Cultivated Tomato Plants Research Articles

Development and validation of a multiplex real‐time RT‐PCR test for the screening of tomato (Solanum lycopersicum) for the detection of pepino mosaic virus

AbstractPepino mosaic virus (PepMV) is known to cause a wide range of symptoms in cultivated tomato plants, damaging fruits and crops. Currently, five genotypes of PepMV are known (US1, CH2, EU, LP and PES), which can all infect tomato plants. Tomato seed is a proven pathway for PepMV, and the virus is known to easily spread mechanically during crop handling. A multiplex real‐time reverse transcriptase‐polymerase chain reaction (RT‐PCR) test was developed and validated for the specific identification of PepMV isolates from tomato seeds. This test is designed to be used for diagnostics and seed health tests as a pre‐screen to distinguish negative PepMV samples from suspect samples or as a confirmation test of a positive ELISA or bioassay test result. The multiplex real‐time RT‐PCR test consists of two PepMV‐specific real‐time RT‐PCR tests and a Bacopa chlorosis virus real‐time RT‐PCR test as an internal amplification control. The analytical specificity of the developed test was evaluated by in vitro and in silico analyses. The analytical sensitivity was evaluated by creating three dilution series of naturally PepMV‐infected leaf tissue in healthy tomato seed extracts and the diagnostic specificity and sensitivity were validated on a collection of seed lots.

Response of leaf photosynthesis, chlorophyll content and yield of hydroponic tomatoes to different water salinity levels.

Tomato (Solanum lycopersicum L.) is an important vegetable crop that grows easily under controlled conditions, such as in greenhouses and hydroponics. To overcome freshwater scarcity, researchers are searching for alternatives to groundwater sources such as desalinated water (saline water) for irrigation. High salinity in irrigation water alters physiological functions and crop development, thereby reducing the yield. Best management practices and the use of grafted tomato plants on salt-tolerant rootstocks can alleviate salinity stress. The present study was conducted to address the impact of salinity stress on leaf transpiration (Tr), stomatal conductance (gs), photosynthesis (Pn), leaf chlorophyll content, proline content, and yield of hydroponically cultivated tomato plants. Saline (NaCl) water was used for the preparation of nutrient solution with three salinity levels, electrical conductivity (EC, dS m-1) of 2.5 (control), 6.0, and 9.5. Three commercial tomato cultivars (Valouro-RZ, Ghandora-F1, and Feisty-Red) were used. Both self-rooted plants and plants grafted onto Maxifort rootstocks were transplanted onto a perlite substrate. The recorded data revealed that all studied cultivars were critically affected by higher salinity (≈ 9.5 dS m-1) compared to low (≈ 2.5 dS m-1) and medium (≈ 6.0 dS m-1) salinity levels. The Variations in Tr, Pn, gs, chlorophyll content of leaf, and yield between medium and high salinity trials were reported at 3%, 5%, 9%, 5%, and 7.1%, respectively, whereas no significant differences were observed between low and medium salinities. However, at medium salinity levels, grafted plants performed better in photosynthesis than non-grafted plants. This is due to the accumulation of leaf proline, which maintains osmotic regulation and photosynthetic activity by preventing cell damage at medium salinities. Hence, this study confirmed the use of saline water for growing tomatoes under hydroponic conditions up to an EC of 6.0 dS m-1 including the EC of nutrient fertilizers.

α-Tomatine gradient across artificial roots recreates the recruitment of tomato root-associated Sphingobium.

