Drought Stress Affects the Response of Italian Local Tomato (Solanum lycopersicum L.) Varieties in a Genotype-Dependent Manner

New olive-pomace fertilizer tested with a 2-tiers approach: Biomarkers on Eisenia fetida, physiochemical effects on Solanum lycopersicum and Olea europaea

Every year, the olive oil industry generates a substantial amount of pomace, a semi-solid residue made up of skin, pulp, pit, and kernel fragments. Rather than being disposed of, the pomace can be dried and transported to an extraction facility where pomace oil can be extracted. Utilizing its high thermal capacity, the extracted pomace can be used as a supplementary fuel in the drying process, resulting in the production of ashes. In this study, the effect of pomace waste applied to the soil was investigated by testing two mixtures with different proportions of de-oiled pomace flour and kernel ash (50:50 and 70:30, respectively) in powder and pellet form. We used a dual approach, evaluating the effects of the mixtures on both soil communities and plant physiology and productivity, to assess the actual usability of the fertilizer in agriculture. The biomarker approach was valuable in assessing the sublethal effects of the two mixtures in powder form in soil. After 30 days of exposure, the bioindicator organism Eisena fetida showed lipid peroxidation, glutathione S-transferase and lactate dehydrogenase levels similar to the control, while lysozyme activity was reduced in all treatments. The powder mixture was lethal to the tomato plants, while there was no evidence of any damage to the olive trees. During 60 days of monitoring, both mixtures in pellet form showed a slight increase in physiological parameters, suggesting a benefit to the photosynthetic system. The improved carbon assimilation in tomato plants treated with the mixtures results in increased plant productivity, both in terms of number and weight of fruits, while maintaining the antioxidant content. This study paves the way for the use of the pomace mixture as a soil improver, thus increasing the value of this waste product.

Lupenone, a wonder chemical obtained from Euphorbia segetalis to boost affinity for the transcriptional factor escalating drought-tolerance in Solanum Lycopersicum: A cutting-edge computational biology approach

Drought is the single greatest abiotic factor influencing crop yield worldwide. Plants remain in one area for extended periods, making them vulnerable to natural and man-made influences. Understanding plant drought responses will help us develop strategies for breeding drought-resistant crops. Large proteome analysis revealed that leaf and root tissue proteins respond to drought differently depending on the plant's genotype. Commonly known as tomatoes, Solanum Lycopersicum is a globally important vegetable crop. However, drought stress is one of the most significant obstacles to tomato production, making the development of cultivars adapted to dry conditions an essential goal of agricultural biotechnology. Breeders have put quite a lot of time and effort into the tomato to increase its productivity, adaptability, and resistance to biotic and abiotic challenges. However, conventional tomato breeding has only improved drought resistance due to the complexity of drought traits. The resilience of tomatoes under drought stress has been the subject of extensive study. Using contemporary sequencing approaches like genomics, transcriptomics, proteomics, and metabolomics has dramatically aided in discovering drought-responsive genes. One of the most prominent families of plant transcription factors, WRKY genes, plays a crucial role in plant growth and development in response to natural and abiotic stimuli. To develop plants that can withstand both biotic and abiotic stress, understanding the relationships between WRKY-proteins (transcription factors) and other proteins and ligands in plant cells is essential. This is despite the fact that tomatoes have a long history of domestication. This research aims to utilize Lupenone, a hormone produced in plant roots in response to stress, to increase drought resistance in plants. Lupenone exhibits a strong affinity for the WRKY protein at -9.64 kcal/mol. Molecular docking and modeling studies show that these polyphenols have a significant role in making Solanum Lycopersicum drought-resistant and improving the quality of its fruit. As a result of climate change, droughts are occurring more frequently and persisting for more extended periods, making it necessary to breed crops resistant to drought. While considerable variability for tolerance exists in wild cousins, little is known about the processes and essential genes influencing drought tolerance in cultivated tomato species.

