Infected Tomato Research Articles

The Enhanced Expression of Cruzipain-Like Molecules in the Phytoflagellate Phytomonas serpens Recovered From the Invertebrate and Plant Hosts.

Phytomonas serpens is a protozoan parasite that alternates its life cycle between two hosts: an invertebrate vector and the tomato fruit. This phytoflagellate is able to synthesize proteins displaying similarity to the cysteine peptidase named cruzipain, an important virulence factor from Trypanosoma cruzi, the etiologic agent of Chagas disease. Herein, the growth of P. serpens in complex medium (BHI) supplemented with natural tomato extract (NTE) resulted in the increased expression of cysteine peptidases, as verified by the hydrolysis of the fluorogenic substrate Z-Phe-Arg-AMC and by gelatin-SDS-PAGE. Phytoflagellates showed no changes in morphology, morphometry and viability, but the proliferation was slightly reduced when cultivated in the presence of NTE. The enhanced proteolytic activity was accompanied by a significant increase in the expression of cruzipain-like molecules, as verified by flow cytometry using anti-cruzipain antibodies. In parallel, parasites incubated under chemically defined conditions (PBS supplemented with glucose) and added of different concentration of NTE revealed an augmentation in the production of cruzipain-like molecules in a typically dose-dependent way. Similarly, P. serpens recovered from the infection of mature tomatoes showed an increase in the expression of molecules homologous to cruzipain; however, cells showed a smaller size compared to parasites grown in BHI medium. Furthermore, phytoflagellates incubated with dissected salivary glands from Oncopeltus fasciatus or recovered from the hemolymph of infected insects also showed a strong enhance in the expression of cruzipain-like molecules that is more relevant in the hemolymph. Collectively, our results showed that cysteine peptidases displaying similarities to cruzipain are more expressed during the life cycle of the phytoflagellate P. serpens both in the invertebrate and plant hosts.

Trichoderma-Induced Resistance to Botrytis cinerea in Solanum Species: A Meta-Analysis.

With the idea of summarizing the outcomes of studies focusing on the resistance induced by Trichoderma spp. against Botrytis cinerea in tomato, the present paper shows, for the first time, results of a meta-analysis performed on studies published from 2010 to 2021 concerning the cross-talk occurring in the tomato–Trichoderma-B. cinerea system. Starting from an initial set of 40 papers, the analysis was performed on 15 works and included nine parameters, as a result of a stringent selection mainly based on the availability of more than one article including the same indicator. The resulting work not only emphasizes the beneficial effects of Trichoderma in the control of grey mold in tomato leaves (reduction in disease intensity, severity and incidence and modulation of resistance genes in the host), but carefully drives the readers to reply to two questions: (i) What are the overall effects of Trichoderma on B. cinerea infection in tomato? (ii) Do the main effects of Trichoderma differ based on the tomato species, Trichoderma species, amount, type and duration of treatment? At the same time, this meta-analysis highlights some weak points of the available literature and should be seen as an invitation to improve future works to better the conceptualization and measure.

Development of a Lamp Assay for Real-Time Detection of Criniviruses Infecting Tomato

Development of a Lamp Assay for Real-Time Detection of Criniviruses Infecting Tomato

Studies on histopathological changes in the tomato roots colonized by arbuscular mycorhizal fungus, Rhizophagus intraradices and infested by root knot nematodes, Meloidogyne incognita

Observations on histological changes on root knot nematode, Meloidogyne incognita infected tomato roots helps to understand the cell wall dynamics and nematode penetration in roots. The present study was conducted not only to understand the host cell wall modifications due to root knot nematodes but also the biocontrol activity of arbuscular mycorhizal fungus Rhizophagus intraradices to suppress the nematode invasion in roots. The results of observations on histopathology of R. intraradices and M. incognita infested roots revealed that, the hypha penetrated the epidermis and produced vesicles and arbuscles before nematode invasion and fewer numbers of giant cells with reduced size were observed compared to M. incognita alone infested roots.

Rapid Extraction of Plant Nucleic Acids by Microneedle Patch for In-Field Detection of Plant Pathogens.

