Infected Tomato Plants Research Articles

Microencapsulation of Bacillus megaterium in Humic Acid-Supplied Alginate Beads Enhances Tomato Growth and Suppresses the Root-Knot Nematode Meloidogyne javanica Under Greenhouse Conditions

In recent years, interest in using encapsulated plant growth-promoting rhizobacteria (PGPR) as a biocontrol agent against root-knot nematodes has increased. Root-knot nematodes are soil-borne parasites that mostly cause annual commercial losses globally by infecting tomato plants (Solanum lycopersicum). In this work, tomato plants (cv. GS) were grown in a greenhouse to test the effectiveness of encapsulated Bacillus megaterium with or without humic acid or in liquid form at different inoculum levels against Meloidogyne javanica and their impact on different growth parameters. A scanning electron microscope (SEM) was used to visualize the microencapsulation of B. megaterium as well as viability and protease production In vitro. In a greenhouse experiment, humic acid-encapsulated B. megaterium resulted in a significant decrease in nematode parameters compared to the control group. When compared to other inoculants, the use of 10 capsules/plant decreased nematode infestation and enhanced plant growth parameters, antioxidant enzymes, and photosynthetic pigments. These results are reflected in increased dehydrogenase activity, total bacterial count, and acidic and alkaline phosphatase in soil 30 and 60 days after transplanting. Therefore, to increase the development dynamics of tomato plants and reduce nematode infestation, we advise using B. megaterium capsules supplemented with humic acid.

Infection of tomato plants by tomato yellow leaf curl virus (TYLCV) potentiates the ethylene and salicylic acid pathways to fend off root-knot nematode (Meloidogyne incognita) parasitism

In nature, it is common for plants to be infected by multiple pathogens simultaneously, and deciphering the underlying mechanisms of such interactions has remained elusive. The occurrence of root-knot nematode (RKN), Meloidogyne incognita, and tomato yellow leaf curl virus (TYLCV; Begomovirus coheni) has been reported in most tomato cultivation areas. We investigated the interaction between RKN and TYLCV in tomato plants at phenotypic, biochemical, and gene expression levels. Several treatments were considered including mock inoculation, inoculation with TYLCV or RKN alone, simultaneous inoculation with both TYLCV and RKN, and sequential inoculations with a five-day interval. Among them, simultaneous inoculation showed the highest impact on RKN suppression compared to mock-inoculated plants. Biochemical assays in the time-point experiments demonstrated that the pick of defense capacity of plants occurs at 48- and 72-h post-inoculation. Gene expression analyses utilizing marker genes from main hormonal pathways involved in plant defense, including salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), indicated that ET and SA are highly involved in the potentiation of TYLCV-induced defense against RKN. To validate the action of SA and ET in the induction of defense against RKN by TYLCV, transgenic lines deficient in SA (NahG) and ET (ACD) accumulation were co-inoculated with TYLCV and RKN. Both transgenic lines failed to express TYLCV-induced defense against RKN. These findings demonstrate an antagonistic effect of TYLCV against RKN in tomato plants, mediated by SA and ET signaling pathways.

Tomato Root Exudates Infected by Meloidogyne incognita Impact the Colonization of Nematicidal Proteus vulgaris.

Root exudates play a pivotal role in shaping the microbial community in the rhizosphere and can impact the efficacy of bacteria in controlling nematode populations. This study identified Proteus vulgaris BX-1 as significantly effective in controlling Meloidogyne incognita. The infection of tomato plants with this nematode induced noticeable alterations in the composition of tomato root exudates and led to an increased colonization rate of strain BX-1. Further investigation into how strain BX-1 responded to changes in tomato root exudates revealed that specific metabolites, such as caffeic acid, coumarin, salicylic acid, sebacic acid, and butyric acid, strongly attracted strain BX-1. This attraction potentially contributed to its enhanced colonization and improved efficiency in controlling nematodes. Understanding the correlation between specific metabolites in root exudates and the response of antagonistic bacteria provides valuable insights for enhancing their effectiveness as biological control agents against plant-parasitic nematodes.

