The Effects of Saline Water Drip Irrigation on Tomato Yield, Quality, and Blossom-End Rot Incidence --- A 3a Case Study in the South of China

A Targeted and an Untargeted Metabolomics Approach to Study the Phytochemicals of Tomato Cultivars Grown Under Different Salinity Conditions

In this study, we evaluated the effect of increasing the salinity of irrigation water on the metabolic content and profiles of two tomato cultivars ('Jaune Flamme' (JF) and 'Red Pear' (RP)) using targeted and untargeted metabolomics approaches. Irrigation of tomato plants was performed with four different salt concentrations provided by chloride (treatment 1) and sulfate (treatment 2) salts. Targeted analysis of the methanolic extract resulted in the identification of nine major polyphenols. Among them, chlorogenic acid, rutin, and naringenin were the prominent compounds in both cultivars. In addition, the quantification of 18 free amino acids from both tomato cultivars showed that different salinity treatments significantly enhanced the levels of glutamine, glutamic acid, and γ-aminobutyric acid (GABA). Using the untargeted metabolomic approach, we identified 129 putative metabolites encompassing a diverse array of phytochemicals including polyphenols, organic acids, lipids, sugars, and amino acids. Principal component analysis (PCA) of mass spectral data acquired under positive and negative ionization modes showed a clear separation between the two cultivars. However, only positive ionization showed separation among different salinity treatments. Unsupervised and supervised learning algorithms were applied to mine the generated data and to pinpoint metabolites different from the two cultivars. These findings suggest that different salinity conditions significantly influenced the accumulation of phytochemicals in tomato cultivars. This study will help tomato breeding programs to develop value-added tomato cultivars under varying environmental conditions.

Smart high-yield tomato cultivation: precision irrigation system using the Internet of Things

The Internet of Things (IOT)-based smart farming promises ultrafast speeds and near real-time response. Precision farming enabled by the Internet of Things has the potential to boost efficiency and output while reducing water use. Therefore, IoT devices can aid farmers in keeping track crop health and development while also automating a variety of tasks (such as moisture level prediction, irrigation system, crop development, and nutrient levels). The IoT-based autonomous irrigation technique makes exact use of farmers' time, money, and power. High crop yields can be achieved through consistent monitoring and sensing of crops utilizing a variety of IoT sensors to inform farmers of optimal harvest times. In this paper, a smart framework for growing tomatoes is developed, with influence from IoT devices or modules. With the help of IoT modules, we can forecast soil moisture levels and fine-tune the watering schedule. To further aid farmers, a smartphone app is currently in development that will provide them with crucial data on the health of their tomato crops. Large-scale experiments validate the proposed model's ability to intelligently monitor the irrigation system, which contributes to higher tomato yields.

Role of Polyamines in the Response to Salt Stress of Tomato

Plants irrigated with saline solutions undergo osmotic and oxidative stresses, which affect their growth, photosynthetic activity and yield. Therefore, the use of saline water for irrigation, in addition to the increasing soil salinity, is one of the major threats to crop productivity worldwide. Plant tolerance to stressful conditions can be improved using different strategies, i.e., seed priming and acclimation, which elicit morphological and biochemical responses to overcome stress. In this work, we evaluated the combined effect of priming and acclimation on salt stress response of a tomato cultivar (Solanum lycopersicum L.), very sensitive to salinity. Chemical priming of seeds was performed by treating seeds with polyamines (PAs): 2.5 mM putrescine (PUT), 2.5 mM spermine (SPM) and 2.5 mM spermidine (SPD). Germinated seeds of primed and non-primed (controls) were sown in non-saline soil. The acclimation consisted of irrigating the seedlings for 2 weeks with tap water, followed by irrigation with saline and non-saline water for 4 weeks. At the end of the growth period, morphological, physiological and biochemical parameters were determined. The positive effects of combined treatments were evident, when primed plants were compared to non-primed, grown under the same conditions. Priming with PAs improved tolerance to salt stress, reduced the negative effects of salinity on growth, improved membrane integrity, and increased photosynthetic pigments, proline and enzymatic and non-enzymatic antioxidant responses in all salt-exposed plants. These results may open new perspectives and strategies to increase tolerance to salt stress in sensitive species, such as tomato.