α-Tomatine is a major saponin that accumulates in tomatoes (Solanum lycopersicum). We previously reported that α-tomatine secreted from tomato roots modulates root-associated bacterial communities, particularly by enriching the abundance of Sphingobium belonging to the family Sphingomonadaceae. To further characterize the α-tomatine-mediated interactions between tomato plants and soil bacterial microbiota, we first cultivated tomato plants in pots containing different microbial inoculants originating from three field soils. Four bacterial genera, namely, Sphingobium, Bradyrhizobium, Cupriavidus, and Rhizobacter, were found to be commonly enriched in tomato root-associated bacterial communities. We constructed a pseudo-rhizosphere system using a mullite ceramic tube as an artificial root to investigate the influence of α-tomatine in modifying bacterial communities. The addition of α-tomatine from the artificial root resulted in the formation of a concentration gradient of α-tomatine that mimicked the tomato rhizosphere, and distinctive bacterial communities were observed in the soil close to the artificial root. Sphingobium was enriched according to the α-tomatine concentration gradient, whereas Bradyrhizobium, Cupriavidus, and Rhizobacter were not enriched in α-tomatine-treated soil. The tomato root-associated bacterial communities were similar to the soil bacterial communities in the vicinity of artificial root-secreting exudates; however, hierarchical cluster analysis revealed a distinction between root-associated and pseudo-rhizosphere bacterial communities. These results suggest that the pseudo-rhizosphere device at least partially creates a rhizosphere environment in which α-tomatine enhances the abundance of Sphingobium in the vicinity of the root. Enrichment of Sphingobium in the tomato rhizosphere was also apparent in publicly available microbiota data, further supporting the tight association between tomato roots and Sphingobium mediated by α-tomatine.

Analisis Harga Pokok Tomat di Kelurahan Kaisabu Baru Kecamatan Sorawolio Kota Baubau

This research examines the price of tomatoes in Kaisabu Baru Village, Sorawolio District and Baubau City. In Kaisabu Baru Village, Sorawolio District, Baubau City, this research seeks to determine the cost of goods sold for tomatoes and determine what variables are obstacles to tomato production. Data analysis used to answer the first goal is by Break Even Point (BEP) analysis, and the second goal is answered using descriptive statistical analysis such as percentages and averages. The samples in this study were farmers who cultivated tomato plants in Kaisabu Baru Village, Sorawolio District, Baubau City, with as many as 33 people. In the calculation of the sample, the Slovin formula is used. Data is collected by directly interviewing farmers, observing research objects, and recording data already available in related offices. The results of this study show: 1) The total average cost of goods sold by respondents per tomato farm is IDR123,224 / planting season, and the average cost of goods sold per hectare is IDR647,412 / planting season.

A single-nucleotide polymorphism in WRKY33 promoter is associated with the cold sensitivity in cultivated tomato.

Natural variations in cis-regulatory regions often affect crop phenotypes by altering gene expression. However, the mechanism of how promoter mutations affect gene expression and crop stress tolerance is still poorly understood. In this study, by analyzing RNA-sequencing (RNA-Seq) data and reverse transcription quantitative real-time PCR validation in the cultivated tomato and its wild relatives, we reveal that the transcripts of WRKY33 are almost unchanged in cold-sensitive cultivated tomato Solanum lycopersicum L. 'Ailsa Craig' but are significantly induced in cold-tolerant wild tomato relatives Solanum habrochaites LA1777 and Solanum pennellii LA0716 under cold stress. Overexpression of SlWRKY33 or ShWRKY33 positively regulates cold tolerance in tomato. Variant of the critical W-box in SlWRKY33 promoter results in the loss of self-transcription function of SlWRKY33 under cold stress. Analysis integrating RNA-Seq and chromatin immunoprecipitation sequencing data reveals that SlWRKY33 directly targets and induces multiple kinases, transcription factors, and molecular chaperone genes, such as CDPK11, MYBS3, and BAG6, thus enhancing cold tolerance. In addition, heat- and Botrytis-induced WRKY33s expression in both wild and cultivated tomatoes are independent of the critical W-box variation. Our findings suggest nucleotide polymorphism in cis-regulatory regions is crucial for different cold sensitivity between cultivated and wild tomato plants.

Heat-shock protein 70-a hub gene-underwent adaptive evolution involved in whitefly-wild tomato interaction.

