Recent trends in studies on botanical fungicides in agriculture

Isolation of a novel Bacillus subtilis HF1 strain that is rich in lipopeptide homologs and has strong effects on the resistance of plant fungi and growth improvement of broilers

Bacillus subtilis is an important probiotic microorganism that secretes a variety of antimicrobial compounds, including lipopeptides, which are a class of small molecule peptides with important application value in the fields of feed additives, food, biopesticides, biofertilizers, medicine and the biological control of plant diseases. In this study, we isolated a novel B. subtilis HF1 strain that is rich in lipopeptide components and homologs, has a strong antagonistic effect on a variety of plant fungi, and is highly efficient in promoting the growth of broilers. The live B. subtilis HF1 and its fermentation broth without cells showed significant inhibitory effects on 20 species of plant fungi. The crude extracts of lipopeptides in the fermentation supernatant of B. subtilis HF1 were obtained by combining acid precipitation and methanol extraction, and the lipopeptide compositions were analyzed by ultrahigh-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The results showed that HF1 could produce 11 homologs of surfactin and 13 homologs of fengycin. Among the fengycin homologs, C13-C19 fengycin A and C15-C17 fengycin B were identified; among the surfactin homologs, C11-C17 surfactin A and C13-C16 surfactin B were characterized. C13 fengycin A, C11 surfactin A and C17 surfactin A were reported for the first time, and their functions are worthy of further study. In addition, we found that HF1 fermentation broth with and without live cells could be used as a feed additive to promote the growth of broilers by significantly increasing body weight up to 15.84%. HF1 could be a prospective strain for developing a biocontrol agent for plant fungal diseases and an efficient feed additive for green agriculture.

Design, Synthesis, and Antifeedant Activity Evaluation of 13/14-Arylthioether Matrine Derivatives

Introducing a sulfur atom into active agricultural molecules is an important strategy for pesticide development. Matrine, an environmentally friendly botanical pesticide, has the advantage of being easily degraded and has drawn attention in the agricultural field. To explore the novel matrine-type pesticides, in this study, we designed and synthesized 13/14-arylthioether matrine derivatives by introducing various aryl sulfide motifs into bioactive matrine. Most of the synthesized arylthioether matrines exhibited good antifeedant activity against Spodoptera exigua. Among them, compound 2q showed the best antifeedant effect with an EC50 value of 0.038 mg/mL, which is approximately 125-fold more activity than matrine and reached the activity level of commercial standard azadirachtin A. Furthermore, compound 2q exhibited an inhibitory effect on antifeedant-related enzyme carboxylesterase (CarE) from S. exigua. In short, the high activity of arylthioether matrines offers new insights into developing new antifeedants.

Exploring Endophytic Fungi as Natural Antagonists against Fungal Pathogens of Food Crops

The yield and quality of cultivated food crops are frequently compromised by the prevalent threat from fungal pathogens that can cause widespread damage in both the pre-harvest and post-harvest stages. This paper investigates the challenges posed by fungal pathogens to the sustainability and yield of essential food crops, leading to significant economic and food security repercussions. The paper critiques the long-standing reliance on synthetic fungicides, emphasizing the environmental and health concerns arising from their widespread and occasionally inappropriate use. In response, the paper explores the potential of biological control agents, specifically endophytic fungi in advancing sustainable agricultural practices. Through their diverse symbiotic relationships with host plants, these fungi exhibit strong antagonistic capabilities against phytopathogenic fungi by producing various bioactive compounds and promoting plant growth. The review elaborates on the direct and indirect mechanisms of endophytic antagonism, such as antibiosis, mycoparasitism, induction of host resistance, and competition for resources, which collectively contribute to inhibiting pathogenic fungal growth. This paper consolidates the crucial role of endophytic fungi, i.e., Acremonium, Alternaria, Arthrinium, Aspergillus, Botryosphaeria, Chaetomium, Cladosporium, Cevidencealdinia, Epicoccum, Fusarium, Gliocladium, Muscodor, Nigrospora, Paecilomyces, Penicillium, Phomopsis, Pichia, Pochonia, Pythium, Ramichloridium, Rosellinia, Talaromyces, Trichoderma, Verticillium, Wickerhamomyces, and Xylaria, in biological control, supported by the evidence drawn from more than 200 research publications. The paper pays particular attention to Muscodor, Penicillium, and Trichoderma as prominent antagonists. It also emphasizes the need for future genetic-level research to enhance the application of endophytes in biocontrol strategies aiming to highlight the importance of endophytic fungi in facilitating the transition towards more sustainable and environmentally friendly agricultural systems.

What are the 100 most cited fungal genera?

The global diversity of fungi has been estimated between 2 to 11 million species, of which only about 155 000 have been named. Most fungi are invisible to the unaided eye, but they represent a major component of biodiversity on our planet, and play essential ecological roles, supporting life as we know it. Although approximately 20 000 fungal genera are presently recognised, the ecology of most remains undetermined. Despite all this diversity, the mycological community actively researches some fungal genera more commonly than others. This poses an interesting question: why have some fungal genera impacted mycology and related fields more than others? To address this issue, we conducted a bibliometric analysis to identify the top 100 most cited fungal genera. A thorough database search of the Web of Science, Google Scholar, and PubMed was performed to establish which genera are most cited. The most cited 10 genera are Saccharomyces, Candida, Aspergillus, Fusarium, Penicillium, Trichoderma, Botrytis, Pichia, Cryptococcus and Alternaria. Case studies are presented for the 100 most cited genera with general background, notes on their ecology and economic significance and important research advances. This paper provides a historic overview of scientific research of these genera and the prospect for further research. Citation: Bhunjun CS, Chen YJ, Phukhamsakda C, Boekhout T, Groenewald JZ, McKenzie EHC, Francisco EC, Frisvad JC, Groenewald M, Hurdeal VG, Luangsa-ard J, Perrone G, Visagie CM, Bai FY, Błaszkowski J, Braun U, de Souza FA, de Queiroz MB, Dutta AK, Gonkhom D, Goto BT, Guarnaccia V, Hagen F, Houbraken J, Lachance MA, Li JJ, Luo KY, Magurno F, Mongkolsamrit S, Robert V, Roy N, Tibpromma S, Wanasinghe DN, Wang DQ, Wei DP, Zhao CL, Aiphuk W, Ajayi-Oyetunde O, Arantes TD, Araujo JC, Begerow D, Bakhshi M, Barbosa RN, Behrens FH, Bensch K, Bezerra JDP, Bilański P, Bradley CA, Bubner B, Burgess TI, Buyck B, Čadež N, Cai L, Calaça FJS, Campbell LJ, Chaverri P, Chen YY, Chethana KWT, Coetzee B, Costa MM, Chen Q, Custódio FA, Dai YC, Damm U, de Azevedo Santiago ALCM, De Miccolis Angelini RM, Dijksterhuis J, Dissanayake AJ, Doilom M, Dong W, Alvarez-Duarte E, Fischer M, Gajanayake AJ, Gené J, Gomdola D, Gomes AAM, Hausner G, He MQ, Hou L, Iturrieta-González I, Jami F, Jankowiak R, Jayawardena RS, Kandemir H, Kiss L, Kobmoo N, Kowalski T, Landi L, Lin CG, Liu JK, Liu XB, Loizides M, Luangharn T, Maharachchikumbura SSN, Makhathini Mkhwanazi GJ, Manawasinghe IS, Marin-Felix Y, McTaggart AR, Moreau PA, Morozova OV, Mostert L, Osiewacz HD, Pem D, Phookamsak R, Pollastro S, Pordel A, Poyntner C, Phillips AJL, Phonemany M, Promputtha I, Rathnayaka AR, Rodrigues AM, Romanazzi G, Rothmann L, Salgado-Salazar C, Sandoval-Denis M, Saupe SJ, Scholler M, Scott P, Shivas RG, Silar P, Souza-Motta CM, Silva-Filho AGS, Spies CFJ, Stchigel AM, Sterflinger K, Summerbell RC, Svetasheva TY, Takamatsu S, Theelen B, Theodoro RC, Thines M, Thongklang N, Torres R, Turchetti B, van den Brule T, Wang XW, Wartchow F, Welti S, Wijesinghe SN, Wu F, Xu R, Yang ZL, Yilmaz N, Yurkov A, Zhao L, Zhao RL, Zhou N, Hyde KD, Crous PW (2024). What are the 100 most cited fungal genera? Studies in Mycology 108: 1-411. doi: 10.3114/sim.2024.108.01.