Tomato responses to salinity stress: From morphological traits to genetic changes

Tomato is an essential annual crop providing human food worldwide. It is estimated that by the year 2050 more than 50% of the arable land will become saline and, in this respect, in recent years, researchers have focused their attention on studying how tomato plants behave under various saline conditions. Plenty of research papers are available regarding the effects of salinity on tomato plant growth and development, that provide information on the behavior of different cultivars under various salt concentrations, or experimental protocols analyzing various parameters. This review gives a synthetic insight of the recent scientific advances relevant into the effects of salinity on the morphological, physiological, biochemical, yield, fruit quality parameters, and on gene expression of tomato plants. Notably, the works that assessed the salinity effects on tomatoes were firstly identified in Scopus, PubMed, and Web of Science databases, followed by their sifter according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and with an emphasis on their results. The assessment of the selected studies pointed out that salinity is one of the factors significantly affecting tomato growth in all stages of plant development. Therefore, more research to find solutions to increase the tolerance of tomato plants to salinity stress is needed. Furthermore, the findings reported in this review are helpful to select, and apply appropriate cropping practices to sustain tomato market demand in a scenario of increasing salinity in arable lands due to soil water deficit, use of low-quality water in farming and intensive agronomic practices.

Tomato (Solanum lycopersicum) WRKY23 enhances salt and osmotic stress tolerance by modulating the ethylene and auxin pathways in transgenic Arabidopsis

Osmotic stress is one of the biggest problems in agriculture, which adversely affects crop productivity. Plants adopt several strategies to overcome osmotic stresses that include transcriptional reprogramming and activation of stress responses mediated by different transcription factors and phytohormones. We have identified a WRKY transcription factor from tomato, SlWRKY23, which is induced by mannitol and NaCl treatment. Over-expression of SlWRKY23 in transgenic Arabidopsis enhances osmotic stress tolerance to mannitol and NaCl and affects root growth and lateral root number. Transgenic Arabidopsis over-expressing SlWRKY23 showed reduced electrolyte leakage and higher relative water content than Col-0 plants upon mannitol and NaCl treatment. These lines also showed better membrane integrity with lower MDA content and higher proline content than Col-0. Responses to mannitol were governed by auxin as treatment with TIBA (auxin transport inhibitor) negatively affected the osmotic tolerance in transgenic lines by inhibiting lateral root growth. Similarly, responses to NaCl were controlled by ethylene as treatment with AgNO₃ (ethylene perception inhibitor) inhibited the stress response to NaCl by suppressing primary and lateral root growth. The study shows that SlWRKY23, a osmotic stress inducible gene in tomato, imparts tolerance to mannitol and NaCl stress through interaction of the auxin and ethylene pathways.

Physiological mechanism of exogenous brassinolide alleviating salt stress injury in rice seedlings

Brassinolide (BR) is a sterol compound, which can regulate plant seed germination, flowering, senescence, tropism, photosynthesis, stress resistance, and is closely related to other signaling molecules. This study aimed to evaluate the ability of soaking with BR to regulate growth quality at rice seedling stage under salt stress. Results demonstrated that salt stress increases the contents of ROS, MDA, Na⁺ and ABA, reduces the the SPAD value, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum fluorescence (Fm), variable fluorescence (Fv), the effective photochemical efficiency of PSII (Fv/Fo) and the maximum photochemical efficiency of PSII (Fv/Fm), reduces the biomass production and inhabits plant growth. All of these responses were effectively alleviated by BR soaking treatment. Soaking with BR could increase the activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and the contents of ascorbic acid, glutathione as well as soluble protein and proline, while BR soaking treatment inhibited the accumulation of ROS and reduced the content of MDA. BR soaking significantly reduced the contents of Na⁺ and increased the contents of K⁺ and Ca²⁺, indicating that soaking with BR is beneficial to the excretion of Na⁺, the absorption of K⁺ and Ca²⁺ and the maintenance of ion balance in rice seedlings under salt stress. BR also maintained endogenous hormone balance by increasing the contents of indoleacetic acid (IAA), zeatin (ZT), salicylic acid (SA), and decreasing the ABA content. Soaking with BR significantly increased the SPAD value, Pn and Tr and enhanced the Fm, Fv/Fm and Fv/Fo of rice seedlings under NaCl stress, protected the photosythetic system of plants, and improved their biomass. It is suggested that BR was beneficial to protect membrane lipid peroxidation, the modulation of antioxidant defense systems, ion balance and endogenous hormonal balance with imposition to salt stress.

Early Growth Stage Characterization and the Biochemical Responses for Salinity Stress in Tomato

Salinity is one of the most significant environmental stresses for sustainable crop production in major arable lands of the globe. Thus, we conducted experiments with 27 tomato genotypes to screen for salinity tolerance at seedling stage, which were treated with non-salinized (S1) control (18.2 mM NaCl) and salinized (S2) (200 mM NaCl) irrigation water. In all genotypes, the elevated salinity treatment contributed to a major depression in morphological and physiological characteristics; however, a smaller decrease was found in certain tolerant genotypes. Principal component analyses (PCA) and clustering with percentage reduction in growth parameters and different salt tolerance indices classified the tomato accessions into five key clusters. In particular, the tolerant genotypes were assembled into one cluster. The growth and tolerance indices PCA also showed the order of salt-tolerance of the studied genotypes, where Saniora was the most tolerant genotype and P.Guyu was the most susceptible genotype. To investigate the possible biochemical basis for salt stress tolerance, we further characterized six tomato genotypes with varying levels of salinity tolerance. A higher increase in proline content, and antioxidants activities were observed for the salt-tolerant genotypes in comparison to the susceptible genotypes. Salt-tolerant genotypes identified in this work herald a promising source in the tomato improvement program or for grafting as scions with improved salinity tolerance in tomato.