The whitefly Bemisia tabaci causes severe damage to cultivated tomato plants, but actively avoids the wild tomato Solanum habrochaites. Moreover, the mortality of whitefly increases significantly after feeding with the wild tomato. However, additional experiments are warranted to more carefully elucidate the specific molecular elements underlying the interaction between whitefly and wild tomato. Our results showed that S. habrochaites significantly increases the mortality of whitefly adults and decreases both their fertility and fecundity. In addition, the expression of stress-response genes in whitefly after exposure to S. habrochaites was analyzed using RNA sequencing. Weighted gene co-expression network analysis was conducted to identify the hub genes to determine their potential associations with the mortality of whitefly. These results suggested that the expression of heat-shock protein (HSP), multicopper oxidase, and 2-Oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU) decarboxylase genes were induced in whitefly. To validate the gene associations with whitefly mortality, a high-throughput in vivo model system and RNAi-based gene silencing were used. The results revealed that the RNAi-mediated depletion of the HSP gene, which belongs to the HSP70 subfamily, increased the mortality of whitefly. Furthermore, the selection pressure analysis showed that a total of five amino acid sites of positive selection were identified, three of which were located in the nucleotide-binding domain and the other two in the substrate-binding domain. This is the first report on the potential implication of HSPs in whitefly-wild plant interactions. This study could more precisely identify the molecular mechanisms of whitefly in response to wild tomatoes. © 2022 Society of Chemical Industry.

Application of Phenomics to Elucidate the Influence of Rootstocks on Drought Response of Tomato

The cultivation of nutritionally and economically important crops like tomato are often threatened by dry spells due to drought as these crops largely depend on an assured water supply. The magnitude and intensity of drought is predicted to intensify under climate change scenarios, particularly in semi-arid regions, where water is already a scarce resource. Hence, it is imperative to devise strategies to mitigate the adverse effects of drought on tomato through improvement in the plant’s efficiency to utilise the moisture in the growth medium. Since the root is the entry point for water, its intrinsic structure and functions play a crucial role in maintaining the soil–water–plant continuum during moisture deficit at the rhizosphere. Grafting offers a great opportunity to replace the root system of the cultivated tomato plants with that of wild species and hence provide a rapid solution to modulate root system architecture in contrast to the time-consuming conventional breeding approach. However, the success in developing the best graft combination of cultivated tomato and rootstock depends on the source of rootstock and selection methods. In this study, we used a high throughput phenomics facility to assess the efficiency of tomato, grafted on the rootstocks of different genetic backgrounds, at different levels of moisture in the soil. Rootstocks included tomato cultivars and the hybrids, derived from the crosses involving wild relatives, as donor parents. Among the rootstocks, an interspecific (Solanum lycopersicum × S. pennellii) derivative RF4A was highly efficient in terms of productive use of water. The RF4A rootstock-grafted plants were more conservative in water use with higher plant water status through relatively better stomatal regulation and hence were more efficient in generating greater biomass under water stress conditions. These plants could maintain a higher level of PSII efficiency, signifying better photosynthetic efficiency even under water stress. The distinct response of interspecific rootstock, RF4A, to water stress can be ascribed to the effective root system acquired from a wild parent (S. pennellii), and hence efficient water uptake. Overall, we demonstrated the efficient use of a phenomics platform and developed a protocol to identify promising rootstock–scion combinations of tomato for optimization of water use.