Immunomodulating melatonin-decorated silica nanoparticles suppress bacterial wilt (Ralstonia solanacearum) in tomato (Solanum lycopersicum L.) through fine-tuning of oxidative signaling and rhizosphere bacterial community

BackgroundTomato (Solanum lycopersicum L.) production is severely threatened by bacterial wilt, caused by the phytopathogenic bacterium Ralstonia solanacearum. Recently, nano-enabled strategies have shown tremendous potential in crop disease management.ObjectivesThis study investigates the efficacy of biogenic nanoformulations (BNFs), comprising biogenic silica nanoparticles (SiNPs) and melatonin (MT), in controlling bacterial wilt in tomato.MethodsSiNPs were synthesized using Zizania latifolia leaves extract. Further, MT containing BNFs were synthesized through the one-pot approach. Nanomaterials were characterized using standard characterization techniques. Greenhouse disease assays were conducted to assess the impact of SiNPs and BNFs on tomato plant immunity and resistance to bacterial wilt.ResultsThe SiNPs and BNFs exhibited a spherical morphology, with particle sizes ranging from 13.02 nm to 22.33 nm for the SiNPs and 17.63 nm to 21.79 nm for the BNFs, indicating a relatively uniform size distribution and consistent shape across both materials. Greenhouse experiments revealed that soil application of BNFs outperformed SiNPs, significantly enhancing plant immunity and reducing bacterial wilt incidence by 78.29% in tomato plants by maintaining oxidative stress homeostasis via increasing the activities of antioxidant enzymes such as superoxide dismutase (31.81%), peroxidase (32.9%), catalase (32.65%), and ascorbate peroxidase (47.37%) compared to untreated infected plants. Additionally, BNFs induced disease resistance by enhancing the production of salicylic acid and activating defense-related genes (e.g., SlPAL1, SlICS1, SlNPR1, SlEDS, SlPD4, and SlSARD1) involved in phytohormones signaling in infected tomato plants. High-throughput 16 S rRNA sequencing revealed that BNFs promoted growth of beneficial rhizosphere bacteria (Gemmatimonadaceae, Ramlibacter, Microscillaceae, Anaerolineaceae, Chloroplast and Phormidium) in both healthy and diseased plants, while suppressing R. solanacearum abundance in infected plants.ConclusionOverall, these findings suggest that BNFs offer a more promising and sustainable approach for managing bacterial wilt disease in tomato plants.Graphical

OCURRENCIA DE TOBRFV EN INVERNADEROS DE TOMATE (Solanum lycopersicum L.) EN OAXACA, MÉXICO

<p><strong>Background.</strong> Tomato brown rugose fruit virus (ToBRFV) is an emerging pathogen distributed in different regions of Mexico. <strong>Objective.</strong> To test the presence of ToBRFV in tomato plants of the Mesías variety (HM-Clause) in five greenhouses located in San Pablo Guilá, Oaxaca. <strong>Methodology.</strong> Using ImmunoStrip (Agdia, Elkhart, USA) a serological assay was performed on the five samples collected from the greenhouse. Using a modified version of Koch's postulates, tomato plants var.192-536 F1 were mechanically inoculated. A biological indexing assay was also performed, where 30-day-old plants of <em>Chenopodium amaranticolor</em> and <em>Nicotiana longiflora</em> were inoculated from infective sap prepared from each sample collected. The sandwich ELISA (DAS-ELISA) was performed 30 days post inoculation (dpi). Subsequently, a fragment of the 475 bp region was amplified by reverse transcription (RT) and polymerase chain reaction (PCR). <strong>Results.</strong> The ImmunoStrip assay was positive for ToBRFV, inoculation of plants 30 dpi, expressed symptoms of blistering, yellowing, mosaic and leaf deformation. <em>N. longiflora</em> plants showed local necrotic lesions, while <em>Ch. amaranticolor</em> expressed the formation of local chlorotic lesions. Likewise, the samples run by DAS-ELISA yielded a positive diagnosis for ToBRFV. The RT-PCR products obtained amplified a 475 bp fragment confirming the presence of ToBRFV in the five samples studied. <strong>Implications.</strong> There are limited reports confirming the presence of ToBRFV in Mexican states. <strong>Conclusions.</strong> To our knowledge, this is the first occurrence of ToBRFV infecting tomato plants in greenhouses in Oaxaca, Mexico.</p>

Nematode-trapping fungus Arthrobotrys oligospora recruited rhizosphere microorganisms to cooperate in controlling root-knot nematodes in tomato.