Shift in rhizospheric and endophytic bacterial communities of tomato caused by salinity and grafting

Saline water has to be used as an alternative resource in modern agriculture due to the increasing lack of fresh water. Approaches that promote the growth of crops under saline conditions have, therefore, become crucial. Grafting has been reported to be effective for this; however, the associated bacterial community remains unclear. To obtain a deeper understanding of the underlying microbial mechanisms, both grafted and non-grafted tomatoes were irrigated with three types of water having different electrical conductivity values. The experiment lasted 2.5 months, after which, the soil chemical properties and tomato heights were assessed. The rhizospheric and endophytic bacterial communities of samples from the different treatments were assessed by Illumina sequencing. The results showed that saline water significantly affected leaf-associated endophytic bacterial communities, whereas rhizosphere and root- and stem-associated bacterial communities were not affected. Increasing salinity increased the abundance of Gammaproteobacteria, but decreased the abundance of Actinobacteria, Alphaproteobacteria, Bacilli, and Acidobacteria at the class level of the leaf-associated bacterial community. Moreover, under higher salinity levels, grafting increased the diversity of the leaf-endophytic bacterial community. Overall, this study provides a comprehensive understanding of the rhizosphere and endophytic bacterial communities of tomato under saline conditions. The results highlight the importance of leaf-endophytic bacteria for salt response in plants. This is an important complementary finding to previous studies on the effect of salinity, which mainly focused on plant rhizosphere and root bacterial communities.

Interactive effects of salinity and silicon application on Solanum lycopersicum growth, physiology and shelf-life of fruit produced hydroponically

BACKGROUND

Using water with high salinity for plant fertigation may have detrimental effects on plant development and total yield and on the quality of the crop produced. As a possible means to alleviate the negative effects of salinity, silicon (Si) can be incorporated in the nutrient solution supplied to plants. In the present study, hydroponically grown tomato (Solanum lycopersicum Mill.) plants were subjected to two different salinity levels (0 and 50 mmol L^-1 NaCl) with and without the application of Si (0 and 2 mmol L^-1 K₂ SiO₃ ) in order to evaluate its possible positive impact on mitigation of salinity stress-induced symptoms. An additional experiment was implemented with postharvest Si application (sodium silicate) to investigate effects on the shelf-life of tomato fruit.

RESULTS

Salinity (50 mmol L^-1 NaCl) decreased plant size, total yield and fresh fruit weight while a high percentage of blossom end rot symptoms of tomato fruit was also observed. The application of Si in the nutrient solution counteracted these detrimental effects, generating a higher yield and healthier fruit (lower blossom end rot incidence) compared to the untreated plants (no application of Si). Salinity improved several quality-related traits in tomato fruit, resulting in higher marketability, whereas the addition of Si (pre- and postharvest) maintained fruit firmness following storage thereby increasing the shelf-life of tomato fruit.

CONCLUSIONS

These findings indicate that Si application (pre- and postharvest) could provide an effective means of alleviating the unfavorable effects of using low-quality water in plant fertigation on tomato plant development, fruit yield and post-harvest quality, through increased fruit firmness. © 2019 Society of Chemical Industry.

The Ca2+ Sensor Calcineurin B-Like Protein 10 in Plants: Emerging New Crucial Roles for Plant Abiotic Stress Tolerance

