Bacterial Antagonists Research Articles

<i>In vitro</i> studies on the development of microbial consortia for the management of major diseases in coconut and citrus

Microbial consortia for disease suppression involve combining multiple beneficial microorganisms to enhance their effectiveness in plant disease management. In present study, development of microbial consortia for the management of major diseases in coconut and citrus was carried out using bacteria Pseudomonas fluorescens, Pseudomonas putida (striata), Bacillus subtilis and fungi – Trichoderma reesei, T. harzianum, T. asperellum against major pathogens viz. Ganoderma lucidum, Thielaviopsis paradoxa, Phytopthora palmivora, Lasiodiplodia theobromae isolated from the coconut rhizosphere, and Fusarium solani isolated from the citrus rhizosphere. The promising fungal and bacterial antagonists were identified and studied for compatibility. Non-volatile compounds of consortia inhibited the test pathogens with an increase in concentration from 10 % to 75% with fungal consortia and bacterial consortia and also with mixed consortia which is composed of bacterial consortia + fungal consortia. Superior growth suppression was recorded with mixed consortia even at 10% concentration (59.44% to 65.83%) against the test pathogens in the ascending order of L. theobromae (59.44%) T. paradoxa (63.89%), G. lucidum (65.83%), P. palmivora (63.61%) and F. solani (62.78%). A similar trend was observed in 75% concentration where inhibition observed in the order of Thielaviopsis paradoxa (90.28%), G. lucidum (89.44%), F. solani (82.50%), L. theobromae (81.94%) and P. palmivora (81.39%). Volatile effect by bacterial consortia recorded the superior inhibition on test pathogens in the order of Ganoderma (85.28%), F. solani (75.28%), T. paradoxa (71.94%), P. palmivora (71.67%) and L. theobrome (67.50%) compared to the individual bioagents. Similarly, the fungal consortia showed the superior inhibitory effect on test pathogens in the order of G. lucidum (83.25%), P. palmivora (82.50%), L. theobromae (83.06%), F. solani (80.56%) and T. paradoxa (73.61%). Since there was no zone of inhibition between the strains, the interactions between Pseudomonas and Bacillus strains of Trichoderma spp. were compatible with one another. Neem cake recorded superior CFU population from 9.43 X 106 CFU at seven days by T. asperellum. Shelf life study on mixed consortia with bacterial + fungal bioagents in talc formulation indicated that all the bacterial and fungal CFU count recorded in 106 dilution for 90 days.

Sustainable management of blister and grey blight diseases of tea using antagonistic and plant growth promoting microbes in Western Ghats of India

The blister and grey blights are the devastating leaf diseases in tea. The severity of blister and grey blight diseases in tea ranged from 22% to 68% and 11.41%–57.02%, respectively in a survey conducted in Southern India during 2022–2023. The morphological and molecular identifications of pathogens revealed that Exobasidium vexans and Neopestalotiopsis clavispora were responsible for causing blister and grey blights on tea in southern India. The conventional management strategy with foliar spray of synthetic fungicides result in fungicidal residue in tea causes environmental pollution and health hazards to human. To overcome this the current study aims to manage the blister and grey blight diseases of tea through the microbial biocontrol agents. The bacterial biocontrol agents viz., Bacillus subtilis (BBV57), Bacillus amyloliquefaciens (TNAU), Pseudomonas fluorescens (Pf1) and the fungal antagonist, Trichoderma asperellum (TV 1) were evaluated for their efficacy against the both blight diseases. All the bio agents have significantly reduced the basidiospore germination and the mycelial growth of E. vexans and N. clavispora, respectively. Among the bio agents, B. amyloliquefaciens registered 88.36% reduction in the germination of E. vexans basidiospore and 85.56% of mycelial growth reduction of N. clavispora in vitro (P < 0.05). Under field conditions the combined soil and foliar application of bacterial antagonists viz., B. subtilis, B. amyloliquefaciens and P. fluorescens each with 1 ˟ 1011 CFU/ml @ 5% concentration at 7 days interval significantly reduced the blister blight incidence with 53.53% & 51.53% reduction over control and 51.53% & 43.65% of reduction over initial during first and second year, respectively. The combined application also reduced the grey blight incidence with 53.53% & 52.00% reduction over control and 56.81% & 47.65% of reduction over initial during first and second year, respectively. This treatments with bioagents were almost comparable with synthetic treatments, such as copper oxy chloride (0.25%) and hexaconazole (0.25%) with 64.63% and 64.76% reduction of blister and grey blight reduction in first year; 59.74%, 51.11% reduction in second year over control (P < 0.05), respectively. Thus, the application of B. subtilis, B. amyloliquefaciens and P. fluorescens can be recommended for the sustainable management of tea blister and grey blight diseases in tea gardens.