Plant diseases pose a significant threat to global food security. Molecular diagnosis currently plays a crucial role in mitigating the negative impacts of plant diseases by accurately identifying the disease-causing pathogens and revealing their genotypes. However, current molecular assays are constrained to the laboratory because of the cumbersome protocols involved in plant nucleic acid extraction. To streamline this, we have developed a polymeric microneedle (MN) patch-based nucleic acid extraction method, which can be applied to various plant tissues and easily performed in field settings without using bulky laboratory equipment. The MN patch instantly isolates both host and pathogen's DNA and RNA from plant leaves by two simple steps: press and rinse with a buffer solution or nuclease-free water. The MN-extracted DNA and RNA are purification-free and directly applicable to downstream molecular assays such as polymerase chain reaction (PCR), reverse transcription-polymerase chain reaction (RT-PCR), loop-mediated isothermal amplification (LAMP), and reverse transcription loop-mediated isothermal amplification (RT-LAMP). Here, we describe the fabrication procedures of the MN patch and demonstrate the application of the MN method by extracting Phytophthora infestans DNA and tomato spotted wilt virus (TSWV) RNA from infected tomato leaves. After MN extraction, we directly utilize the MN-extracted nucleic acid samples to run PCR, RT-PCR, LAMP, or RT-LAMP reactions to amplify various biomarker genes, such as the ribulose-bisphosphate carboxylase (rbcL) gene of host tomato DNA, internal transcribed spacer (ITS) region of P. infestans DNA, and nucleocapsid (N) gene of TSWV RNA. Furthermore, this simple and rapid nucleic acid method can be integrated with portable nucleic acid amplification platforms such as smartphone-based microscopy devices to achieve "sample-to-answer" detection of plant pathogens directly in the field.

Impact of Irrigation Systems and Applied Water on Crop Yield, WUE, Certain Nematicides Efficiency, and Plant-Parasitic Nematodes Activity Infected Tomato Plants

Impact of Irrigation Systems and Applied Water on Crop Yield, WUE, Certain Nematicides Efficiency, and Plant-Parasitic Nematodes Activity Infected Tomato Plants

Satureja montana L. essential oil, montmorillonite and nanoformulation reduce Xanthomonas euvesicatoria infection, modulating redox and hormonal pathways of tomato plants

Xanthomonas euvesicatoria (Xeu) is one of the etiological agents of bacterial spot of tomato (Bs), which is a devastating threat to tomato production worldwide. The emergence of Xeu field isolates showing resistance to agrochemicals, like copper-based bactericides, urged for developing new biocontrol strategies. Satureja montana essential oil (EO) has antimicrobial capacity against xanthomonads, and its combination with nanocarriers might benefit stability and controlled delivery in the field. The nanoclay montmorillonite (NMT) is a promising EO nanocarrier. This work aims to assess the impact of the S. montana’s EO, NMT and the nanoformulation incorporating both (EO+NMT) on X. euvesicatoria's amount, and their effects in the pathosystem (Xeu-tomato) at a molecular and physiological level. Uninfected and infected tomato plants var. cerasiforme were treated with S. montana EO, NMT and EO+NMT. The S. montana’s EO, NMT, and their EO+NMT combination were able to reduce the bacterial density and Bs symptoms. The treatment with NMT, alone or as carrier of EO (EO+NMT), also stimulated, in uninfected plants, the enzymatic antioxidant capacity and expression of some defense pathways, while EO alone induced an antioxidant effect. In infected plants, all treatments were able to downregulate key-transcripts of the oxidative, phenylpropanoid, jasmonic acid and abscisic acid pathways to levels close to those of the uninfected-untreated control. In infected plants, NMT treatment also increased the enzymatic/non-enzymatic antioxidant capacity through stimulating antiradical activity and catalase activity. Overall, these findings demonstrate the potential of NMT and S. montana EO as natural control agents of Xeu causing bacterial spot mainly due to their antibacterial capacity. These results indicate the potential to upgrading these natural compounds to new commercial products against Xeu. Furthermore, there is a potential for these products to be applied also as prophylactic treatments in field conditions.