Ca²⁺ is a second messenger that mediates plant responses to abiotic stress; Ca²⁺ signals need to be decoded by Ca²⁺ sensors that translate the signal into physiological, metabolic, and molecular responses. Recent research regarding the Ca²⁺ sensor CALCINEURIN B-LIKE PROTEIN 10 (CBL10) has resulted in important advances in understanding the function of this signaling component during abiotic stress tolerance. Under saline conditions, CBL10 function was initially understood to be linked to regulation of Na⁺ homeostasis, protecting plant shoots from salt stress. During this process, CBL10 interacts with the CBL-interacting protein kinase 24 (CIPK24, SOS2), this interaction being localized at both the plasma and vacuolar (tonoplast) membranes. Interestingly, recent studies have exposed that CBL10 is a regulator not only of Na⁺ homeostasis but also of Ca²⁺ under salt stress, regulating Ca²⁺ fluxes in vacuoles, and also at the plasma membrane. This review summarizes new research regarding functions of CBL10 in plant stress tolerance, predominantly salt stress, as this is the most commonly studied abiotic stress associated with the function of this regulator. Special focus has been placed on some aspects that are still unclear. We also pay particular attention on the proven versatility of CBL10 to activate (in a CIPK-dependent manner) or repress (by direct interaction) downstream targets, in different subcellular locations. These in turn appear to be the link through which CBL10 could be a key master regulator of stress signaling in plants and also a crucial participant in fruit development and quality, as disruption of CBL10 results in inadequate Ca²⁺ partitioning in plants and fruit. New emerging roles associated with other abiotic stresses in addition to salt stress, such as drought, flooding, and K⁺ deficiency, are also addressed in this review. Finally, we provide an outline of recent advances in identification of potential targets of CBL10, as CBL10/CIPKs complexes and as CBL10 direct interactions. The aim is to showcase new research regarding this master regulator of abiotic stress tolerance that may be essential to the maintenance of crop productivity under abiotic stress. This is particularly pertinent when considering the scenario of a projected increase in extreme environmental conditions due to climate change.

Cost-benefit analysis of tomato in soilless culture systems with saline water under greenhouse conditions

BACKGROUND

The current need to produce food for a growing population, from diminishing natural resources, such as water and energy, and with minimum environmental degradation, demands the optimization of production. We compare the economic feasibility of tomato production in an open system with a perlite substrate, a closed system with the nutrient film technique (NFT), and a hydroponic crop (deep flow technique, DFT) using three levels of salinity that are found within the normal range for irrigation water quality in southeastern Spain.

RESULTS

Production with DFT resulted in an increase in the cost of phytosanitary treatments and the cost of maintenance. Production with perlite resulted in an increase in the cost of irrigation water and fertilization, and the use of NFT resulted in an increase in energy costs. The point of price equilibrium was exceeded in the three soilless systems when using low salinity water, and in perlite, with intermediate salinity water.

CONCLUSION

Profitability was reduced in the following order: perlite > NFT > DFT. There were positive results when using irrigation water with low salinity, and in the case of perlite, with intermediate salinity. In every case, salinity reduced the profitability of the operation, and this was greater when NFT was employed. The analysis of these soilless systems should be continued to determine the possibility of reducing cultivation costs. © 2019 Society of Chemical Industry.

Development and Evaluation of an Emitter with a Low-Pressure Drip-Irrigation System for Sustainable Eggplant Production

Drip-irrigation can improve uniformity in water distribution, water use efficiency, and crop productivity in the saline and nonsaline regions of South Asia and in Bangladesh where the availability and quality of water resources are scare for sustainable crop production. However, the currently available drip-irrigation systems (DIS) have limitations especially in the design and field performance of emitters. A new type of emitter with low pressure (gravity) was developed, installed and evaluated using the locally produced materials in two locations (nonsaline and saline zones) of Bangladesh. The emitter discharge rate was measured for the variable operating heads of 1.5, 2, and 2.5 meter (m) with 0%, 1%, and 1.5% slopes with eggplant (Solanum melongena L.), a commonly grown vegetable in the region. The tested parameters of the emitter were manufacturer coefficient of variation (CVm), emission uniformity (EU), coefficient of uniformity (CU), and the statistical uniformity (Us) of water application. Our results reveal that the discharge rates of the emitter varied from 3 to 5 L h−1 under the operating head of 1.5 to 2.5 m with the slope of 0–1.5%, with better performance of the DIS at 2 m operating pressure head and for slopes of 0% and 1%. The CU of all the test parameters was more than 80%, implying that the DIS was designed and installed with appropriate dimensions for the efficient application and distribution of water to the individual plants, with the emitter performance classified as fair to excellent considering water application and distribution, as well as crop yield. The new emitter used for DIS in field conditions showed that the eggplant yield, water use, and water productivity were greater by 4.6%, 38%, and 70%, respectively, compared to farmers’ irrigation practice. We conclude that the DIS has a great prospect to save water, and could be a convenient irrigation water application method for sustainable crop production in saline and nonsaline regions of Bangladesh and similar soil and climatic conditions in South Asia.