Biological control of cucumber (Cucumus sativus L.) and ridge gourd [Luffa detangula L. (Roxb.)] damping-off by fungal and bacterial antagonist

Biological control of cucumber (Cucumus sativus L.) and ridge gourd [Luffa detangula L. (Roxb.)] damping-off by fungal and bacterial antagonist

Isolation and characterization of native antagonistic rhizobacteria against Fusarium wilt of chilli to promote plant growth.

In the eastern coastal regions of Odisha, wilt caused by Fusarium oxysporum f. sp.capsici is an extremely damaging disease in chilli. This disease is very difficult to manage with chemical fungicides since it is soil-borne in nature. The natural rhizosphere soil of the chilli plant was used to isolate and test bacterial antagonists for their effectiveness and ability to promote plant growth. Out of the fifty-five isolates isolated from the rhizosphere of healthy chilli plants, five isolates, namely Iso 01, Iso 17, Iso 23, Iso 24, and Iso 32, showed their highly antagonistic activity against F. oxysporum f. sp. capsici under in vitro. In a dual culture, Iso 32 (73.3%) and Iso 24 (71.5%) caused the highest level of pathogen inhibition. In greenhouse trials, artificially inoculated chilli plants treated with Iso 32 (8.8%) and Iso 24 (10.2%) had decreased percent disease incidence (PDI), with percent disease reduction over control of 85.6% and 83.3%, respectively. Iso 32 and Iso 24 treated chilli seeds have shown higher seed vigor index of 973.7 and 948.8, respectively, as compared to untreated control 636.5. Furthermore, both the isolates significantly increased plant height as well as the fresh and dry weight of chilli plants under the rolled paper towel method. Morphological, biochemical, and molecular characterization identified Bacillus amyloliquefaciens (MH491049) as the key antagonist. This study demonstrates that rhizobacteria, specifically Iso 32 and Iso 24, can effectively protect chilli plants against Fusarium wilt while promoting overall plant development. These findings hold promise for sustainable and eco-friendly management of Fusarium wilt in chilli cultivation.

Isolation and screening rhizobacteria to control &lt;i&gt;Gilbertella persicaria&lt;/i&gt; causing dragon fruit rot

&lt;i&gt;Gilbertella persicaria&lt;/i&gt; is a fungus causing dragon fruit rot discovered recently and there is still no effective measure to control this fungus. Several studies demonstrated that microorganisms were applied for controlling &lt;i&gt;G. persicaria&lt;/i&gt; on other crops. The purpose of this study was to evaluate the potential application of rhizobacteria in the &lt;i&gt;in vitro&lt;/i&gt; control of &lt;i&gt;G. persicaria&lt;/i&gt;. Eighty-nine bacterial isolates were collected from eleven rhizosphere soil samples. Four isolates, including LA2.9, LA3.2, LA4.5, and LA6.1, were screened based on inhibitory zone diameters and the ratio between the diameter of the inhibitory zone and the diameter of the bacterial growth zone. All of these four isolates were identified as belonging to the &lt;i&gt;Bacillus&lt;/i&gt; genus and were compatible with each other. Random combinations of the selected strains could increase the&lt;i&gt; in vitro&lt;/i&gt; growth inhibition of &lt;i&gt;Gilbertella persicaria&lt;/i&gt; GTC2.3.1 in some cases. These results once again showed that the individual or multiple applications of the antagonistic bacterial strains was a promising approach to control &lt;i&gt;G. persicaria&lt;/i&gt;. Therefore, it is necessary to isolate and collect more bacterial antagonists to develop targeted fungicidal formulations.

