Tomato Research Articles

Salicylic Acid Modulates Volatile Organic Compound Profiles During CEVd Infection in Tomato Plants

Background:Citrus Exocortis Viroid (CEVd) is a non-coding RNA pathogen capable of infecting a wide range of plant species, despite its lack of protein-coding ability. Viroid infections induce significant alterations in various physiological and biochemical processes, particularly impacting plant metabolism. This study shows the metabolic changes upon viroid infection in tomato plants (Solanum lycopersicum var. ‘MoneyMaker’) exhibiting altered levels of salicylic acid (SA), a key signal molecule involved in the plant defence against this pathogen. Methods: Transgenic RNAi_S5H lines, which have the salicylic acid 5-hydroxylase gene silenced to promote SA accumulation, and NahG lines, which overexpress a salicylate hydroxylase to degrade SA into catechol and prevent its accumulation, were used to establish different SA levels in plants, resulting in varying degrees of resistance to viroid infection. The analysis was performed by using gas chromatography–mass spectrometry (GC-MS) to explore the role of volatile organic compounds (VOCs) in plant immunity against this pathogen. Results: Our results revealed distinct volatile profiles associated with plant immunity, where RNAi_S5H-resistant plants showed significantly enhanced production of monoterpenoids upon viroid infection. Moreover, viroid-susceptible NahG plants emitted a broad range of VOCs, whilst viroid-tolerant RNAi_S5H plants exhibited less variation in VOC emission. Conclusions: This study demonstrates that SA levels significantly influence metabolic responses and immunity in tomato plants infected by CEVd. The identification of differential emitted VOCs upon CEVd infection could allow the development of biomarkers for disease or strategies for disease control.

Relative Susceptibility of Tomato and Pepper Crops to Root-Knot Nematodes in Georgia, Fall 2023

Southern root-knot nematodes (Meloidogyne incognita) are sedentary endoparasites that reduce crop yield. These pests are problematic in U.S. vegetable production where sandy soils and plasticulture favor nematode reproduction. In Georgia multiple crops are grown under the same plastic mulch over multiple seasons and tomato (Solanum lycopersicum) or pepper (Capsicum annuum) are selected as the first crop. We evaluated the susceptibility of pepper cultivar ‘Regulator’ and tomato cultivar ‘STM2255’ to root-knot nematodes, with and without 1,3-dichloropropene. Results showed lower nematode populations and galling severity in ‘Regulator’ compared to ‘STM2255,’ demonstrating that selecting the less-susceptible pepper cultivar can reduce nematode population further.

Foliar Application of Equisetum arvense Extract Enhances Growth, Alleviates Lipid Peroxidation and Reduces Proline Accumulation in Tomato Plants Under Salt Stress

Salinity is a major abiotic stress that affects physiological and biochemical processes in plants, reducing the growth, yield, and quality of crops. This problem has been intensified with the reduction of the cultivated area. This study evaluated the response of hydroponically grown tomato plants under salt stress to foliar applications of E. arvense extracts. Macro- and micronutrients, as well as silicon and phenolic compounds, were extracted using magnetic stirring and water reflux methods, the latter being the most effective. To evaluate the efficacy of E. arvense extracts, spraying was applied at two different doses: EQ-R-1 (23.6 mg·L−1 Si and 0.5 mM phenolic compounds) and EQ-R-2 (5.9 mg·L−1 Si and 0.125 mM phenolic compounds). Foliar application of both extracts alleviated salinity effects by reducing sodium uptake. E. arvense extracts mitigated oxidative stress by a decrease in electrolyte leakage by 29% and malondialdehyde and H2O2 concentrations by 69% and 39%, respectively, for the extract with the lowest dose. In addition, EQ-R-2 was also more effective by reducing 51.5% proline accumulation. These findings showed the potential use of E. arvense extracts as biostimulants to enhance plant tolerance to salinity providing new perspectives in agricultural systems.

