Potential Biopesticide Research Articles

Effects of surfactin stress on gene expression and pathological changes in Spodoptera litura

Spodoptera litura (S. litura) is a polyphagous pest of the family Lepidoptera, which causes damage and yields losses to many crops. The long-term use of chemical pesticides for control not only seriously threatens environmental health, but also causes S. litura to develop drug resistance. Therefore, there is an urgent need to develop environmentally safe and friendly biogenic pesticides. However, the mechanism of action of the secondary metabolite (surfactin) of Bacillus Vélezensis (B. vélezensis) on lepidopteran pests (S. litura) has not been reported yet. We found that several metabolites and genes in S. litura were affected by surfactin exposure. The expressions of the metabolites (protoporphyrinogen (PPO), gluconolactone (GDL), and L-cysteate) were significantly down-regulated while glutamate and hydroxychloroquine were significantly up-regulated. The expression levels of genes related to drug metabolism and detoxification, include the glutathione s-transferase (GST) gene family and acetaldehyde dehydrogenase (ALDH), and apoptosis-inhibiting genes (seven in absentia homolog 1(SIAH1)) were significantly decreased. In addition, pathological changes occurred in intestinal wall cells, Malpighian tubule cells, and nerve cells of S. litura under surfactin stress. Conclusively, our results suggest that surfactin induces an increase in reactive oxygen species (ROS) and damages S. litura cells. Furthermore, based on the integrated analysis of transcriptomic and metabolomic data, it is hypothesized that surfactin may also trigger neurotoxicity and cardiotoxicity in S. litura while hindering the insect’s detoxification processes. This study lays a foundation for further exploration of surfactin as a potential biopesticide.

Bench to Any Side—The Pharmacology and Applications of Natural and Synthetic Alkylated Hydroxy Cinnamates and Cinnamides

Natural alkylated hydroxy cinnamates (AHCs) isolated from medicinal plants and the thereby designed and synthesized cinnamides are derivatives of hydroxy cinnamic acids such as p-coumaric, sinapic, ferulic, and caffeic acids, which are naturally derived from human dietary sources. The pharmacological properties displayed by AHCs based on their inherent structure range include antioxidant, antimicrobial, antiplasmodial, anti-tyrosinase, Alzheimer’s and Parkinson’s disease therapy, anticancer therapy, metabolic disease therapy, and biopesticides, which have not been reviewed together. Based on their inherent antioxidant, antimicrobial, and UV absorption and their structure–activity relationships, these cinnamyl esters and amides can be used for food preservation in emulsions and oils, as sun-protective components of skin care formulations, and in many other multifunctional applications. In conclusion, the fine-tuning of the structural features such as the type of hydroxy cinnamic acid used, the length of alkyl chains for variable lipophilicity, conversion from cinnamic to propanoic for antioxidants, the increase in methoxy or the change to amino groups to increase the molar absorption coefficient and loss of absorption values, the substitution by halides or amino groups for potent biopesticides, and conversion from esters to amide bonds leads to different AHCs for biomedical, cosmetic, and agriculture applications as an emerging field of investigation that can overall provide natural, safe, biodegradable, and sustainable molecules.

Formulation and bio-efficacy of different isolates of Beauveria bassiana against adults and third nymphal instar of desert locust (Schistocerca gregaria Forskål)