Unveiling the efficacy of a bacterial antagonist in the management of tomato wilt disease caused by Ralstonia solanacearum

The long-term application of agrochemicals, including pesticides, in intensive agricultural practices to protect crops from biotic stresses results in the emergence of resistance among phytopathogens and the ineffectiveness of chemical applications. The microbiological strategies, in contrast, minimize the reliance on chemicals and, hence, reduce environmental and human health risks. Bacterial wilt of tomato induced by Ralstonia solanacearum is one of the most destructive diseases worldwide that requires urgent attention to develop a safer and more efficient method to control the phytopathogen. The present work was conducted in the year 2022-2023. In this study, the bacterial wilt was managed by an antagonist bacterium, Pseudomonas fluorescens, exhibiting variable morphological, biochemical, and plant growth-promoting activities. The P. fluorescens inhibited the growth of R. solanacearum in plate assay at different time intervals (0-48 h). The SEM image of R. solanacearum cells cultured with P. fluorescens revealed pores, distortion, and fragmented cell envelope, while the untreated bacterial cells were uniform and smooth. Tomato plants infected with R. solanacearum showed 89% disease incidence compared to uninfected but PGPR-inoculated tomato plants. Application of P. fluorescens reduced disease incidence by 63% compared to R. solanacearum infested plants. Furthermore, plant length enhanced by 21 and 26% significantly following bacterial inoculation after three and four weeks of growth. Conclusively, this study emphasizes the effectiveness of using PGPR as a potent strategy for managing wilt disease in vegetable crops, especially tomato.

Unveiling the Biocontrol Potential of Rhizoplane Bacillus Species against Sugarcane Fusarium Wilt through Biochemical and Molecular Analysis.

Biocontrol is regarded as a viable alternate technique for managing sugarcane wilt disease caused by Fusarium sacchari. Many fungal antagonists against F. sacchari, have been reported, but the potential of bacterial antagonists was explored to a limited extent, so the present study evaluated the antagonistic potential of rhizoplane Bacillus species and their mode of action. A total of twenty Bacillus isolates from the rhizoplane of commercially grown sugarcane varieties were isolated. The potential isolate SRB2 had shown inhibition of 52.30, 33.33, & 44.44% and SRB20 of 35.00, 33.15, & 36.85% in direct, indirect, and remote confrontation respectively against F. sacchari. The effective strains were identified as Bacillus inaquosorum strain SRB2 and B. vallismortis strain SRB20, by PCR amplification of 16S-23S intergenic region. The biochemical studies on various direct and indirect biocontrol mechanisms revealed the production of IAA, Protease, Cellulase, Siderophores, and P solubilization. The molecular analysis revealed the presence of antimicrobial peptides biosynthetic genes like fenD (Fengycin), bmyB (Bacyllomicin) ituC (Iturin) and spaS (Subtilin) which provided a competitive edge to these isolates compared to other Bacillus strains. Under greenhouse experiments, the sett bacterization with SRB2, significantly (P < 0.001) reduced the seedling mortality by > 70% followed by SRB20 in F. sacchari inoculated pots. The study revealed that the isolates B. inaquosorum SRB2 and B. vallismortis SRB20 can be used as potential bioagents against sugarcane Fusarium wilt.

