigation (RDI) were assayed on olive trees for table olive production. RDI provides hydroSOStainable crops. The effect of RDI treatments on the quality of raw and table olives was determined based on their: weight, pit weight, fruit/pit ratio, size, texture, colour, mineral content, antioxidant activity, total phenol content and organic acid and sugar profile. RESULTS: HydroSOStainable olives showed the most attractive shape and colour: highest fruit weight, roundest fruit, hardest texture and a lightest and greenest colour than control olives. Minerals, antioxidants, phenols and organic acids and sugars of hydroSOStainable olives were similar to control olives. After processing to table olives, calcium, potassium, antioxidants and phenols contents decreased, whereas sugars and organic acids profiles changed in both types of olives. CONCLUSIONS: HydroSOStainable table olives offer environmental and quality advantages over control olives given the reduced use of fresh water and favourable morphological traits, which are more attractive for consumers. © 2018 Society of Chemical Industry.

Effect of preharvest fruit bagging on fruit quality characteristics and incidence of fruit physiopathies in fully irrigated and water stressed pomegranate trees.

BACKGROUND: This report studied the response of pomegranate fruit under full irrigation (FI) and water stress conditions to bagging with externally glossy, single-layer, cellulosic paper bags, open at the bottom, from the end of fruit thinning to harvest time. RESULTS: Bagging decreased fruit size and the maturity index, and increased antioxidant activity in FI conditions. Moreover, fruit bagging substantially reduced the incidence of peel sunburn in both irrigation conditions. CONCLUSION: The delay in fruit growth and ripening as a result of pomegranate fruit bagging is outweighed by the very important commercial benefit in terms of the reduced incidence of peel sunburn and the increase in fruit antioxidant activity. © 2018 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Study of commercial quality parameters, sugars, phenolics, carotenoids and plastids in different tomato varieties.

The aim of this study was to assess commercial quality parameters, sugars, phenolics, carotenoids and plastid in diverse and little studied tomato varieties to gain insight into their commercial and functional quality and reveal possible noticeable differences. Five cherry tomato varieties and six common (i.e., non-cherry) tomatoes were evaluated. The highest levels of lycopene were detected in 'Tigerella' and 'Byelsa', and those of phytoene in 'Orange', those of phenolics in 'Green Zebra', all of them common tomatoes. The levels of sugars in both groups of tomatoes were comparable. Interesting differences in plastid carotenoid-accumulating sub-structures as a function of the carotenoid profile were observed. Given the importance of chromoplasts in the deposition of carotenoids in plants and their release during digestion, this information can be valuable in investigations on the regulation of the biosynthesis and the bioavailability of tomato carotenoids.

Antioxidants (carotenoids and phenolics) profile of cherry tomatoes as influenced by deficit irrigation, ripening and cluster.

The purpose of this study was to assess the relationship between the effect of regulated deficit irrigation, cluster, developmental stages and two seasons (autumn 2015 and spring 2016) on the commercial and functional quality (carotenoids and plenolics levels) in 'Lazarino' and 'Summerbrix' tomatoes. Autumn had a positive effect on the commercial quality, with larger fruits (22% in 'Summerbrix'; 26% in 'Lazarino') and higher soluble solids (16% in 'Summerbrix'; 12% in 'Lazarino'). Total carotenoids did not change significantly with irrigation and variety while total phenolics did with the cluster and season. In most cases, the main amounts of carotenoids and phenolic were found in the higher cluster and carotenoids in ripe fruit. Thus, irrigation of such varieties could be reduced drastically (ca. 80%) without affecting considerably the overall quality of their fruits (changes not greater than 30%).

Effect of the fruit position on the cluster on fruit quality, carotenoids, phenolics and sugars in cherry tomatoes (Solanum lycopersicum L.).

Cherry tomato varieties are widely consumed in many countries. They contain nutrients and health-promoting compounds like phenolics and carotenoids. The main purpose of this study was to determine how the fruit position on the cluster affected quality parameters of diverse nature (weight, soluble solids, firmness, colour, carotenoids, phenolic compounds and sugars). For this purpose the fourth cluster of two cherry varieties (Summerbrix and Lazarino) were studied. The results indicated that the fruit position on the cluster decreased the fruit size between 14 and 16% and weight 40%; firmness in 'Lazarino' increased 56%; C*ab increased 12% in 'Lazarino' and decreased 13% in 'Summerbrix'; hab increased 9% in 'Summerbrix'. Total carotenoid levels were not statistically different in two positions, and in the other position the contents were higher, with a difference of 36% between these two values. The highest total phenolic levels were observed in the PII position. However, total sugars increased 36%, fructose 36% and glucose 35% from the PI to PIII position in 'Lazarino', while, in 'Summerbrix' higher values were observed in the PIII position.

Effect of regulated deficit irrigation on quality parameters, carotenoids and phenolics of diverse tomato varieties (Solanum lycopersicum L.).

This study aims to evaluate the effects of regulated deficit irrigation (RDI) and of cluster position (CI: first and second cluster; CII: third and fourth cluster; CIII: fifth and sixth cluster) on fruit quality parameters, carotenoids and phenolics in tomatoes. Three common ('Tigerella', 'Palamós' and 'Byelsa') and two cherry varieties ('Lazarino' and 'Summerbrix') were studied. The results showed that the regulated deficit irrigation with reduction of 40 and 50% in the leaf water potential in common and cherry tomatoes did not affect greatly the organoleptic quality of common tomatoes and 'Summerbrix', while cherry varieties were significantly affected with the cluster position. In most case, significant changes in the levels of carotenoids were observed depending on the treatment and the cluster position in all varieties. Significant changes with the treatment and no change with the cluster position were observed in phenolic compounds. Thus, in general, increased total carotenoid levels and reduced the content of phenolic compounds were observed. Considering the significance of changes in the levels of these groups of compounds it was concluded that 'Lazarino' was more susceptible to water deficit, whereas 'Summerbrix' and 'Palamós' were more resistant. On the other hand, the organoleptic and functional quality changed with the variety.

Antioxidant capacity, fatty acids profile, and descriptive sensory analysis of table olives as affected by deficit irrigation.

BACKGROUND: The influence of three irrigation treatments (T0, no stress; T1, soft stress; and, T2, moderate stress) on the key functional properties [fatty acids, sugar alcohols, organic acids, minerals, total polyphenols content (TPC), and antioxidant activity (AA)], sensory quality, and consumers' acceptance of table olives, cv. 'Manzanilla', was evaluated. RESULTS: A soft water stress, T1, led to table olives with the highest oil and dry matter contents, with the highest intensities of key sensory attributes and slightly, although not significant, higher values of consumer satisfaction degree. Besides, RDI in general (T1 and T2) slightly increased green colour, the content of linoleic acid, but decreased the content of phytic acid and some minerals. CONCLUSION: The soft RDI conditions are a good option for the cultivation of olive trees because they are environmentally friendly and simultaneously maintain or even improve the functionality, sensory quality, and consumer acceptance of table olives. © 2016 Society of Chemical Industry.