Recently, the Horn of Africa witnessed a swift increase in the incidence of desert locust (Schistocerca gregaria) invasion. During outbreaks, pesticides are applied through aerial or ground spraying to kill the insects, and/or to prevent their spread to new grounds. However, after decades of extensive use, many drawbacks such as contamination of the environment, toxicity to non-target organisms, harmful residues on food, pest resistance, and bioaccumulation in the food chains emerged. Entomopathogenic fungi offer viable alternatives to chemical pesticides against many insect invasions, but few studies have tested their bio-efficacy in desert locusts. Therefore, the current study aimed at isolating, formulating local isolates 231, 334, 333, 341, 349, 351, 339 of Beauveria bassiana, and testing their bio-efficacy against larval and adult desert locusts. The 21-day experiment was conducted under controlled conditions in a greenhouse. Soil samples were collected from two agroecological zones in Isiolo and Laikipia Counties in Kenya. B. bassiana was isolated from the soil samples using the Galleria bait method and cultivated in Sabouraud Dextrose Agar Yeast (SDAY). The isolates were identified based on molecular techniques (DNA and PCR amplification). The conidia of the isolates were screened and bioassays on 30 locusts was conducted for 14 days. The best isolates eliciting over 90 % mortality during screening were used for formulations using three carrier materials (liquid paraffin, Diatomaceous Earth, and whey) which were again tested against adult and 3rd nymphal instars of the locusts. The stability of the formulations was also tested after 1 and 2 months. All the tested isolates of B. bassiana significantly outperformed the control and thus pathogenic to the adults and 3rd nymphal instars of S. gregaria under laboratory conditions. They caused mortality ranging from 57.8–100 % after 14 days post-incubation. The isolates 341, 231, and, 334 elicited 50 % mortality responses at concentrations 1.1 × 105 conidia/ml, 2.5 × 105 conidia/ml and 1.7 × 106 conidia/ml respectively in adults and 1.1 × 105 conidia/ml, 2.5 × 105 conidia/ml and, 1.7 × 106 conidia/ml respectively in 3rd nymphal instars. Formulations with 341–1, 341–2, and, 334–1 had the highest efficacy (>99 %) against the adult locusts. There was a significant 3-way interaction (P < 0.05) of isolate for the formulation, carrier material and, time in determining the Cfu of the B. bassiana formulations. After 1 month, the best Cfu occurred in formulation with isolates 231 and 341 formulated using Diatomaceous Earth, while the highest Cfu was observed in formulation with isolate 334 formulated with either liquid paraffin or whey. After 2 months, the highest Cfu occurred in formulation with isolates 231, 341, and, 334 formulated using liquid paraffin. This study provides encouraging data for the development of potential biopesticides formulated with different carrier materials against desert locusts.

Study of the Effects of Bioactive Compounds of Cyanobacterium Desmonostoc alborizicum on Pathogenic Fungi of Wheat

Wheat, as one of the most economically important crops, constitutes a major part of the human diet. One of the major challenges in wheat preservation is combating various pests, including fungi, through different pesticides. Due to the toxicity caused in agricultural fields by chemical pesticides, there is a growing inclination towards using biopesticides instead. These biopesticides not only possess antimicrobial properties but also aid in the growth and development of crops. In this context, the bioactive compounds present in cyanobacteria are considered as potential biopesticide candidates. Therefore, the aim of this study is to observe the antifungal effect of bioactive compounds from the cyanobacterium Desmonostoc alborizicum on pathogenic fungi affecting wheat. For this purpose, after culturing the cyanobacterial strain Desmonostoc alborizicum for 14 days, the cyanobacterial extract was applied to wheat plants infected with the fungi Alternaria alternata, Fusarium oxysporum, Aspergillus terreus, and Phytophthora nicotiana var. The activity of antioxidant enzymes and MTT assay on 4T1 cells were then evaluated. The results showed that Aspergillus terreus exhibited the highest resistance, while Fusarium oxysporum showed the highest sensitivity to the cyanobacterial extract of Desmonostoc alborizicum. The activity of the enzymes guaiacol peroxidase, superoxide dismutase, catalase, and glutathione peroxidase in infected plants treated with the cyanobacterial extract significantly decreased (p&lt;0.05), indicating effective stress control and enhanced immune response in these treatments. Therefore, the results of this study suggest that the use of Desmonostoc alborizicum extract can be effective as an antifungal agent in protecting wheat and other agricultural crops.

Cymbopogon citratus Allelochemical Volatiles as Potential Biopesticides against the Pinewood Nematode.