The objective of this study was to elucidate the role and mechanism of changes in the rhizosphere microbiome following A. oligospora treatment in the biological control of root-knot nematodes and identify the key fungal and bacterial species that collaborate with A. oligospora to biocontrol root-knot nematodes. We conducted a pot experiment to investigate the impact of A. oligospora treatment on the biocontrol efficiency of A. oligospora against Meloidogyne incognita infecting tomato. We analyzed the rhizosphere bacteria and fungi communities of tomato by high-throughput sequencing of the 16S rRNA gene fragment and the internal transcribed spacer (ITS). The results indicated that the application of A. oligospora resulted in a 53.6% reduction in the disease index of M. incognita infecting tomato plants. The bacterial diversity of rhizosphere soil declined in the A. oligospora-treated group, while fungal diversity increased. The A. oligospora treatment enriched the tomato rhizosphere with Acidobacteriota, Firmicutes, Bradyrhizobium, Sphingomonadales, Glomeromycota and Purpureocillium. These organisms are involved in the utilization of rhizosphere organic matter, nitrogen, and glycerolipids, or play the role of ectomycorrhiza or directly kill nematodes. The networks of bacterial and fungal co-occurrence exhibited a greater degree of stability and complexity in the A. oligospora treatment group. This study demonstrated the key fungal and bacterial species that collaborate with the A. oligospora in controlling the root-knot nematode and elaborated the potential mechanisms involved. The findings offer valuable insights and inspiration for the advancement of bionematicide based on nematode-trapping fungus.

Characterization of Botrytis cinerea, the causal agent of tomato grey mould, and its biocontrol using Bacillussubtilis

Botrytis cinerea infects more than 1400 plant species globally, resulting in severe damage pre- and post-harvest. This study aimed to isolate and identify B. cinerea from tomato plants from local greenhouses and assess the inhibitory capacities of local Bacillus strains against B. cinerea. Various B. cinerea strains isolated from infected tomato plants exhibited characteristic symptoms. The ITS sequences and phylogenetic analysis of isolates exhibited 99 % homology with B. cinerea. Pathogenicity tests on healthy tomato vegetative growth or detached leaves using QB13, QBuk1, and QUna fungal isolates fulfilled Koch's postulates. Symptomatic characteristics resulting from the artificial inoculations of tomato grey mould closely resembled those of the original diseased leaves and stems collected from the field after 7 DPI when seven strains of Bacillus subtilis (64C1, 88D, 65D, 64C2, 41D1, 23A2, and 102) tested in-vitro against B. cinerea demonstrated that all of Bacillus subtilis isolates displayed notably strong antagonistic effects against B. cinerea. Mycelial growth inhibition ranged from 37 % (isolate 65D) to 60 % (isolate 102) compared to the untreated control. The most substantial inhibitory effects against B. cinerea were statistically observed with isolates 88D and 102, which exhibited inhibition rates of 58 % and 60 %, respectively. Morphological and molecular identification and pathogenicity analysis revealed that all 20 B. cinerea isolates obtained from infected tomato plants from greenhouses exhibited a highly pathogenic effect on tomato plants. This study states the basis for developing natural biocontrol agents to combat grey mould caused by B. cinerea on tomato plants.

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.

Interação fungicida-requeima na síntese de compostos fenólicos e atividade de enzimas de defesa em tomateiro

Due to the significant impact of late blight (LB) (Phytophthora infestans [Mont.]) on tomato (Solanum lycopersicum L.), we investigated the interaction between fungicides and this disease to understand how some plant defense mechanisms are affected over time. Following a randomized design, we evaluated the synthesis of phenolic compounds (PHE) and the activity of phenylalanine ammonium lyase (PAL), peroxidases (POX) and superoxide dismutase (SOD). The experiment involved the application of fosetyl-Al and fluoxastrobin (fungicides with dual modes of action) on healthy and infected tomato plants. LB severity was assessed weekly and leaf samples were collected at various intervals for biochemical analysis. The Kruskal-Wallis test (α = 0.05) analyzed main effects of infection, fungicide, and time on response variables, followed by Bonferroni post hoc for significant group differences and regression models to evaluate variable effects over time. The application of fungicides had no effect on enzymatic activity or PHE accumulation. While PAL and SOD activities were not significantly affected by infection, POX activity was significantly higher in healthy plants (4793.8 U g-1 fresh weight) compared to infected plants (1858.1 U g-1 fresh weight). A complex interaction between PHE accumulation in relation to LB severity and time was observed, with a notable increase in PHE levels at 50 days after transplant when disease severity was between 25 and 50%. Future studies should consider including a broader range of genotypes and isolates of P. infestans, a more extensive set of biochemical responses, and evaluations of the overexpression of genes related to plant defense.

