Eco-friendly Biocontrol Agent Research Articles

Evaluating the efficacy of endophytic bacteria in controlling rice sheath blight: In vitro and In vivo studies

Rice production is highly susceptible to various pathogens, including Rhizoctonia solani, Curvularia lunata, and Epicoccum rostratum, which are major threats in Asia. Exploring biological control methods using endophytic bacteria offers promising opportunities to enhance rice resilience against these lethal diseases. Using 16S RNA sequencing, we identified four endophytic isolates of Bacillus spp. from rice roots, stems, and leaves. We evaluated the antagonistic activity of these endophytic bacterial isolates against rice pathogens both in vitro and in vivo. These isolates inhibited the growth of C. lunata by 82 %, R. solani by 79 %, and E. rostratum by 88 % in vitro. The detached leaf assay for sheath blight (ShB) disease severity in strains ranged from 10.4 % to 73.3 %. In vivo results showed that B. amyloliquefaciens (R-19) exhibited the lowest disease intensity at 7.2 % and the highest disease suppression at 78.8 %. The fungicide propiconazole at 0.1 % treatment showed the lowest disease intensity of 7.7 % and the highest disease suppression of 73.4 %, compared to the infected control. Besides biocontrol efficacy, endophytic isolates enhance plant growth parameters, including shoot height, root length, fresh and dry weights, number of tillers, and grains per tiller. Plant hormones abscisic acid (ABA) and gibberellic acids (GA3) increased by 35 % and 53 %, respectively, due to B. subtilis (R-20) and B. amyloliquefaciens (R-19), while flavonoid and indole acetic acid (IAA) concentrations surged by 30%–80 %. Similarly, chlorophyll (a, b), carotenoids, antioxidant enzymatic activity, phenolic content, carbohydrates, and proline contents were higher compared to the control. This study provides a foundation for future studies on novel and eco-friendly biocontrol agents. In addition, our study recommends the integration of endophytic bacteria into sustainable agriculture for enhancing rice production and reducing disease impacts.

Biocontrol potential of Bacillus velezensis SEC-024A against southern blight of industrial hemp

Agroathelia rolfsii is the causative agent of southern blight of industrial hemp, which is a soil-borne infection resulting in grave economic losses in industrial hemp (Cannabis sativa L.). Chemical pesticides are currently the primary means of controlling this disease, but their use is harmful to human health as well as to the environment. Urgent action is needed to screen eco-friendly biocontrol agents against this pathogen. An endophytic bacterium SEC-024A was isolated from the leaf tissue of industrial hemp and exhibited a significant antagonistic effect on A. rolfsii, with a plate inhibition rate of 80.5 % and a pot control effect of 74.1 %. Through whole genome sequencing, SEC-024A was identified to be Bacillus velezensis. It contained multiple gene clusters involved in secondary metabolite biosynthesis and the genes that promote plant growth, colonization, and pathogen defense. Bacillus velezensis SEC-024A produces volatile organic compounds (VOCs) that serve as its primary fungistatic agents. Nine VOCs produced by SEC-024A were detected through gas chromatography-mass spectrometry. These VOCs were individually tested for their antifungal effects. Four volatiles, namely isobutyric acid, tiglic acid, trans-2-octenal, and 2-decanone, exhibited notable inhibitory effects on A. rolfsii with EC50 values of 0.012, 0.038, 0.009, and 0.046 μL/mL, respectively. Additionally, trans-2-octenal demonstrated broad-spectrum antifungal activity against various soil-borne pathogens. Together, this study suggests that B. velezensis SEC-024A holds promise as a novel microbial agent for improving plant growth and controlling diseases.

Exploration of Phage-Agrochemical Interaction Based on a Novel Potent Phage LPRS20-Targeting Ralstonia solanacearum.