Traditional pesticides are based on toxic compounds that can reduce biodiversity, degrade the environment, and contribute to less healthy living. Plant allelochemicals can provide more environmentally friendly and sustainable alternatives. Essential oils (EOs) are complex mixtures of plant secondary metabolites that show strong biological activities. In the present study, the EOs of Cymbopogon citratus were screened for activity against the pinewood nematode (PWN), the causal agent of pine wilt disease. To understand their nematicidal properties, EOs were fractioned into hydrocarbon molecules and oxygen-containing compounds, and their main compounds were acquired and tested separately against the PWN. The EO oxygen-containing molecules fraction was highly active against the PWN (EC50 = 0.279 µL/mL), with citral and geraniol showing higher activities (EC50 = 0.266 and 0.341 µL/mL, respectively) than emamectin benzoate (EC50 = 0.364 µL/mL), a traditional nematicide used against the PWN. These compounds were additionally reported to be less toxic to non-target organisms (fish, invertebrates, and algae) and safer to human health (with higher reported toxicity thresholds) and predicted to exert fewer environmental impacts than traditional nematicides. Resorting to approved natural compounds can quickly leverage the development of sustainable alternatives to traditional nematicides.

Biochemical characterisation and production kinetics of high molecular-weight (HMW) putative antibacterial proteins of insect pathogenic Brevibacillus laterosporus isolates

BackgroundBacterial genomes often encode structures similar to phage capsids (encapsulins) and phage tails which can be induced spontaneously or using genotoxic compounds such as mitomycin C. These high molecular-weight (HMW) putative antibacterial proteins (ABPs) are used against the competitive strains under natural environment. Previously, it was unknown whether these HMW putative ABPs originating from the insect pathogenic Gram-positive, spore-forming bacterium Brevibacillus laterosporus (Bl) isolates (1821L, 1951) are spontaneously induced during the growth and pose a detrimental effect on their own survival. Furthermore, no prior work has been undertaken to determine their biochemical characteristics.ResultsUsing a soft agar overlay method with polyethylene glycol precipitation, a narrow spectrum of bioactivity was found from the precipitated lysate of Bl 1951. Electron micrographs of mitomycin C- induced filtrates showed structures similar to phage capsids and contractile tails. Bioactivity assays of cell free supernatants (CFS) extracted during the growth of Bl 1821L and Bl 1951 suggested spontaneous induction of these HMW putative ABPs with an autocidal activity. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of spontaneously induced putative ABPs showed appearance of ~ 30 kDa and ~ 48 kDa bands of varying intensity across all the time intervals during the bacterial growth except in the initial hours. Statistically, spontaneously induced HMW putative ABPs of Bl 1951 exhibited a significant decrease in the number of viable cells of its producer strain after 18 h of growth in liquid. In addition, a significant change in pH and prominent bioactivity of the CFS of this particular time period was noted. Biochemically, the filtered supernatant derived from either Bl 1821L or Bl 1951 maintained bioactivity over a wide range of pH and temperature.ConclusionThis study reports the spontaneous induction of HMW putative ABPs (bacteriocins) of Bl 1821L and Bl 1951 isolates during the course of growth with potential autocidal activity which is critically important during production as a potential biopesticide. A narrow spectrum of putative antibacterial activity of Bl 1951 precipitate was found. The stability of HMW putative ABPs of Bl 1821L and Bl 1951 over a wide range of pH and temperature can be useful in expanding the potential of this useful bacterium beyond the insecticidal value.

Chitosan as an Antimicrobial, Anti-Insect, and Growth-Promoting Agent for Potato (Solanum tuberosum L.) Plants.

A growing trend in plant protection is replacing chemical preparations with environmentally friendly biological compositions. Chitosan, due to its biocompatibility, biodegradability, and bioactivity, is an effective agent against plant diseases. The purpose of the study was to evaluate chitosan as a potential biopesticide for potato plants. Three variants of chitosan were tested: high (310-375 kDa, >75% deacetylated), medium (190-310 kDa, 75-85% deacetylated), and low (50-190 kDa, 75-85% deacetylated) molecular weight. The chitosan variants were dissolved in lactic and succinic acids and tested for antibacterial and antifungal properties against eight strains of mould and two strains of bacteria responsible for potato diseases. The possible cytotoxicity of chitosan was evaluated against different cell lines: insect Sf-9, human keratinocyte HaCaT, and human colon carcinoma Caco-2. The bioprotective activities of the chitosan were also evaluated in situ on potato tubers. Chitosan inhibited the growth of almost all the selected phytopathogens. The most active was medium molecular chitosan in lactic acid. This formula was characterized by low toxicity towards human cells and high toxicity towards Sf-9 cells. It was also found to have positive effects on the growth of stems and roots, gas exchange, and chlorophyll index in potato plants. Selected chitosan formulation was proposed as a functional biopesticide for potato protection against phytopathogens.