Infection with Tomato Mosaic Virus Reduces Lycopene Accumulation in Tomato Fruits

Despite Lycopene content in tomato germplasm (both local and exotic) was evaluated against isolates of tomato mosaic virus (ToMV), using a locally preferred hybrid i.e., Rio Grande as a control. Promising lines with resistance to ToMV were assessed by total carotenoid and lycopene content in virus-challenged tomato genotypes using spectrophotometry and RP-HPLC. Our data showed that virus infection significantly lessens the total carotenoid and lycopene content in tomato fruit. Lycopene content was significantly reduced in infected tomato compared to healthy, in locally cultivated hybrid Rio Grande. The germplasm GT-47 (CLN-2123-E) showed 60% decrease in lycopene content in infected tomato when in comparison to healthy produce. The virus infection, however, exhibited less deleterious effect on DPPH-based anti-oxidant potential of the ToMV infected tomato genotypes.

Interplay between abiotic (drought) and biotic (virus) stresses in tomato plants.

With climate warming, drought becomes a vital challenge for agriculture. Extended drought periods affect plant–pathogen interactions. We demonstrate an interplay in tomato between drought and infection with tomato yellow leaf curl virus (TYLCV). Infected plants became more tolerant to drought, showing plant readiness to water scarcity by reducing metabolic activity in leaves and increasing it in roots. Reallocation of osmolytes, such as carbohydrates and amino acids, from shoots to roots suggested a role of roots in protecting infected tomatoes against drought. To avoid an acute response possibly lethal for the host organism, TYLCV down‐regulated the drought‐induced activation of stress response proteins and metabolites. Simultaneously, TYLCV promoted the stabilization of osmoprotectants' patterns and water balance parameters, resulting in the development of buffering conditions in infected plants subjected to prolonged stress. Drought‐dependent decline of TYLCV amounts was correlated with HSFA1‐controlled activation of autophagy, mostly in the roots. The tomato response to combined drought and TYLCV infection points to a mutual interaction between the plant host and its viral pathogen.

Impact of Biochar Soil Amendment on Tomato mosaic virus Infection, Growth and Nutrients Uptake of Tomato Plants

Biochar soil amendment was applied as an eco-friendly approach to control Tomato mosaic virus (ToMV) and improve tomato growth and nutritional status. Three concentrations of biochar, 0.5, 1.0 and 1.5% were used as soil amendments. Using biochar at the rate of 1 and 1.5% reduced the ToMV incidence and delayed symptoms appearance as compared with plants grown in non-amended soil. Infection percentage and disease severity of ToMV were reduced by 33.3 and 50%, respectively, 15 days after inoculation of plants of soil amended with 1.5% biochar. ToMV relative concentration, using indirect ELISA was significantly reduced in plants of biochar 1% and 1.5% treatments. The lowest virus concentration was recorded at 21 days after inoculation in plants of 1.5% biochar amended soil. The shoot fresh weight was increased at biochar rates of 1.5 and 0.5% in non-infected and ToMV infected tomato, respectively. Significant increase was obtained in shoot K content amended with 1.0 and 1.5% biochar treatments of healthy and ToMV-infected tomato plants, respectively. Whereas, shoot Na content was diminished in infected plants grown in biochar amended soil at all tested biochar concentrations. Overall, the biochar application to soil enhanced resistance to ToMV infection, stimulated growth and K content increment and Na content decrement in tomato plants. In conclusion, application of biochar to agricultural soil could be considered a practical tool for minimizing the change effects of climate through carbon sequestration, improve plant productivity and increase diseases tolerance for sustainable agriculture.

Effect of the Nanoparticle Exposures on the Tomato Bacterial Wilt Disease Control by Modulating the Rhizosphere Bacterial Community.