Phage therapy has the potential to alleviate plant bacterial wilt. However, the knowledge gap concerning the phage-agrochemical interaction impedes the broader application of phages in agriculture. This study characterized a phage isolate and investigated its interactions with agrochemicals. A novel species within the Ampunavirus genus was proposed, serving phage LPRS20 as a type phage with a broad lytic range and significant antibacterial activity against Ralstonia solanacearum strains infecting tobacco, chili, or tomato. Sensory evaluation of the morphology of tobacco leaves suggested that phage application resulted in negligible harm to plants. Investigations into phage-agrochemical interactions revealed synergisms when LPRS20 was delivered 4 h before thiodiazole-copper as well as LPRS20 in combination with low-concentration berberine. Overall, our findings reveal that phage LPRS20 represents a novel, effective, and eco-friendly biocontrol agent against tobacco bacterial wilt in vivo and in vitro and contributes to the potential integration of phages and agrochemicals for controlling soil-borne pathogens.

Bio-perfume guns: Antifungal volatile activity of Bacillus sp. LNXM12 against postharvest pathogen Botrytis cinerea in tomato and strawberry

Gray mold disease, caused by Botrytis cinerea is a major postharvest disease impacting fruits such as strawberries and tomatoes. This study explores the use of volatile organic compounds (VOCs) produced by Bacillus spp. as eco-friendly biocontrol agents against B. cinerea. In vitro experiments demonstrated that VOCs from Bacillus sp. LNXM12, B. thuringiensis GBAC46, and B. zhanghouensis LLTC93-VOCs inhibited fungal growth by 61.2%, 40.5%, and 21.6%, respectively, compared to the control. LNXM12 was selected for further experiments due to its highest control efficacy of 58.3% and 76.6% on tomato and strawberry fruits, respectively. The LNXM12 VOCs were identified through gas chromatography–mass spectrometry (GC–MS) analysis, and 22 VOCs were identified. Synthetic VOCs with the highest probability percentage, namely ethyloctynol, 3-methyl-2-pentanone (3M2P), 1,3-butadiene-N, N-dimethylformamide (DMF), and squalene were used in experiments. The results showed that the synthetic VOCs ethyloctynol and 3M2P were highly effective, with an inhibition rate of 56.8 and 57.1% against fungal mycelium radial growth at 120 μg/mL on agar plates. Trypan blue staining revealed strongly disrupted, deeper blue, and lysed mycelium in VOC-treated B. cinerea. The scanning and transmission electron microscope (SEM and TEM) results showed that fungal mycelium was smaller, irregular, and shrunken after synthetic VOC treatments. Furthermore, the synthetic VOCs Ethyloctynol and 3M2P revealed high control efficacy on tomatoes and strawberries infected by B. cinerea. The control efficacy on leaves was 67.2%, 66.1% and 64.5%, 78.4% respectively. Similarly, the control efficiency on fruits was 45.5%, 67.3% and 46.3% 65.1%. The expression of virulence genes in B. cinerea was analyzed, and the results revealed that selected genes BcSpl1, BcXyn11A, BcPG2, BcNoxB, BcNoxR, and BcPG1 were downregulated after VOCs treatment. The overall result revealed novel mechanisms by which Bacillus sp. volatiles control postharvest gray mold disease.

Isolation and Identification of Competitive Fungi on Medium for Black Wood Ear Mushroom in Korea and In Vitro Selection of Potential Biocontrol Agents

Black wood ear mushroom (<i>Auricularia auricula-judae</i>) is one of the most economically important mushrooms in China, Japan, and Korea. The cultivation of wood ear mushrooms on artificial substrates is more efficient in terms of time and cost compared with their natural growth on trees. However, if the substrate cultivation is infected by fast-growing fungi, the relatively slow-growing ear mushroom will be outcompeted, leading to economic losses. In this study, we investigated the competitive fungal isolates from substrates infected with fast-growing fungi for the cultivation of ear mushrooms in Jangheung and Sunchon, Korea. We collected 54 isolates and identified them by sequencing their internal transcribed spacer region with morphological identification. Among the isolates, the dominant isolates were <i>Trichoderma</i> spp. (92.6%), <i>Penicillium</i> spp. (5.6%), and <i>Talaromyces</i> sp. (1.8%). To find an appropriate eco-friendly biocontrol agent, we used five <i>Streptomyces</i> spp. and Benomyl, as controls against <i>Trichoderma</i> spp. and <i>Penicillium</i> spp. Among the six <i>Streptomyces</i> spp., <i>Streptomyces</i> sp. JC203-3 effectively controlled the fungi <i>Trichoderma</i> spp. and <i>Penicillium</i> spp., which pose a significant problem for the substrates of black wood ear mushrooms. This result indicated that this <i>Streptomyces</i> sp. JC203-3 can be used as biocontrol agents to protect against <i>Trichoderma</i> and <i>Penicillium</i> spp.