Electroantennogram and machine learning reveal a volatile blend mediating avoidance behavior by Tuta absoluta females to a wild tomato plant

Tomato cultivation is threatened by the infestation of the nocturnal invasive tomato pinworm, Tuta absoluta. This study was based on field observations that a wild tomato plant, Solanum lycopersicum var. cerasiforme, grown in the Mount Kenya region, Kenya, is less attacked by T. absoluta, unlike the cultivated tomato plants like S. lycopersicum (var. Rambo F1). We hypothesized that the wild tomato plant may be actively avoided by gravid T. absoluta females because of the emission of repellent allelochemical constituents. Therefore, we compared infestation levels by the pest in field monocrops and intercrops of the two tomato genotypes, characterized the headspace volatiles, then determined the compounds detectable by the insect through gas chromatography-linked electroantennography (GC-EAG), and finally performed bioassays using a blend of four EAG-active compounds unique to the wild tomato. We found significant reductions in infestation levels in the monocrop of the wild tomato, and intercrops of wild and cultivated tomato plants compared to the monocrop of the cultivated tomato plant. Quantitative and qualitative differences were noted between volatiles of the wild and cultivated tomato plants, and between day and night volatile collections. The most discriminating compounds between the volatile treatments varied with the variable selection or machine learning methods used. In GC-EAG recordings, 16 compounds including hexanal, (Z)-3-hexenol, α-pinene, β-myrcene, α-phellandrene, β-phellandrene, (E)-β-ocimene, terpinolene, limonene oxide, camphor, citronellal, methyl salicylate, (E)-β-caryophyllene, and others tentatively identified as 3,7,7-Trimethyl-1,3,5-cycloheptatriene, germacrene D and cis-carvenone oxide were detected by antennae of T. absoluta females. Among these EAG-active compounds, (Z)-3-hexenol, α-pinene, α-phellandrene, limonene oxide, camphor, citronellal, (E)-β-caryophyllene and β-phellandrene are in the top 5 discriminating compounds highlighted by the machine learning methods. A blend of (Z)-3-hexenol, camphor, citronellal and limonene oxide detected only in the wild tomato showed dose-dependent repellence to T. absoluta females in wind tunnel. This study provides some groundwork for exploiting the allelochemicals of the wild tomato in the development of novel integrated pest management approaches against T. absoluta.

Effects of Root Temperature and Cluster Position on Fruit Quality of Two Cocktail Tomato Cultivars

Managing root temperature can strongly influence plant growth in various species. Our previous work has shown that a positive effect of root cooling on the nutritional quality (sugars, vitamin C, and carotenoids levels) of two cocktail tomato cultivars, while the yield and mineral content was moderately reduced in two seasons. But few studies have investigated which cluster quality is more influenced by root temperature. The main purpose of this study was to evaluate the effects of root temperature and different cluster positions (the first to the fourth clusters) on fruit quality parameters of two cocktail tomato cultivars (‘Amoroso’ and ‘Delioso’). Two root temperatures, cool (10 °C) and control (18–22 °C), were applied to the roots of hydroponically cultivated tomato plants after inflorescence until the final harvest in the greenhouse. The results showed that root cooling has no influence on the biomass of fruits (both dry weight and fresh weight) of all clusters, but it increased the sugar (6.1–8.4%) and vitamin C (9.1–12.5%) concentration of the second cluster of ‘Amoroso’ and the third cluster of ‘Delioso’ compared to the control. In most cases, significant positive changes (8–23.8%) in the levels of lycopene were observed in response to low root temperature treatment, but the effect was dependent on different cluster positions and different cultivars. Most mineral element levels showed no response to the root temperature. Significant reductions (10% and 17.6%) along with the root cooling was only found in the level of zinc and potassium of the first and the second cluster of ‘Delioso’, respectively. It was concluded that the fruits from the second or third clusters containing more sugars, vitamin C, and lycopene, were more influenced by root cooling. In addition, the effect of cluster position on fruit quality was different between two root temperature groups. Root cooling reduced the heterogeneity in fruit quality parameters among the clusters of ‘Amoroso’ and increased the differences in ‘Delioso’.

2-oxoglutarate-dependent dioxygenases drive expansion of steroidal alkaloid structural diversity in the genus Solanum.