Ralstonia Solanacearum is one of the most infectious soil-borne bacterial plant pathogens, causing tomato bacterial wilt (TBW). Nanotechnology is an emerging area of research, particularly the application of nanoparticles (NPs) as nanopesticides to manage plant disease is gaining attention nowadays. However, the interaction between NPs and rhizosphere bacterial communities remains largely elusive. This study indicated that metal NPs (CuO, ZnO, and FeO) reduced the incidence of bacterial wilt to varying degrees and affected the composition and structure of the rhizosphere bacterial community. The results revealed that the application of metal oxide NPs can improve the morphological and physiological parameters of TBW infected tomato plants. Among all, CuONPs amendments significantly increase the Chao1 and Shannon index. In the early stage (the second week), it significantly reduces the relative abundance of pathogens. However, the relative abundance of beneficial Streptomyces bacteria increased significantly, negatively correlated with the relative abundance of pathogenic bacteria. In addition, the nano-treatment group will enrich some potential beneficial bacteria such as species from Sphingomonadaceae, Rhizobiaceae, etc. In general, our research provides evidence and strategies for preventing and controlling soil-borne disease tomato bacterial wilt with metal oxide NPs.

Satureja montana Essential Oil, Zein Nanoparticles and Their Combination as a Biocontrol Strategy to Reduce Bacterial Spot Disease on Tomato Plants

Tomato bacterial spot (Bs), caused by Xanthomonas spp., including X. euvesicatoria (Xeu) remains a major threat for tomato production. The emergence of copper resistance strains of Xeu calls urgently for eco-friendly phytosanitary treatments as sustainable green alternatives for disease control. Satureja spp. essential oil (EO) has antimicrobial activity against xanthomonads and combined with zein nanoparticles (ZNPs), might offer a viable option for field applications. This study aims to evaluate the effects of S. montana EO, of ZNPs, and their combination in a nanoformulation, on Xeu quantity, and how these compounds modulate molecular and physiological changes in the pathosystem. Uninfected and infected tomato plants (var. Oxheart) were treated with EO; ZNPs and nanoformulation (EO + ZNPs). Treatments reduced Xeu amount by a minimum of 1.6-fold (EO) and a maximum of 202-fold (ZNPs) and improved plants’ health. Nanoformulation and ZNPs increased plants’ phenolic content. ZNPs significantly increased GPX activity and reduced CAT activity. Overall treatments upregulated transcripts of the phenylpropanoid pathway in infected plants, while ZNPs and nanoformulation upregulated those transcripts in uninfected plants. Both sod and aao transcripts were downregulated by treatments in infected plants. These findings demonstrate that S. montana EO, ZNPs and their nanoformulation are suitable to integrate tomato bacterial spot management strategies, mainly due to their antimicrobial activity on Xeu, however further field studies clarifying the long-term action of these products are required. These results also support the prophylactic potential of ZNPs on tomato bacterial spot.

Detection and Characterization of Viroids via Biological Assays on Herbaceous Hosts.

The characterization of the elusive disease agent of the potato spindle tuber disease, potato spindle tuber viroid (PSTVd), was aided by the ability to obtain large amounts of infected tomato tissue in a simple bioassay where PSTVd was easily mechanically transmissible to an alternate herbaceous host in which it thrived and produced dramatic symptoms in a relatively short period (Diener, Viroids. Handbook of plant virus infections: comparative diagnosis. Elsevier/North-Holland, Amsterdam, pp 913-934, 1981; Diener, Virology 45:411-428, 1971; Raymer and O'Brien, Am Pot J, 39:401-408, 1962). Reactions in the primary, or secondary, herbaceous indicator host can range from asymptomatic to severe depending upon the viroid strain, host species, and environmental conditions and can provide evidence of a viroid infection, but do not permit identification of the viroid in question. Further characterization by molecular hybridization, RT-PCR, and sequence analysis is used to determine the etiology of the disease agent. In this chapter, methods are described for mechanical inoculation of viroids to herbaceous hosts to determine the viroid nature of diseases and the experimental host range of the viroid or to shorten the time required for obtaining relatively large amounts of viroid for subsequent purification and characterization.

A comparison of induced antiviral resistance by the phytoprotein CAP-34 and isolate P1f of the rhizobacterium Pseudomonas putida.