RNA-Seq analysis reveals the gene expression changes of Bemisia tabaci in response to destruxin A treatment

ABSTRACT Bemisia tabaci is an important agricultural pest that has been causing significant economic losses to crops across the globe. Destruxins are secondary metabolites of entomopathogenic fungi which can be used as a potential biopesticide against B. tabaci. However, little is known about the molecular mechanism involved in the regulation of the immune response of B. tabaci post-destruxin application. In this study, we explored the molecular responses of B. tabaci exposed to destruxin A (DA) using RNA-Seq. A total of 1702, 616, and 555 differentially expressed genes (DEGs) were identified in B. tabaci after 4, 8, and 12 h of DA treatment. In addition, 39 putative detoxification-related DEGs including 29 cytochrome P450s (P450s), 5 glutathione S-transferases (GSTs), and 5 carboxylesterases (CarEs) were also identified. Quantitative real-time PCR analysis indicated that the expression profiles of 19 random DEGs were consistent with the RNA-Seq results. These findings serve as valuable information for a better understanding of the interaction and molecular mechanisms involved in the defense response of B. tabaci against DA.

A Cytochrome P450 Catalyzes Oxidative Coupling Formation of Insecticidal Dimeric Indole Piperazine Alkaloids.

Cytochrome P450 (CYP450)-catalyzed oxidative coupling is an efficient strategy for using simple building blocks to construct complex structural scaffolds of natural products. Among them, heterodimeric coupling between two different monomers is relatively scarce, and the corresponding CYP450s are largely undiscovered. In this study, we discovered a fungal CYP450 (CpsD) and its associated cps cluster from 37208 CYP450s of Pfam PF00067 family member database and subsequently identified a group of new skeleton indole piperazine alkaloids (campesines A-G) by combination of genome mining and heterologous synthesis. Importantly, CYP450 CpsD mainly catalyzes intermolecular oxidative heterocoupling of two different indole piperazine monomers to generate an unexpected 6/5/6/6/6/6/5/6 eight-ring scaffold through the formation of one C-C bond and two C-N bonds, illuminating its first dimerase role in this family of natural products. The proposed catalytic mechanism of CpsD was deeply investigated by diversified substrate derivatization. Moreover, dimeric campesine G shows good insecticidal activity against the global honeybee pest Galleria mellonella. Our study shows a representative example of discovering new skeleton monomeric and dimeric indole piperazine alkaloids from microbial resources, expands our knowledge of bond formation by CYP450s and supports further development of the newly discovered and engineered campesine family compounds as potential biopesticides.

A Cytochrome P450 Catalyzes Oxidative Coupling Formation of Insecticidal Dimeric Indole Piperazine Alkaloids

AbstractCytochrome P450 (CYP450)‐catalyzed oxidative coupling is an efficient strategy for using simple building blocks to construct complex structural scaffolds of natural products. Among them, heterodimeric coupling between two different monomers is relatively scarce, and the corresponding CYP450s are largely undiscovered. In this study, we discovered a fungal CYP450 (CpsD) and its associated cps cluster from 37208 CYP450s of Pfam PF00067 family member database and subsequently identified a group of new skeleton indole piperazine alkaloids (campesines A−G) by combination of genome mining and heterologous synthesis. Importantly, CYP450 CpsD mainly catalyzes intermolecular oxidative heterocoupling of two different indole piperazine monomers to generate an unexpected 6/5/6/6/6/6/5/6 eight‐ring scaffold through the formation of one C−C bond and two C−N bonds, illuminating its first dimerase role in this family of natural products. The proposed catalytic mechanism of CpsD was deeply investigated by diversified substrate derivatization. Moreover, dimeric campesine G shows good insecticidal activity against the global honeybee pest Galleria mellonella. Our study shows a representative example of discovering new skeleton monomeric and dimeric indole piperazine alkaloids from microbial resources, expands our knowledge of bond formation by CYP450s and supports further development of the newly discovered and engineered campesine family compounds as potential biopesticides.