Enhanced control efficacy of Bacillus subtilis NM4 via integration of chlorothalonil on potato early blight caused by Alternaria solani

Early blight caused by Alternaria solani is a common foliar disease of potato around the world, and serious infections result in reduced yields and marketability due to infected tubers. The major aim of this study is to figure out the synergistic effect between microorganism and fungicides and to evaluate the effectiveness of Bacillus subtilis NM4 in the control of early blight in potato. Based on its colonial morphology and a 16S rRNA analysis, a bacterial antagonist isolated from kimchi was identified as B. subtilis NM4 and it has strong antifungal and anti-oomycete activity against several phytopathogenic fungi and oomycetes. The culture filtrate of strain NM4 with the fungicide effectively suppressed the mycelial growth of A. solani, with the highest growth inhibition rate of 83.48%. Although exposure to culture filtrate prompted hyphal alterations in A. solani, including bulging, combining it with the fungicide caused more severe hyphal damage with continuous bulging. Surfactins and fengycins, two lipopeptide groups, were isolated and identified as the main compounds in two fractions using LC-ESI-MS. Although the surfactin-containing fraction failed to inhibit growth, the fengycin-containing fraction, alone and in combination with chlorothalonil, restricted mycelial development, producing severe hyphal deformations with formation of chlamydospores. A pot experiment combining strain NM4, applied as a broth culture, with fungicide, at half the recommended concentration, resulted in a significant reduction in potato early blight severity. Our results indicate the feasibility of an integrated approach for the management of early blight in potato that can reduce fungicide application rates, promoting a healthy ecosystem in agriculture.

ПОЧВЕННЫЕ БАКТЕРИИ ИЗ АВТОХТОННЫХ МИКРОБНЫХ СООБЩЕСТВ ЦЕНТРАЛЬНОЙ СИБИРИ В БИОЛОГИЧЕСКОЙ ЗАЩИТЕ ПШЕНИЦЫ ОТ ALTERNARIA TENUISSIMA

The aim of the study is to find the strongest soil microorganisms from autochthonous microbial communities of Central Siberia against phytopathogenic micromycetes Alternaria tenuissima. The object of the study is autochthonous soil bacteria isolated from the soils of the Krasnoyarsk forest-steppe in the Sukhobuzimsky District. Soil samples were taken from under spring wheat Novosibirskaya 15 and from under perennial grasses. The soil cover is represented by ordinary leached chernozem. Ammonium nitrate was used (34.7 kg/ha active ingredient). The climatic conditions are moderately dry and continental. The studies were carried out in 2022–2023. Antagonistic activity was measured on the GRM Saburo. With a general growth of the test culture and soil bacteria, the strongest antagonists were found in the suppression zone of Alternaria tenuissima. The identification of the most powerful bacterial antagonists in reducing the intensity and prevalence of root rot was carried out using the method of artificial infection with Alternaria tenuissima. Before infection with micromycete, bacterization of spring wheat seeds Novosibirskaya 15 with the studied bacterial isolates was carried out. Mathematical processing of the obtained results was carried out by one-way variance analysis and two-sample F-test for variance. The results of the study on the use of soil autochthonous antagonist microorganisms in biological protection of spring wheat from the causative agents of root rot Alternaria tenuissima showed that the studied bacterial isolates statistically significantly (p &lt; 0.01) reduced the intensity and prevalence of this disease. The maxi-mum effect in reducing the intensity and prevalence of the disease was shown by isolates B2 and B4. Also, the studied bacterial strains showed a significant effect (p &lt; 0.001) on the length of sprouts. The greatest increase in length in spring wheat sprouts was in the experimental variant with strain B2. This strain can be recommended not only for protection against Alternaria tenuissima, but also for stimuli-ting wheat growth.

Biocontrol potential of some selected native bacterial antagonists against tomato (&lt;em&gt;Solanum lycopersicum&lt;/em&gt; L.) early blight causal agent &lt;em&gt;Alternaria alternata&lt;/em&gt;