Efficacy of Commercial Biocontrol Products for the Management of Verticillium and Fusarium Wilt in Greenhouse Tomatoes: Impact on Disease Severity, Fruit Yield, and Quality

Verticillium dahliae (Vd) and Fusarium oxysporum f. sp. lycopersici (Fol) are two major fungal pathogens that infect tomato plants, causing significant challenges in their control since both pathogens can persist in the soil for several years even in the absence of a host plant and no effective fungicides are available at present. This study investigated the efficacy of two biocontrol formulations, Clonotri (containing Trichoderma and Clonostachys microorganisms) and Strepse (comprising Streptomyces and Pseudomonas microorganisms), against Vd and Fol and their impact on tomato fruit quality and yield under greenhouse conditions. The pathogenicity experiment demonstrated that the Clonotri formulation, containing Trichoderma and Clonostachys spores, significantly reduced Fusarium wilt disease by 32% compared to the control group. However, in the Vd pathogenicity experiment, the formulations did not exhibit disease reduction, although treatment with Strepse, containing Streptomyces and Pseudomonas microorganisms, resulted in a preserved total fruit number when compared to uninfected plants. Analysis of fruit quality attributes revealed no significant differences among the various interventions. Furthermore, Fol infection in the first fruit set significantly increased fruit firmness, while Vd infection resulted in elevated levels of total soluble solids in fruits. These findings demonstrate that the evaluated biocontrol formulations provide a degree of protection against fungal wilt pathogens in tomato plants and can increase yield in greenhouse conditions while having minimal impact on overall fruit quality attributes.

Direct Isolation Method for Tomato-Infecting Phytophthora infestans

Infection of Phytophthora infestans at high altitudes in tropical regions causes symptoms of tomato late blight throughout the year. Even though it is very easy to find in the field, P. infestans is often very difficult to isolate aseptically in the laboratory. This study aims to evaluate direct isolation techniques that can increase the success of isolating P. infestans. Isolation was carried out on a non-specific medium, consisting of potato dextrose agar (PDA), corn meal agar (CMA), oatmeal agar (OMA), and water agar (WA) with three alternative types of antibiotics, i.e. chloramphenicol, amoxicillin, and rifampicin. Observations were carried out to determine the effect of the medium on sporangia induction and the age of the original colony’s growth in CMA and OMA media. The results showed that the isolation of P. infestans using the direct method was successfully carried out on non-specific PDA, CMA, OMA and WA medium. The highest isolation success rate was obtained on CMA medium with the addition of 50 mg L-1 rifampicin. The fastest sporangia induction (8 days) was shown by colonies grown on OMA medium with the addition of 50 mg L-1 rifampicin based on the category of abundant sporangia after 20 days of incubation. Rejuvenation of P. infestans colonies for research purposes in the laboratory is recommended to be carried out routinely twice a month. This research provides practical guidance for understanding the bioecology of P. infestans infecting tomato plants, especially for further study on oomycetes fungi.

Morphological and Biochemical Characterization of Strains of Ralstonia solanacearum, Causal Agent of Bacterial Wilt in Tomatoes in Cameroon and Screening of Virulent Strains

Ralstonia solanacearum is a major constraint in tomato production. The aim of this work was to identify the different biovars and races of R. solanacearum which infect tomato plants in Cameroon and determine the most virulent in a gnotobiotic environment. Thirty (30) samples were collected in the field of 03 different agro-ecological zones considered as major tomato production area in Cameroon. The bacteria were isolated on modified Kelman solid medium, and identified based on morphological and biochemical characterization. The pathogenicity test was performed in a gnotobiotic environment by root inoculation. Twenty-nine (29) isolates showed colonies characteristic of virulent strains. Water, motility, catalase, KOH, Kovac oxidase, glucose reduction, and sucrose tests were positive. However, gram staining, spore production, arginine test and sulfate reduction were negative. The biovar tests carried out revealed the presence16.66% biovar 2 (bv 2) and 76.66% biovar 3(bv 3). The tobacco hypersensitivity tests carried out revealed the presence of two (02) races: race 1 and race 3 (majority). A predominance of race3 biovar 3 was observed in Cameroon. Results from pathogenicity test revealed that two (02) strains, FM6 (race 3 bv2) and BFo (race 3 bv 3) were high virulent, causing up to 100% loss of seedlings on the sixth day post-inoculation.