Comparison of floating-bed wetland and gravel filter amended with limestone and sawdust for sewage treatment

Advancements in the design and technology of constructed wetlands for efficient removal of wastewater contaminants are ever in progress to develop situation-based economical systems. Here, we entrenched two horizontal sub-surface flow constructed wetlands (HSFCW) with either chemical, viz. limestone (HSFCW-LS) or organic, viz. sawdust (HSFCW-SD) substrates, and compared them with biological method, viz. growing of water spinach in floating-bed-constructed wetland (FBCW-WS) to enhance the performance of CWs. Same sewage wastewater was used as influent in each fortified CW replicated thrice. Sewage was replaced weekly, for a total of 12 weeks of experimentation. Sampling of raw sewage from influent was undertaken at the inlet in the beginning, and that of treated effluent from the outlet after a week of treatments. Quality of raw sewage used weekly during experimentation remained almost uniform and near to the wastewater standards. Cumulative data of treated wastewater depicted that the FBCW-WS achieved the highest performance in the removal of total nitrogen (TN), [Formula: see text]-N, and total phosphorus (TP) with average removal efficiencies of 75.9, 90.5, and 94.3%, respectively. Whereas, HSFCW-SD performed better for [Formula: see text]-N, FC, and TSS with corresponding removal efficiency of 77.5, 64.3, and 74.2% while HSFCW-LS showed average performance. This study concludes that performance of biological method of macrophyte cultivation (FBCW-WS) is significantly superior to chemical and organic substrates, so it could be more effective, economical, and sustainable approach for sewage treatment.

The effect of covering material on the yield, quality and chemical composition of greenhouse-grown tomato fruit

BACKGROUND

During the last few decades, greenhouse technology for horticultural crops has focused on retaining optimum conditions within the greenhouse environment that could allow for a compromise between maximum yields and minimum production costs. The aim of this study was to evaluate the effect of three greenhouse covering materials and five harvesting dates on the yield and quality parameters of hydroponically produced tomato fruit, as well as on energy consumption.

RESULTS

Plants had a higher growth rate at early stages for S-PE cover material, while differences were minimized at later stages. Tocopherol content was the highest for ID-PE material and harvesting later than 170 days after transplanting (DAT), while sugar content (fructose and glucose) was the highest for S-PE material and 157 DAT. Organic acid content was the highest at early harvestings, especially for 7-PE and S-PE cover materials, while it exhibited decreasing trends at later harvesting dates. Antioxidant properties showed a varied response to cover materials and harvesting dates, while β-carotene, carotenoids and chlorophylls were the highest for 7-PE material.

CONCLUSIONS

The results showed that both cover materials and harvesting date may affect significantly tomato fruit quality, especially sugar and organic acid contents which are associated with fruit taste, as well as tocopherols which contribute to antioxidant properties and pigments that are associated with fruit ripening and earliness of marketable maturity. © 2018 Society of Chemical Industry.

Transgenic tomatoes for abiotic stress tolerance: status and way ahead

Tomato (Solanum lycopersicum) is one of the most important vegetable crops; its production, productivity and quality are adversely affected by abiotic stresses. Abiotic stresses such as drought, extreme temperature and high salinity affect almost every stage of tomato life cycle. Depending upon the plant stage and duration of the stress, abiotic stress causes about 70% yield loss. Several wild tomato species have the stress tolerance genes; however, it is very difficult to transfer them into cultivars due to high genetic distance and crossing barriers. Transgenic technology is an alternative potential tool for the improvement of tomato crop to cope with abiotic stress, as it allows gene transfer across species. In recent decades, many transgenic tomatoes have been developed, and many more are under progress against abiotic stress using transgenes such as DREBs, Osmotin, ZAT12 and BADH2. The altered expression of these transgenes under abiotic stresses are involved in every step of stress responses, such as signaling, control of transcription, proteins and membrane protection, compatible solute (betaines, sugars, polyols, and amino acids) synthesis, and free-radical and toxic-compound scavenging. The stress-tolerant transgenic tomato development is based on introgression of a gene with known function in stress response and putative tolerance. Transgenic tomato plants have been developed against drought, heat and salt stress with the help of various transgenes, expression of which manages the stress at the cellular level by modulating the expression of downstream genes to ultimately improve growth and yield of tomato plants and help in sustainable agricultural production. The transgenic technology could be a faster way towards tomato improvement against abiotic stress. This review provides comprehensive information about transgenic tomato development against abiotic stress such as drought, heat and salinity for researcher attention and a better understanding of transgenic technology used in tomato improvement and sustainable agricultural production.

Genetic engineering of the biosynthesis of glycinebetaine enhances the fruit development and size of tomato