CAP-34 is a previously reported phytoprotein isolated from Clerodendrum aculeatum (syn. Volkameria aculeata), inducing systemic antiviral resistance against plant virus infection in susceptible plants. This paper compares the resistance inducing efficacy of CAP-34 and a rhizobacterial isolate P1f on tomato (systemic) and tobacco Xanthi-nc (hypersensitive), against tobacco mosaic virus (TMV). The PGPR isolate was identified as an isolate of Pseudomonas putida through molecular and biochemical characterization, and it exhibited PGPR traits such as production of auxin and siderophore. GC-MS examination of the volatiles produced by P1f included several that are implicated in antimicrobial activity, growth promotion and induced systemic resistance. Foliar treatment of tobacco plants with P1f and CAP-34 led to an induced antiviral state in hypersensitive tobacco that persisted for 5 and 3days, post-treatment, respectively, with a percent reduction in lesion number greater than 90. A higher accumulation of hydrogen peroxide and production of peroxidase enzyme was recorded in P1f-treated leaves, in comparison to those with CAP-34 treatment. The disease incidence in tomato plants treated with CAP-34 and P1f was 30 and 60 percent, respectively, 28dpi. A significant increase was noted in growth parameters such as number of branches and flowers in CAP-34 treated plants, while a significant enhancement in plant height and dry shoot and root weight was observed in P1f-treated set, compared to the control set. ELISA values for the presence of TMV were significantly lower in the infected tomato plants in the treated sets, as compared to the control set, with CAP-34 treatment exhibiting better results as against the P1f-treated set. In the resistant plants from either set, no viral RNA or viral coat protein was detected through RT-PCR and serology. These results suggest that CAP-34 affords more pronounced protection against virus infection compared to the rhizobacterial isolate P1f.

Green Synthesis of Silver Nanoparticles Using Pomegranate and Orange Peel Extracts and Their Antifungal Activity against Alternaria solani, the Causal Agent of Early Blight Disease of Tomato.

This study aimed to synthesize silver nanoparticles (AgNPs) by pomegranate and orange peel extracts using a low concentration of AgNO3 solution to controlearly blight of tomato caused by Alternaria solani. The pathogen was isolated from infected tomato plants growing in different areas of Saudi Arabia. The isolates of this pathogen were morphologically and molecularly identified. Extracts from peels of pomegranate and orange fruits effectively developed a simple, quick, eco-friendly and economical method through a synthesis of AgNPs as antifungal agents against A. solani. Phenolic content in the pomegranate peel extract was greater than orange peel extract. Phenolic compounds showed a variation of both peel extracts as identified and quantified by High-Performance Liquid Chromatography. The phenolic composition displayed variability as the pomegranate peel extract exhibited an exorbitant amount of Quercitrin (23.62 mg/g DW), while orange peel extract recorded a high amount of Chlorogenic acid (5.92 mg/g DW). Biosynthesized AgNPs were characterized using UV- visible spectroscopy which recorded an average wavelength of 437 nm and 450 nm for pomegranate and orange peels, respectively. Fourier-transform infrared spectroscopy exhibited 32x73.24, 2223.71, 2047.29 and 1972.46 cm−1, and 3260.70, 1634.62, 1376.62 and 1243.76 cm−1 for pomegranate and orange peels, respectively. Transmission electron microscopy showed spherical shape of nanoparticles. Zetasizer analysis presented negative charge values; −16.9 and −19.5 mV with average particle sizes 8 and 14 nm fin case of pomegranate and orange peels, respectively. In vitro, antifungal assay was done to estimate the possibility of biosynthesized AgNPs and crude extracts of fruit peels to reduce the mycelial growth of A. solani. AgNPs displayed more fungal mycelial inhibition than crude extracts of two peels and AgNO3. We recommend the use of AgNPs synthesized from fruit peels for controlling fungal plant pathogens and may be applied broadly and safely in place by using the chemical fungicides, which display high toxicity for humans.

Pseudomonas syringae effector HopZ3 suppresses the bacterial AvrPto1-tomato PTO immune complex via acetylation.