Metarhizium dianzhongense sp. nov. and New Record of M. bibionidarum (Clavicipitaceae, Hyocreales) Attacking Insects from China

The genus Metarhizium is one of the most significant entomopathogenic fungi with diverse morphological characteristics and host species. Species of Metarhizium have been widely used for pest control as an environmentally safe alternative to chemical pesticides. This study reports a new species of Metarhizium and a new record of M. bibionidarum from China. The taxonomic positions of the two species within Metarhizium were assessed by morphological and multi-gene phylogenetic data. This assessment confirmed that the new species M. dianzhongense on white grubs (Coleoptera) is a sister to M. ellipsoideum on adult leafhoppers (Hemiptera) and represents a distinctive fungus according to the morphological and phylogenetic evidence. The two species, M. dianzhongense and M. bibionidarum, were described and illustrated. Pathogenicity tests by M. bibionidarum and M. dianzhongense were performed on early instar larvae of the significant agricultural pest Spodoptera frugipera (Lepidoptera). The results demonstrated that both M. bibionidarum and M. dianzhongense exhibit significant insecticidal activity against larvae of S. frugipera, providing new fungal resources for the development of an eco-friendly biocontrol agent against this pest.

Management of Fusarium Wilt of Chickpea Using Integrated Approaches Leading Induced Systemic Resistance

The objective of the research was to investigate the impact of Trichoderma harzianum, Pseudomonas fluorescens, and Rhizobium, separately and together, on inducing systemic resistance in chickpea plants when exposed to Fusarium oxysporum f.sp ciceris. Various parameters such as wilt incidence, plant growth promotion, yield, peroxidase activity, polyphenol oxidase activity, and total phenol content were assessed after treating chickpea seeds (GNG-469) with these bioagents. The findings from in vitro experiments indicated that the treatment T14, which involved the combination of 1% T. harzianum, 2% P. fluorescens, and 2% Biochar, was the most potent combination of bioagents. Compared to the untreated control, this treatment considerably reduced wilt incidence and enhanced root length, shoot length, and overall yield. Furthermore, treatment T14 increased peroxidase activity by 1.4%, polyphenol oxidase activity by 1.6%, and total phenol content by 2.3% in chickpea plants during Fusarium wilt disease. These findings have crucial implications for creating innovative formulations utilizing fungal and bacterial bioagents to effectively control wilt disease in chickpea plants. Rhizobium exhibited the lowest growth inhibition (23.13%), and T. harzianum showed the highest growth inhibition (66.38%) in vitro compared to control. New generation fungicide such as Amistar top T5 (18%), the positive control, was highly effective against this soil-borne pathogen; however, chemical pesticides with hazardous implications must be replaced by ecofriendly biocontrol agents.. KEYWORDS :Systemic resistance, Chickpea wilt, Fusarium oxysporum ciceris, Biochar, Fungicides, Bioagents

Towards unlocking the biocontrol potential of Pichia kudriavzevii for plant fungal diseases: in vitro and in vivo assessments with candidate secreted protein prediction