Effects of Water Deficit on Growth and Productivity in Tomato Crops Irrigated with Water Treated with Very Low-Frequency Electromagnetic Resonance Fields

The tomato crop is very sensitive to stress conditions. A water deficit is defined as when precipitation is less than the evapotranspiration (ETc) of the crop in a given period, and in this scenario of climate change, it is identified as responsible for global productivity losses. The use of potential technologies for better irrigation management, such as electromagnetically treated water, remains controversial. Thus, the objective of the present work was to investigate the effects of very low-frequency electromagnetic resonance field treatment on water for tomato crops submitted to different irrigation rates. For this, an experiment was carried out under controlled conditions with different types of water: electromagnetically treated water (WTVLF) and untreated water (UNW), as well as four water replacement rates: 40, 60, 80, and 100% ETc. The electromagnetic treatment of the water was carried out using the commercial equipment AQUA4D®. The experiment was carried out in pots with five replications per treatment. Lower activity of SOD, POD, CAT, and APX enzymes was observed in plants irrigated with water treated with very low-frequency electromagnetic resonance fields (WTVLF), indicating less oxidative stress caused by water deficit. Water deficit reduced chlorophyll content, but the effects were less harmful with WTVLF water. The water deficit resulted in less accumulation of dry matter and less productivity in a linear relationship. However, plants irrigated with WTVLF showed increments of about 20% in dry matter accumulation and 20% in fruit production concerning plants irrigated with untreated water, independent of the irrigation rates. We can conclude that irrigation with WTVLF can be a solution to reduce the damage caused by water deficits and increase the productivity of tomato crops.

Tomato Biodiversity and Drought Tolerance: A Multilevel Review

Ongoing global climate change suggests that crops will be exposed to environmental stresses that may affect their productivity, leading to possible global food shortages. Among these stresses, drought is the most important contributor to yield loss in global agriculture. Drought stress negatively affects various physiological, genetic, biochemical, and morphological characteristics of plants. Drought also causes pollen sterility and affects flower development, resulting in reduced seed production and fruit quality. Tomato (Solanum lycopersicum L.) is one of the most economically important crops in different parts of the world, including the Mediterranean region, and it is known that drought limits crop productivity, with economic consequences. Many different tomato cultivars are currently cultivated, and they differ in terms of genetic, biochemical, and physiological traits; as such, they represent a reservoir of potential candidates for coping with drought stress. This review aims to summarize the contribution of specific physio-molecular traits to drought tolerance and how they vary among tomato cultivars. At the genetic and proteomic level, genes encoding osmotins, dehydrins, aquaporins, and MAP kinases seem to improve the drought tolerance of tomato varieties. Genes encoding ROS-scavenging enzymes and chaperone proteins are also critical. In addition, proteins involved in sucrose and CO₂ metabolism may increase tolerance. At the physiological level, plants improve drought tolerance by adjusting photosynthesis, modulating ABA, and pigment levels, and altering sugar metabolism. As a result, we underline that drought tolerance depends on the interaction of several mechanisms operating at different levels. Therefore, the selection of drought-tolerant cultivars must consider all these characteristics. In addition, we underline that cultivars may exhibit distinct, albeit overlapping, multilevel responses that allow differentiation of individual cultivars. Consequently, this review highlights the importance of tomato biodiversity for an efficient response to drought and for preserving fruit quality levels.

Transcriptomic analysis reveals the gene regulatory networks involved in leaf and root response to osmotic stress in tomato

Introduction

Tomato (Solanum lycopersicum L.) is a major horticultural crop that is cultivated worldwide and is characteristic of the Mediterranean agricultural system. It represents a key component of the diet of billion people and an important source of vitamins and carotenoids. Tomato cultivation in open field often experiences drought episodes, leading to severe yield losses, since most modern cultivars are sensitive to water deficit. Water stress leads to changes in the expression of stress-responsive genes in different plant tissues, and transcriptomics can support the identification of genes and pathways regulating this response.

Methods

Here, we performed a transcriptomic analysis of two tomato genotypes, M82 and Tondo, in response to a PEG-mediated osmotic treatment. The analysis was conducted separately on leaves and roots to characterize the specific response of these two organs.

Results

A total of 6,267 differentially expressed transcripts related to stress response was detected. The construction of gene co-expression networks defined the molecular pathways of the common and specific responses of leaf and root. The common response was characterized by ABA-dependent and ABA-independent signaling pathways, and by the interconnection between ABA and JA signaling. The root-specific response concerned genes involved in cell wall metabolism and remodeling, whereas the leaf-specific response was principally related to leaf senescence and ethylene signaling. The transcription factors representing the hubs of these regulatory networks were identified. Some of them have not yet been characterized and can represent novel candidates for tolerance.