The plant pathogen Pseudomonas syringae secretes multiple effectors that modulate plant defenses. Some effectors trigger defenses due to specific recognition by plant immune complexes, whereas others can suppress the resulting immune responses. The HopZ3 effector of P. syringae pv. syringae B728a (PsyB728a) is an acetyltransferase that modifies not only components of plant immune complexes, but also the Psy effectors that activate these complexes. In Arabidopsis, HopZ3 acetylates the host RPM1 complex and the Psy effectors AvrRpm1 and AvrB3. This study focuses on the role of HopZ3 during tomato infection. In Psy-resistant tomato, the main immune complex includes PRF and PTO, a RIPK-family kinase that recognizes the AvrPto effector. HopZ3 acts as a virulence factor on tomato by suppressing AvrPto1Psy-triggered immunity. HopZ3 acetylates AvrPto1Psy and the host proteins PTO, SlRIPK and SlRIN4s. Biochemical reconstruction and site-directed mutagenesis experiments suggest that acetylation acts in multiple ways to suppress immune signaling in tomato. First, acetylation disrupts the critical AvrPto1Psy-PTO interaction needed to initiate the immune response. Unmodified residues at the binding interface of both proteins and at other residues needed for binding are acetylated. Second, acetylation occurs at residues important for AvrPto1Psy function but not for binding to PTO. Finally, acetylation reduces specific phosphorylations needed for promoting the immune-inducing activity of HopZ3’s targets such as AvrPto1Psy and PTO. In some cases, acetylation competes with phosphorylation. HopZ3-mediated acetylation suppresses the kinase activity of SlRIPK and the phosphorylation of its SlRIN4 substrate previously implicated in PTO-signaling. Thus, HopZ3 disrupts the functions of multiple immune components and the effectors that trigger them, leading to increased susceptibility to infection. Finally, mass spectrometry used to map specific acetylated residues confirmed HopZ3’s unusual capacity to modify histidine in addition to serine, threonine and lysine residues.

Molecular mechanism of modulating miR482b level in tomato with botrytis cinerea\xa0infection

BackgroundPlant miRNAs are involved in the response to biotic and abiotic stresses by altering their expression levels, and they play an important role in the regulation of plant resistance to stress. However, the molecular mechanism that regulates the expression levels of miRNAs in plants with biotic and abiotic stress still needs to be explored. Previously, we found that the expression of the miR482 family was changed in tomato infected by Botrytis cinerea. In this study, we investigated and uncovered the mechanism underlying the response of miR482 to B. cinerea infection in tomato.ResultsFirst, RT-qPCR was employed to detect the expression patterns of miR482b in tomato infected by B. cinerea, and results showed that miR482b primary transcripts (pri-miR482b) were up-regulated in B. cinerea-infected leaves, but the mature miR482b was down-regulated. Subsequently, we used rapid amplification cDNA end method to amplify the full-length of pri-miR482b. Result showed that the pri-miR482b had two isoforms, with the longer one (consisting 300 bp) having an extra fragment of 53 bp in the 3’-end compared with the shorter one. In vitro Dicer assay indicated that the longer isoform pri-miR482b-x1 had higher efficiency in the post-transcriptional splicing of miRNA than the shorter isoform pri-miR482b-x2. In addition, the transcription level of mature miR482b was much higher in transgenic Arabidopsis overexpressing pri-miR482b-x1 than that in OE pri-miR482b-x2 Arabidopsis. These results confirmed that this extra 53 bp in pri-miR482b-x1 might play a key role in the miR482b biogenesis of post-transcription processing.ConclusionsExtra 53 bp in pri-miR482b-x1 enhanced miR482b biogenesis, which elevated the transcription level of miR482b. This study clarified the response of miR482 to B. cinerea infection in tomato, thereby helping us further understand the molecular mechanisms that regulate the expression levels of other miRNAs.

Tomato Yellow Leaf Curl Virus (TYLCV) Promotes Plant Tolerance to Drought.

A growing body of research points to a positive interplay between viruses and plants. Tomato yellow curl virus (TYLCV) is able to protect tomato host plants against extreme drought. To envisage the use of virus protective capacity in agriculture, TYLCV-resistant tomato lines have to be infected first with the virus before planting. Such virus-resistant tomato plants contain virus amounts that do not cause disease symptoms, growth inhibition, or yield loss, but are sufficient to modify the metabolism of the plant, resulting in improved tolerance to drought. This phenomenon is based on the TYLCV-dependent stabilization of amounts of key osmoprotectants induced by drought (soluble sugars, amino acids, and proteins). Although in infected TYLCV-susceptible tomatoes, stress markers also show an enhanced stability, in infected TYLCV-resistant plants, water balance and osmolyte homeostasis reach particularly high levels. These tomato plants survive long periods of time during water withholding. However, after recovery to normal irrigation, they produce fruits which are not exposed to drought, similarly to the control plants. Using these features, it might be possible to cultivate TYLCV-resistant plants during seasons characterized by water scarcity.