BackgroundPlant fungal pathogens cause substantial economic losses through crop yield reduction and post-harvest storage losses. The utilization of biocontrol agents presents a sustainable strategy to manage plant diseases, reducing the reliance on hazardous chemical. Recently, Pichia kudriavzevii has emerged as a promising biocontrol agent because of its capacity to inhibit fungal growth, offering a potential solution for plant disease management.ResultsTwo novel Pichia kudriavzevii strains, Pk_EgyACGEB_O1 and Pk_EgyACGEB_O2, were isolated from olive brine samples. The microscopic characterization of the strains revealed similar structures. However, there were noticeable differences in their visual morphology. Based on their internal transcribed spacer (ITS) DNA sequences, Pk_EgyACGEB_O1 and Pk_EgyACGEB_O2 strains assigned by GenBank IDs MZ507552.1 and MZ507554.1 shared high sequence similarity (~ 99.8% and 99.5%) with P. kudriavzevii, respectively. Both strains were evaluated in vitro against plant pathogenic fungi. The strains revealed the ability to consistently inhibit fungal growth, with Pk_EgyACGEB_O2 showing higher effectiveness. In addition, both P. kudriavzevii strains effectively controlled grey mold disease caused by B. cinerea in golden delicious apples, suggesting their potential as sustainable and eco-friendly biocontrol agents for post-harvest diseases. Based on a comprehensive bioinformatics pipeline, candidate-secreted proteins responsible for the potent antifungal activity of P. kudriavzevii were identified. A total of 59 proteins were identified as common among the P. kudriavzevii CBS573, SD108, and SD129 strains. Approximately 23% of the secreted proteins in the P. kudriavzevii predicted secretome are hydrolases with various activities, including proteases, lipases, glycosidases, phosphatases, esterases, carboxypeptidases, or peptidases. In addition, a set of cell-wall-related proteins was identified, which might enhance the biocontrol activity of P. kudriavzevii by preserving the structure and integrity of the cell wall. A papain inhibitor was also identified and could potentially offer a supplementary defense against plant pathogens.ConclusionOur results revealed the biocontrol capabilities of P. kudriavzevii against plant pathogenic fungi. The research focused on screening novel strains for their ability to inhibit the growth of common pathogens, both in vitro and in vivo. This study shed light on how P. kudriavzevii interacts with fungal pathogens. The findings can help develop effective strategies for managing plant diseases.

Crude extract and effective fractions from Andrographis paniculata for immature Aedes aegypti and Culex quinquefasciatus mosquito

In the quest for environmentally friendly alternatives to combat the challenges of resistance development and environmental toxicity associated with synthetic insecticides in mosquito control, the aim of this study is to explore the potential of fractions derived from Andrographis paniculata as environmentally friendly alternatives for controlling Aedes aegypti and Culex quinquefasciatus mosquitoes, with a focus on assessing their larvicidal, pupicidal, and ovicidal activities. Initially, crude extracts of hexane, chloroform, and methanol from A. paniculata leaves were evaluated for their efficacy against Ae. aegypti and Cx. quinquefasciatus mosquitoes, with the methanol extract showing promising activity. Subsequently, a comprehensive methanol extraction of A. paniculata leaves was conducted, followed by fractionation via column chromatography using various eluents, including chloroform, ethyl acetate, methanol, and their combinations. This process yielded 80 fractions, which were consolidated into 10 fractions based on thin-layer chromatography (TLC) profiles. Each fraction was assessed for ovicidal, larvicidal, and pupicidal activity across concentrations of 2.5, 5.0, 7.5, and 10 ppm. Among these fractions, ‘F-4’ exhibited exceptional efficacy against the larvae, pupae, and eggs of both mosquito species. At a concentration of 10 ppm, ‘F-4’ achieved 100% larval mortality, with LC50 values of 7.2 ppm for Ae. aegypti and 5.0 ppm for Cx. quinquefasciatus. Additionally, ‘F-4’ demonstrated substantial pupicidal activity, with LC50 values of 7.6 ppm for Ae. aegypti and 5.7 ppm for Cx. quinquefasciatus. Furthermore, ‘F-4’ exhibited ovicidal activity, with efficacy ranging between 77% and 78%. These results highlight ‘F-4’ from A. paniculata shows promise as an eco-friendly biocontrol agent against Ae. aegypti and Cx. quinquefasciatus mosquitoes, warranting further investigation for sustainable mosquito control.

