Antagonistic Potential Research Articles

Enhanced antagonistic potential of gamma-irradiated Trichoderma spp. against Phytophthora capsici : An in vitro study

Enhancing the biocontrol efficacy of microorganisms is a crucial element in advancing sustainable agricultural practices, particularly in the management of soilborne fungal phytopathogens. Among the various methods employed to augment the effectiveness of biocontrol agents, gamma radiation has emerged as a particularly promising approach due to its ability to induce genetic mutations that can enhance antagonistic properties. In the present study, an efficient gamma irradiation technique was employed to induce genetic modifications in three biocontrol agents: Trichoderma guizhouense , T. koningiopsis , and T. asperellum. The efficacy of these genetically altered strains was then evaluated against the pathogen Phytophthora capsici. Mutant isolates were generated through exposure to varying doses of gamma radiation and were initially screened based on their growth rates. These were subsequently subjected to a series of in vitro antagonistic tests. The results demonstrated that five selected mutants Ta 200-1, Ta 250-2, Tg 200-1, Tg 250-2, and Ta 150-3 exhibited significantly enhanced antagonistic potential compared to their parent strains. Importantly, these mutants retained their improved traits even after ten rounds of subculturing, with growth inhibition percentages ranging from 72.11% to 68.11%. The findings from the in vitro antagonistic studies suggest that gamma irradiation represents an effective strategy for enhancing the antagonistic capabilities of Trichoderma species, thereby contributing to the development of more robust biocontrol agents in plant health management.

Biological management of rhizome rot in ginger (Zingiber officinale ) plants and stored ginger seeds

Two endospore-forming endophytic bacteria (EEB1 A8 and EEB2 B13) were isolated from ginger rhizome collected from the fields of College of Agriculture, Vellayani and identified as Bacillus spp. Their antagonistic potential against Pythium myriotylum , the soft rot pathogen of ginger, was analyzed in vitro by dual culture plate assay and the agar well diffusion method. They tested positive for biocontrol traits such as the production of hydrogen cyanide, siderophore and volatile organic compounds. The bacterial isolates were applied to ginger plants to test biocontrol efficiency against P. myriotylum , individually and in combination with Piriformospora indica , a fungal root endophyte capable of promoting plant growth and enhancing plant defense. A lesser percent disease index (PDI) was observed in plants where the combination of EEB1 A8 and P. indica was applied. The activity of enzymes pertinent to protective mechanisms against pathogens, like peroxidase, phenylalanine ammonia-lyase, super oxide dismutase (SOD) and polyphenol oxidase (PPO) in the plants were analyzed before challenging, 1st, 3rd and 5th day after challenging with pathogen. The values followed the same trend in all treatments as it increased after inoculation up to 3rd day and then decreased for peroxidase (PO) and SOD. The plants treated with EEB1 A8 and combination of EEB1 A8 and P. indica showed the highest values for the level of defense enzyme production. In a storage study, when ginger seed rhizomes were treated with individual bacterial isolates and as a consortium of both, followed by inoculation with the pathogen P. myriotylum , rhizomes treated with consortium were more tolerant to rhizome rot. Applying endospore-forming bacteria with biocontrol properties is a propitious method for controlling rhizome rot in ginger, in the field and during seed storage.

Antagonistic Potential of a Phosphate Solubilizing Bacteria (B. cereus PS1.1, B. cereus PS1.2, B. cereus PS1.4) Against the Patogent Fungus Ganoderma sp. Isolated from Basal Stem of Oil Palm (Elaeis guineensis Jacq.) with Rot Disease

Ganoderma sp. is a pathogenic fungus whose attack can cause basal stem rot disease of oil palm (Elaeis guineensis Jacq.). Disease control using phosphate solubilizing bacteria (PSB), namely Bacillus cereus can be an alternative to biological control. The purpose of this study was to determine the antagonistic ability of PSB (B. cereus PS1.1, B. cereus PS1.2, B. cereus PS1.4) in inhibiting the growth of Ganoderma sp. BP1 and changes in hyphal morphology of Ganoderma sp. BP1 after antagonistic testing. The research was conducted from January to May 2023 at the Microbiology Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, Tanjungpura University, Pontianak. Antagonist testing used a completely randomized design (CRD) with the treatments consisted of Ganoderma sp. BP1 (negative control), 1% hexaconazole fungicide (positive control), PSB isolates PS1.1, PS1.2 and PS1.4. The test method used the dual culture on Sabouraud Dextrose Agar (SDA) media with each treatment repeated four times so that 20 experimental units were obtained. The results showed that PSB isolate PS1.4 had strong inhibition with an inhibition zone diameter of 11.01 mm, while isolates PS1.1 and PS1.2 had moderate inhibition with inhibition zone diameters of 9.43 mm and 9.45 mm, respectively, against Ganoderma sp. BP1. Hyphal morphology changes in of Ganoderma sp. BP1 that occurred after the antagonist test consist of lysed hyphae, twisted hyphae, hook-like hyphal tips, curly hyphae, bulbous hyphae, branched hyphae and bent hyphal ends.