Solanum steroidal glycoalkaloids (SGAs) are renowned defence metabolites exhibiting spectacular structural diversity. Genes and enzymes generating the SGA precursor pathway, SGA scaffold and glycosylated forms have been largely identified. Yet, the majority of downstream metabolic steps creating the vast repertoire of SGAs remain untapped. Here, we discovered that members of the 2-OXOGLUTARATE-DEPENDENT DIOXYGENASE (2-ODD) family play a prominent role in SGA metabolism, carrying out three distinct backbone-modifying oxidative steps in addition to the three formerly reported pathway reactions. The GLYCOALKALOID METABOLISM34 (GAME34) enzyme catalyses the conversion of core SGAs to habrochaitosides in wild tomato S. habrochaites. Cultivated tomato plants overexpressing GAME34 ectopically accumulate habrochaitosides. These habrochaitoside enriched plants extracts potently inhibit Puccinia spp. spore germination, a significant Solanaceae crops fungal pathogen. Another 2-ODD enzyme, GAME33, acts as a desaturase (via hydroxylation and E/F ring rearrangement) forming unique, yet unreported SGAs. Conversion of bitter α-tomatine to ripe fruit, nonbitter SGAs (e.g. esculeoside A) requires two hydroxylations; while the known GAME31 2-ODD enzyme catalyses hydroxytomatine formation, we find that GAME40 catalyses the penultimate step in the pathway and generates acetoxy-hydroxytomatine towards esculeosides accumulation. Our results highlight the significant contribution of 2-ODD enzymes to the remarkable structural diversity found in plant steroidal specialized metabolism.

Assessment of Nutrient Usage and Discharge in Tomato Greenhouse

One of the contributors to eutrophication is from agricultural wastewater which contained nutrients such as nitrogen and phosphorus. The agricultural industry in Japan has practice greenhouse plantation recently. In this study, the amount of nutrient concentration and load in the wastewater were investigated. Water samples from water supply, soil medium and effluent were collected at a greenhouse in Japan which cultivated tomato plants in coconut husk medium. The assessment was conducted every two weeks for regular monitoring for three months. The results showed that concentrations of all nutrients have same concentration level in the water supply samples from January 13th to March 15th. The concentration of supplied nutrient on March 29th increased due to high concentration of nutrients in medium water samples which preventing the nutrient uptake by the plant. The nutrient uptake by the plants were in the same range which NH4-N was between 13.6 mg/L to 14.99 mg/L, NO2-N was between 2.3 to 2.5 mg/L, NO3-N was between 135.9 mg/L to 152.5 mg/L and PO4-P was between 70.12 to 76.64 mg/L. The concentration of nutrients in drainage was below the permissible limit of Japan’s Effluent Standard. As a result, it can be concluded that using greenhouses as an alternative farming method contributes in reducing nutrient discharge by controlling the nutrient supply to the plants.

Effects of Clonostachys rosea f. catenula Inoculum on the Composting of Cabbage Wastes and the Endophytic Activities of the Composted Material on Tomatoes and Red Spider Mite Infestation.

Globally, fungal inocula are being explored as agents for the optimization of composting processes. This research primarily evaluates the effects of inoculating organic vegetable heaps with the entomopathogenic fungus Clonostachys rosea f. catenula (Hypocreales) on the biophysicochemical properties of the end-product of composting. Six heaps of fresh cabbage (Brassica oleracea var. capitata) waste were inoculated with C. rosea f. catenula conidia and another six were not exposed to the fungus. The composted materials from the fungus- and control-treated heaps were subsequently used as a medium to cultivate tomatoes (Solanum lycopersicum). The biophysicochemical characteristics of the composted materials were also assessed after composting. In addition, the protective effect of the fungal inoculum against red spider mite (Tetranychus urticae) infestations in the tomatoes was evaluated through the determination of conidial colonization of the plant tissue and the number of plants infested by the insect. Furthermore, phytotoxicity tests were carried out post experiment. There were few significant variations (p < 0.05) in heap temperature or moisture level between treatments based on the weekly data. We found no significant differences in the levels of compost macronutrient and micronutrient constituents. Remarkably, the composted materials, when incorporated into a growth medium from fungus-treated heaps, induced a 100% endophytic tissue colonization in cultivated tomato plants. While fewer red spider mite infestations were observed in tomato plants grown in composted materials from fungus-treated heaps, the difference was not significant (χ2 = 0.96 and p = 0.32). The fungal treatment yielded composted materials that significantly (p < 0.05) enhanced tomato seed germination, and based on the phytotoxicity test, the composted samples from the heaps exposed to the C. rosea f. catenula inoculum were not toxic to tomato seeds and seedlings. In conclusion, this study showed that C. rosea f. catenula improved the quality of composted materials in terms of fungal endophytism and seed germination.