Antifungal Activity of Ribosome-Inactivating Proteins

The control of crop diseases caused by fungi remains a major problem and there is a need to find effective fungicides that are environmentally friendly. Plants are an excellent source for this purpose because they have developed defense mechanisms to cope with fungal infections. Among the plant proteins that play a role in defense are ribosome-inactivating proteins (RIPs), enzymes obtained mainly from angiosperms that, in addition to inactivating ribosomes, have been studied as antiviral, fungicidal, and insecticidal proteins. In this review, we summarize and discuss the potential use of RIPs (and other proteins with similar activity) as antifungal agents, with special emphasis on RIP/fungus specificity, possible mechanisms of antifungal action, and the use of RIP genes to obtain fungus-resistant transgenic plants. It also highlights the fact that these proteins also have antiviral and insecticidal activity, which makes them very versatile tools for crop protection.

Identification the Pathogen Cause a New Apple Leaf Blight in China and Determination the Controlling Efficacy for Five Botanical Fungicides

Alternaria leaf blight has recently been described as an emerging fungal disease of apple trees which is causing the significant damage in the apple-growing areas of Tianshui and Jingning, Gansu, China. In the present study, the pathogen species involved in apple leaf blight and its biological characteristics were identified, and the inhibitory activity of different botanical fungicides against the pathogen was evaluated in vitro. Four strains were isolated from the symptomatic areas of necrotic apple leaves, and initially healthy leaves showed similar symptoms to those observed in orchards after inoculation with the ABL2 isolate. The ABL2 isolate was identified as Alternaria tenuissima based on the morphological characteristics of its colonies, conidiophores, and conidia, and this was also confirmed by multi-gene sequence (ITS, OPA10-2, Alta-1, and endoPG) analysis and phylogenic analysis. The optimum temperature, pH, carbon source, and nitrogen source for the growth of A. tenuissima mycelia were 28 °C, 6-7, soluble starch, and soy flour, respectively. In addition, the botanical fungicide eugenol exhibited the highest inhibitory effect on the mycelial growth and conidia germination of A. tenuissima, and the median effective concentration (EC50) values were 0.826 and 0.755 μg/mL, respectively. The protective and curative efficacy of eugenol were 86.85% and 76.94% after inoculation in detached apple leaves at a concentration of 4 μg/mL. Our research provides new insights into the control of apple leaf blight disease by applying botanical fungicides.

TMT-Based Proteomic Analysis Reveals the Molecular Mechanisms of Sodium Pheophorbide A against Black Spot Needle Blight Caused by Pestalotiopsis neglecta in Pinus sylvestris var. mongolica

Black spot needle blight is a minor disease in Mongolian Scots pine (Pinus sylvestris var. mongolica) caused by Pestalotiopsis neglecta, but it can cause economic losses in severe cases. Sodium pheophorbide a (SPA), an intermediate product of the chlorophyll metabolism pathway, is a compound with photoactivated antifungal activity, which has been previously shown to inhibit the growth of P. neglecta. In this study, SPA significantly reduced the incidence and disease index and enhanced the chlorophyll content and antioxidant enzyme activities of P. sylvestris var. mongolica. To further study the molecular mechanism of the inhibition, we conducted a comparative proteomic analysis of P. neglecta mycelia with and without SPA treatment. The cellular proteins were obtained from P. neglecta mycelial samples and subjected to a tandem mass tag (TMT)-labelling LC-MS/MS analysis. Based on the results of de novo transcriptome assembly, 613 differentially expressed proteins (DEPs) (p < 0.05) were identified, of which 360 were upregulated and 253 downregulated. The 527 annotated DEPs were classified into 50 functional groups according to Gene Ontology and linked to 256 different pathways using the Kyoto Encyclopedia of Genes and Genomes database as a reference. A joint analysis of the transcriptome and proteomics results showed that the top three pathways were Amino acid metabolism, Carbohydrate metabolism, and Lipid metabolism. These results provide new viewpoints into the molecular mechanism of the inhibition of P. neglecta by SPA at the protein level and a theoretical basis for evaluating SPA as an antifungal agent to protect forests.

Applications and Market of Micro-Organism-Based and Plant-Based Inputs in Brazilian Agriculture

The use of plant-based and micro-organism-based biological inputs is a sustainable agricultural practice. It promotes a suitable and better utilization of non-renewable resources in the environment. The benefits of using micro-organisms are associated with direct and indirect mechanisms, mainly related to improvements in the absorption and availability of nutrients, resulting in a consequent impact on plant growth. The main benefits of using biochemical pesticides are the promotion of sustainability and the management of resistance to pests and diseases. Although the use of micro-organisms and botanical metabolites is a promising agricultural alternative, they are still primarily concentrated in grain crops. There is a huge opportunity to expand the plant-based and micro-organism-based biological inputs used in agriculture due to the wide range of mechanisms of action of those products. At a global level, several terminologies have been adopted to characterize biological inputs, but many terms used conflict with Brazilian legislation. This review will clarify the classes of biological inputs existing in Brazil as well as present the application and evolution of the market for microbiological and plant-based inputs.

Anti-oomycete activities from essential oils and their major compounds on Phytophthora infestans

Botanicals are various plant-based products like plant extracts or essential oils. Anti-fungal activities of selected essential oils were tested on the pathogen causing potato and tomato late blight (Phytophthora infestans). Tests to evaluate anti-oomycete activities of commercial essential oils and their major compounds were carried out in vitro in microplate in liquid media. Anti-oomycete activities on Phytophthora infestans strain were obtained from essential oils/major compounds: Eucalyptus citriodora/citronellal; Syzygium aromaticum (clove)/eugenol; Mentha spicata/D-Carvone, L-Carvone; Origanum compactum/carvacrol; Satureja montana (savory)/carvacrol; Melaleuca alternifolia (tea tree)/terpinen-4-ol, and Thymus vulgaris/thymol. As an active substance of mineral origin, copper sulfate was chosen as a control. All selected essential oils showed an anti-oomycete activity calculated with IC50 indicator. The essential oils of clove, savory, and thyme showed the best anti-oomycete activities similar to copper sulfate, while oregano, eucalyptus, mint, and tea tree essential oils exhibited significantly weaker activities than copper sulfate. Clove essential oil showed the best activity (IC50 = 28 mg/L), while tea tree essential oil showed the worst activity (IC50 = 476 mg/L). For major compounds, three results were obtained: they were statistically more active than their essential oils (carvacrol for oregano, D- and L-Carvone for mint) or as active as their essential oils sources (thymol for thyme, carvacrol for savory, terpinen-4-ol for tea tree) or less active than their original essential oils (eugenol for clove, citronellal for eucalyptus). Microscopical observations carried out with the seven essential oils showed that they were all responsible for a modification of the morphology of the mycelium. The results demonstrated that various essential oils show different anti-oomycete activities, sometimes related to a major compound and sometimes unrelated, indicating that other compounds must play a role in total anti-oomycete activity.

Natural Alkaloid Waltherione F-Derived Hydrazide Compounds Evaluated in an Agricultural Fungicidal Field

In this project, quinoline and quinolone-containing hydrazide compounds were designed and synthesized by introducing a bioactive hydrazide group into the skeleton of waltherione F. The fungicidal activity revealed that some hydrazide compounds exhibited excellent and broad-spectrum fungicidal activity; especially, compounds E8, E12, and E16 showed more than 90% or even 100% inhibition rates against most pathogens at 50 μg·mL-1. The fungicidal mechanism indicated that compound E8 may affect the normal function of the plasma membrane, further generating changes in the morphology and subcellular structure of mycelia. Simultaneously, Fusarium graminearum may resist the E8-treated stress through the metabolic pathways related to l-glutamate, l-glutamine, and glutathione. Finally, the effect of compound E8 on wheat seedling's growth and the toxicity to zebrafish were accomplished. These results will provide important guidance to discover novel fungicidal lead compounds and explore new targets, which are effective ways to alleviate the increasingly severe drug resistance.

Activity of the botanical compound thymol against kiwifruit rot caused by Fusarium tricinctum and the underlying mechanisms

BACKGROUND

Kiwifruit rot is an important disease caused by different fungal pathogens, which can lead to huge economic loss in the kiwifruit industry. The aims of this study were to discover an effective botanical compound that significantly inhibits the pathogens causing kiwifruit rot, evaluate its control efficacy against this disease, and reveal the underlying mechanisms.