Discussion

This work shed new light on the regulatory networks occurring in tomato leaf and root under osmotic stress and set the base for an in-depth characterization of novel stress-related genes that may represent potential candidates for improving tolerance to abiotic stress in tomato.

The Enhanced Affinity of WRKY Reinforces Drought Tolerance in Solanum lycopersicum L.: An Innovative Bioinformatics Study

In the scenario of global climate change, understanding how plants respond to drought is critical for developing future crops that face restricted water resources. This present study focuses on the role of WRKY transcription factors on drought tolerance in tomato, Solanum lycopersicum L., which is a significant vegetable crop. WRKY transcription factors are a group of proteins that regulate a wild range of growth and developmental processes in plants such as seed germination and dormancy and the stress response. These transcription factors are defined by the presence of a DNA-binding domain, namely, the WRKY domain. It is well-known that WRKY transcription factors can interact with a variety of proteins and therefore control downstream activities. It aims to simulate the effect of curcumin, a bioactive compound with regulatory capacity, on the protein-protein interaction events by WRKY transcription factors with an emphasis on drought stress. It was found that curcumin binds to WRKY with an energy of -11.43 kcal/mol with inhibitory concentration (K_i) 0.12 mM and has the potential to improve fruit quality and reinforce drought tolerance of S. lycopersicum, according to the results based on bioinformatics tools. The root means square deviation (RMSD) of the C-α, the backbone of 2AYD with ligand coupled complex, displayed a very stable structure with just a little variation of 1.89 Å. MD simulation trajectory of Cα atoms of 2AYD bound to Curcumin revealed more un-ordered orientation in PC1 and PC10 modes and more toward negative correlation from the initial 400 frames during PCA. Establishing the binding energies of the ligand-target interaction is essential in order to characterize the compound's binding affinity to the drought transcription factor. We think we have identified a phyto-agent called curcumin that has the potential to enhance the drought tolerance. Compared to the part of the mismatch repair-base technique that can be used to fix drought related genes, curcumin performed better in a drop-in crop yield over time, and it was suggested that curcumin is a potential candidate factor for improving drought tolerance in tomatoes, and it needs future validation by experiments in laboratory and field.

A Multi-Level Approach as a Powerful Tool to Identify and Characterize Some Italian Autochthonous Common Bean (Phaseolus vulgaris L.) Landraces under a Changing Environment

A prime role in matters of agrobiodiversity is held by landraces, which serve as a repository gene pool able to meet sustainable development goals and to face the ongoing challenges of climate change. However, many landraces are currently endangered due to environmental and socio-economic changes. Thus, effective characterization activities and conservation strategies should be undertaken to prevent their genetic and cultural erosion. In the current study, the morphological, genetic, and biochemical analyses were integrated with stress response-related studies to characterize the diversity of seven Italian autochthonous common bean landraces. The results showed that the morphological descriptors and the neutral molecular markers represent powerful tools to identify and distinguish diversity among landrace populations, but they cannot correlate with the stress tolerance pattern of genetically similar populations. The study also supported the use of proline as a biochemical marker to screen the most salt-sensitive bean landraces. Thus, to fully elucidate the future dynamics of agrobiodiversity and to establish the basis for safeguarding them while promoting their utilization, a multi-level approach should always be included in any local and national program for the characterization/conservation/use of genetic resources. This study should represent the basis for further joint research that effectively contributes to set/achieve Italian priorities towards sustainability in the framework of emerging environmental, societal, and economic challenges.