Molecular characterization and host reaction to tomato mottle mosaic virus isolated from sweet pepper seeds in Japan.

Many countries have identified tomato mottle mosaic virus (ToMMV) as a serious threat to tomato production. Here, we constructed and characterized infectious clones of ToMMV isolated from Japanese sweet pepper seeds. The genome of the Japanese isolate is 6399 nucleotides in length and exhibits thehighest identity withpreviously characterized isolates. For example, it is 99.7% identical to that of the Mauritius isolate, which occurs worldwide. Phylogenetic analysis based on complete genome sequences revealed that the Japanese isolates clustered in the same clade as those from other countries. When homozygous tomato cultivars with tobamovirus resistance genes were inoculated with an infectious cDNA clone of ToMMV, the virus systemically infected tomato plants with symptoms typical of Tm-1-carrying tomato cultivars. In contrast, tomato cultivars carrying Tm-2 or Tm-22 showed symptoms only on the inoculated leaves. Furthermore, when commercial cultivars of Tm-22 heterozygous tomato were inoculated with ToMMV, systemic infections were observed in all cultivars, with infection frequencies ranging from 25 to 100%. Inoculation of heterozygous sweet pepper cultivars with tobamovirus resistance genes (L1, L3, and L4) with ToMMV resulted in an infection frequency of about 70%, but most of the infected L1, L3, and L4 cultivars were symptomless, and 10-20% showed symptoms of necrosis and yellowing. Tomato mosaic virus strain L11A, an attenuated virus, did not provide cross-protection against ToMMV and led to systemic infection with typical symptoms. These results suggest that ToMMV might cause extensive damage to existing tomato and sweet pepper cultivars commonly grown in Japan.

Molecular characterization of emerging distinct watermelon bud necrosis virus (Orthotospovirus citrullonecrosis) variant causing necrosis disease on tomato in India

Watermelon bud necrosis virus (WBNV) cause serious economic impact on the cultivation of vegetable crops in the Indian subcontinent. In this study, an Orthotospovirus that infect tomato plants with typical severe necrotic symptoms had been identified as WBNV based on N gene sequences. The complete genome sequence of WBNV isolate (22ToNV) was determined and analyzed. The nucleotide sequences of the viral RNA segments in 22ToNV exhibit <91% similarity compared to the published WBNV genome sequence. Whereas, the amino acid sequences encoded by these segments, shared identity of about 96–98.54% among the other WBNV isolates. There is a notable divergence observed specifically within the intergenic regions (IGRs) of the S and M RNAs, with a lower similarity range of 78–84%. Nucleotide sequence comparisons and phylogenetic analysis showed that 22ToNV is a unique WBNV isolate having distinct genetic differences with other known WBNV isolates reported in different geographic regions of the country.

Influence of insectocompost obtained by cultivation of the during beetle &lt;i&gt;Ulomoides dermestoides&lt;/i&gt; on the ecological-trophic composition and development of soil and phytoparasitic nematodes