RESULTS

A strain of Fusarium tricinctum (GF-1), isolated from diseased kiwifruit, could cause fruit rot in both Actinidia chinensis var. chinensis and Actinidia chinensis var. deliciosa. Different botanical chemicals were used for antifungal activity test against GF-1 and thymol was the most effective one with a 50% effective concentration (EC₅₀ ) of 30.98 mg L^-1 . The minimal inhibitory concentration (MIC) of thymol against GF-1 was 90 mg L^-1 . Control efficacy of thymol against kiwifruit rot was evaluated and the results indicated that thymol could effectively decrease the occurrence and spread of kiwifruit rot. The mechanisms underlying the antifungal activity of thymol against F. tricinctum were investigated, and it showed that thymol could significantly damage the ultrastructure, destroy the plasma membrane integrity, and instantaneously increase energy metabolisms of F. tricinctum. Further investigations indicated that thymol could extend shelf life of kiwifruit by increasing their storability.

CONCLUSION

Thymol can effectively inhibit F. tricinctum that is one of the causal agents of kiwifruit rot. Multiple modes of action are involved in the antifungal activity. The results of this study indicate that thymol can be a promising botanical fungicide to control kiwifruit rot and provide useful references for thymol application in agriculture system. © 2023 Society of Chemical Industry.

Antifungal activity of chili pepper extract with potential for the control of some major pathogens in grapevine

BACKGROUND

In recent years, biofungicides have drawn increasing interest in vineyards for a more sustainable integrated and copper-limited pest management. Among alternatives, botanicals could represent valuable tools, being rich sources of biologically active compounds. Conversely to the well-known antioxidant and biological properties in relation to health benefits, investigation on bioactivity of hot pungent Capsicum sp. products against fungal phytopathogens in vineyards is still scarce. Therefore, the present study aimed at exploring the biologically active compounds profile of a chili pepper (Capsicum chinense Jacq.) pod extract and its antimicrobial properties against some of the major fungal and Oomycetes pathogens of grapevine, including Botrytis cinerea Pers., Guignardia bidwellii (Ellis) Viala & Ravaz and Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni.

RESULTS

The ethyl acetate-extracted oleoresin from the most pungent varieties was rich in capsaicinoids and polyphenols (371.09 and 268.5 μg mg-1 dry weight, respectively). Capsaicin and dihydrocapsaicin, hydroxycinnamic and hydroxybenzoic acids and quercetin derivatives were the most abundant, while carotenoids represented only a minor fraction. The oleoresin was efficient to inhibit all three pathogenic fungi and ED50 values were determined, evidencing that G. bidwellii was the more sensitive (0.233 ± 0.034 mg mL-1 ).

CONCLUSION

The results suggested a potentiality of chili pepper extract for the control of some important grapevine pathogens, their possible application being helpful for the recommended limitation in extensive use of copper in vineyard. The complex mixture of high amounts of capsaicinoids, associated to specific phenolic acids and other minor bioactive components might contribute to the observed antimicrobial action of chili pepper extract. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Halobacteria-Based Biofertilizers: A Promising Alternative for Enhancing Soil Fertility and Crop Productivity under Biotic and Abiotic Stresses-A Review

Abiotic and biotic stresses such as salt stress and fungal infections significantly affect plant growth and productivity, leading to reduced crop yield. Traditional methods of managing stress factors, such as developing resistant varieties, chemical fertilizers, and pesticides, have shown limited success in the presence of combined biotic and abiotic stress factors. Halotolerant bacteria found in saline environments have potential as plant promoters under stressful conditions. These microorganisms produce bioactive molecules and plant growth regulators, making them a promising agent for enhancing soil fertility, improving plant resistance to adversities, and increasing crop production. This review highlights the capability of plant-growth-promoting halobacteria (PGPH) to stimulate plant growth in non-saline conditions, strengthen plant tolerance and resistance to biotic and abiotic stressors, and sustain soil fertility. The major attempted points are: (i) the various abiotic and biotic challenges that limit agriculture sustainability and food safety, (ii) the mechanisms employed by PGPH to promote plant tolerance and resistance to both biotic and abiotic stressors, (iii) the important role played by PGPH in the recovery and remediation of agricultural affected soils, and (iv) the concerns and limitations of using PGHB as an innovative approach to boost crop production and food security.

Phytochemicals as alternative fungicides for controlling plant diseases: A comprehensive review of their efficacy, commercial representatives, advantages, challenges for adoption, and possible solutions

Fungal infections are responsible for about 70-80% of the losses in agricultural production brought on by microbial diseases. Synthetic fungicides have been employed to manage plant diseases caused by phytopathogenic fungi but their use has been criticized due to unfavorable side effects. As alternative strategies, botanical fungicides have caught the interest of many researchers in recent years. There are numerous experimental studies on the fungicidal activities of phytochemicals against phytopathogenic fungi, but there is not a thorough review article that summarizes these experimental studies. The purpose of this review is therefore to consolidate data from in vitro and in vivo studies on the antifungal activity of phytochemicals reported by various researchers. This paper describes antifungal activities of plant extracts and compounds against phytopathogenic fungi, approved botanical fungicides, their benefits, obstacles and mitigation strategies. Relevant sources were collected using online data bases such as Google Scholar, PubMed and Science Direct, and comprehensively reviewed for preparation of this manuscript. This review revealed that phytochemicals are effective to manage plant diseases caused by phytopathogenic fungi. Botanical fungicides are endowed with benefits such as resistance inhibition, being ecofriendly, effective, selective, and more affordable compared to synthetic fungicides. However, there are only small number of approved botanical fungicides due to the many challenges that hinder their adoption and utilization for a wider scale production. Farmers' reluctance, lack of standardized formulation techniques, strict legislation, rapid degradation, and other factors hinder their adoption and utilization. The ways to address these challenges include increasing awareness among farmers, conducting more research to identify potential plants with fungicidal properties, standardizing extraction and formulation techniques, implementing the idea of plant breeding to increase bioactive agents, identifying favorable environments for site-specific plant species production, discovering synthetic analogues of the active ingredient to maintain quality standards, establishing reasonable regulation procedures and price points for a quicker market introduction. To put all these into practice, we recommend collaboration of regulatory agencies and researchers from a variety of fields.

Carbendazim: Ecological risks, toxicities, degradation pathways and potential risks to human health

Carbendazim is a highly effective benzimidazole fungicide and is widely used throughout the world. The effects of carbendazim contamination on the biology and environment should be paid more attention. We reviewed the published papers to evaluate the biological and environmental risks of carbendazim residues. The carbendazim has been frequently detected in the soil, water, air, and food samples and disrupted the soil and water ecosystem balances and functions. The carbendazim could induce embryonic, reproductive, developmental and hematological toxicities to different model animals. The carbendazim contamination can be remediated by photodegradation and chemical and microbial degradation. The carbendazim could enter into human body through food, drinking water and skin contact. Most of the existing studies were completed in the laboratory, and further studies should be conducted to reveal the effects of successive carbendazim applications in the field.

Disease Forecasting for the Rational Management of Grapevine Mildews in the Chianti Bio-District (Tuscany)

Downy and powdery mildews are major grapevine diseases. In organic viticulture, a few fungicides with protectant activities (copper and sulphur in particular) can be used, and their preventative application frequently leads to unneeded spraying. The adoption of an epidemiological disease forecasting model could optimise the timing of treatments and achieve a good level of disease protection. In this study, the effectiveness of the EPI (Etat Potentiel d'Infection) model in predicting infection risk for downy and powdery mildews was evaluated in nine organic vineyards located in Panzano in Chianti (FI), over a 2-year period (2020-2021). The reliability of the EPI model was investigated by comparing the disease intensities, the number of fungicide sprayings, the quantities of the fungicides (kg/ha), and the costs of the treatment achieved, with or without the use of the model, in a vineyard. The results obtained over two seasons indicated that, in most cases, the use of the EPI model accurately signalled the infection risk and allowed for a reduction in the frequency and cost of spraying, particularly for powdery mildew control (-40% sprayings, -20% costs compared to the farmer's schedule), without compromising crop protection. The use of the EPI model can, therefore, contribute to more-sustainable disease management in organic viticulture.