Multigenic regulation in the ethylene biosynthesis pathway during coffee flowering

Ethylene regulates different aspects of the plant's life cycle, such as flowering, and acts as a defense signal in response to environmental stresses. Changes induced by water deficit (WD) in gene expression of the main enzymes involved in ethylene biosynthesis, 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and oxidase (ACO), are frequently reported in plants. In this study, coffee (Coffea arabica) ACS and ACO family genes were characterized and their expression profiles were analyzed in leaves, roots, flower buds, and open flowers from plants under well-watered (WW) and water deficit (WD) conditions. Three new ACS genes were identified. Water deficit did not affect ACS expression in roots, however soil drying strongly downregulated ACO expression, indicating a transcriptional constraint in the biosynthesis pathway during the drought that can suppress ethylene production in roots. In floral buds, ACO expression is water-independent, suggesting a higher mechanism of control in reproductive organs during the final flowering stages. Leaves may be the main sites for ethylene precursor (1-aminocyclopropane-1-carboxylic acid, ACC) production in the shoot under well-watered conditions, contributing to an increase in the ethylene levels required for anthesis. Given these results, we suggest a possible regulatory mechanism for the ethylene biosynthesis pathway associated with coffee flowering with gene regulation in leaves being a key point in ethylene production and ACO genes play a major regulatory role in roots and the shoots. This mechanism may constitute a regulatory model for flowering in other woody species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01235-y.

Transcriptome and physiological analysis of increase in drought stress tolerance by melatonin in tomato

Drought stress seriously affects tomato growth, yield and quality. Previous reports have pointed out that melatonin (MT) can alleviate drought stress damage to tomato. To better understand the possible physiological and molecular mechanisms, chlorophyll fluorescence parameters and leaf transcriptome profiles were analyzed in the "Micro Tom" tomato cultivar with or without melatonin irrigation under normal and drought conditions. Polyethylene glycol 6000 (PEG6000) simulated continuous drought treatment reduced plant height, but melatonin treatment improved plant growth rate. Physiological parameter measurements revealed that the drought-induced decreases in maximum efficiency of photosystem II (PSII) photochemistry, the effective quantum yield of PSII, electron transfer rate, and photochemical quenching value caused by PEG6000 treatment were alleviated by melatonin treatment, which suggests a protective effect of melatonin on PSII. Comparative transcriptome analysis identified 447, 3982, 4526 and 3258 differentially expressed genes (DEGs) in the comparative groups plus-melatonin vs. minus-melatonin (no drought), drought vs. no drought (minus-melatonin), drought vs. no drought (melatonin) and plus-melatonin vs. minus-melatonin (drought), respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis revealed that DEGs in the four comparative groups were involved in multiple metabolic processes and closely related to hormone signal transduction and transcription factors. Transcriptome data revealed that melatonin changed the expression pattern of most hormone signal transduction related DEGs induced by drought, and improved plant drought resistance by down-regulating the expression of linoleic acid catabolic enzyme genes. These results provide new insights into a probable mechanism of the melatonin-induced protection of photosynthesis and enhancement of drought tolerance in tomato plants.

Distinct Tomato Cultivars Are Characterized by a Differential Pattern of Biochemical Responses to Drought Stress

Future climate scenarios suggest that crop plants will experience environmental changes capable of affecting their productivity. Among the most harmful environmental stresses is drought, defined as a total or partial lack of water availability. It is essential to study and understand both the damage caused by drought on crop plants and the mechanisms implemented to tolerate the stress. In this study, we focused on four cultivars of tomato, an economically important crop in the Mediterranean basin. We investigated the biochemical mechanisms of plant defense against drought by focusing on proteins specifically involved in this stress, such as osmotin, dehydrin, and aquaporin, and on proteins involved in the general stress response, such as HSP70 and cyclophilins. Since sugars are also known to act as osmoprotectants in plant cells, proteins involved in sugar metabolism (such as RuBisCO and sucrose synthase) were also analyzed. The results show crucial differences in biochemical behavior among the selected cultivars and highlight that the most tolerant tomato cultivars adopt quite specific biochemical strategies such as different accumulations of aquaporins and osmotins. The data set also suggests that RuBisCO isoforms and aquaporins can be used as markers of tolerance/susceptibility to drought stress and be used to select tomato cultivars within breeding programs.