Bacillus velezensis and Paenibacillus peoriae Strains Effective as Biocontrol Agents against Xanthomonas Bacterial Spot

Gram-negative bacteria belonging to the Xanthomonas genus include plant pathogens representing a major challenge in the field of agriculture for a wide variety of economically important crops, such as tomato, pepper, and lettuce. Due to the massive usage of agrochemicals, Xanthomonas spp. are developing resistance to copper pesticides typically used to control microbial infections. An interesting alternative approach to control bacterial phytopathogens consists of using eco-friendly biocontrol agents, often beneficial microorganisms. Here, following the targeted, broad-spectrum screening of thousands of microorganisms isolated from different environmental locations, we isolated Bacillus velezensis strain 71 and Paenibacillus peoriae strain To99 displaying potent antagonistic activity against Xanthomonas spp. We found that oxydifficidin and polymyxin A secreted by B. velezensis 71 and P. peoriae To99, respectively, are mainly responsible for the anti-Xanthomonas activity. We further evaluated the performance of cell suspensions and cell-free supernatants of these isolates in controlling tomato bacterial spot disease in growth chamber and greenhouse conditions to validate the in vitro results. The overall results demonstrate the potential of treatments based on the secondary metabolites from both isolates and their cells as an alternative to copper-based chemicals to control leaf spot diseases caused by Xanthomonas spp. phytopathogens.

Phytochemical Properties of Silk Floss Tree Stem Bark Extract and Its Potential as an Eco-Friendly Biocontrol Agent against Potato Phytopathogenic Microorganisms

In the current study, the ethanolic extract of the stem bark of Ceiba speciosa, the silk floss tree (SFSB), was evaluated against various phytopathogenic microorganisms, including Ralstonia solanacearum, Dickeya solani, Pectobacterium atrosepticum, P. carotovorum, Fusarium oxysporum, and Rhizoctonia solani. At 300 µg/mL concentration, the SFSB extract exhibited the highest inhibition percentages of 83.33 and 86.67 for R. solani and F. oxysporum, respectively. In addition to its antimicrobial activity, SFSB extract exhibited strong antioxidant activity (IC50 value of 140.88 g/mL). HPLC analysis of the extract revealed the presence of various phenolic acids and flavonoids. Among these compounds, naringenin (18,698.83 µg/g), chlorogenic acid (2727.49 µg/g), ferulic acid (1276.18 µg/g), syringic acid (946.26 µg/g), gallic acid (812.34 µg/g), and methyl gallate (651.73 µg/g) were found to be the most abundant constituents. GCMS analysis showed that there were antimicrobial compounds like terpenoids, benzoic acid derivatives, phthalate esters, and different fatty acids. Isopropyl myristate was the most common compound, with a relative abundance of 55.61%. To our knowledge, this is the first investigation on the phytochemical composition and antimicrobial properties of SFSB extract. Consequently, utilizing SFSB extract could hold significant potential as a sustainable and natural approach for controlling and mitigating plant diseases.

Encapsulation of Native Strains of Bioagents Trichoderma asperellum and Pseudomonas putida Using Different Biopolymers

Microencapsulation of biological control agents in biopolymer matrices is a valuable alternative to produce formulations with extended shelf-life. In this work, Trichoderma asperellum TAIK 1 conidia and Pseudomonas putida PIK1 bacterial cells were microencapsulated using different wall materials viz., maltodextrin, sodium alginate, carboxy methyl cellulose (CMC), gum arabic, and a cross linking agent gelatin with a hardening material calcium chloride. The encapsulation methods extrusion, emulsification and spray drying was performed using these wall materials. Spray drying process resulted in compact and smooth surface capsule with each individual cell in comparison to the other two methods, confirmed using scanning electron microscope (SEM). Further the viablility of organisms were checked, among these the combination maltoderxtrin (2%) + gelatin (1.5%) + CaCl2 (2%) resulted in 70% viability. And also effect of spray-drying inlet and outlet air temperatures were standardized for TAIK 1 and PIK1 spores. Highest conidial survival was shown in inlet and outlet temperature, feed rate/h (1300C, 600C, feed rate 60ml/h for TAIK1) and (1200C, 500C, feed rate 60ml/h for PIK1). Therefore, our study obtained the optimal process for encapsulation of bioagents TAIK1 and PIK1. Thus it can be used as sustainable tool for eco-friendly bio-control agents release.