Antifungal Activity of Medicinal Mushrooms and Optimization of Submerged Culture Conditions for Schizophyllum commune (Agaricomycetes)

The main goal of the present study was the exploration of the antifungal properties of Agaricomycetes mushrooms. Among twenty-three tested mushrooms against A. niger, B. cinerea, F. oxysporum, and G. bidwellii, Schizophyllum commune demonstrated highest inhibition rates and showed 35.7%, 6.5%, 50.4%, and 66.0% of growth inhibition, respectively. To reveal culture conditions enhancing the antifungal potential of Sch. commune, several carbon (lignocellulosic substrates among them) and nitrogen sources and their optimal concentrations were investigated. Presence of 6% mandarin juice production waste (MJPW) and 6% of peptone in nutrient medium promoted antifungal activity of selected mushroom. It was determined that, extracts obtained in the presence of MJPW effectively inhibited the grow of pathogenic fungi. Moreover, the content of phenolic compounds in the extracts obtained from Sch. commune grown on MJPW was several times higher (0.87 ± 0.05 GAE/g to 2.38 ± 0.08 GAE/g) than the extracts obtained from the mushroom grown on the synthetic (glycerol contained) nutrient medium (0.21 ± 0.03 GAE/g to 0.88 ± 0.05 GAE/g). Flavonoid contents in the extracts from Sch. commune varied from 0.58 ± 0.03 to 27.2 ± 0.8 mg QE/g. Identification of phenolic compounds composition in water and ethanol extracts were provided by mass spectrometry analysis. Extracts demonstrate considerable free radical scavenging activities and the IC50 values were generally low for the extracts, ranging from 1.9 mg/ml to 6.7 mg/ml. All the samples displayed a positive correlation between their concentration (0.05-15.0 mg/ml) and DPPH radical scavenging activity. This investigation revealed that Sch. commune mushroom has great potential to be used as a source of antifungal and antioxidant substances.

Fabrication of CuO nanoparticles composite ε-polylysine-alginate nanogel for high-efficiency management of Alternaria alternate

Although ε-poly-l-lysine (ε-PL) has a good potential as a green fungicide, high concentration is usually required during its controlling of plant disease. On the other hand, same problems also appeared in the study of CuONP based nano pesticides. In this manuscript, a new composite alginate nanogel (ALGNP) that containing CuONP and ε-PL was fabricated via in situ reduction of CuONP in nanogel and ε-PL surface coating. Based on the chelation of amide bond of ε-PL and Cu²⁺ released by CuONP, the synergy effect between Cu²⁺ and ε-PL layer of the nanogel make the nanogel (CuONP@ALGNP@PL) performed high anti-fungal activity under low Cu²⁺ and ε-PL concentration (Cu concentration was 40.09 μg/mL, ε-PL concentration was 11.90 μg/mL). Study showed that the nanogel could more significantly destroy the fungal cell membrane than CuONP@ALGNP and ALGNP@PL, also better than commercial fungicide CuCaSO₄ (Cu concentration was 120 μg/mL). Furthermore, CuONP@ALGNP@PL could seriously affect the spore production, spore germination rate and bud tube elongation length of Alternaria alternate. Moreover, CuONP@ALGNP@PL also inhibit Botrytis cinerea, Phytophthora, Thanatephorus cucumeris and Fusarium graminearum. These results showed that composite of CuONP and ε-PL based on nanogel can decrease the raw materials application amount, and achieve a high disease controlling ability, which provides a new perspective for preventing fungal diseases.

Lantadene A and boswellic acid isolated from the leaves of Lantana camara L. have the potential to control phytopathogenic Fusarium species

Phytopathogenic Fusarium species are restricting factors causing diseases and yield loss in crop production. As part of exploration for pesticides from medicinal plants, this study aimed to isolate and characterize bioactive compounds from Lantana camara L. and evaluate their efficiency against Fusarium phytopathogens. Phytochemical investigation of ethyl acetate leaf extract led to separation of lantadene A (22-angeloyloxy-9-hydroxy-3-oxo-olean-12-en-28-oic acid) and boswellic acid (11-keto-β-boswellic acid). The chemical structures of the aforementioned compounds were confirmed using physical properties, spectroscopic analysis, and published data. Lantadene A exhibited significant antifungal activity against F. subglutinans, F. proliferatum, F. solani, F. graminearum, and F. semitectum with minimum inhibitory concentration (MIC) less than or equal to 0.63 mg/mL. Boswellic acid exhibited strong activity (MIC = 0.63 mg/mL) against F. subglutinans and F. semitectum. In terms of their toxicity towards Raw 264.7 cells, lantadene A and boswellic acid recorded half-maximal inhibitory concentration values of 84.2 μg/mL and 186.6 μg/mL, respectively. Both lantadene A and boswellic acid had no phytotoxic effect against seed germination and seedling root length. Lantadene A and boswellic acid have strong potential to be further investigated as lead natural fungicides (biopesticides) to control Fusarium crop diseases.

Crucial role of Ca2+ /CN signalling pathway in the antifungal activity of disenecioyl-cis-khellactone against Botrytis cinerea

BACKGROUND

Botrytis cinerea causes grey mould and is one of the most destructive fungal pathogens affecting important fruit and vegetable crops. In preliminary studies, we found that disenecioyl-cis-khellactone (DK) had strong antifungal activity against several fungi species including B. cinerea [half maximal effective concentration (EC₅₀ ) = 11.0 μg mL^-1 ]. In this study, we aimed to further evaluate the antifungal activity of DK against B. cinerea and determine the role of calcium ion/calcineurin (Ca²⁺ /CN) signalling pathway on its antifungal effect.

RESULTS

DK was effective against B. cinerea in both in vitro and in vivo assays. Exogenous Ca²⁺ reduced the antifungal activity of DK. The combination of DK and cyclosporine A (CsA) did not exhibit an additive effect against B. cinerea. In contrast to CsA, DK reduced the intracellular Ca²⁺ concentration in B. cinerea. DK bound to calcineurin A (cnA) and up-regulated the expression of PMC1 and PMR1 genes. Moreover, DK sensitivity of △bccnA significantly decreased compared with that of Bc05.10 strain.

CONCLUSION

DK is a promising lead compound for developing fungicides against B. cinerea. The Ca²⁺ /CN signalling pathway plays a crucial role in the DK antifungal activity, and cnA is one of the targets of DK against B. cinerea. DK directly reacts with cnA, which up-regulates the transcription of Ca²⁺ /CN-dependent target genes PMC1 and PMR1, decreasing the intracellular Ca²⁺ concentration and disturbing the intracellular Ca²⁺ balance, leading to cell death. © 2022 Society of Chemical Industry.

A Phytocomplex Obtained from Salvia officinalis by Cell Culture Technology Effectively Controls the Grapevine Downy Mildew Pathogen Plasmopara viticola

The negative impact of using conventional fungicides in plant disease protection has increased the interest in safer alternatives such as plant secondary metabolites, generally having a better toxicological profile. However, cultivation conditions and plant material strongly affect the quality and quantity of secondary metabolites obtained from field grown plants, limiting the standardization needed for industrial production. Plant cell culture technology can provide highly homogeneous biomasses with specific chemical characteristics. A phytocomplex with high rosmarinic acid content (10.12% w/w) was obtained from a selected cell line of Salvia officinalis and was tested against the grapevine downy mildew pathogen, Plasmopara viticola. Grapevine leaf discs were sprayed with the phytocomplex at 5 g/L and then inoculated with P. viticola sporangia. Sporulation level on each disc was assessed after 7 days with an image processing software. The phytocomplex reduced by 95% the sporulation level compared to the control and was also more effective than rosmarinic acid alone, used at the same concentration found in the phytocomplex. Persistence of the phytocomplex was also assessed: when applied 5 days before inoculation, it reduced by 90% the sporulation level compared to the control. These results highlight the possibility to take advantage of cell culture techniques to produce safer pesticides with high quality standards.

Exploration of Clove Bud (Syzygium aromaticum) Essential Oil as a Novel Attractant against Bactrocera dorsalis (Hendel) and Its Safety Evaluation

The oriental fruit fly Bactrocera dorsalis (Hendel) is a destructive polyphagous species that targets many economically important fruits and vegetables. The primary control of B. dorsalis relies mainly on the use of synthetic chemicals, and excessive use of these chemicals has adverse effects on both the environment and human health. Environmentally friendly management of pests involving plant essential oils is useful for controlling the populations of pests responsible for decreasing the yields and quality of crops. In the present study, we demonstrate that clove bud essential oil (CBEO) is strongly attractive to sexually mature males. Mature males responded to the CBEO differently throughout the day; the strongest response was elicited during the day and decreased at dusk. Virgin and mated mature males did not respond differently to CBEO. No obvious response behaviour to the CBEO was observed in two species of beneficial natural predator ladybirds. In addition, a cytotoxicity assessment demonstrated that CBEO is nontoxic to normal human and mouse cells. Based on our laboratory experiments, CBEO may serve as a promising, sustainable, and environmentally friendly attractant for B. dorsalis males; however, field experiments are needed to confirm this hypothesis.