Seven selected bacterial antagonists isolated from healthy tomato rhizosphere and phyllosphere were evaluated for their biocontrol efficacy against the tomato early blight causal agent Alternaria alternata under in vitro conditions. The causal organism of early blight of tomato was isolated from a tomato leaf sample which showed early blight symptoms and verified it as Alternaria alternata. Healthy tomato rhizosphere soil, fructosphere and phyllosphere extracts were used as the potential sources of antagonists. Thirty bacterial isolates from tomato rhizosphere soil and 22 bacterial isolates from tomato phyllosphere were isolated using serial dilution technique. Out of those isolates, 24 were subjected to antagonists screening procedure. It was observed that, all the bacterial isolates except RA 5, RA 21, PA 1, PA 2, inhibited the growth of A. alternata significantly (p&lt;0.05) in co-cultivation and dual culture showing an average radial growth inhibition of 69 %. Seven different bacterial isolates coded as RA 8, RA 12, RA 17, RA 18, RA 29, PA 4 and PA 12 were selected for further studies. Based on 16 S rRNA analysis, four of these antagonists were identified as Bacillus thuringiensis, Bacillus cereus and Pseudomonas sp. Microscopic observations of A. alternata hyphae subjected to antagonism showed deviations from the normal hyphae including thickenings, swellings and vacuolation. Inhibition of A. alternata spore germination by selected antagonists was significant at p&lt;0.05 level with an average inhibition of 83.7 %. All the selected antagonists produced diffusible antifungal substances and showed hyperparasitism and competition as their mechanisms in antagonizing the fungal pathogen A. alternata. These results suggested that these seven bacterial isolates can be further explored as potential biocontrol agents in controlling early blight disease in tomato.

Thymol as a Component of Chitosan Systems—Several New Applications in Medicine: A Comprehensive Review

Thymol, a plant-derived monoterpene phenol known for its broad biological activity, has often been incorporated into chitosan-based biomaterials to enhance therapeutic efficacy. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, we conducted a systematic literature review from 2018 to 2023, focusing on the biomedical implications of thymol-loaded chitosan systems. A review of databases, including PubMed, Scopus, and Web of Science was conducted using specific keywords and search criteria. Of the 90 articles, 12 were selected for the review. Thymol-loaded chitosan-based nanogels (TLCBS) showed improved antimicrobial properties, especially against multidrug-resistant bacterial antagonists. Innovations such as bipolymer nanocarriers and thymol impregnated with photosensitive chitosan micelles offer advanced bactericidal strategies and show potential for bone tissue regeneration and wound healing. The incorporation of thymol also improved drug delivery efficiency and biomechanical strength, especially when combined with poly(dimethylsiloxane) in chitosan–gelatin films. Thymol–chitosan combinations have also shown promising applications in oral delivery and periodontal treatment. This review highlights the synergy between thymol and chitosan in these products, which greatly enhances their therapeutic efficacy and highlights the novel use of essential oil components. It also highlights the novelty of the studies conducted, as well as their limitations and possible directions for the development of integrated substances of plant and animal origin in modern and advanced medical applications.

Microbial Interactions in the Management of Groundnut Stem Rot

Groundnut (Arachis hypogaea L.) is an important oil seed crop in the world belonging to the Leguminosae family. It is one of the essential food and cash crops of our country. In India, a large number of diseases attack groundnut [1]. Among soil borne diseases, stem rot or white mold caused by Sclerotium rolfsii Sacc. [2] is an important disease causing significant yield losses in several groundnut growing countries (Mehan et al., 1994). Sclerotium rolfsii Sacc. is a destructive soil borne fungal pathogen of oil seed crop in India. Different practices are recommended for management of groundnut stem rot such as deep summer ploughing, destruction of plant debris, crop rotation with jowar and bajra, seed treatment with carbendazim or captan or mancozeb or tebuconazole, soil drenching with hexaconazole, application of ammonium sulphate or calcium ammonium nitrate instead of urea and application of gypsum at flowering stage. Further, no single treatment is full proof and disease continues to cause losses in farmers’ fields. Biological control offers an interesting alternative to fungicides for sustainable management of soil borne diseases. Biocontrol is a non-chemical measure, could be effective as chemical control by various techniques. Among the techniques, the mixture of antagonists was studied to enchance the control efficacy. In most studies, the involvement of only mechanism of biological control is demonstrated. Involvement of more than one mechanism has been reported in only a few systems. Use of several biocontrol agents with several mechanisms of control fits in well with the concepts of integrated disease management, in which several means of disease suppression are applied concurrently. When single or more means of mechanisms are not effective, the others may compensate for the former absence. The present study, involved three major bacterial antagonists viz., Streptomyces violaceusniger, Streptomyces exfoliatus and Pseudomonas fluorescens to find out the effective dose of mixtures. The different doses from 10-1 to 10-5 were studied, the dose 10-1 of Streptomyces violaceusniger have more efficiency of 86.70, than S. exfoliatus. The efficacy of Streptomyces violaceusniger with combination of other antagonists were tested and found that, the mixture of Streptomyces violaceusniger and P. fluorescens have synergistic activity than any other combinations which have synergistic factor greater than one.