Doxorubicin inhibits phosphatidylserine decarboxylase and confers broad-spectrum antifungal activity.

As phospholipids of cell membranes, phosphatidylethanolamine (PE) and phosphatidylserine (PS) play crucial roles in glycerophospholipid metabolism. Broadly, some phospholipid biosynthesis enzymes serve as potential fungicide targets. Therefore, revealing the functions and mechanism of PE biosynthesis in plant pathogens would provide potential targets for crop disease control. We performed analyses including phenotypic characterizations, lipidomics, enzyme activity, site-directed mutagenesis, and chemical inhibition assays to study the function of PS decarboxylase-encoding gene MoPSD2 in rice blast fungus Magnaporthe oryzae. The Mopsd2 mutant was defective in development, lipid metabolism, and plant infection. The PS level increased while PE decreased in Mopsd2, consistent with the enzyme activity. Furthermore, chemical doxorubicin inhibited the enzyme activity of MoPsd2 and showed antifungal activity against 10 phytopathogenic fungi including M. oryzae and reduced disease severity of two crop diseases in the field. Three predicted doxorubicin-interacting residues are important for MoPsd2 functions. Our study demonstrates that MoPsd2 is involved in de novo PE biosynthesis and contributes to the development and plant infection of M. oryzae and that doxorubicin shows broad-spectrum antifungal activity as a fungicide candidate. The study also implicates that bacterium Streptomyces peucetius, which biosynthesizes doxorubicin, could be potentially used as an eco-friendly biocontrol agent.

Trichoderma and its role in biological control of plant fungal and nematode disease.

Trichoderma is mainly used to control soil-borne diseases as well as some leaf and panicle diseases of various plants. Trichoderma can not only prevent diseases but also promotes plant growth, improves nutrient utilization efficiency, enhances plant resistance, and improves agrochemical pollution environment. Trichoderma spp. also behaves as a safe, low-cost, effective, eco-friendly biocontrol agent for different crop species. In this study, we introduced the biological control mechanism of Trichoderma in plant fungal and nematode disease, including competition, antibiosis, antagonism, and mycoparasitism, as well as the mechanism of promoting plant growth and inducing plant systemic resistance between Trichoderma and plants, and expounded on the application and control effects of Trichoderma in the control of various plant fungal and nematode diseases. From an applicative point of view, establishing a diversified application technology for Trichoderma is an important development direction for its role in the sustainable development of agriculture.

Chitinase from Streptomyces mutabilis as an Effective Eco-friendly Biocontrol Agent.

Blood sucking parasites not only cause economic loss but also transmit numerous diseases. Dermanyssus gallinae, an obligatory blood feeding ectoparasite causes huge production loss to the poultry industry. Mosquitoes act as vector for transmitting several viral and parasitic diseases in humans. Acaricide resistance limits the control of these parasites. The present study was aimed to control the parasites using chitinase that have selective degradation of chitin, an important component in exoskeleton development. Chitinase was induced in Streptomyces mutabilis IMA8 with chitin extracted from Charybdis smithii. The enzyme showed more than 50% activity at 30-50°C and the optimum activity at 45°C. The enzyme activity of chitinase was highest at pH 7.0. The kinetic parameters Km and Vmax values of chitinase were determined by non-linear regression using Michaelis-Menten equation and its derivative Hanes-Wolf plot. The larvicidal effect of different concentrations of chitinase was evaluated against all instar larvae (I-IV) and pupae of An. stephensi and Ae. aegypti after 24h of exposure. The percentage of mortality was directly proportional to the chitinase concentration. Bioassay for miticidal activity showed that chitinase had excellent miticidal activity (LC50 = 24.2ppm) against D. gallinae. The present study suggested the usage of Streptomyces mutabilis for preparation of chitinase in mosquito and mite control.