The purpose of the research is to study the effect of insect compost obtained as a result of the vital activity of insects of the Coleoptera order Ulomoides dermestoides on the quantitative and qualitative composition of soil nematodes of various ecological and trophic groups, as well as on the morphological and physiological state of plants and infection of tomato plants with root-knot nematodes.Materials and methods. Under laboratory conditions, soil containing a diverse fauna of nematodes was treated with 1% dry and 0.5; 0.75 and 1% aqueous solutions of biocompost. Insect compost was obtained by keeping the U. dermestoides on a dry nutrient mixture. Then a mixture of lawn grasses was sown in the ground. After 30 days, the composition of nematodes was analyzed. The ability of insect compost to suppress parasitic nematode species was studied using the tomato-knot nematode model system. Tomatoes were infected with Meloidogyne incognita at a rate of 500 larvae (J2) per plant and simultaneously treated with a 0.5% aqueous biocompost solution.Results and discussion. The insect compost U. dermestoides has an effect on quantitative and qualitative indicators in the community of soil nematodes, increasing the number of predatory and saprobiotic nematodes and displacing parasitic ones. And due to the content of various biologically active compounds, it affects the development of rootknot nematodes in tomato roots. When tomatoes are treated with an aqueous solution of insect compost, the infection score and the number of nematodes that penetrate the roots are reduced. The introduction of compost when growing a mixture of lawn grasses and tomatoes can improve the condition of the plants.

Draft genomes of two phylotype I and II Ralstonia solanacearum species complex (RSSC) isolates causing bacterial wilt in tomato plants from Costa Rica.

Bacteria from RSSC hold agricultural significance as they are the causal agents of bacterial wilt. Here, we report the draft genomes of two bacteria extracted from vascular tissues of infected tomato plants. Isolate RALF-MA was classified as Ralstonia pseudosolanacearum (phylotype I) and RALSA-MA as Ralstonia solanacearum (phylotype II).

Bacillus subtilis NBRI-W9 simultaneously activates SAR and ISR against Fusarium chlamydosporum NBRI-FOL7 to increase wilt resistance in tomato.

The study aimed to determine the pathogenicity of Fusarium species currently prevalent in tomato fields having history of chemical fungicide applications and determine the bio-efficacy of Bacillus subtilis NBRI-W9 as a potent biological control agent. Fusarium was isolated from surface-sterilized infected tomato plants collected from fields. Pathogenicity of 30 Fusarium isolates was determined by in vitro and in vivo assays. Following Koch's postulates, F. chlamydosporum (FOL7) was identified as a virulent pathogen. The biological control of FOL 7 by B. subtilis NBRI-W9 (W9) and the colonization potential of W9 were established using spontaneous rifampicin-resistant mutants. W9 showed 82% inhibition of FOL7 on a dual-culture plate and colonization levels in tomato plants of ∼5.5, ∼3.3, and ∼2.2 log10 CFU/g in root, stem, and leaf tissue, respectively. Antagonistic activity was shown by scanning electron microscopy (SEM) and cell-wall-degradative enzymes. W9 reduced FOL7 infection in net-house and field experiments by 60% and 41%, respectively. Biochemical investigation, defence enzymes, defence gene expression analysis, SEM, and field studies provide evidence of hyperparasitism and induced resistance as the mode of biological control. The study also demonstrates that the potent biocontrol agent W9, isolated from Piper, can colonize tomato plants, control fungal disease by inducing induced systemic resistance (ISR) and systemic acquired resistance (SAR) simultaneously, and increase crop yield by 21.58% under field conditions. This study concludes that F. chlamydosporum (NBRI-FOL7) is a potent, fungicide-resistant pathogen causing wilt in tomatoes. NBRI-W9 controlled FOL7 through mycoparasitism and simultaneously activated ISR and SAR in plants, providing an attractive tool for disease control that acts at multiple levels.

Trichoderma afroharzianum TRI07 metabolites inhibit Alternaria alternata growth and induce tomato defense-related enzymes