Resistance to the Insect Vector Bemisia tabaci Enhances the Robustness and Durability of Tomato Yellow Leaf Curl Virus Resistance Conferred by Ty-1.

Tomato yellow leaf curl virus (TYLCV) is a begomovirus (genus Begomovirus, family Geminiviridae) transmitted persistently by the whitefly Bemisia tabaci. It causes tomato yellow leaf curl disease (TYLCD), resulting in significant yield losses worldwide. TYLCD is controlled mainly by using F1 hybrid tomato cultivars harboring the TYLCV resistance gene Ty-1. However, infected Ty-1-bearing tomato plants accumulate viral DNA, which may eventually lead to the emergence of a resistance-breaking TYLCV variant. Recently, a B. tabaci-resistant tomato line derived from the introgression of type IV leaf glandular trichomes and acylsucrose secretion from wild tomato (Solanum pimpinellifolium) was shown to effectively control the spread of TYLCV. In this study, we combined B. tabaci resistance and Ty-1-based TYLCV resistance to increase the robustness and durability of the TYLCD resistance mediated by Ty-1 in tomato plants. Specifically, we characterized and used a Group 2-like isolate of the Israel strain of TYLCV (TYLCV-IL-G2) that contributes to TYLCD epidemics in southeastern Spain. A comparison with isolates of the previously identified TYLCV variant revealed TYLCV-IL-G2 has a similar host range, but it induces a slightly more severe TYLCD in Ty-1-bearing tomato plants. Moreover, we demonstrated that acylsucrose-producing B. tabaci-resistant tomato plants can limit the spread of TYLCV-IL-G2 better than a near-isogenic line lacking type IV trichomes and unable to secrete acylsucrose. Pyramiding Ty-1-based TYLCV resistance and B. tabaci resistance provided by type IV glandular trichomes helped to decrease the effects of TYLCV on Ty-1-bearing tomato plants as well as the likelihood of TYLCV evolution in infected plants.

An Evaluation of the Energy Potential of Agri-Food Waste: Green Residues from Tomato (Solanum lycopersicum L.) and Shea Nutshells (Vitellaria paradoxa)

Addressing the agricultural challenges of agri-food waste accumulation, this study assessed the energy potential of green residues from tomato (Solanum lycopersicum L. cv. Kmicic) plants in different fertilizer configurations and Shea nutshell (Vitellaria paradoxa) waste. Two key parameters were compared: (I) Calorific Value (CV), representing thermal treatment, and (II) Biogas and Biomethane production potential, representing biochemical treatment. Potential was estimated using the Baserga method and the fermentable organic matter (FOM) method. Additionally, the effect of tomato fertilization on the elemental composition and energy potential of its waste was analyzed. Shea waste showed better properties for both thermal and biochemical utilization, with a CV of 16.29 MJ/kg. The Baserga and FOM methods of estimation showed that the highest Biogas yields from Shea waste were 504.18 and 671.39 LN/kg DM, respectively. Among fertilized tomato residues, volcanic tuff fertilizer additive resulted in an optimal C/N ratio (28.41) and a high Biogas production potential of 457.13 LN/kg DM (Baserga) and 542.85 LN/kg DM (FOM). These findings demonstrate the feasibility of employing tomato waste and Shea waste as promising feedstock for energy production.

Comparative Evaluation of the Efficacy of Three Nutrient Solutions for Hydroponic Tomato (Solanum lycopersicum L.) Production in Côte d'Ivoire