Italian Tomato Cultivars under Drought Stress Show Different Content of Bioactives in Pulp and Peel of Fruits

Background: This study aims to evaluate the performance, in terms of accumulation of antioxidant compounds in fruits, of nine local and three commercial Italian tomato cultivars subjected to drought stress. The same local cultivars had been previously studied at morpho-physiological level. Methods: The present manuscript analyzes drought stress as a tool to increase the amount of secondary metabolites that can enhance fruit quality. Nutraceutical characterization of the fruits was performed by analyzing the content of antioxidants, phenols, flavonoids, lycopene, ascorbic acid (vitamin C), rutin, caffeic acid, and naringenin. At the same time, plant sensitivity to stress during the reproductive phase was monitored in terms of flower abscission, fruit drop, and seed germination. Results: Perina turns out to be the tomato cultivar with the best nutraceutical properties in the absence of stress while the Quarantino cultivar is so for flavonoid content (control plants) and lycopene and vitamin C content (stressed plants). Perina and Quarantino are the cultivars with the best response to drought and Perina has the highest concentrations of bioactives. Quarantino responds most effectively to stress in the reproductive phase. Conclusions: data confirm that drought stress increases bioactive production in some local cultivars of tomato, which produce higher quality fruits.

Effect of long-term drought on tomato leaves: the impact on metabolic and antioxidative response

Water deficit triggers physiological, biochemical, and molecular changes in leaves that could be important for overall plant adaptive response and it can affect tomato yield and quality. To assess the influence of long-term moderate drought on leaves, four tomato accessions from MAGIC TOM populations were selected on the basis of their differences in fruit size and were grown in a glasshouse under control and water deficit conditions. Drought affected stomatal conductance more in large fruit genotypes compared to cherry genotypes and this could be related to higher abscisic acid (ABA) leaf content. Compared to large fruits, cherry tomato genotypes coped better with water stress by reducing leaf area and maintaining photochemical efficiency as important adaptive responses. Accumulation of soluble sugars in the cherry genotypes and organic acid in the leaves of the larger fruit genotypes indicated their role in the osmoregulation and the continuum of source/sink gradient under stress conditions. Long-term moderate drought induced upregulation of NCED gene in all four genotypes that was associated with ABA production. The increase in the expression of ZEP gene was found only in the LA1420 cherry genotype and indicated its possible role in the protection against photooxidative stress induced by prolonged water stress. In addition, upregulation of the APX genes, higher accumulation of vitamin C and total antioxidant capacity in cherry genotype leaves highlighted their greater adaptive response against long-term drought stress compared to larger fruit genotypes that could also reflect at fruit level.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01102-2.

Morpho-Physiological Classification of Italian Tomato Cultivars (Solanum lycopersicum L.) According to Drought Tolerance during Vegetative and Reproductive Growth

Irrigation is fundamental for agriculture but, as climate change becomes more persistent, there is a need to conserve water and use it more efficiently. It is therefore crucial to identify cultivars that can tolerate drought. For economically relevant crops, such as tomatoes, this purpose takes on an even more incisive role and local agrobiodiversity is a large genetic reservoir of promising cultivars. In this study, nine local Italian cultivars of tomatoes plus four widely used commercial cultivars were considered. These experienced about 20 d of drought, either at vegetative or reproductive phase. Various physio-morphological parameters were monitored, such as stomatal conductance (gs), photosynthesis (A), water use efficiency (WUE), growth (GI) and soil water content (SWC). The different responses and behaviors allowed to divide the cultivars into three groups: tolerant, susceptible, and intermediate. The classification was also confirmed by a principal component analysis (PCA). The study, in addition to deepening the knowledge of local Italian tomato cultivars, reveals how some cultivars perform better under stress condition than commercial ones. Moreover, the different behavior depends on the genotype and on the growth phase of plants. In fact, the Perina cultivar is the most tolerant during vegetative growth while the Quarantino cultivar is mostly tolerant at reproductive stage. The results suggest that selection of cultivars could lead to a more sustainable agriculture and less wasteful irrigation plans.

Impact of Peels Extracts from an Italian Ancient Tomato Variety Grown under Drought Stress Conditions on Vascular Related Dysfunction