Flavonoids as Insecticides in Crop Protection-A Review of Current Research and Future Prospects.

Pesticide overuse in agricultural systems has resulted in the development of pest resistance, the impoverishment of soil microbiota, water pollution, and several human health issues. Nonetheless, farmers still depend heavily on these agrochemicals for economically viable production, given the high frequency at which crops are affected by pests. Phytopathogenic insects are considered the most destructive pests on crops. Botanical pesticides have gained attention as potential biopesticides and complements to traditional pesticides, owing to their biodegradability and low toxicity. Plant-based extracts are abundant in a wide variety of bioactive compounds, such as flavonoids, a class of polyphenols that have been extensively studied for this purpose because of their involvement in plant defense responses. The present review offers a comprehensive review of current research on the potential of flavonoids as insecticides for crop protection, addressing the modes and possible mechanisms of action underlying their bioactivity. The structure-activity relationship is also discussed. It also addresses challenges associated with their application in pest and disease management and suggests alternatives to overcome these issues.

Antifungal Activity and Mechanism of Xenocoumacin 1, a Natural Product from Xenorhabdus nematophila against Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum (Lib.) de Bary, a polyphagous necrotrophic fungal pathogen, has brought about significant losses in agriculture and floriculture. Until now, the most common method for controlling S. sclerotiorum has been the application of fungicides. Xenocoumacin 1 (Xcn1) is a potential biopesticide having versatile antimicrobial activities, generated by Xenorhabdus nematophila. This study was intended to isolate Xcn1 from X. nematophila YL001 and clarify its efficacies for S. sclerotiorum control. Xcn1 demonstrated a wider antifungal spectrum against 10 plant-pathogenic fungi. It also exhibited a strong inhibitory effect on the mycelial growth of S. sclerotiorum with an EC50 value of 3.00 μg/mL. Pot experiments indicated that Xcn1 effectively inhibited disease extension on oilseed rape and broad bean plants caused by S. sclerotiorum. Morphological and ultrastructural observations revealed that the hyphae of S. sclerotiorum became twisted, shriveled, and deformed at the growing points after treatment with Xcn1 at 3.00 μg/mL and that the subcellular fractions also became abnormal concurrently, especially the mitochondrial structure. Moreover, Xcn1 also increased cell membrane permeability and decreased the content of exopolysaccharide as well as suppressing the activities of polygalacturonase and cellulase of S. sclerotiorum, but exerted no effects on oxalic acid production. This study demonstrated that Xcn1 has great potential to be developed as a new biopesticide for the control of S. sclerotiorum.

Bio-pesticidal, Antimicrobial, and Anti-inflammatory Potentials of n-Hexane Fraction of Zanthoxylum armatum DC and its Chemical Profiling

Zanthoxylum armatum DC, commonly known as toothache tree, is utilized for treating inflamed gums. The plant’s volatile constituent possesses a robust fragrance and contributes to its tangy taste. This study investigates the bioactivities, including bio-pesticidal, antimicrobial, and anti-inflammatory properties as well as the chemical profiling of the n-hexane fraction based on GC-MS analysis. The evaluated activities involve contact toxicity, microplate alamar blue assay, against three different insects, five bacteria, and seven fungi, and oxidative burst assay. The NIST library serves as a standard reference database for constituent identification. Remarkable insecticidal activities comparable to the standard drug permethrin were observed, particularly against Rhyzopertha dominica (100%), Tribolium castaneum (60%), and Sitophilus oryzae (50%). The fraction exhibited significant antifungal activity against Fusarium lini (85%) and notable inhibition against B. subtillis (67.27%) and S. aureus (65.25%). Potent anti-inflammatory effects were noted with an IC50 value of 11.2±1.9 μg/ml, equivalent to standard ibuprofen at various concentrations. GC-MS analysis identified twenty compounds, with major ones including trans-13-octadecenoic acid (36.08%), cis-9 hexadecenoic acid (18.66%), and 2-propenoic acid 3 phenyl methyl ester (11.08%). The diverse bioactivities observed may be attributed to the varied nature of compounds such as polyunsaturated fatty acids and their oxides. This research revealed the potential of Z. armatum as a potential bio-pesticide, anti-inflammatory, and antimicrobial agent.