Background: The growing demand for tomatoes (Solanum lycopersicum L.) in Côte d'Ivoire requires the development of new cultivation techniques and methods across the country. The regular consumption of tomatoes or tomato-based products contributes to the food and nutritional security of the population. However, its low production does not satisfy the Ivorian population. Objectives: This study was carried out to develop an effective nutrient solution to improve the yield of hydroponic tomatoes in Côte d'Ivoire with the aim of reducing dependence on arable land. Methodology: Conducted in Bouaké, in the center of the country, this study evaluated three formulations of nutrient solutions on the Mongal F1 tomato variety. Due to the complexity of developing nutrient solutions suitable for all vegetable species, three nutrient solution formulations were prepared by dissolving commercial fertilizers available in local markets. Observations and measurements were made on growth and yield parameters. All data were subjected to an analysis of variance at the 5% level. In case of significant differences, the Tukey test was used for the separation of the means. Results: The results showed that hydroponics registers to early flowering 28 to 29 days after transplanting, regardless of the nutrient solution used. The height of the plants with solution 1 was lower than that of the plants with solutions 2 and 3, i.e. 58.7 cm compared to 68.2 cm and 67.7 cm. Nutrient Solution 3 produced the highest number of fruits per plant, with 25 fruits, compared to 19 for Solution 2 and 20.5 for Solution 1. This solution proved to be numerically more efficient, with 1128.3 g of marketable fruit per plant, compared to 941.1 g for solution 2 and 1055 g for solution 1. The highest rate of non-marketable fruit was recorded with solution 1, i.e. 4% compared to 3.8% of solution 2 and 2.8% solution 3. Conclusion: In view of these results, nutrient solution 3 may represent an effective alternative to improve the yield of tomatoes in hydroponics in Côte d'Ivoire. Using this solution will allow growers to adjust nutrient rates and irrigation systems to maximize the yield and quality of marketable fruit.

Determining the function of ripening associated genes and biochemical changes during tomato (Solanum lycopersicum L.) fruit maturation.

This article examines biochemical alterations and gene expression changes during tomato fruit physiology. The chroma index increases from mature green (41.27) to red ripe (48.36) stages, and the texture softens from mature green (43.56 N) to red ripe (24.75 N). Reducing sugar and total carotenoid levels rise at the red ripe stage. Free radical content was elevated in the early stages (7nM) of ripening and declined at the later stages (4nM). The specific activity of α-mannosidase and β-N-acetyl hexosaminidase was high at the breaker (0.077 & 0.075 U/mg, respectively) stages, while polygalacturonase activity was high at red ripe (1.173 U/mg) stage. qPCR experiments revealed that the α-mannosidase was upregulated during the breaker (1.2 fold) stages of tomato ripening, the β-N-acetyl Hexosaminidase was upregulated throughout the breaker (2 fold), and pink (1.2 fold) stages of tomato ripening, and the β-xylosidase was upregulated significantly during the breaker stage (3.9 fold) of tomato ripening. The current findings revealed that the α-Mannosidase (0.77), β-N-acetylhexosaminidase (0.99), xylosidase (0.85), ethylene-responsive factors (0.86), aminocylco propane carboxylic oxidase (0.90), and pectin methylesterase (0.83), were significantly associated with textural softening. Polygalacturonase (0.75) positively correlated to reducing sugar formation, aminocylco propane carboxylic synthase 4 (0.96) expression correlates with chroma changes during tomato fruit ripening. These correlations illustrate the complex interplay between gene expression and the physical and biochemical changes occurring during tomato fruit ripening.

Comparative Transcriptome Analysis Reveals Expression of Defense Pathways and Specific Protease Inhibitor Genes in Solanum lycopersicum in Response to Feeding by Tuta absoluta

Understanding plant-insect interactions can help control the harm of herbivorous pests. According to transcriptome data, transcripts of Solanum lycopersicum responding to feeding by Tuta absoluta were screened for important endopeptidase inhibitors. These genes were annotated as serine-type endopeptidase inhibitors from the potato inhibitor I family, potato type II proteinase inhibitor family, and soybean trypsin inhibitor (Kunitz) family. Based on the analysis of expression patterns, Solyc09g084480.2, Solyc03g020080.2, Solyc03g098760.1, and Solyc01g009020.1 were identified as key genes in the defense system of S. lycopersicum. The major endopeptidase genes such as Tabs008250, Tabs007396, and Tabs005701 in the larval stages of T. absoluta were also detected as potential targets of the plant endopeptidase inhibitors. The interaction mode between these endopeptidase and endopeptidase inhibitors was predicted based on the protein structure construction. This study aims to reveal the molecular response of S. lycopersicum to feeding by T. absoluta with high throughput sequencing and bioinformatics analysis.