A Rhizobacterium, Streptomyces albulus Z1-04-02, Displays Antifungal Activity against Sclerotium Rot in Mungbean

Sclerotium rot causes damping-off and stem rot in seedlings and mature mungbeans, which negatively impacts cultivation. The use of a rhizobacterium to control soil-borne diseases is an alternative method to the excess use of synthetic fungicides; therefore, this study aims to screen rhizosphere actinobacteria with fungicidal activities against Sclerotium rolfsii, the pathogen that causes sclerotium rot in mungbeans. Primary screening showed that the Streptomyces sp. isolate Z1-04-02 displayed the highest effectiveness against S. rolfsii in dual culture plates, with a percentage inhibition of 74.28%. An assay containing enzymes that degrade cell walls, of the cell-free culture filtrate (CF) of Z1-04-02, showed that the activities of chitinase and β-1,3-glucanase were 0.0209 and 1.0210 U/mL, respectively, which was significantly higher than that of the control (media alone). The cell-free CF of Z1-04-02, incubated at 37 °C and 100 °C, using agar well diffusion, effectively inhibited the growth of S. rolfsii with inhibition percentages of 37.78% and 27.78%, respectively. Solid-phase microextraction (SPME) was applied to trap volatiles released from Z1-04-02 and gas chromatography-mass spectrometry (GC/MS); volatile antifungal compounds were tentatively identified as bicyclic monoterpene (1R)-(-)-myrtenal. The application of the cell-free CF, and the spore suspension of Z1-04-02, showed disease severity indexes (DSIs) of 12.5% and 8.25%, respectively, which were significantly lower than those showing inoculation by S. rolfsii alone. The identification of this strain by morphology, biochemistry tests, and 16s rDNA sequences revealed that Z1-04-02 was Streptomyces albulus. This finding revealed that S. albulus Z1-04-02 displayed diverse fungicidal activities against S. rolfsii, and it has the potential to act as a biological control agent in terms of inhibiting sclerotium rot in mungbeans.

Efficacy of Plant-Derived Fungicides at Inhibiting Batrachochytrium salamandrivorans Growth

The emerging fungal amphibian pathogen, Batrachochytrium salamandrivorans (Bsal), is currently spreading across Europe and given its estimated invasion potential, has the capacity to decimate salamander populations worldwide. Fungicides are a promising in situ management strategy for Bsal due to their ability to treat the environment and infected individuals. However, antifungal drugs or pesticides could adversely affect the environment and non-target hosts, thus identifying safe, effective candidate fungicides for in situ treatment is needed. Here, we estimated the inhibitory fungicidal efficacy of five plant-derived fungicides (thymol, curcumin, allicin, 6-gingerol, and Pond Pimafix®) and one chemical fungicide (Virkon® Aquatic) against Bsal zoospores in vitro. We used a broth microdilution method in 48-well plates to test the efficacy of six concentrations per fungicide on Bsal zoospore viability. Following plate incubation, we performed cell viability assays and agar plate growth trials to estimate the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of each fungicide. All six fungicides exhibited inhibitory and fungicidal effects against Bsal growth, with estimated MIC concentrations ranging from 60 to 0.156 μg/mL for the different compounds. Allicin showed the greatest efficacy (i.e., lowest MIC and MFC) against Bsal zoospores followed by curcumin, Pond Pimafix®, thymol, 6-gingerol, and Virkon® Aquatic, respectively. Our results provide evidence that plant-derived fungicides are effective at inhibiting and killing Bsal zoospores in vitro and may be useful for in situ treatment. Additional studies are needed to estimate the efficacy of these fungicides at inactivating Bsal in the environment and treating Bsal-infected amphibians.

Macrolides from Streptomyces sp. SN5452 and Their Antifungal Activity against Pyricularia oryzae

Pyricularia oryzae causes rice blast, the major destructive disease in nearly all rice fields. In order to obtain highly active compounds against P. oryzae, four new 20-membered macrolides named venturicidins G-J (1-4) were isolated from the culture broth of Streptomyces sp. SN5452 along with two known ones, venturicidins A (5) and B (6). Their structures were determined by the cumulative analyses of nuclear magnetic resonance (NMR) spectroscopy and high-resolution electrospray ionization mass spectrometry (HRESIMS) data. All isolated compounds were evaluated for their antifungal activity against P. oryzae. Interestingly, these compounds exhibited obvious inhibition to mycelial growth and conidial germination of P. oryzae. Remarkably, the EC50 values of venturicidins A (5), B (6), and I (3) against mycelial growth were 0.11, 0.15 and 0.35 µg/mL, and their EC50 values of conidial germination were 0.27, 0.39 and 1.14 µg/mL, respectively. The analysis of structure-activity relationships (SARs) revealed that the methylated positions might be involved in the antifungal activity of venturicidins. These results indicate that the venturicidins are prospective candidates for novel fungicides that can be applied in controlling rice blast.

Cell-free supernatant of Bacillus velezensis suppresses mycelial growth and reduces virulence of Botrytis cinerea by inducing oxidative stress

As a notorious pathogenic fungus, Botrytis cinerea has been reported to infect more than 1400 species of plants and cause postharvest gray mold of numerous economic fruits, leading to substantial economic losses. Traditional chemical fungicides in pathogen control have potential issues regarding environmental pollution, disease resistance and human health. More safety and efficacious prevention technique of postharvest gray mold are in urgent demand. This study aims to investigate the potential function and mechanism of Bacillus velezensis to control gray mold for harvested fruits. The results showed that the cell-free supernatant (CFS) generated from B. velezensis strain A4 was able to inhibit spore germination, germ tube elongation and hyphal growth of B. cinerea in vitro, and impair the pathogenicity of B. cinerea on the four tested fruits. Further analysis demonstrated that CFS significantly reduced the expression of genes associated with growth and pathogenicity and weakened the ability of B. cinerea spores to penetrate plant cell walls in a dose-dependent manner. Moreover, the CFS destroyed the membrane of hyphae, resulting in exosmosis of cell contents and caused hyphal cells to accumulate excessive reactive oxygen species (ROS), leading to hyphal oxidative damage. Our findings indicate that B. velezensis CFS can damage B. cinerea mycelial cells by promoting excessive accumulation of ROS to realize its biological control function.

The 1-aminocyclopropane-1-carboxylic acid deaminase-producing Streptomyces violaceoruber UAE1 can provide protection from sudden decline syndrome on date palm

In the United Arab Emirates (UAE), sudden decline syndrome (SDS) is one of the major fungal diseases caused by Fusarium solani affecting date palm plantations. To minimize the impact of the causal agent of SDS on date palm, native actinobacterial strains isolated from rhizosphere soils of healthy date palm plants were characterized according to their antifungal activities against F. solani DSM 106836 (Fs). Based on their in vitro abilities, two promising biocontrol agents (BCAs), namely Streptomyces tendae UAE1 (St) andStreptomyces violaceoruber UAE1 (Sv), were selected for the production of antifungal compounds and cell wall degrading enzymes (CWDEs), albeit their variations in synthesizing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD). Although both isolates showed antagonism when applied 7 days before the pathogen in the greenhouse experiments, the ACCD-producing Sv was relatively superior in its efficacy against SDS over the non-ACCD-producing St. This was evident from the symptoms of SDS in diseased date palm seedlings which were greatly reduced by Sv compared to St. On a scale of 5.0, the estimated disease severity indices in Fs-diseased seedlings were significantly (P < 0.05) reduced from 4.8 to 1.5 and 0.5 by St and Sv, respectively. Thus, the number of conidia of Fs recovered from plants pre-treated with both BCAs was comparable, but significantly (P < 0.05) reduced compared to plants without any BCA treatment. In addition, a significant (P < 0.05) decrease in ACC levels of both the root and shoot tissues was detected inSv + Fs seedlings to almost similar levels of healthy seedlings. However, in planta ACC levels highly increased in seedlings grown in soils infested with the pathogen alone or amended with St prior to F. solani infestation (St + Fs). This suggests a major role of ACCD production in relieving the stress of date palm seedlings infected with F. solani, thus supporting the integrated preventive disease management programs against this pathogen. This is the first report of effective rhizosphere actinobacterial BCAs to provide protection against SDS on date palm, and to help increase agricultural productivity in a more sustainable manner in the UAE and the other arid regions.