Glycinebetaine has been widely considered as an effective protectant against abiotic stress in plants, and also found to promote plant growth under normal growing conditions, especially during the reproductive stage. Betaine aldehyde dehydrogenase (BADH) and choline oxidase (COD) are two key enzymes which have been used to confer glycinebetaine synthesis in plant which normally does not synthesis glycinebetaine. In this study, we used the tomato (Solanum lycopersicum, cv 'Moneymaker') plants of wild-type and the transgenic lines codA (L1, L2) and BADH (2, 46), which were transformed with codA and BADH, respectively, to study the impact of glycinebetaine on tomato fruit development. Our results showed that the codA and BADH transgenes induced the formation of enlarged flowers and fruits in transgenic tomato plants. In addition, the transgenic tomato plants had a higher photosynthetic rate, higher assimilates content, and higher leaf chlorophyll content than the wild-type plants. We also found that the enlargement of fruit size was related to the contents of phytohormones, such as auxin, brassinolide, gibberellin, and cytokinin. Additionally, qPCR results indicated that the expressions levels of certain genes related to fruit growth and development were also elevated in transgenic plants. Finally, transcriptome sequencing results revealed that the differences in the levels of gene expression in tomato fruit between the transgenic and wild-type plants were observed in multiple pathways, predominantly those of photosynthesis, DNA replication, plant hormone signal transduction, and biosynthesis. Taken together, our results suggest that glycinebetaine promotes tomato fruit development via multiple pathways. We propose that genetic engineering of glycinebetaine synthesis offers a novel approach to enhance the productivity of tomato and other crop plants.

NMR-Based Metabolomics Approach To Study the Influence of Different Conditions of Water Irrigation and Greenhouse Ventilation on Zucchini Crops

This study describes the approach of ¹H NMR metabolomic profiling for the differentiation of zucchini produced under different conditions of water irrigation (desalinated seawater -0.397 dS/m, 0.52 €/m³ vs groundwater -2.36 dS/m, 0.29 €/m³) and ventilation (surface area of the vent openings/greenhouse area was 15.0% for one sector and 9.8% for the other). Overall, 72 extracts of zucchini ( Cucubirta pepo L. cv Victoria) under four different conditions were regularly analyzed during the spring-summer cycle from April to July 2017. We have found that zucchini plants irrigated with desalinated seawater increased the zucchini production yield, presented fruits with higher concentration of glucose, fructose, and vitamin B3, and displayed an increased antioxidant activity. On the contrary, plant groundwater irrigation produced the increment of sucrose level that could rise the sweetness perception of the fruits. Finally, the ventilation variable produced a higher concentration of trigonelline, histidine, and phenylalanine but only on those zucchinis irrigated with groundwater.

Exogenous Melatonin Improves Fruit Quality Features, Health Promoting Antioxidant Compounds and Yield Traits in Tomato Fruits under Acid Rain Stress

Acid rain is a serious worldwide environmental problem which reduces the growth and yield of crops. Melatonin, as a pleiotropic molecule has been known to improve stress tolerance by limiting the oxidative damage of plants exposed to adverse environments. However, the role of exogenous melatonin particularly on the yield and antioxidant compounds in tomato fruits under abiotic stress condition remains inexpressible. This observation aims to identify the influence of melatonin treatment under simulated acid rain (SAR) condition on fruit qualities, phenolics, flavonoids, and carotenoids concentration in fruits, and yield of tomatoes. Our study results showed that the fruits of SAR-stressed plants had higher quality traits and antioxidant bioactive compounds by increasing antioxidant activities against SAR-induced oxidative stress compared with fruits of control plants. Nonetheless, these improvements to antioxidant activities in fruits under SAR-condition remained unable to prevent the reduction of the yield. However, SAR-stressed plants treated by melatonin exhibited upgradation on the fruit quality traits, antioxidant compounds and yield attributes through accelerating oxidant-scavenging antioxidant actions in fruits compared with fruits of SAR-stressed plants. Meanwhile, our results suggest that exogenous melatonin plays an important role in improvement of bioactive compounds and yield traits in tomato fruits through regulating antioxidant system.

The SlCBL10 Calcineurin B-Like Protein Ensures Plant Growth under Salt Stress by Regulating Na+ and Ca2+ Homeostasis

Characterization of a new tomato (Solanum lycopersicum) T-DNA mutant allowed for the isolation of the CALCINEURIN B-LIKE PROTEIN 10 (SlCBL10) gene whose lack of function was responsible for the severe alterations observed in the shoot apex and reproductive organs under salinity conditions. Physiological studies proved that SlCBL10 gene is required to maintain a proper low Na⁺/Ca²⁺ ratio in growing tissues allowing tomato growth under salt stress. Expression analysis of the main responsible genes for Na⁺ compartmentalization (i.e. Na⁺/H⁺ EXCHANGERs, SALT OVERLY SENSITIVE, HIGH-AFFINITY K+ TRANSPORTER 1;2, H⁺-pyrophosphatase AVP1 [SlAVP1] and V-ATPase [SlVHA-A1]) supported a reduced capacity to accumulate Na⁺ in Slcbl10 mutant leaves, which resulted in a lower uploading of Na⁺ from xylem, allowing the toxic ion to reach apex and flowers. Likewise, the tomato CATION EXCHANGER 1 and TWO-PORE CHANNEL 1 (SlTPC1), key genes for Ca²⁺ fluxes to the vacuole, showed abnormal expression in Slcbl10 plants indicating an impaired Ca²⁺ release from vacuole. Additionally, complementation assay revealed that SlCBL10 is a true ortholog of the Arabidopsis (Arabidopsis thaliana) CBL10 gene, supporting that the essential function of CBL10 is conserved in Arabidopsis and tomato. Together, the findings obtained in this study provide new insights into the function of SlCBL10 in salt stress tolerance. Thus, it is proposed that SlCBL10 mediates salt tolerance by regulating Na⁺ and Ca²⁺ fluxes in the vacuole, cooperating with the vacuolar cation channel SlTPC1 and the two vacuolar H⁺-pumps, SlAVP1 and SlVHA-A1, which in turn are revealed as potential targets of SlCBL10.