Comparative Response of Tomato and Pepper to 1, 3-Dichloropropene and Fluopyram for Root-Knot Nematode Management in Georgia, Spring 2023

Southern root-knot nematodes (Meloidogyne incognita) are sedentary endoparasites that thrive in sandy soils and plasticulture systems, severely impacting vegetable yields. In Georgia, vegetable growers often plant multiple crops on the same plastic mulch across multiple seasons, with tomato (Solanum lycopersicum) or pepper (Capsicum annuum) commonly selected as the first crop. We evaluated the susceptibility of pepper cultivar ‘Regulator’ and tomato cultivar ‘STM2255’ to root-knot nematodes, with and without 1,3-dichloropropene and fluopyram. While pepper treatments had numerically lower nematode density than tomato, both 1,3-dichloropropene and fluopyram significantly reduced nematode density and galling severity at harvest, demonstrating their effectiveness for nematode management.

Combined effects of gibberellin and vermiwash on the life history and antioxidant system of Phthorimaea absoluta (Meyrick) in tomato plants

Tomato (Lycopersicon esculentum Miller), is a globally important agricultural product, yet it is under significant threat from pests such as the tomato leaf miner, Phthorimaea absoluta (Meyrick) (Lepidoptera: Gelechiidae). This study investigates the combined effects of gibberellin and vermiwash treatment on the life history and antioxidant system of P. absoluta. Given the pest’s resistance to many chemical pesticides, alternative control methods are crucial. Gibberellins are plant growth hormones known for their role in plant development and stress responses, while vermiwash is a bio-fertilizer rich in nutrients and microbial agents. We applied gibberellin and vermiwash (GV treatment) to tomato plants and assessed the impact on P. absoluta developmental stages, reproduction, and enzymatic activities. Our results show significant differences in larval development times (32.06 ± 0.39) and survival rates (0.53 ± 0.09) between treated and control groups (27.38 ± 0.35 and 0.80 ± 0.07, respectively). The GV treatment prolonged the total lifespan of P. absoluta (44.31 ± 0.51) but reduced its intrinsic rate of increase (r) (0.086 ± 0.009) and finite rate of increase (λ) (1.090 ± 0.009). Enzymatic assays revealed altered antioxidant and detoxifying enzyme activities in treated larvae. This study suggests that gibberellin and vermiwash treatments could be incorporated into pest management strategies for sustainable tomato production.

Can fungal endophytes suppress Trialeurodes vaporariorum and the transmission of tomato infectious chlorosis and chlorosis viruses in field conditions?

Field trials were conducted for two seasons in two experimental sites (Mwea in Kirinyaga and Ngoliba in Kiambu counties of Kenya) to assess the efficacy of fungal endophytes Hypocrea lixii F3ST1 and Trichoderma asperellum M2RT4 in the control of Trialeurodes vaporariorum vector of tomato infectious chlorosis virus (TICV) and tomato chlorosis virus (ToCV) through seeds inoculation. TICV and ToCV’s disease incidence, severity and the yield were also evaluated. All the fungal endophytes successfully colonized all the tomato plant parts, but the highest root colonization was observed in H. lixii F3ST1 compared to the T. asperellum M2RT4 in both seasons. The number of nymphs was significantly lower in the endophytically colonized tomato plants than the control treatments in all the seasons and at both sites. However, the lowest number of nymphs was recorded in H. lixii F3ST1 compared to T. asperellum M2RT4. On the other hand, the TICV and ToCV disease incidence and severity rates were lower in endophytically colonized tomato crops compared to the control plots. This could be attributed to the reduction in the virus replication and lower feeding ability of T. vaporariorum that was characterized by less excretion of honeydew causing sooty mold. However, no significant difference was observed in ToCV disease severity rates among the treatments and across the seasons. The yield was significantly higher in endophyte plots than the control treatments in both sites and across the two seasons. This study demonstrates that H. lixii F3ST1 and T. asperellum M2RT4 endophytically colonized tomato plants and conferred systemic resistance against T. vaporariorum vector, and significantly reduced the transmission of TICV and ToCV, contributing to high reduction of both diseases’ incidence and severity in the field. However, further studies are warranted to confirm these results at large scale trials.