Identifying a viable substitute for the limited array of current antifungal agents stands as a crucial objective in modern agriculture. Consequently, extensive worldwide research has been undertaken to unveil eco-friendly and effective agents capable of controlling pathogens resistant to the presently employed fungicides. This study explores the efficacy of Trichoderma isolates in combating tomato leaf spot disease, primarily caused by Alternaria alternata. The identified pathogen, A. alternata Alt3, was isolated and confirmed through the ITS region (OQ888806). Six Trichoderma isolates were assessed for their ability to inhibit Alt3 hyphal growth using dual culture, ethyl acetate extract, and volatile organic compounds (VOCs) techniques. The most promising biocontrol isolate was identified as T. afroharzianum isolate TRI07 based on three markers: ITS region (OQ820171), translation elongation factor alpha 1 gene (OR125580), and RNA polymerase II subunit gene (OR125581). The ethyl acetate extract of TRI07 isolate was subjected to GC–MS analysis, revealing spathulenol, triacetin, and aspartame as the main compounds, with percentages of 28.90, 14.03, and 12.97%, respectively. Analysis of TRI07-VOCs by solid-phase microextraction technique indicated that the most abundant compounds included ethanol, hydroperoxide, 1-methylhexyl, and 1-octen-3-one. When TRI07 interacted with Alt3, 34 compounds were identified, with major components including 1-octen-3-one, ethanol, and hexanedioic acid, bis(2-ethylhexyl) ester. In greenhouse experiment, the treatment of TRI07 48 h before inoculation with A. alternata (A3 treatment) resulted in a reduction in disease severity (16.66%) and incidence (44.44%). Furthermore, A3 treatment led to improved tomato growth performance parameters and increased chlorophyll content. After 21 days post-inoculation, A3 treatment was associated with increased production of antioxidant enzymes (CAT, POD, SOD, and PPO), while infected tomato plants exhibited elevated levels of oxidative stress markers MDA and H2O2. HPLC analysis of tomato leaf extracts from A3 treatment revealed higher levels of phenolic acids such as gallic, chlorogenic, caffeic, syringic, and coumaric acids, as well as flavonoid compounds including catechin, rutin, and vanillin. The novelty lies in bridging the gap between strain-specific attributes and practical application, enhancing the understanding of TRI07’s potential for integrated pest management. This study concludes that TRI07 isolate presents potential natural compounds with biological activity, effectively controlling tomato leaf spot disease and promoting tomato plant growth. The findings have practical implications for agriculture, suggesting a sustainable biocontrol strategy that can enhance crop resilience and contribute to integrated pest management practices.

Yeast Solution Spray and Ozone Gas Fumigation as Methods of Protecting Tomato Plants Against Diseases

Abstract The aim of the study was to determine the effect of ozone fumigation and spraying with microorganisms, i.e. yeast, on selected physiological parameters, and the extent of disease infection of tomato plants. Tomato plants were grown in the ground under covers. Throughout the 2021 and 2022 growing season, the plants were exposed to variable factors, i.e. fumigation with gaseous ozone at a dose of 2 ppm for 1 minute and spraying with yeast. After ozonation and spraying with yeast, physiological measurements were made on tomato plants, such as: selected parameters of chlorophyll fluorescence (maximum quantum yield of PSII photochemistry, maximum quantum yield of primary photochemistry) and gas exchange parameters (transpiration rate, stomatal conductivity and intercellular CO2 concentration). In addition, the content of chlorophyll using the SPAD method as well as plant infection by diseases was determined. Compared to the control sample, ozonation resulted in a slight decrease in the physiological parameters of tomato plants. In addition, no visible leaf damage was observed after the ozone gas fumigation process. However, the use of microorganisms did not significantly change the examined physiological parameters. Both after the application of gaseous ozone and microorganisms, a significant impact of the tested variable factors was found on reducing the infection of tomato plants by diseases such as: tomato late blight, tomato alter-nariosis, gray mold, bacterial canker of tomato and bacterial spot of tomato.

Molecular characterization of mungbean yellow mosaic India virus infecting Vigna radiata in Oman

AbstractThe full‐genome sequences of a bipartite begomovirus were identified in a mungbean (Vigna radiata) crop displaying symptoms such as yellow mosaics and stunting in the Al‐Batinah North region (23.6867° N 57.9058° E), Oman. Initial detection and confirmation of the virus genome were carried out through polymerase chain reaction, followed by obtaining complete genomes using rolling circle amplification. Bioinformatics analysis on both genomic components, DNA‐A and DNA‐B, revealed over 99% nucleotide sequence identity to the mungbean yellow mosaic India virus (MYMIV), previously known to infect tomato plants. Pairwise sequence analysis using the STD tool and subsequent phylogenetic analysis unveiled that the DNA‐A of the MYMIV isolate formed a cluster with closely related DNA‐A sequences of MYMIV from GenBank, while the DNA‐B clustered with the corresponding DNA‐B of the MYMIV isolate. Additionally, no evidence of recombination events was observed in the recombination analysis. Similarly, the nucleotide substitution rates between the DNA‐A and DNA‐B segments of MYMIV did not show significant differences. This finding represents the first documented instance of bipartite MYMIV infecting V. radiata in Oman.