Background: Tomato by-products contain a great variety of biologically active substances and represent a significant source of natural antioxidant supplements of the human diet. The aim of the work was to compare the antioxidant properties of a by-product from an ancient Tuscan tomato variety, Rosso di Pitigliano (RED), obtained by growing plants in normal conditions (-Ctr) or in drought stress conditions (-Ds) for their beneficial effects on vascular related dysfunction. Methods: The antioxidant activity and total polyphenol content (TPC) were measured. The identification of bioactive compounds of tomato peel was performed by HPLC. HUVEC were pre-treated with different TPC of RED-Ctr or RED-Ds, then stressed with H₂O₂. Cell viability, ROS production and CAT, SOD and GPx activities were evaluated. Permeation of antioxidant molecules contained in RED across excised rat intestine was also studied. Results: RED-Ds tomato peel extract possessed higher TPC than compared to RED-Ctr (361.32 ± 7.204 mg vs. 152.46 ± 1.568 mg GAE/100 g fresh weight). All extracts were non-cytotoxic. Two hour pre-treatment with 5 µg GAE/mL from RED-Ctr or RED-Ds showed protection from H₂O₂-induced oxidative stress and significantly reduced ROS production raising SOD and CAT activity (* p < 0.05 and ** p < 0.005 vs. H₂O₂, respectively). The permeation of antioxidant molecules contained in RED-Ctr or RED-Ds across excised rat intestine was high with non-significant difference between the two RED types (41.9 ± 9.6% vs. 26.6 ± 7.8%). Conclusions: RED-Ds tomato peel extract represents a good source of bioactive molecules, which protects HUVECs from oxidative stress at low concentration.

Exploring Genetic Variability among and within Hail Tomato Landraces Based on Sequence-Related Amplified Polymorphism Markers

Landraces are valuable sources of genetic characteristics, which are of plant breeders’ interest to include in breeding programs for crop improvement. We assess the inter- and intra-genetic variability among 96 accessions representing three Hail tomato landrace using DNA-based marker sequence-related amplified polymorphism (SRAP). Seven SRAP primer combinations generated 55 alleles with a polymorphism of 100%, and an average of 7.86 polymorphic alleles per pair of primers. All primers showed an average of 0.68 polymorphic information content (PIC) value and discrimination power (DP) of 14.29. Principal coordinate analysis (PCoA) confirmed the clustering produced via the UPGMA similarity dendrogram allowed for the grouping of the 96 accessions according to its gene bank accession numbers and showed relatively good separation between landraces. A similarity value ranged from 0.04 to 1.0 among accessions of Hail 747, 0.05 to 1.0 in Hail 1072, and from 0.16 to 0.92 in Hail 548. These results showed the landraces harbor a wide range of genetic diversity at both inter and intra-variation levels. AMOVA showed that most of the genetic variation was because of differences within populations (87%). Tomato Hail landraces have well-differentiated genetic populations and admixtures, where Hail 747 formed their separate group, and both Hail 548 and Hail 1072 were admixed, and some accessions showed more diversity pattern. We have to take the SRAP technique’s effectiveness in the study of genetic variability among and within landraces into consideration in the tomato-breeding programs through marker-assessed selection.

Similar Yield Benefits of Hybrid, Conventional, and Organic Tomato and Sweet Pepper Varieties Under Well-Watered and Drought-Stressed Conditions

Global agrobiodiversity is threatened by the replacement of traditional, locally adapted crop varieties with high-yielding and hybrid varieties during the past 60 years, resulting in associated losses of crop, variety, and allele diversity. Locally adapted, traditional varieties are known to perform equal or even better under environmental stress conditions and to be more resilient in unstable cultivation environments. Therefore, European organic vegetable breeding organizations conserve local, traditional varieties and breed new varieties in low-input organic environments, aiming to increase the range of varieties for sustainable cultivation under sub-optimal growing conditions. However, performance of organic vegetable varieties, in comparison to conventional high-yielding and hybrid varieties, under different environmental conditions has not been intensively researched. To contribute to this scientific field, we compared the agronomic and quality performance between hybrid, conventional, and organic tomato and sweet pepper varieties, two economically important species on the EU market under a) well-watered and b) drought stress conditions, using five different varieties (i.e., 30 varieties) as replicates in each of the six groups. Performance of both species was negatively affected by drought, regardless of the breeding background. Equally, for tomato and sweet pepper, hybrids produced higher amounts of individual fruits, however total yield in kg was comparable for hybrid, conventional and organic plants. Considering the agro-ecological importance of enlarging and securing variety diversity in light of changing environmental conditions, we show that the assumed benefits of the hybrids can also be delivered by the organic and conventional varieties. These varieties should be considered as an important source of genetic resources, supporting farmers to adapt to their local climate and environmental conditions in the future.