Stutzerimonas stutzeri culture enhances microbial community structure and tomato seedling growth in saline soil.

Plant growth-promoting rhizobacteria (PGPR) improve microbial community structure, promote crop growth, and reduce greenhouse gas emissions in agricultural soils; however, the effects of PGPR fermentation on the growth and salt tolerance of tomato plants remain unclear. In this study, we aimed to investigate the effects of the PGPR Stutzerimonas stutzeri NRCB010 on the microbial communities, tomato growth, and nitrous oxide (N2O) emissions in saline soil by performing a greenhouse pot experiment. The experiment was conducted under two soil salt concentrations (0 and 3 g kg-1 NaCl) and three treatments (LSFJ broth, NRCB010 cells, and NRCB010 culture). Both salt stress and NRCB010 treatments significantly affected the physicochemical properties and microbial community structure of tomato rhizosphere soil. Treatment with 3 g kg-1 NaCl significantly reduced the shoot and root dry weights of the plants compared with those of the control plants. Application of NRCB010 cells as well as that of culture promoted the growth of tomato seedlings and alleviated salt stress. The copy number changes in the nosZⅠ gene on day 3 and amoA gene on day 25 demonstrated that NRCB010 cells significantly reduced soil N2O emissions when treated with 0 g kg-1 NaCl. Furthermore, soil physicochemical properties, plant biomass, and soil microbial diversity were correlated with each other. The results emphasize the enormous potential of S. stutzeri NRCB010 culture to resist abiotic stress, promote crop growth, and improve the rhizosphere soil microenvironment; however, its ability to decrease N2O emissions is constrained by soil salinity.

Tomato mitogen-activated protein kinase: mechanisms of adaptation in response to biotic and abiotic stresses

Plants live under various biotic and abiotic stress conditions, and to cope with the adversity and severity of these conditions, they have developed well-established resistance mechanisms. These mechanisms begin with the perception of stimuli, followed by molecular, biochemical, and physiological adaptive measures. Tomato (Solanum lycopersicum) is a globally significant vegetable crop that experiences several biotic and abiotic stress events that can adversely impact its quality and production. Mitogen-activated protein kinases (MAPKs) in tomato plants have crucial functions of mediating responses to environmental cues, internal signals, defense mechanisms, cellular processes, and plant development and growth. MAPK cascades respond to various environmental stress factors by modulating associated gene expression, influencing plant hormone synthesis, and facilitating interactions with other environmental stressors. Here, we review the evolutionary relationships of 16 tomato SlMAPK family members and emphasize on recent studies describing the regulatory functions of tomato SlMAPKs in both abiotic and biotic stress conditions. This review could enhance our comprehension of the MAPK regulatory network in biotic and abiotic stress conditions and provide theoretical support for breeding tomatoes with agronomic traits of excellent stress resistance.