Biological performance and oviposition preference of tomato pinworm Tuta absoluta when offered a range of Solanaceous host plants

The tomato pinworm Tuta absoluta (Lepidoptera: Gelechuidae) is native to South America and has now become the main tomato pest in Europe, Africa and Asia. The wide range of host plants attacked by this pest has been reported as one of the main reasons for the success of this important insect species. However, the information currently available on the biological performance of T. absoluta on Solanaceae has been obtained from a limited number of host species. The Solanaceae family is composed of thousands of species, many of which are potential hosts for T. absoluta. Our results showed that the highest oviposition rates occurred on cultivated tomato plants, potato and wild tomato. The lowest rates occurred on “gilo”, “jurubeba”, green pepper and pepper. The highest survival rates of the immature stages occurred on potato and the lowest on pepper, green pepper and “jurubeba”. Female fertility, following infestation of the different plant species, was highest for insects that developed on tomato or potato and the lowest rates were seen on American black nightshade. The net reproductive rate and the intrinsic growth rate were highest on potato and tomato. Cluster analysis grouped tomato and potato as highly susceptible to attack, American black nightshade, juá, eggplant, gilo and wild tomato as moderately susceptible, whilst pepper, green pepper and jurubeba were categorized as resistant to T. absoluta. These results clearly demonstrate that the choice of solanaceous host plant species has a direct impact on the fitness parameters of the tomato pinworm as well as survival potential, dispersion and establishment at new sites. These results are important for the planning of integrated pest management strategies.

Hormetic doses of UV‐C light decrease the susceptibility of tomato plants to Botrytis cinerea infection

AbstractPreharvest hormetic doses of UV‐C radiation can decrease the susceptibility of tomato leaves to Botrytis cinerea L. infection. UV‐C light treatments have been shown to be very effective for reducing disease development in several species, including tomato (Solanum lycopersicum L.). Treating cultivated tomato plants with UV‐C light is of interest not only because of the disinfecting effects of UV‐C light but also because of its ability to stimulate plant defences (SDP) against diseases, provided that the applied doses are high enough to be effective while low enough to prevent deleterious effects. In the present study, the effects of UV‐C light on plants were evaluated by biochemical analyses, including analyses of the activities of antioxidant enzymes and phenylalanine lyase (PAL); the concentration of malondialdehyde (MDA), an indicator of membrane integrity; and chlorophyll fluorescence parameters, such as the maximum quantum efficiency of photosystem II (FV/FM) and the Strasser performance index (PI). In this work, treatments with single doses of 0.85 kJ/m2 of UV‐C light were found to significantly increase plant defences against B. cinerea, reducing the affected leaf area by 51% compared to the affected area of control plants. This decrease in susceptibility was associated with increased PAL activity and the amount of bound phenolics compared to levels in control plants (not treated with UV‐C).