Evaluating the Antifeedant Effects of Andrographolide-based Formulations against Lampides boeticus L., under Laboratory Condition

Aims: To evaluate the antifeedant activity of Lampides boeticus (Linnaeus,1767), larvae exposed to various concentrations of Andrographolide-based formulations under laboratory conditions.&#x0D; Study Design: Completely Randomized Design&#x0D; Place and Duration of Study: Department of Entomology, College of Agriculture, Vellayani and NCESS, Kerala during 2019- 2023.&#x0D; Methodology: The experiment was conducted with 9 treatments and 4 replications, treatments included various concentrations (1,3,5 and 7%) of formulations A (Andrographolide (70%) + Neem oil (20%) + Triton X-100 (10%)) and B (Andrographolide (70%) + Pungam oil (20%) + Triton X-100 (10%)). To assess the impact of formulations in the feeding behaviour of freshly moulted third instar larvae of L.boeticus L., no choice bioassay method was used. Each Petri plate lined with moist filter paper, confined a single larva with the treated pods of each specific concentration. The weight of the food consumed by the larvae was recorded at an interval of 24 hours after treatment and calculated percent feeding, per cent feeding inhibition, antifeedant activity (protection over control) and preference index of L. boeticus L., larvae against the formulations.&#x0D; Results: The results revealed that 7% of formulation A exhibits the highest larval feeding inhibition (93.05%), followed by 7% of formulation B (87.81%). Both formulations at 5% concentrations also demonstrate significant antifeedant effects. Preference index values categorize 7% of formulations A and B as extremely antifeedant. The findings highlight the efficacy of these formulations in inhibiting larval feeding, with potential applications in pest management strategies.&#x0D; Conclusion: The present findings have demonstrated the notable efficacy of formulations A and B, particularly at the 7% concentration, in significantly inhibiting larval feeding of L.boeticus L., and the reduction in larval feeding percentages, coupled with high antifeedant activity and feeding inhibition rates, highlights the potential of andrographolide based formulations as potent biopesticides.

Eco-friendly biopesticide of Beauveria bassiana to control sweet potato weevil Cylas formicarius (Coleoptera: Curculionidae)

Cylas formicarius is a major pest of sweet potato in various countries, with yield losses reaching 100%. Control technology using chemical pesticides is not successful. This study aims to examine the efficacy of the entomopathogenic fungus Beauveria bassiana compared to chemical pesticides against C. formicarius, which was conducted in Lumajang Regency, East Java, from May to September 2021. The results showed that the highest tuber productivity occurred in innovative technology, reaching 43 t/ha with only 1% tuber damage. While the productivity of the existing technology is only 20 t/ha with a tuber damage rate of 21%. The advantages of innovative technology can also be seen in the abundance of both predatory an parasitoid insects. The application of B. bassiana to control the tuber borer at the base of the stem is safer for the survival of useful insects, especially predators, and parasitoids. In addition, the tubers obtained are more organic, so the selling price of these commodities is more expensive than conventional ones. The entomopathogenic fungus B. bassiana has a great opportunity to be used as a potential biopesticide candidate to be developed as a technological innovation to replace the efficacy of chemical pesticides.

Improved Expression of a Thermostable GH18 Bacterial Chitinase in Two Different Escherichia coli Strains and Its Potential Use in Plant Protection and Biocontrol of Phytopathogenic Fungi.