Integration of Deep Learning with Fox Optimization Algorithm for Early Detection and Classification of Tomato Leaf and Fruit Diseases

Tomato is a common vegetable crop extensively cultivated in the farming lands in India. The hot climate of India is perfect for its development, but particular weather conditions along with many other aspects affect the growing of tomato plants. Apart from these natural disasters and weather conditions, plant diseases consist a major issue in crop production. Precisely classifying leaf and fruit diseases in tomato plants is a vital step toward computerizing processes. Traditional disease detection models for tomato crops often fall short in predictability. To address this, Machine Learning (ML) and Deep Learning (DL) models have been developed, presenting advanced classification capabilities and the ability to manage the vast variability in agricultural data that conventional computer vision models struggle with. This work presents an Integration of DL with Fox Optimization Algorithm (FOA) for the Recognition and Classification of Tomato Leaf and Fruit Diseases (IDLFOA-DCTLFD). The major objective of the proposed IDLFOA-DCTLFD model is to enhance the detection and classification outcomes of tomato leaf and fruit diseases. At the initial stage, the Median Filter (MF) model is used for pre-processing and the Efficient Channel Attention-SqueezeNet (ECA-SqueezeNet) model is employed for feature extraction. For the hyperparameter tuning process, the proposed IDLFOA-DCTLFD technique implements the FOA. Finally, a Wasserstein Generative Adversarial Network (WGAN) is utilized for the detection of tomato leaf and fruit diseases. The IDLFOA-DCTLFD method is experimentally examined in a tomato leaf and fruit dataset. The experimental validation of the IDLFOA-DCTLFD methodology portrayed a superior accuracy value of 98.02%, surpassing the existing techniques.

Bioadsorbent effect of Abutilon indicum, L., on paper mill effluent and its impact on the Physico chemical characteristics of Lycopersicum esculentum, Mill.

Phytoremediation is the use of plant’s natural ability to degrade, or remove toxic chemicals and pollutants from soil or water. In this regard, phytoremediation study was carried out by the biomass of commonly available weed plant Abutilon indicum, L. in different concentrations (0.5%, 1%, 1.5% and 2% (w/v)) with 30% (v/v) concentration of paper mill effluent on the growth and biochemical characteristics of Lycopersicum esculentum, Mill. After the phytotreatment of paper mill effluent with Abutilon indicum, L all the physicochemical parameters especially, total dissolved solids, biological oxygen demand, chemical oxygen demand, electrical conductivity and oil and grease were significantly reduced when compared to the untreated paper mill effluent. The beneficial effects of the phytotreated paper mill effluent were studied by treating the seedlings of Lycopersicum esculentum, Mill. from the 7th day of sowing and continued till 21st day; then the seedlings of Lycopersicum esculentum were analyzed for their growth and biochemical characteristics and compared with the control maintained with water and 30% effluent. The growth and biochemical characteristics were found to be improved significantly than with the application of untreated paper mill effluent. The photosynthetic pigment content such as chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, soluble sugar and protein contents were increased after the application of phytotreated effluent. But as a contrast, anthocyanin, aminoacid, proline, leaf nitrate, total phenol and enzyme activities such as catalase and peroxidase were found to be reduced in the phytoremediated effluent treated seedlings. In the present study, it is concluded that, Abutilon indicum, L., is a suitable alternate for the remediation of paper mill effluent by reducing all the pollutants from the effluent and relieved the experimental plants from stress.

Halophyte-based crop managements induce biochemical, metabolomic and proteomic changes in tomato plants under saline conditions.