Effect of modified greenhouse covers on the development of plants of lycopersicon esculentum mill

The influence of six greenhouse cover types on the development of the vegetative phase of cultivated tomato plants (Lycopersicon esculentum Mill.) was analyzed. The cover films were manufactured by extrusion – blow molding. Special emphasis was put on measuring root, stem and leaf length and dry matter content of the plants, the results of which were compared to those obtained from plants sown outdoors. As expected, the cultivated plants exhibited more vigorous growth when compared to that of the plants grown under free exposure. Films additivated with polymers allowing higher percentages of light transmission and haze determined higher greenhouse inner temperatures, which, in turn, promoted biomass production in the plantation. The presence of an infrared blocker in the plastic film formulations prevented the temperature inside the greenhouses from decreasing drastically below the outer temperature overnight. Additives such as the UV absorber SMARTLIGHT RL1000™ and the red pigment IRGALITE BASF® 2BP™, which increase the amount of red light received by the plants, thus modifying the R:RF ratio, were found to affect the morphology of the studied plants. Although the effect of photomorphogenesis is weak, a slight decrease in the length and area of the tomato leaves could be observed when the R:RF ratio was high.

Natural mortality factors of tomato leafminer Tuta absoluta in open-field tomato crops in South America.

Little importance has been given to the role of natural mortality factors (biotic and abiotic) in the regulation of tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) populations. The present study determined the action of mortality factors on T. absoluta populations infesting cultivated tomato crops. Eighty ecological life tables for T. absoluta in field cultivated tomato plants were constructed and analyzed. Total T. absoluta mortality was 99.08%, with 38.76% mortality during the egg phase, 57.20% in the larva phase and 3.12% in the pupal phase. The main mortality factors during the egg stage were predation, parasitism and egg inviability. In the larval stage, the main mortality factors were predation, parasitism, entomopathogenic agents and physiological disorders. In the pupal stage, the main mortality factor was predation. The larvae of the third and fourth instar were more susceptible to the action of mortality factors and the predatory wasp, Protonectarina sylveirae, was the main insect predator of these larvae. The T. absoluta population is regulated under field conditions by the action of natural enemies of the larvae. The predatory wasp P. sylveirae is very important in the regulation of T. absoluta populations in open-field tomato crops in Brazil. © 2018 Society of Chemical Industry.

Overexpression of a SDD1-Like Gene From Wild Tomato Decreases Stomatal Density and Enhances Dehydration Avoidance in Arabidopsis and Cultivated Tomato.

Stomata are microscopic valves formed by two guard cells flanking a pore, which are located on the epidermis of most aerial plant organs and are used for water and gas exchange between the plant and the atmosphere. The number, size and distribution of stomata are set during development in response to changing environmental conditions, allowing plants to minimize the impact of a stressful environment. In Arabidopsis, STOMATAL DENSITY AND DISTRIBUTION 1 (AtSDD1) negatively regulates stomatal density and optimizes transpiration and water use efficiency (WUE). Despite this, little is known about the function of AtSDD1 orthologs in crop species and their wild stress-tolerant relatives. In this study, SDD1-like from the stress-tolerant wild tomato Solanum chilense (SchSDD1-like) was identified through its close sequence relationship with SDD1-like from Solanum lycopersicum and AtSDD1. Both Solanum SDD1-like transcripts accumulated in high levels in young leaves, suggesting that they play a role in early leaf development. Arabidopsis sdd1-3 plants transformed with SchSDD1-like under a constitutive promoter showed a significant reduction in stomatal leaf density compared with untransformed sdd1-3 plants. Additionally, a leaf dehydration shock test demonstrated that the reduction in stomatal abundance of transgenic plants was sufficient to slow down dehydration. Overexpression of SchSDD1-like in cultivated tomato plants decreased the stomatal index and density of the cotyledons and leaves, and resulted in higher dehydration avoidance. Taken together, these results indicate that SchSDD1-like functions in a similar manner to AtSDD1 and suggest that Arabidopsis and tomatoes share this component of the stomatal development pathway that impinges on water status.

WRKY1 acts as a key component improving resistance against Alternaria solani in wild tomato, Solanum arcanum Peralta.