Suppression of Cephalosporium maydis by the resistance inducer beta-sitosterol

Late wilt, a vascular disease caused by the fungus of Cephalosporium maydis, is considered one of Egypt’s most severe maize threats. The purpose of this study was to investigate the suppressive effect of the resistance inducer beta-sitosterol on C. maydis, as well as its involvement in reducing the incidence of late wilt infection under greenhouse and field conditions. In in vitro studies on potato dextrose yeast extract agar (PDYA) and/or potato dextrose yeast extract broth (PDYB) with doses of 50, 100, 150, 200, and 250 ppm, beta-sitosterol significantly reduced colony diameter and spore germination of C. maydis. The efficiency of beta-sitosterol increased with concentration, with 250 ppm being the most efficient, reducing colony development by 100% and spore germination by 77.3%. Experiments were conducted in greenhouse and field trials using the split-plot design with three beta-sitosterol 250 ppm application methods (maize grain dipping, maize foliar spraying, and maize grain dipping with foliar spraying) and two maize cultivars (a land race and the cultivar fine seed 1005). In both trials, the combination treatment of maize grain dipping and foliar spraying with beta-sitosterol 250 ppm was most effective. Under greenhouse conditions, beta-sitosterol treatments significantly improved the growth parameters (plant height, plant fresh weight, and plant dry weight) of the two maize cultivars. Under similar conditions, beta-sitosterol significantly increased the activity of protective enzymes (peroxidase, polyphenoloxidase, and chitinase) and the levels of chlorophyll, total phenols, and flavonoids in the two maize cultivars. When compared to the untreated control, beta-sitosterol application reduced the incidence of late wilt disease under greenhouse and field conditions. The ear yield of the two maize cultivars was significantly increased in plots treated with beta-sitosterol 250 ppm in a field trial. The findings showed that beta-sitosterol inhibited C. maydis growth in vitro and improved maize plant resistance to late wilt infection in vivo. As a result, this plant resistance inducer could be used to improve the resistance of maize cultivars to late wilt disease.

Negative cross-resistance of a pyrethroid-resistant Drosophila mutant to Phryma leptostachya-derived haedoxan A

Voltage-gated sodium channels are the primary target of pyrethroid insecticides. Mutations in sodium channel confer knockdown resistance (kdr) to pyrethroids in various arthropod pests. Haedoxan A (HA) is the major insecticidal component from Phryma leptostachya. It has been shown that HA alters electrical responses at the Drosophila neuromuscular junction and modifies the gating properties of cockroach sodium channels expressed in Xenopus oocytes. However, whether sodium channel mutations that confer pyrethroid resistance also affect the action of HA is unknown. In this study, we conducted bioassays using HA and permethrin in two Drosophila melanogaster strains: w¹¹¹⁸ , an insecticide-susceptible strain, and para^ts1 , a pyrethroid-resistant strain due to a I265N mutation in the sodium channel, and identified a new case of negative cross-resistance (NCR) between permethrin and HA. Both para^ts1 larvae and adults were more resistant to permethrin, as expected. However, both para^ts1 larvae and adults were more sensitive to HA compared to w¹¹¹⁸ . We confirmed that the I265N mutation reduced the sensitivity to permethrin of a Drosophila sodium channel variant, DmNa_v 22, expressed in Xenopus oocytes. Interestingly, the I265N mutation also abolished the effect of HA on sodium channels. Further characterization showed that I265 on the sodium channels is critical for the action of both pyrethroids and HA on sodium channels, pointing to an overlapping mode of action between pyrethroids and HA on the sodium channel. Overall, our results suggest an I265N-independnt mechanism(s) in para^ts1 flies that is responsible for the NCR between permethrin and HA at the whole insect level.

Development of 1,3,4-Oxadiazole Derived Antifungal Agents and Their Application in Maize Diseases Control

Maize is an important food crop and its fungal disease has become a limiting factor to improve the yield and quality of maize. In the control of plant pathogens, commercial fungicides have no obvious effect on corn diseases due to the emergence of drug resistance. Therefore, it is of great significance to develop new fungicides with novel structure, high efficiency, and low toxicity to control maize diseases. In this paper, a series of 1,3,4-oxadiazole derivatives were designed and synthesized from benzoyl hydrazine and aromatic aldehydes through condensation and oxidation cyclization reaction. The antifungal activity of oxadiazole derivatives against three maize disease pathogens, such as Rhizoctonia solani (R. solani), Gibberella zeae (G. zeae), and Exserohilum turcicum (E. turcicum), were evaluated by mycelium growth rate method in vitro. The results indicated that most of the synthesized derivatives exhibited positive antifungal activities. Especially against E. turcicum, several compounds demonstrated significant antifungal activities and their EC 50 values were lower than positive control carbendazim. The EC 50 values of compounds 4k, 5e, and 5k were 50.48, 47.56, 32.25 μg/ml, respectively, and the carbendazim was 102.83 μg/ml. The effects of active compounds on E. turcicum microstructure were observed by scanning electron microscopy (SEM). The results showed that compounds 4k, 5e, and 5k could induce the hyphae of E. turcicum to shrink and collapse obviously. In order to elucidate the preliminary mechanism of oxadiazole derivatives, the target compounds 5e and 5k were docked with the theoretical active site of succinate dehydrogenase (SDH). Compounds 5e and 5k could bind to amino acid residues through hydrophobic contact and hydrogen bonds, which explained the possible mechanism of binding between the inhibitor and target protein. In addition, the compounds with antifungal activities had almost no cytotoxicity to MCF-7. This study showed that 1,3,4-oxadiazole derivatives were worthy for further attention as potential antifungal agents for the control of maize diseases.

Antifungal activity of l-azetidine-2-carboxylic acid isolated from Disporopsis aspera rhizomes against Podosphaera xanthii

BACKGROUND

Powdery mildew is one of the fungal diseases commonly occurring in the process of cucurbits protected and open cultivation. Cucumbers, melons and pumpkins are extremely susceptible. The secondary metabolites produced by plants are important sources of fungicides with low toxicity and environment-friendly characteristics. The aim of this study was to reveal the main active ingredient in the crude extracts of Disporopsis aspera rhizomes that inhibit cucurbits powdery mildew and evaluate its activities.

RESULTS

In this study, the crude extracts of Disporopsis aspera rhizomes were found to exhibit excellent antifungal activity aganist Podosphaera xanthii, a causal agent of cucurbits powdery mildew. Based on the bioassay-guided method, l-azetidine-2-carboxylic acid (l-Aze) was isolated from this genus for the first time. l-Aze showed unique curative and eradicative activity against Podosphaera xanthii in vivo, which has never been reported before. Microscopic observation revealed that the curative spraying of l-Aze could effectively inhibit the mycelial growth, resulting in hollow parts of the mycelia, not forming conidiophores, and interrupting the life cycle of powdery mildew. The eradicative spraying of l-Aze caused the fracture of mycelia and deformity of conidiophores, which could not continue to produce conidia.

CONCLUSION

l-Aze was the main active ingredient of D. aspera against Podosphaera xanthii, which had both curative and eradicative effects. The results provided a strong possibility of using the crude extracts of D. aspera rhizomes and its main effective component, l-Aze as biocontrol agents to control cucurbits powdery mildew.

Induce defense response of DADS in eggplants during the biotrophic phase of Verticillium dahliae

PURPOSE

Verticillium wilt is a destructive vascular disease in eggplants. The complex defensive mechanisms of eggplant against this disease are very limited.

METHODS

Our work examined the bioactive properties of garlic allelochemical diallyl disulfide (DADS) as potential biostimulants for defense against V. dahliae in eggplant seedlings. We, therefore, foliar sprayed DADS on eggplants to study the defense response during the early biotrophic phase of V. dahliae (a hemibiotroph).

RESULTS

DADS application significantly increased root peroxidase (POD), phenylalanine-ammonia lyase (PAL) enzyme activity, and reduced H₂O₂ levels after 24 h of fungal inoculation. Salicylic acid (SA) in leaves and roots was significantly increased while, the jasmonic acid (JA), indole acetic acid (IAA), and abscisic acid (ABA) levels were decreased. The microscopic examinations of V. dahliae infection in roots displayed that the progression of infection was restricted in DADS-treated plants. Depositions of lignin and phenolic compounds such as ferulic acid, p-coumaric acid, and caffeic acid content were significantly higher in DADS-treated plants at 48 h post-inoculation. Similarly, the DADS application up-regulated pathogenesis-related (PR1, PR2, and PR5), mitogen-activated protein kinase (MPK1), and lipoxygenase (LOX) genes. Furthermore, DADS-treated plants exhibited a lower disease severity index (23.3% vs. 57.0% in controls), indicating successful defense against V. dahliae.