Entomopathogenic nematodes for the control of oriental fruit fly Bacterocera dorsalis (Diptera: Tephritidae)

BackgroundFruit fly species are most damaging pests around the globe which reduced the commercial value of fruits at maturity. Entomopathogenic nematodes (EPNs) from genera Heterorhabditis and Steinernema cause death by inducing septicimia in insect pests in the soil, moreover, endemic nearly all soils. Current study was planned to manage the oriental fruit fly, Bacterocera dorsalis (Hendel.) (Diptera: Tephritidae) hazards by using indigenous EPNs (Heterorhabditis bacteriophora, H. indica, Steinernema asiticum, S. corpocapsae and S. glasseri) as they have host finding ability and recognise as potential eco-friendly biocontrol agent over synthetic chemicals. MethodsStudy for the assessment of EPNs concentrations, various temperatures, soil type and soil moisture levels against mortality (%) of fruit fly (B. dorsalis) larvae was conducted in completely randomized design (CRD) under factorial arrangements. ResultsEPNs concentrations (70 IJs/ml, 110 IJs/ml, 150 IJs/ml) showed that S. asiaticum (150 IJs/ml) showed maximum mortality (94.97 %) of B. dorsalis as compared to other used EPNs along with their respective concentrations. Impact of various temperatures (20 °C, 24 °C, 28 °C, 32 °C, 36 °C) with respect to used EPNs exhibited that H. indica (36 °C) showed maximum mortality (94.33 %) of B. dorsalis as compared to all other treatment. Various soil types (Sandy, Sandy loam, Loam, Clay) impacted the infectivity of EPNs against fruit fly, In case of sandy loam soil, S. asiaticum showed maximum mortality (98.05 %) of B. dorsalis followed by all used treatments. Soil moisture level (12 %, 18 %, 24 %, 30 %) also significantly influenced the infectivity of EPNs against mortality of fruit fly. In case of 12% moisture level, S. asiaticum showed maximum mortality (99.06 %) of B. dorsalis over all the applied treatments along with respective moisture levels. ConclusionIn crux, Steinernema asiaticum higher concentration exhibited efficient control of fruit fly larvae in sandy loam soil with 12 % moisture level at 36 °C over the used EPN species. While application of EPNs against fruit fly is most suitable strategy to manage the fruit fly hazards and it should be included as a part of integrated pest management control programme.

The parasitic impact of Romanomermis iyengari Welch (Nematoda: Mermithidae) on the survival and biology of the common mosquito, Culex pipiens L. (Diptera: Culicidae)

The extensive use of chemical insecticides to control mosquitoes led to the development of insecticide resistance and environmental health hazards. This caused a surge in interest in eco-friendly biocontrol agents. The present study aimed to explore the susceptibility of different instar larvae of the common mosquito, Culex pipiens Linnaeus, 1758, to the mermithid nematode, Romanomermis iyengari Welch, 1964. Moreover, the effects of R. iyengari on the mosquito pupal developmental time, adult emergence, longevity, female fecundity, as well as egg-hatching rate were determined after larval treatment with an LC50 quantity of the nematode pre-parasites. Different instars of Cx. pipiens (1st–4th) were exposed separately to R. iyengari at concentrations of 1–6 pre-parasites/mosquito larva. Mortality rates of mosquito larvae were observed and the LC50 values were calculated. The estimated LC50 values for the 1st–4th larval instars were 3.18, 2.73, 3.79 and 4 pre-parasites/larva, respectively. Mean percent mortality of the 1st–4th larval instars ranged from 10–94%, 16–100%, 4–100% and 0–52%, respectively. The results indicated that exposure of 4th larval instar to the LC50 of R. iyengari pre-parasites significantly prolonged the duration of pupal development, reduced the percentage of emerged adults and reduced mosquito female fecundity compared with the control. In contrast, adult longevity and the egg-hatching rate did not differ between the control and the exposed group. In conclusion, this isolate of R. iyengari could be a promising biocontrol agent for Egyptian Cx. pipiens. Other trials are required to assess the biocontrol potential of this parasite in field conditions.