Chitinases are enzymes that can break down chitin, a major component of the exoskeleton of insects and fungi. This feature makes them potential biopesticides in agriculture since they are considered a safe and environmentally friendly alternative to synthetic pesticides. In this work, we performed a comparative study between two different bacterial expression strains to produce a recombinant chitinase with improved stability. Escherichia coli strains Origami B and BL21 (DE3) were selected for their distinct cytosolic environment to express BhChitA chitinase of Bacillus halodurans C-125 and to investigate the role of disulfide bond formation and proper folding on its stability and activity. Expression of the recombinant BhChitA in bacterial strain containing oxidative cytosol (Origami B) improved its activity and stability. Although both expression systems have comparable biochemical properties (temperature range 20-80°C and pH spectrum 3-10), BhChitA expressed in Origami strain seems more stable than expressed in BL21. Furthermore, the optimal expression conditions of the recombinant BhChitA has been carried out at 30°C during 6h for the Origami strain, against 20°C during 2h for BL21. On the other hand, no significant differences were detected between the two enzymes when the effect of metal ions was tested. These findings correlate with the analysis of the overall structure of BhChitA. The model structure permitted to localize disulfide bond, which form a stable connection between the substrate-binding residues and the hydrophobic core. This link is required for efficient binding of the chitin insertion domain to the substrate. BhChitA exhibited in vitro antifungal effect against phytopathogenic fungi and suppressed necrosis of Botrytis cinerea on detached tomato leaves. In vitro assays showed the influence of BhChitA on growth suppression of Botrytis cinerea (53%) Aspergillus niger (65%), Fusarium graminearum (25%), and Fusarium oxysporum (34%). Our results highlight the importance of the bacterial expression system with oxidative cytosol in producing promising biopesticides that can be applied for post-harvest processing and crop protection.

Newly Isolated Trichoderma spp. Show Multifaceted Biocontrol Strategies to Inhibit Potato Late Blight Causal Agent Phytophthora infestans both In Vitro and In Planta

Potato growers worldwide have been at war for more than 150 years with an enemy whose lifecycle, genome size and architecture, infection rate, and economic impacts are the epitome of a plant pathogen. Phytophthora infestans is an oomycete that causes the notorious late blight infection in potato and tomato fields. This study explored the benefits of the multitalented plant symbiotic fungi Trichoderma spp. and their metabolites as potential biopesticides against P. infestans. Eleven strains of Trichoderma spp. were obtained from soil and tree barks and were identified using DNA sequence analysis of three molecular markers. The antagonistic potential of the strains against P. infestans was first evaluated in vitro. In dual-culture assays, P. infestans growth was significantly inhibited (53 to 95%) by different Trichoderma spp. through direct mycoparasitism, competition for space and nutrients, or antibiosis. The cell-free filtrates (CFFs) of different Trichoderma strains were obtained and characterized for anti- Phytophthora activities as well as biochemical stability. The obtained results indicated that Trichoderma CFFs were chemically stable and strongly decreased P. infestans’ mycelial growth and zoospore motility and viability. Similarly, in leaf-disk assays, Trichoderma CFFs showed significant protection against P. infestans infection. Ultraperformance liquid chromatography analysis revealed the presence of harzianic acid, iso-harzianic acid, and 6-pentyl-2H-pyran-2-one as major compounds in different Trichoderma CFFs. Furthermore, selected Trichoderma strains significantly protected potato plants against soil-mediated late blight infection. Finally, Trichoderma spp. showed high compatibility with a copper-based fungicide, especially at lower concentrations, suggesting that both protective agents could be combined in integrated pest management programs. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Production of biopesticide from Melia azedarach Linn extract obtained by supercritical fluid extraction for the control of Tetranychus urticae