CONCLUSIONS

Our findings concluded that the biological function of garlic allelochemical DADS has a prominent role in the higher defense resistance of eggplants during the early infection of V. dahliae.

A Review of the Potency of Plant Extracts and Compounds from Key Families as an Alternative to Synthetic Nematicides: History, Efficacy, and Current Developments

The global nematicides market is expected to continue growing. With an increasing demand for synthetic chemical-free organic foods, botanical nematicides are taking the lead as replacements. Consequently, in the recent years, there have been vigorous efforts towards identification of the active secondary metabolites from various plants. These include mostly glucosinolates and their hydrolysis products such as isothiocyanates; flavonoids, alkaloids, limonoids, quassinoids, saponins, and the more recently probed essential oils, among others. And despite their overwhelming potential, variabilities in quality, efficacy, potency and composition continue to persist, and commercialization of new botanical nematicides is still lagging. Herein, we have reviewed the history of botanical nematicides and regional progresses, the potency of the identified phytochemicals from the key important plant families, and deciphered some of the impediments involved in standardization of the active compounds in addition to the concerns over the safety of the purified compounds to non-target microbial communities.

Status and Prospects of Botanical Biopesticides in Europe and Mediterranean Countries

Concerning human and environmental health, safe alternatives to synthetic pesticides are urgently needed. Many of the currently used synthetic pesticides are not authorized for application in organic agriculture. In addition, the developed resistances of various pests against classical pesticides necessitate the urgent demand for efficient and safe products with novel modes of action. Botanical pesticides are assumed to be effective against various crop pests, and they are easily biodegradable and available in high quantities and at a reasonable cost. Many of them may act by diverse yet unexplored mechanisms of action. It is therefore surprising that only few plant species have been developed for commercial usage as biopesticides. This article reviews the status of botanical pesticides, especially in Europe and Mediterranean countries, deepening their active principles and mechanisms of action. Moreover, some constraints and challenges in the development of novel biopesticides are highlighted.

Characterization and survival of broad-spectrum biocontrol agents against phytopathogenic fungi

The current study intended to isolate, characterize and identify biocontrol bacteria possessing broad-spectrum antifungal activity from the phyllosphere of different crops including maize, wheat and potato and to assess their growth-promoting activity. In this study 14/113 biocontrol bacteria showed antifungal activity. Bacterial isolates M11 and M33 from maize out of 113 were re-selected on the basis of their strong (more than 50%) broad spectrum antifungal activity after their assessment against four economically important phytopathogenic fungi including Alternaria alternata, Rhizoctonia solani, Fusarium oxysporum and Fusarium verticillioides. The isolates were further assessed for plant growth promoting traits, i.e., indole-3-acetic acid production, phosphate solubilization, production of cellulase, microbial volatile compounds, hydrogen cyanide and siderophores. All fourteen isolates showed positive results for the production of indole-3-acetic acid hormone and cellulase enzyme, 10 isolates were positive for hydrogen cyanide production; siderophores production was observed in 7 isolates while 5 isolates showed ability to solubilize inorganic phosphate. Microbial volatile compounds were only synthesized by M11 and M33, which were identified as Bacillus amyloliquefaciens and Bacillus subtilis respectively by 16S rRNA gene sequencing. The survival study revealed that biocontrol bacteria B. amyloliquefaciens and B. subtilis have the ability to survive in cost effective molasses containing carrier material up to a three-month period.

Warburgia ugandensis Leaf and Bark Extracts: An Alternative to Copper as Fungicide against Downy Mildew in Organic Viticulture?

In organic viticulture, copper-based fungicides are commonly used to suppress Downy Mildew infection, caused by the oomycete Plasmopara viticola. However, the frequent and intensive use of such fungicides leads to accumulation of the heavy metal in soil and nearby waters with adverse effects on the ecosystem. Therefore, alternative, organic fungicides against Downy Mildew are urgently needed to reduce the copper load in vineyards. In this study, the use of Warburgia ugandensis Sprague (Family Canellacea) leaf and bark extracts as potential fungicides against Downy Mildew were evaluated. In vitro (microtiter) and in vivo (leaf discs, seedlings) tests were conducted, as well as field trials to determine the efficacy of the extracts against Downy Mildew. The results revealed an MIC100 of 500 µg/mL for the leaf extract and 5 µg/mL for the bark extract. Furthermore, experiments with leaf discs and seedlings demonstrated a strong protective effect of the extracts for up to 48 h under (semi-) controlled conditions. However, in field trials the efficacy of the extracts distinctly declined, regardless of the extracts' origin and concentration.

Electrochemical detection of methyl-paraoxon based on bifunctional cerium oxide nanozyme with catalytic activity and signal amplification effect

A new electrochemical sensor for organophosphate pesticide (methyl-paraoxon) detection based on bifunctional cerium oxide (CeO₂) nanozyme is here reported for the first time. Methyl-paraoxon was degraded into p-nitrophenol by using CeO₂ with phosphatase mimicking activity. The CeO₂ nanozyme-modified electrode was then synthesized to detect p-nitrophenol. Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode, which indicates that the signal enhancement effect may attribute to the coating of CeO₂ nanozyme. The current research also studied and discussed the main parameters affecting the analytical signal, including accumulation potential, accumulation time, and pH. Under the optimum conditions, the present method provided a wider linear range from 0.1 to 100 μmol/L for methyl-paraoxon with a detection limit of 0.06 μmol/L. To validate the proof of concept, the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples, i.e., Coix lacryma-jobi, Adenophora stricta and Semen nelumbinis. Our findings may provide new insights into the application of bifunctional nanozyme in electrochemical detection of organophosphorus pesticide.

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A new electrochemical method for methyl-paraoxon detection by using bifunctional nanozyme was presented.

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The cerium oxide nanozyme modified glassy carbon electrode was prepared to improve the sensitivity.

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The developed method has been successfully applied in three herbal plant samples.

Recent Approaches towards Control of Fungal Diseases in Plants: An Updated Review

Recent research demonstrates that the number of virulent phytopathogenic fungi continually grows, which leads to significant economic losses worldwide. Various procedures are currently available for the rapid detection and control of phytopathogenic fungi. Since 1940, chemical and synthetic fungicides were typically used to control phytopathogenic fungi. However, the substantial increase in development of fungal resistance to these fungicides in addition to negative effects caused by synthetic fungicides on the health of animals, human beings, and the environment results in the exploration of various new approaches and green strategies of fungal control by scientists from all over the world. In this review, the development of new approaches for controlling fungal diseases in plants is discussed. We argue that an effort should be made to bring these recent technologies to the farmer level.

Effective In Vitro Control of Two Phytopathogens of Agricultural Interest Using Cell-Free Extracts of Pseudomonas fluorescens and Chitosan

A biofungicide is a natural product that can be derived from various sources such as, among others, microorganisms, higher plants, animal products, phytochemicals, semiochemicals, and antagonist microorganisms. One of the most important approaches for the production of biofungicides is the combination of biocontrol agents. This study showed the inhibition growth of Alternaria alternata and Fusarium solani treated with cell-free extracts of P. fluorescens. Using thin-layer chromatography and plate assays it was also demonstrated that the cell-free extracts of P. fluorescens contained siderophores and derivates of 4-diacetylphloroglucinol and phenazine. Moreover, the combination of cell-free extracts of P. fluorescens and chitosan [50–1.5% (v/v)] had a synergistic effect since they notably inhibited the mycelial growth of A. altenata and F. solani. Various morphological alterations to the mycelia and conidia of the treated fungi as a result of this combination were also observed. The present study could be a starting point to control other fungal phytopathogens using different cell-free extracts and chitosan as biocontrol agents.

Synthesis, Antifungal Activity, DFT Study and Molecular Dynamics Simulation of Novel 4-(1,2,4-Oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide Derivatives

In order to find novel potential antifungal agrochemicals, a series of new 4-(1,2,4-oxadiazol-3-yl)-N-(4-phenoxyphenyl)benzamide derivatives 3a-j were designed, synthesized and characterized by their ¹ H-, ¹³ C-NMR and HRMS spectra. The preliminary antifungal assay in vitro revealed that compounds 3a-j exhibited moderate to good antifungal activity against five plant pathogenic fungi. Especially, compound 3e presented significant antifungal activity against Alternaria solani, Botrytis cinerea and Sclerotinia sclerotiorum, superior to positive control boscalid. In the in vivo antifungal assay on tomato plants and cucumber leaves, compound 3e presented good inhibition rate against B. cinerea at 200 mg/L. Molecular dynamics simulation revealed that compound 3e could bind with the active site of class II histone deacetylase (HDAC).