Study on carbohydrate contents of potato by using biocontrol agent Pseudomonas fluorescens with farm yard manure

An attempt was made to study the bio-control efficacy of Pseudomonas flourescens on carbohydrate contents of potato crop .Three types of treatments; soil treatment, seed treatment and foliar treatment in combination with farm yard manure were given. The result was recorded at the time of harvest. The best result was recorded in soil treatment followed by foliar treatment and seed treatment in comparison with control. Therefore from present investigation, it is concluded that an eco-friendly biocontrol agent Pseudomonas fluorescens is very easy to use and having no adverse effect on crops, people or animals and they can be applied to prevent and control several pathogenic fungi and grow healthy crop. The Pseudomonas fluorescens can be used as a bio-control agent as it is low cost and profitable dependent system and it also helps in conserving the natural resource.

Potential Antagonistic Bacteria against Verticillium dahliae Isolated from Artificially Infested Nursery

As an ecofriendly biocontrol agent, antagonistic bacteria are a crucial class of highly efficient fungicides in the field against Verticillium dahliae, the most virulent pathogen for cotton and other crops. Toward identifying urgently needed bacterial candidates, we screened bacteria isolated from the cotton rhizosphere soil for antagonisitic activity against V. dahliae in an artificially infested nursery. In preliminary tests of antagonistic candidates to characterize the mechanism of action of on culture medium, 88 strains that mainly belonged to Bacillus strongly inhibited the colony diameter of V. dahliae, with inhibiting efficacy up to 50% in 9 strains. Among the most-effective bacterial strains, Bacillus sp. ABLF-18, and ABLF-50 and Paenibacillus sp. ABLF-90 significantly reduced the disease index and fungal biomass of cotton to 40–70% that of the control. In further tests to elucidate the biocontrol mechanism (s), the strains secreted extracellular enzymes cellulase, glucanase, and protease, which can degrade the mycelium, and antimicrobial lipopeptides such as surfactin and iturin homologues. The expression of PAL, MAPK and PR10, genes related to disease resistance, was also elicited in cotton plants. Our results clearly show that three candidate bacterial strains can enhance cotton defense responses against V. dahliae; the secretion of fungal cell-wall-degrading enzymes, synthesis of nonribosomal antimicrobial peptides and induction of systemic resistance shows that the strains have great potential as biocontrol fungicides.

Biocontrol of citrus bacterial canker caused by Xanthomonas citri subsp. citri by Bacillus velezensis

Microorganisms with biocontrol capabilities against plant pathogens are considered as one of the most promising approaches for healthy crop management. In this study, ethyl acetate extracts of 25 Bacillus strains were investigated for their antagonistic effect on Xanthomonas citri subsp. citri (Xcc), which causes the citrus bacterial canker (CBC) disease. Among them, 21 strains exerted antibacterial activity against wild-type Xcc strains. Based on the strength of the antibacterial activity, nine Bacillus strains were selected for 16S rRNA analysis. 16S rRNA sequence homology revealed that several strains were closely related to B. velezensis, where strains with no antibacterial activity grouped as the soil-associated community of B. amyloliquefaciens. B. velezensis Bv-21 exhibited the highest antibacterial activity against wild type and streptomycin resistant Xcc with inhibition zones of 22.91 ± 0.45 and 20.28 ± 0.53, respectively. Furthermore, B. velezensis Bv-21 strain was tested for biocontrol activity against a streptomycin-resistant XccM4 in detached susceptible citrus leaves. The strain reduced the incidence of CBC by 26.30% and pathogen density of XccM4 by 81.68% over control. The results of the study strongly suggest that B. velezensis can be used as an effective and eco-friendly biocontrol agent either by itself or as an active compound, against both, the wild-type and streptomycin-resistant Xcc.