Ethyl acetate extract of Streptomyces spp. isolated from Egyptian soil for management of Fusarium oxysporum: The causing agent of wilt disease of tomato

Tomato crops faced dangerous problems due to their attack by Fusarium oxysporum f. sp. lycopersici , the causing agent of wilt disease. Chemical treatments of such diseases caused many hazardous impacts to soil and human. For this reason, the biological control is considered as an alternative and sustainable tool for curing several plant diseases. The present work is undertaken with the aim of treating Fusarium -contaminated tomato seeds with ethyl acetate extracts from isolated Steptomyces spp., in greenhouse studies. Fifteen Steptomyces spp., isolated from native tomato rhizospheric soils, were evaluated for their antagonistic potential against Fusarium wilt pathogen . Three isolates that exhibited higher antagonistic effect were molecularly identified. Their ethyl acetate extracts (EAE) exhibited antifungal activity against the target pathogen, with higher potential with S. carpaticus EGY-S7 strain. Greenhouse assay indicated that seed treatment by the selected EAE of Steptomyces spp., isolates significantly reduced disease severity and possessed seedlings growth promoting potential of tomato ranging from 72.6 to 83.0% compared to infected control (63.4%) and chemical fungicide (76.2%). Accordingly, strain S. carpaticus EGY-S7 showed higher control efficacy (83.0%) as well as significantly increased the biomass of tomato seedlings (plant height, leaves number, fresh and dry weight) compared to a positive control (with infested soil). Additionally, it was superior to other strains, in which total polyphenols, polyphenoloxidase and peroxidase enzymes were significantly enhanced in tomato seedlings compared with untreated-infected control. Gas chromatography-mass spectrometry (GC-MS) analysis of EAE derived from S. carpaticus EGY-S7 strain was also identified. • Isolation of the fungal pathogens ( Fusarium spp.) from infected tomato plants. • Isolation of Streptomyces spp. from the surroundings soil of infected plants. • Measuring the antagonistic effect between isolates. • Production of bioactive compounds from Streptomyces spp. • Studying the effect of Streptomyces spp. extracts on the growth of tomato seedlings.

Design, Synthesis, and Structure-Activity Relationship Studies of Magnolol Derivatives as Antifungal Agents.

Plant pathogenic fungi seriously affect agricultural production and are difficult to control. The discovery of new leads based on natural products is an important way to innovate fungicides. In this study, 30 natural-product-based magnolol derivatives were synthesized and characterized on the basis of NMR and mass spectroscopy. Bioactivity tests on phytopathogenic fungi (Rhizoctonia solani, Fusarium graminearum, Botrytis cinerea, and Sclerotinia sclerotiorum) in vitro of these compounds were performed systematically. The results showed that 11 compounds were active against four kinds of phytopathogenic fungi with EC50 values in the range of 1.40-20.00 μg/mL, especially compound L5 that exhibited excellent antifungal properties against B. cinerea with an EC50 value of 2.86 μg/mL, approximately 2.8-fold more potent than magnolol (EC50 = 8.13 μg/mL). Moreover, compound L6 showed the highest antifungal activity against F. graminearum and Rhophitulus solani with EC50 values of 4.39 and 1.40 μg/mL, respectively, and compound L7 showed good antifungal activity against S. sclerotiorum. Then, an in vivo experiment of compound L5 against B. cinerea was further investigated in vivo using infected tomatoes (curative effect, 50/200 and 36%/100 μg/mL). The physiological and biochemical studies illustrated that the primary action mechanism of compound L5 on B. cinerea might change the mycelium morphology, increase cell membrane permeability, and destroy the function of mitochondria. Furthermore, structure-activity relationship (SAR) studies revealed that hydroxyl groups play a key role in antifungal activity. To sum up, this study provides a reference for understanding the application of magnolol-based antifungal agents in crop protection.