Toxics or Lures? Biological and Behavioral Effects of Plant Essential Oils on Tephritidae Fruit Flies

The family Tephritidae (Diptera) includes species that are highly invasive and harmful to crops. Due to globalization, international trade, and human displacement, their spread is continuously increasing. Unfortunately, the control of tephritid flies is still closely linked to the use of synthetic insecticides, which are responsible for detrimental effects on the environment and human health. Recently, research is looking for alternative and more eco-friendly tools to be adopted in Integrated Pest Management (IPM) programs. In this regard, essential oils (EOs) and their main compounds represent a promising alternative to chemical insecticides. EOs are made up of phytoconstituents formed from the secondary metabolism of many plants and can act as attractants or toxics, depending on the dose. Because of this unique characteristic, EOs and their main constituents are promising tools that can be used both in Sterile Insect Technique (SIT) programs and in the "lure and kill" technique, exploiting the attractiveness of the product in the former case and its toxicity in the latter. In this article, current knowledge on the biological and behavioral effects of EOs and their main constituents on tephritid fruit flies is reviewed, mainly focusing on species belonging to the Anastrepha, Bactrocera, Ceratitis, and Zeugodacus genera. The mechanisms of action of EOs, their real-world applications, and challenges related to their use in IPM are critically discussed.

Clerodane Diterpenoids Identified from Polyalthia longifolia Showing Antifungal Activity against Plant Pathogens

In the search for new natural resources showing plant disease control effects, we found that the methanol extract of Polyalthia longifolia suppressed fungal disease development in plants. To identify the bioactive substances, the methanol extract of P. longifolia was extracted by organic solvents, and consequently, four new 2-oxo-clerodane diterpenes (1-4), a new 4(3 → 2)-abeo-clerodane diterpene (5), together with ten known compounds (6-16) were isolated and identified from the extracts. Of the new compounds, compound 2 showed a broad spectrum of antifungal activity with moderated minimum inhibitory concentration (MIC) values in a range of 50-100 μg/mL against tested fungal pathogens. Considering with the known compounds, compound 6 showed the most potent antifungal activity with an MIC value in the range of 6.3-12.5 μg/mL. When compound 6 was evaluated for an in vivo antifungal activity against rice blast, tomato late blight, and pepper anthracnose, compound 6 reduced the plant disease by at least 60% compared to the untreated control at concentrations of 250 and 500 μg/mL. Together, our results suggested that the methanol extract of twigs and leaves of P. longifolia and its major compound 6 could be used as a source for the development of eco-friendly plant protection agents.

Inhibitory Effect of Osthole from Cnidium monnieri (L.) Cusson on Fusarium oxysporum, a Common Fungal Pathogen of Potato

Fusarium wilt of potato is one of the most common diseases of potato in China, and is becoming a serious threat in potato production. It has been reported that osthole from Cnidium monnieri (L.) Cusson can inhibit plant pathogens. Here, we test the anti-fungal activity of C. monnieri osthole against Fusarium oxysporum in potatoes. The results showed that at a concentration of 5 mg/mL, osthole was able to obviously inhibit mycelial growth of F. oxysporum. We found that osthole caused changes of mycelial morphology, notably hyphal swelling and darkening. Osthole significantly reduced the spore germination of Fusarium by 57.40%. In addition, osthole also inhibited the growth of other pathogens such as Fusarium moniliforme J. Sheld, Thanatephorus cucumeris Donk, and Alternaria alternata (Fr.) Keissl, but not Alternaria solani Jonesetgrout and Valsa mali Miyabe and G. Yamada. Our results suggest that osthole has considerable potential as an agent for the prevention and treatment of potato Fusarium wilt.

Isolation, Identification, Biocontrol Activity, and Plant Growth Promoting Capability of a Superior Streptomyces tricolor Strain HM10

Streptomyces is a genus with known biocontrol activity, producing a broad range of biologically active substances. Our goal was to isolate local Streptomyces species, evaluate their capacity to biocontrol the selected phytopathogens, and promote the plant growth via siderophore and indole acetic acid (IAA) production and phosphate solubilization. Eleven isolates were obtained from local soil samples in Saudi Arabia via the standard serial dilution method and identified morphologically by scanning electron microscope (SEM) and 16S rRNA amplicon sequencing. The biocontrol of phytopathogens was screened against known soil-borne fungi and bacteria. Plant growth promotion capacity was evaluated based on siderophore and IAA production and phosphate solubilization capacity. From eleven isolates obtained, one showed 99.77% homology with the type strain Streptomyces tricolor AS 4.1867, and was designated S. tricolor strain HM10. It showed aerial hyphae in SEM, growth inhibition of ten known phytopathogens in in vitro experiments, and the production of plant growth promoting compounds such as siderophores, IAA, and phosphate solubilization capacity. S. tricolor strain HM10 exhibited high antagonism against the fungi tested (i.e., Colletotrichum gloeosporides with an inhibition zone exceeding 18 mm), whereas the lowest antagonistic effect was against Alternaria solani (an inhibition zone equal to 8 mm). Furthermore, the most efficient siderophore production was recorded to strain HM8, followed by strain HM10 with 64 and 22.56 h/c (halo zone area/colony area), respectively. Concerning IAA production, Streptomyces strain HM10 was the most effective producer with a value of 273.02 μg/ml. An autochthonous strain S. tricolor HM10 should be an important biological agent to control phytopathogens and promote plant growth.

Inhibitory Effect of Cinnamaldehyde on Main Destructive Microorganisms of Nanhai No. 1 Shipwreck

Nanhai No. 1, a shipwreck in the Southern Song Dynasty, China, has a history of more than 800 years. It was salvaged in 2007 and is now on display in the Guangdong Maritime Silk Road Museum. Due to the fact that the hull is a wooden cultural relic and exposed to the air, the biological corrosion and biodegradation caused by microorganisms are key problems of hull protection. At present, the antimicrobial agent Euxyl® K100 (isothiazolinone) has a significant antimicrobial effect in the field, but it has a certain negative impact on the environment and archeologists. In order to reduce the use of chemical antimicrobial agents, we evaluated the inhibitory effects of cinnamaldehyde on the main destructive microorganisms of Nanhai No. 1. Cinnamaldehyde is the main active component of cinnamon, and has broad-spectrum antimicrobial properties. The paper diffusion method, gas diffusion method and minimum inhibitory concentration experiment were used to detect the inhibitory effects of cinnamaldehyde on the main microorganisms of Nanhai No. 1. We found that cinnamaldehyde had significant inhibitory effects on Bacillus tequilensis NK-NH5, Bacillus megaterium NK-NH10, Bacillus velezensis NK-NH11, Bacillus sp. NK-NH15, Bacillus sp. NK-NH16, Bacillus sp. NK-NH17, Fusariumsolani NK-NH1 and Scedosporiumapiospermum NK.W1-3. At the same time, cinnamaldehyde had more inhibitory effects on fungi than bacteria. Finally, we verified that cinnamaldehyde can effectively inhibit the growth of microorganisms in water, for storing the scattered wood blocks of the Nanhai No. 1 hull through laboratory simulation experiments. Cinnamaldehyde, as an environment-friendly antimicrobial agent, is of great significance to protecting water-saturated wooden relics from microbial corrosion and degradation in the future.

Hormesis-Inducing Essential Oil Nanodelivery System Protects Plants against Broad Host-Range Necrotrophs

Botrytis cinerea, a broad host-range necrotrophic (BHN) phytopathogen, establishes compatible interactions with hosts by deploying multigene infection strategies, rendering simply inherited resistance ineffective to fight off this pathogen. Since essential oils (EOs) serve as intermediators during phytobiome communication, we hypothesize that they have the potential to enhance the quantitative disease resistance against BHN by eliciting the adaptive stress response (hormesis) in plants. However, using EOs is challenging due to their poor solubility in water. Nanoemulsification of EOs enhances not only the solubility of EOs but also their potency and stability. Here, we demonstrate the potential use of essential oil nanoemulsions (EONEs) to control infections caused by BHN. Using basic engineering principles of nanocarrier design, we demonstrate the efficacy of a robust EONEs design for controlling B. cinerea infection in a model plant, Arabidopsis thaliana. Our nanoemulsion delivery system significantly enhanced the disease resistance of the host by reducing the necrotic area by up to 50% compared to untreated plants. RNA-seq analysis indicated that successful treatments upregulated autophagy, ROS scavenging, and activation of the jasmonic acid signaling pathway.