Potentiality of fungal and bacterial antagonists against Fusarium pallidoroseum (Cooke) Sacc. Causing wilt of coriander in vitro

Potentiality of fungal and bacterial antagonists against Fusarium pallidoroseum (Cooke) Sacc. Causing wilt of coriander in vitro

Cryptic bacterial pathogens of diatoms peak during senescence of a winter diatom bloom.

Diatoms are globally abundant microalgae that form extensive blooms in aquatic ecosystems. Certain bacteria behave antagonistically towards diatoms, killing or inhibiting their growth. Despite their crucial implications to diatom blooms and population health, knowledge of diatom antagonists in the environment is fundamentally lacking. We report systematic characterisation of the diversity and seasonal dynamics of bacterial antagonists of diatoms via plaque assay sampling in the Western English Channel (WEC), where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during characteristic spring diatom blooms, but coincided with a winter bloom of Coscinodiscus, suggesting that these bacteria likely influence distinct diatom host populations. We isolated multiple bacterial antagonists, spanning 4 classes and 10 bacterial orders. Notably, a diatom attaching Roseobacter Ponticoccus alexandrii was isolated multiple times, indicative of a persistent environmental presence. Moreover, many isolates had no prior reports of antagonistic activity towards diatoms. We verified diatom growth inhibitory effects of eight isolates. In all cases tested, these effects were activated by pre-exposure to diatom organic matter. Discovery of widespread 'cryptic' antagonistic activity indicates that bacterial pathogenicity towards diatoms is more prevalent than previously recognised. Finally, examination of the global biogeography of WEC antagonists revealed co-occurrence patterns with diatom host populations in marine waters globally.

Элементы технологии производства микробиопрепаратов на основе перспективных бактериальных штаммов антагонистов возбудителя сухой гнили подсолнечника

The elements of production technologies of microbiopreparations in a preparative form wetting powder at a stationary surface cultivation of promising bacterial antagonist strains of a dry rot pathogen on sunflower. The optimal sources of nitrogen and carbon-based and compound nutrient media for cultivation of three promising bacterial strains from the genera Bacillus and Pseudomonas. An excellent source of nitrogen for a strain 5B-1 Bacillus subtilis is corn steep liquor, and of carbon – glycerin and molasses. The highest weight of dry bacterial biomass of a strain D 1-1 Bacillus sp. was on a nutrient medium where sodium nitrogen was used as a nitrogen source and sucrose and molasses – as a carbon-based source. For both bacterial strains of a genus Bacillus the optimal were such compound nutrient media as Chapek’s for bacteria and Tylon-3. For cultivation of a strain 14-4 Pseudomonas sp. the best nitrogen sources were corn steep liquor and sodium nitrogen, and carbon-based – sucrose. The most optimal compound nutrient medium for these strains were King B and Chapek’s for bacteria.

Indigenous Biopreparations and Biocontrol Agents for Growth and Disease Management in Black Pepper Nursery