Halophytes display distinctive physiological mechanisms that enable their survival and growth under extreme saline conditions. This makes them potential candidates for their use in saline agriculture. In this research, tomato (Solanum lycopersium Mill.) was cultivated in moderately saline conditions under two different managements involving Arthrocaulon macrostachyum L., a salt accumulator shrub: intercropping, i.e., co-cultivation of tomato/halophyte; and crop rotation, in which tomato is grown where the halophyte was previously cultivated. The effect of these crop managements was evaluated in tomato plants in comparison with tomato in monoculture, with regards to physiological and biochemical variables and metabolomic and proteomic profiles. Both halophyte-based managements reduced soil salinity. Crop rotation enhanced photosynthesis and protective mechanisms at the photosynthetic level. In addition, both crop managements altered the hormone profile and the antioxidant capacity, whereas a reactive oxygen species over-accumulation in leaf tissues indicated the establishment of a controlled mild oxidative stress. However, tomato production remained unchanged. Metabolomic and proteomic approaches suggest complex interactions at the leaf level, driven by the influence of the halophyte. In this regard, an interplay of ROS/lipid-based signalling pathways is proposed. Moreover, improved photosynthesis under crop rotation was associated with accumulation of sugar metabolism-related compounds and photosynthesis-related proteins. Likewise, acylamino acid-releasing enzymes, a class of serine-proteases, remarkably increased under both halophyte-based managements, which may act to modulate the antioxidant capacity of tomato plants. In summary, this work reveals common and distinctive patterns in tomato under intercropping and crop rotation conditions with the halophyte, supporting the use of A. macrostachyum in farming systems.

Novel ZnO-TiO2@MSC nanomaterial based on corn stover template enhances disease resistance in tomato plants.

Crop diseases significantly threaten global food security, driving the need for innovative control strategies. This study explored using ZnO-TiO2@MSC, a novel nanomaterial synthesized using a corn stover template, to enhance disease resistance in tomato plants. In vitro assays demonstrated potent antimicrobial activity of ZnO-TiO2@MSC against the pathogen Pseudomonas syringae pv. tomato DC3000 (Pst. DC3000) by disrupting bacterial cell membranes and modulating oxidative stress-related gene expression. When applied to tomato leaves in pot trials, ZnO-TiO2@MSC achieved 79.83% control of bacterial leaf spot disease while promoting plant growth and photosynthesis. The nanomaterial triggered plant defense mechanisms, upregulating resistance genes and increasing the activities of key enzymes. Metabolomic profiling revealed elevated lipids, lipid-like molecules, and organic acid derivative levels in treated leaves, suggesting cell membrane remodeling as part of the defense response. These findings highlight the potential of biologically-templated nanomaterials like ZnO-TiO2@MSC as multifunctional tools for sustainable disease management in crops. The corn stover-based synthesis approach also provides a way to valorize agricultural waste. Further research is needed to understand the long-term impacts and viability of field-scale application of ZnO-TiO2@MSC as an alternative to conventional pesticides.

Biocontrol of Fusarium solani: Antifungal Activity of Chitosan and Induction of Defence Enzymes

In this work, the efficiency of chitosan as a biocontrol agent against Fusarium solani on tomato plants was determined and the antifungal activity and the induction of defence enzymes were evaluated. Treatments were carried out with different concentrations of chitosan (1, 2 and 3 g L−1) combined with a synthetic fungicide (carbendazim). The results showed that all chitosan treatments significantly inhibited the mycelial growth and biomass of F. solani, with the most effective results obtained with the 3 g L−1 treatment. Scanning electron microscopy revealed that chitosan causes severe structural damage to F. solani, including cell lysis and the deformation of mycelium and spores. In addition, plants treated with chitosan showed significant improvements in height, stem diameter, root dry biomass and root length compared to those treated with synthetic fungicide and the control (no chitosan application). Enzyme assays showed that chitosan significantly increased superoxide dismutase, catalase, peroxidase and phenylalanine ammonia-lyase activity, indicating an increased defensive response. These results suggest that chitosan is a viable and less toxic alternative for the management of disease caused by F. solani in tomato plants, promoting both plant health and growth.