SummaryEarly blight (EB), caused by Alternaria solani, is a major threat to global tomato production. In comparison with cultivated tomato (Solanum lycopersicum), a wild relative, S. arcanum exhibits strong resistance against EB. However, molecular cascades operating during EB resistance in wild or cultivated tomato plants are largely obscure. Here, we provide novel insight into spatio‐temporal molecular events in S. arcanum against A. solani. Transcriptome and co‐expression analysis presented 33‐WRKYs as promising candidates of which 12 SaWRKYs displayed differential expression patterns in resistant and susceptible accessions during EB disease progression. Among these, SaWRKY1 exhibited induced expression with significant modulation in xyloglucan endotrans hydrolase 5 (XTH5) and MYB2 expressions that correlated with the disease phenotypes. Electro‐mobility shift assay confirmed physical interaction of recombinant SaWRKY1 to SaXTH5 and SaMYB2 promoters. Comparative WRKY1 promoter analysis between resistant and susceptible plants revealed the presence of crucial motifs for defence mechanism exclusively in resistant accession. Additionally, many defence‐related genes displayed significant expression variations in both the accessions. Further, WRKY1 overexpressing transgenic plants exhibited higher levels of EB resistance while RNAi silencing lines had increased susceptibility to A. solani with altered expression of XTH5 and MYB2. Overall, these findings demonstrate the positive influence of WRKY1 in improving EB resistance in wild tomato and this could be further utilized as a potential target through genetic engineering to augment protection against A. solani in crop plants.

Transcriptome Analysis of the Sm-Mediated Hypersensitive Response to Stemphylium lycopersici in Tomato.

Gray leaf spot disease caused by Stemphylium lycopersici is a major disease in cultivated tomato plants and threatens tomato-growing areas worldwide. Sm is a single dominant gene that confers resistance to tomato gray leaf spot disease agent. However, the underlying molecular mechanism remains unclear. Here, resistant (cv. Motelle, containing the Sm gene) and susceptible (cv. Moneymaker) plants were inoculated with virulent Stemphylium lycopersici isolate at a time point at which both cultivars showed a strong response to S. lycopersici infection. Transcriptome analyses were performed in both cultivars using RNA-seq. The number of differentially expressed genes (DEGs) was higher in Motelle than Moneymaker. Functional classification revealed that most DEGs were involved in plant–pathogen interactions, plant hormone signal transduction, regulation of autophagy, glycerophospholipid metabolism, and α-linolenic acid metabolism. Moreover, the genes that were significantly up-regulated in Sm tomatoes were involved in plant–pathogen interaction pathways. A total of 26 genes were selected for confirmation of differentially expressed levels by quantitative real-time PCR. This knowledge will yield new insights into the molecular mechanism of Sm responses to S. lycopersici infection.

Tomato tolerance to abiotic stress: a review of most often engineered target sequences

Tomato is one of the most often cultivated vegetable species worldwide. Due to the anti-oxidative and anti-cancer properties of lycopene, tomato consumption as well as production is still increasing. However, its productivity is impaired by a wide range of abiotic stresses, and the establishment of stress-tolerant crops is a key challenge for agricultural biotechnology. Until now, a few genetic approaches have been used to achieve stress tolerance in cultivated tomato plants. Such achievements are based on current knowledge concerning plant adaptation. The presence of adverse environmental factors like extreme temperatures, salinity or drought cause definite biochemical and physiological consequences. Mostly, these are the changes in the metabolic pathways, the expression of stress-inducible genes or the accumulation of low-molecular compounds that play a crucial role in maintaining the plasticity of reactions. The biotechnological methods used to modify tomato to produce “upgraded” plants are based on introgression of several genes coding enzymes known to mitigate stress or genes contributing to signalling and diverse regulatory pathways. Here, we present an overview of the most often chosen target sequences/molecules that are genetically delivered or engineered to obtain tolerance to environmental constraints. Since adverse conditions cause interrelated stress responses, it is the tolerance molecular players that are consecutively presented in this paper rather than the typically reviewed division of stress types.