The present study was carried out at Agricultural Research Station, Thiruvalla, Kerala, India during December, 2020–July, 2021 to evaluate the efficacy of native biocontrol agents and fermented organic preparations viz; fish-jaggery extract, egg-lemon juice extract and jeevamrutha on growth enhancement and suppression of Phytophthora infection in black pepper nursery. The plants were challenge inoculated with Phytophthora capsici at the collar region. The plant growth parameters were recorded before and one month after treatment application. Results showed that a considerable increase in plant height (49.30%) and number of leaves (57.89%) with the application of bacterial antagonists A1 and S2 respectively. Application of fish-jaggery extract increased the shoot girth by 29.6%. Soil application of Trichoderma combined with spraying of bacterial antagonists A1 and S2 also increased the shoot girth considerably. Application of jeevamrutha increased the total leaf area by 49.98% and chlorophyll contents viz. chlorophyll a, chlorophyll b and total chlorophyll was also maximum with this application. Phytophthora infection at collar region was not observed in plants treated with potassium phosphonate and fish-jaggery extract. Application of egg-lemon juice extract, jeevamrutha and bioagents also recorded less infection on collar region. The study indicated the efficacy of fermented organic fertilizers and bioagents in improving plant growth and also in reducing pathogen infection at nursery stage. Hence a combination of native antagonistic microflora and indigenous biopreparations could be effectively utilized in commercial production of healthy planting materials in black pepper nurseries.

Selectivity of chemical and biological foliar treatments on the phyllosphere communities of bacteria and fungi antagonistic to Fusarium verticillioides in maize

AbstractMaize grain production in the tropics is affected by Fusarium verticillioides, leading to significant losses in yield and quality. Fungicides are commonly used to control foliar diseases and increase grain yield, but have limited efficacy against F. verticillioides and may even stimulate the fungus to produce mycotoxins. Biocontrol can reduce F. verticillioides populations and fumonisin, but little is known about the resulting microbial interactions on the phylloplane and their relationship with F. verticillioides. This study aimed at evaluating the impact of different foliar treatments on the cultivable phylloplane community of fungi and bacteria and their potential in controlling F. verticillioides in maize. Results showed that two sprays of Bacillus subtilis BIOUFLA2 increased the percentage of native phylloplane antagonist bacteria and fungi against F. verticillioides by 25.0% and 27.3%, respectively, compared with the water control. However, two sprays with a triazole + strobilurin fungicide at different phenological stages in maize reduced such antagonistic communities. From field trials, 34 bacteria and 13 fungi from the phylloplane were selected for their inhibitory activity against F. verticillioides, with most coming from the exclusive treatment with BIOUFLA2. The study also revealed that the biocontrol agent‐recruited phylloplane indigenous lineages act through antibiosis, competition, and parasitism. Therefore, the adoption of biocontrol to limit F. verticillioides population build‐up not only has a direct activity on the pathogen but also recruits fungal and bacterial antagonists that may act additively or synergistically with the applied biocontrol agent.

Exploitation of epiphytic microorganisms and organic preparations for the management of Choanephora pod rot of cowpea

Exploration of epiphytic microorganisms from different plant parts and their exploitation for the management of plant pathogens is a relevant approach in view of greater awareness of pollution free environment. The aim of the present study was to analyze the microbial communities with special focus on antagonists isolated from the fructosphere of cowpea (Vigna unguiculata L. Walp.) and the use of organic preparations such as panchagavya, jeevamruth, compost tea, vermiwash and fish amino acid for suppression of Choanephora cucurbitarum, the pathogen inciting pod rot in cowpea. A collection of six isolates of bacteria and fungi were isolated through serial dilution technique, and their efficacy in suppressing the pathogen were tested under in vitro conditions. Among the six isolates, the bacteria and fungi with maximum inhibitory activity against the targeted pathogen were selected for further identification and in vivo assay. Based on the cultural, morphological and biochemical characters, the bacterial and fungal antagonists were identified as Pseudomonas fluorescens and Trichoderma virens, respectively. In vitro assay of the organic preparations revealed that vermiwash (5% and 10%), jeevamurth (10%) and panchagavya (10%) completely inhibited the growth of pathogen. Application of effective dose of organic preparations and the selected antagonists on the excised cowpea pods revealed that, among organic preparations jeevamurth (10%) exhibited maximum suppression of pod rot by 60.64%, however the selected bacterial antagonist, i.e., P. fluorescens gave complete suppression of the pathogen. Under in vivo conditions, jeevamurth (10%), vermiwash (5%), T. virens (106cfu/ml), and P. fluorescens (106cfu/ml) showed the maximum suppression of the pathogen and the percentage suppression was recorded as 87.33, 75.22, 75.27 and 72.31% respectively. Therefore, the present study revealed that the organic preparations such as jeevamurth (10%), vermiwash (5%), and the indigenous species of Pseudomonas fluorescens and Trichoderma virens obtained from the fructosphere can be used in integrated disease management strategies against Choanephora pod rot of cowpea.