Floor Management and Amendment Applications Affected Dry-farmed Tomato Production during a 2020 Experiment in the Willamette Valley of Oregon

‘Early Girl’ tomato (Solanum lycopersicum) was dry-farmed during 2020 to determine the effects of floor management and amendment treatments on the total and unblemished yields, average fruit weight, blossom-end rot (BER) incidence, sunscald incidence, plant size, soil water tension, predawn leaf water potential (PDLWP), and leaf and soil nutrient concentrations. Floor management treatments included leaf mulching (4 inches of semi-composted leaf mulch), dust mulching (mechanical tillage to a depth of 6 to 8 inches after rain events), and a weedy treatment (weeds were not controlled). Amendment treatments included high compost (additional 73.5 wet tons/acre), high nitrogen (N) (160 lb/acre N applied as composted chicken manure and feather meal), low N (40 lb/acre N), and gypsum (2075 lb/acre gypsum). All these treatments were compared with a clean-cultivated control fertilized at 100 lb/acre N. No floor management treatment performed better (referring to total yield, unblemished yield, fruit count, fruit weight, BER incidence, sunscald incidence, and PDLWP) than the clean-cultivated control, and the leaf mulch and weedy treatments performed significantly worse. The leaf mulch treatment decreased the average fruit weight (30%), increased the BER incidence (34%), and increased the necrotic BER incidence (88%) when compared with the control. However, the leaf mulch treatment also used soil moisture more slowly than the control did. The weedy treatment decreased total yields (65%) and unblemished yields (88%), decreased the total fruit count (53%), decreased the average fruit weight (25%), increased the BER incidence (53%) and necrotic BER incidence (82%), decreased PDLWP (suggesting that the plants were more drought-stressed) on 20 Jul (27%) and 3 Aug (44%), and resulted in smaller plants when compared with those treated with the control. No amendment treatment performed better than the control, and the high compost treatment performed significantly worse. When compared with the control, the high compost treatment decreased the average fruit weight (15%), increased the BER incidence (39%), increased the necrotic BER incidence (67%), and increased plant aboveground biomass at the end of the experiment (34%). Increasing applications of organic fertilizers increased the BER incidence, with 48% BER at 40 lb/acre N and 62% BER at 160 lb/acre N. These data suggest that excess fertilizer applications and factors that increase drought stress (e.g., weeds) induce BER in dry-farmed tomato. Dust mulching may not be necessary, and shallow cultivation can be used instead for weed management. Dry farmers in the Willamette Valley must control weeds and avoid excess soil fertility and leaf mulches because they can result in large plants with a large fruit set; however, these fruit are more susceptible to BER.

Specific sets of geranylgeranyl diphosphate synthases and phytoene synthases control the production of carotenoids and ABA in different tomato tissues.

Plant carotenoids are plastid-synthesized isoprenoids with roles as photoprotectants, pigments, and precursors of bioactive molecules such as the hormone abscisic acid (ABA). The first step of the carotenoid biosynthesis pathway is the production of phytoene from geranylgeranyl diphosphate (GGPP), catalyzed by phytoene synthase (PSY). GGPP produced by plastidial GGPP synthases (GGPPS) is channeled to the carotenoid pathway by direct interaction of GGPPS and PSY enzymes. Three plastid-localized GGPPS isoforms (referred to as SlG1-3) and three PSY enzymes (PSY1-3) are present in tomato (Solanum lycopersicum). Our previous work showed that SlG1 and PSY3 function together in the roots, whereas the rest of the isoforms are required in aerial tissues. Here we generated and analyzed combinations of double mutants lacking PSY1 or PSY2 and SlG2 or SlG3 to investigate the contribution of specific GGPPS and PSY pairs to the production of carotenoids and ABA in different tissues of the tomato plant. Despite that the loss of individual enzymes was found to trigger compensatory mechanisms that complicate interpretation of the results, the results confirm a major role for SlG3 in providing GGPP to PSY2 for housekeeping carotenoid biosynthesis in leaves, whereas SlG2 and PSY1 become most relevant when a more active production is required in flowers and breaker fruits, i.e., at the onset of ripening. We could also confirm that ABA production in the fruit pericarp is more dependent on PSY1 activity than on total carotenoid levels and that fruit size correlates with ABA levels accumulated in ripe rather than breaker fruits.