Compounds derived from plant extracts, such as those from the fruits and leaves of Melia azedarach Linn (chinaberry tree), which contain azadirachtin, have been utilized for crop pest control. However, these natural compounds are susceptible to degradation during extraction and in field conditions. To address this, extraction processes involving supercritical fluid and microencapsulation via spray drying may be employed to obtain and preserve biopesticidal molecules. This study focuses on producing a biopesticide from M. azedarach L. fruit extract using supercritical CO2, and microencapsulation via spray drying with a blend of cheese whey and gum Arabic. The extract was obtained from chinaberry fruits rich in azadirachtin (736.92 μg/L) using supercritical CO2 at 250 bar and 50 °C for 120 min, with a yield of 3.44%. The extract was then encapsulated using cheese whey and gum Arabic (70:30) as encapsulating agents at extract:encapsulating agents ratios of 1:10 and 1:15. Mortality rates of Tetranychus urticae Koch adult females and their eggs, in contact and residual assays with both non-encapsulated and encapsulated extract, did not significantly differ (p > 0.05) from the commercial acaricide abamectin. This study introduces a potential new biopesticide that utilizes chinaberry extract obtained through supercritical CO2 extraction and encapsulation for industrial scale-up studies, and this approach holds promise for the production of an effective biopesticide for crops affected by two-spotted spider mites.

A life-and-death struggle: interaction of insects with entomopathogenic fungi across various infection stages.

Insects constitute approximately 75% of the world's recognized fauna, with the majority of species considered as pests. Entomopathogenic fungi (EPF) are parasitic microorganisms capable of efficiently infecting insects, rendering them potent biopesticides. In response to infections, insects have evolved diverse defense mechanisms, prompting EPF to develop a variety of strategies to overcome or circumvent host defenses. While the interaction mechanisms between EPF and insects is well established, recent findings underscore that their interplay is more intricate than previously thought, especially evident across different stages of EPF infection. This review primarily focuses on the interplay between EPF and the insect defense strategies, centered around three infection stages: (1) Early infection stage: involving the pre-contact detection and avoidance behavior of EPF in insects, along with the induction of behavioral responses upon contact with the host cuticle; (2) Penetration and intra-hemolymph growth stage: involving the initiation of intricate cellular and humoral immune functions in insects, while symbiotic microbes can further contribute to host resistance; (3) Host insect's death stage: involving the ultimate confrontation between pathogens and insects. Infected insects strive to separate themselves from the healthy population, while pathogens rely on the infected insects to spread to new hosts. Also, we discuss a novel pest management strategy underlying the cooperation between EPF infection and disturbing the insect immune system. By enhancing our understanding of the intricate interplay between EPF and the insect, this review provides novel perspectives for EPF-mediated pest management and developing effective fungal insecticides.

Displacement of toxigenic Fusarium species by atoxigenic Aspergillus flavus (Aflasafe KE01) application in maize fields in lower Eastern Kenya

Maize is grown in areas with environmental conditions that are ideal for growth of most cereal pathogens such as Fusarium fungi. However, there is lack of effective fungicides to control fumonisin producing Fusarium. This study was conducted to determine the efficacy of atoxigenic Aspergillus flavus (Aflasafe KE01) on the population of Fusarium species in maize fields. The study was carried out in four sub counties in lower Eastern Kenya (Kaiti, Kathiani, Nzambani and Wote). Twenty-four maize fields were selected in each sub county where 12 fields were treated with Aflasafe KE01, while 12 fields comprised the untreated controls. Aflasafe KE01 was applied by hand broadcasting in the maize fields two to three weeks before tasselling of maize. Maize grain samples were collected from each field at harvest and ground using a Bunn coffee mill grinder. Fusarium species were isolated from the ground maize using pour plate method following serial dilution on low strength potato dextrose agar (PDA)and Spezieller Nahrstoffarmer. The results showed that application of Aflasafe KE01 effectively displaced toxigenic Fusarium species in maize fields. Maize samples from Aflasafe KE01 treated maize fields recorded significantly lower incidence (41%) of the Fusarium species compared to untreated maize fields (60%) (p≤0.01). These results indicate that Aflasafe KE01 is a potential biopesticide for the biocontrol of Fusarium species in maize. Key words: Aflasafe KE01, atoxigenic Aspergillus sp, Fusarium species, maize.