Metagenomic Approach Deciphers the Role of Community Composition of Mycobiome Structured by Bacillus velezensis VB7 and Trichoderma koningiopsis TK in Tomato Rhizosphere to Suppress Root-Knot Nematode Infecting Tomato.

The soil microbiome is crucial for maintaining the sustainability of the agricultural environment. Concerning the role of diverse mycobiomes and their abundance toward the suppression of root-knot nematode (RKN) infection in vegetable crops, our understanding is unclear. To unveil this issue, we examined the fungal microbiome in tomato rhizosphere augmented with bioagents challenged against RKN at taxonomic and functional levels. Composition of the mycobiome in tomato rhizosphere treated with Bacillus velezensis VB7 and Trichoderma koningiopsis TK differed significantly from the infected tomato rhizosphere. The abundance and diversity of fungal species, however, were significantly higher in the combined treatments of bioagents than for individual treatments. Fungal microbiome diversity was negatively correlated in the RKN-associated soil. Network analysis of the fungal biome indicated a larger and complex network of fungal biome diversity in bioagent-treated soil than in nematode-associated tomato rhizosphere. The diversity index represented by that challenging the RKN by drenching with consortia of B. velezensis VB7 and T. koningiopsis TK, or applying them individually, constituted the maximum abundance and richness of the mycobiome compared to the untreated control. Thus, the increased diverse nature and relative abundance of the mycobiome in tomato rhizosphere was mediated through the application of either T. koningiopsis TK or B. velezensis VB7, individually or as a consortium comprising both fungal and bacterial antagonists, which facilitated engineering the community composition of fungal bioagents. This in turn inhibited the infestation of RKN in tomato. It would be interesting to explore further the possibility of combined applications of B. velezensis VB7 and T. koningiopsis TK to manage root-knot nematodes as an integrated approach for managing plant parasitic nematodes at the field level.

The use of biological agents in controlling diseases of shallots for tss production

Stemphylium disease caused by Stemphylium vesicarium is an important disease that becomes an obstacle in TSS production. The disease attacks can lead to seed harvest failure. In the field. Stemphylium disease is associated with purple spot disease caused by the fungus Alternaria porri. The purpose of this study was to obtain biological agents that were effective in controlling S vesicarium and A porri on TSS production. The tests were carried out in-vitro in the laboratory and in planta in the field under a plastic shade. The experimental design used a randomized block design with 11 treatments (Bacillus sp.1. Bacillus sp. 3., Pseudomonas florescens (Pf)., Trichoderma sp.2., Trichoderma sp.3., Bacillus sp.1 + Trichoderma sp.2 + Pf., Bacillus sp.3 + Trichoderma sp.2 + Pf., Bacillus sp.1 + Trichoderma sp.3 + Pf., Bacillus sp.3 + Trichoderma sp.3 + Pf, and Control). Each treatment was repeated 3 times. The results showed that the biological agents Trichoderma sp., Bacillus sp., and Pseudomonas fluorescent as antagonist agents have varying inhibitory abilities against pathogens Stemphylium vesicarium and Alternaria porri. Inhibition by Bacillus sp. against S. vesicarium by 60.51-63.75% and by Trichoderma sp. by 25.78-31.47%. Meanwhile for A. porri. both bacterial and fungal antagonist agents had an inhibition between 45.09-79.15%. Antagonist agents Trichoderma sp.3 alone and the combination of Bacillus sp.1 + Trichoderma sp.3 + Pseudomonas fluorescens can increase the number of leaves and the number of seedlings of shallots. Antagonist agent Trichoderma sp.3 alone and in combination between Bacillus sp.3 + Trichoderma sp.3 + P. fluorescens can reduce the attacks intensity of S. vesicarium and A. porri diseases.