Assessment on the coupling effects of drip irrigation and organic fertilization based on entropy weight coefficient model

Water and fertilizer are two important factors influencing crop growth, development and yield formation. To investigate their combined effects on the soil-plant system, and to find out the optimal water and organic fertilizer coupling strategy for tomato (Solanum lycopersicum L), an experiment was carried out from May to October in 2016 in the south of China. The experiment consisted of three drip irrigation quotas (150, 180, 210 m³/ha) and three organic fertilizer application amounts (2,800, 3,600, 4,400 kg/ha). A water-fertilizer treatment (abbreviated as CK) that is in line with local practice was used for comparison. The tomato marketable yield, sugar/acid ratio (SAR) and irrigation water use efficiency (IWUE), as well as the soil salinity and available nutrient concentrations were measured. The results showed that the marketable yield was highly significantly (p < 0.01) affected by irrigation or fertilization. The SAR of tomato were significantly (p < 0.05) affected by irrigation or/and fertilization. The fertilization had an highly significant (p < 0.01) effect on the concentrations of soil nutrients (N, P, K), while the coupling effect of irrigation and fertilization was not pronounced. According to the multi-index analysis and the computed result by the entropy weight coefficient model, a 180 m³/ha irrigation quota in combination with 4,400 kg/ha organic fertilizer application amount was the optimal water-fertilizer coupling strategy which owned the most satisfactory comprehensive benefits. The marketable yield, SAR and IWUE under this optimal strategy were 122.4 t/ha, 9.2, 32.4 kg/m³, respectively, and by 28.0%, 29.6% and 28.1% higher compared to that under CK.

The Tomato DOF Daily Fluctuations 1, TDDF1 acts as flowering accelerator and protector against various stresses

Adaptation to environmental changes is an important fitness trait for crop development. Photoperiod is an essential factor in seasonal control of flowering time. Sensing of day-length requires an interaction between the Photoperiod and the endogenous rhythms that is controlled by plant circadian clock. Thus, circadian clock is a critical regulator and internal molecular time-keeping mechanism, controlling key agricultural traits in crop plants such as the ability to adjust their growth and physiology to anticipate diurnal environmental changes. Here, we describe the gene Tomato Dof Daily Fluctuations 1 (TDDF1), which is involved in circadian regulation and stress resistance. Large daily oscillations in TDDF1 expression were retained after transferring to continuous dark (DD) or light (LL) conditions. Interestingly, overexpressing TDDF1 induce early flowering in tomato through up-regulation of the flowering-time control genes, moreover, by protein-protein interaction with the floral inducer SFT gene. Notably, overexpressing TDDF1 in tomato was associated with chlorophyll overaccumulation by up-regulating the related biosynthetic genes. TDDF1 expression results in improved drought, salt, various hormones stress tolerance alongwith resistance to late blight caused by Phytophthora infestans. This study can be a distinctive strategy to improve other economically important crops.

Growth, Water Use, and Nitrate-15N Uptake of Greenhouse Tomato as Influenced by Different Irrigation Patterns, 15N Labeled Depths, and Transplant Times

Increasing water use efficiency and reducing nitrogen pollutant discharge are important tasks for modern agriculture. To evaluate the effect of alternate partial root-zone irrigation (APRI) on tomato plant growth, water use efficiency and nitrate-15N uptake, an experiment was conducted from June to December in 2014 under greenhouse condition in northern China. The experiment contained two irrigation patterns [APRI and conventional irrigation (CI)], two 15N labeled depths in soil (10 and 50 cm) and two transplant time (early and late summer). Results showed that, compared to CI, APRI did not significantly (p > 0.05) impact the growth and biomass accumulation in aboveground part of tomato, while it enhanced the root, reflecting by greater length density, and more dry mass. APRI produced marginally lower yields, but saved 34.9% of irrigation water, and gave a 37.6-49.9% higher water use efficiency relative to CI. In addition, APRI improved fruit quality, mainly through increasing the contents of soluble solid (by 12.8-21.6%), and vitamin C (2.8-12.7%), and the sugar/acid ratio (3.5-8.5%). The 15N utilization efficiency (15NUE) in APRI was higher than that in CI, which was more evident when 15N was labeled at 50 cm depth. Significant (p < 0.05) 15N recovery increase of 10.2-13.2% and 15N loss decrease of 35.4-54.6% were found for APRI compared to CI. The overall results suggest that APRI under greenhouse could benefit the nitrate-N recovery and increase the water use efficiency in tomato.

SSR marker-assisted screening of commercial tomato genotypes under salt stress

Salt stress was applied to tomato commercial genotypes to study adverse effects on their phenotypic traits. Three were saline tolerant (San Miguel, Romelia and Llanero), two were mildly tolerant (Perfect peel HF1 and Heinz 1350) whereas the remaining were sensitive. Genotyping cultivars using 19 polymorphic SSRs out of 25 tested produced a total of 70 alleles with an average of 3.68 alleles per locus and PIC values ranging from 0.22 (SSR 26, 92, 66 and TG35) to 0.82 (SSR 356). Principal component analysis (PCA) showed two contrasting panels discriminating tolerant and sensitive groups and one panel with scattered genotypes. STRUCTURE analysis clustered genotypes within three groups in accordance with their salt stress behavior. The success of tomato salt-tolerance breeding programs can be enhanced through molecular characterization of diversity within commercial cultivars that adapt differently to stress conditions. To this end, we combined phenotypes and SSR marker-genotypes to seek sources of salt tolerance that might be tomato species-specific. We integrated and represented genotype-phenotype associations from multiple loci into a multi-layer network representation. It is a systemic view linking discriminating genotypes to salt stress phenotypes, which may guide strategies for the introgression of valuable traits in target tomato varieties to overcome salinity.

Soil Salt Distribution and Tomato Response to Saline Water Irrigation under Straw Mulching

To investigate better saline water irrigation scheme for tomatoes that scheduling with the compromise among yield (Y_t), quality, irrigation water use efficiency (IWUE) and soil salt residual, an experiment with three irrigation quotas and three salinities of irrigation water was conducted under straw mulching in northern China. The irrigation quota levels were 280 mm (W1), 320 mm (W2) and 360 mm (W3), and the salinity levels were 1.0 dS/m (F), 3.0 dS/m (S1) and 5.0 dS/m (S2). Compared to freshwater, saline water irrigations decreased the maximum leaf area index (LAI_m) of tomatoes, and the LAI_m presented a decline tendency with higher salinity and lower irrigation quota. The best overall quality of tomato was obtained by S2W1, with the comprehensive quality index of 3.61. A higher salinity and lower irrigation quota resulted in a decrease of individual fruit weight and an increase of the blossom-end rot incidence, finally led to a reduction in the tomato Y_t and marketable yield (Y_m). After one growth season of tomato, the mass fraction of soil salt in plough layer under S2W1 treatment was the highest, and which presented a decline trend with an increasing irrigation quota. Moreover, compared to W1, soil salts had a tendency to move to the deeper soil layer when using W2 and W3 irrigation quota. According to the calculation results of projection pursuit model, S1W3 was the optimal treatment that possessed the best comprehensive benefit (tomato overall quality, Y_t, Y_m, IWUE and soil salt residual), and was recommended as the saline water irrigation scheme for tomatoes in northern China.

Surface Drainage and Mulching Drip-Irrigated Tomatoes Reduces Soil Salinity and Improves Fruit Yield

A study on the effects of mulched drip irrigation combined with surface drainage on saline soil and tomatoes was conducted in coastal areas of eastern China, where the crops are subjected to excessive salt. The treatments contained three irrigation rates—200, 250 and 300 m³/ha—and three drain ditch depths—10, 20 and 30 cm. The contents of soil salinity, organic matter and available nutrient were observed, and the tomato plant height, stem diameter and leaf area index during different growth periods were recorded. Results showed that the total removal rate of salt from soil at a 0–1 m depth was 8.7–13.2% for the three drainages. Compared with the control, the treatments increased the content of available N (by 12.1–47.1%) and available K (by 5.0–21.9%) in the soils inside the mulch and decreased the content of available N (by 3.4–22.1%) and available K (by 7.5–16.4%) in the soils outside the mulch. For tomatoes, the plant height and the stem diameter was increased significantly by the irrigations but was not significantly affected by the drainages, and the leaf area index was increased by 0.39~1.76, 1.10~2.90 and 2.80~6.86 respectively in corresponding to the seedling, flowering and fruit-set stage. Moreover, yield-increase rates of 7.9–27.6% were found for the treatments compared to the control with a similar amount of applied water.