Viability of microencapsulated species of Trichoderma as a strategy to optimize use in biological control.

The increasing use of chemical fungicides without effective control of phytopathogens has led to the development of resistance in microorganisms. As a promising alternative, products formulated with Trichoderma have emerged for their sustainable and effective potential in integrated disease management. However, the predominant formulations do not offer the necessary protection against abiotic factors. In this study, we investigated Trichoderma species encapsulated in sodium alginate through storage viability experiments and their antagonistic potential. The viability and storage conditions of the capsules were evaluated by plating at 5, 15, 30, 45, 60, and 150 days after production, kept in dry or refrigerated environments. The antagonistic potential was determined by the culture pairing method using the phytopathogen Fusarium sp. The results demonstrated that it was possible to maintain the viability of the conidia, with no differences between storage environments. Additionally, the capsule provided UV protection to the conidia encapsulated species possess antagonistic potential, inhibiting 52.54% of Fusarium sp. growth. Consequently, encapsulation is an alternative formulation method that ensures the viability of Trichoderma conidia and optimizes its use in biological control.

Antagonistic potential of Bacillus velezensis S26 endospores against gray mold in grapevines

Antagonistic potential of Bacillus velezensis S26 endospores against gray mold in grapevines

In vitro inhibition mechanisms of Trichoderma yunnanense TM10 against Pyricularia oryzae and Rhizoctonia solani causing blast and sheath blight diseases in rice (Oryza sativa L.)

Blast and sheath blight diseases, caused by Pyricularia oryzae and Rhizoctonia solani, respectively, are major threats to rice production worldwide. Efforts should be made to limit the spread of these phytopathogens, preferably through sustainable methods. In this study, we investigated the antagonistic potential of the local isolate Trichoderma yunnanense TM10 against the pathogenic fungi P. oryzae and R. solani. The results demonstrated that T. yunnanense TM10 inhibited the growth of P. oryzae and R. solani through mechanisms such as competition, mycoparasitism, and antibiosis. Dual culture, filtrate culture, and double plate assays showed that T. yunnanense TM10 could inhibit the growth of both P. oryzae and R. solani. Slide culture and scanning electron microscope (SEM) tests confirmed that T. yunnanense TM10 exhibited mycoparasitic activity, including attachment, coiling, penetration, lysis, and destruction of pathogen hyphae. Additionally, T. yunnanense TM10 was capable of producing cell wall-degrading enzymes (CWDEs) such as chitinase and cellulase, as well as volatile organic compounds (VOCs) such as hydrogen cyanide (HCN). The multifaceted abilities of T. yunnanense TM10 for limiting the growth of P. oryzae and R. solani underscore its potential as an effective biocontrol agent for enhancing productivity and sustainability in rice cultivation.

Biocontrol Potential of a Native Trichoderma Collection Against Fusarium oxysporum f. sp. cubense Subtropical Race 4

The Canary Islands lead banana (Musa acuminata) production in the EU. Different fungal pathogens affect this crop in subtropical areas, with Fusarium oxysporum f. sp. cubense subtropical race 4 (Foc-STR4) being the most important in the Canary Islands. With the aim of developing environmentally sustainable techniques for disease control, this study presents the results of the evaluation of the antifungal capacity of a native Trichoderma collection (12 species, 109 isolates) obtained from banana soils. The results demonstrate the diversity of biocontrol genes and the in vitro antagonistic potential of different native Trichoderma species/isolates against two Foc-STR4 strains obtained from plants with Panama disease symptoms. Trichoderma virens (TF18), a dominant species in banana soils in the Canary Islands, showed a high capacity to inhibit the growth of Foc-STR4 in different in vitro assays. Trichoderma atrobrunneum (TF01) showed mycoparasitism capacity through the spiral coil around the hyphae of the pathogen. In addition, the genome analysis of T. atrobrunneum (TF03) showed 69 putative biosynthetic gene clusters, with the notable presence of the trichothecene tri5 gene. Finally, our work demonstrates that the soils of the Canary Islands banana crops are a potential source of environmentally adapted biological control agents to control or reduce the incidence of Foc-STR4.

The Public Health Risks of β-Hemolytic Bacillus pumilus Bacteria Resistant to Gastrointestinal Conditions from Medicinal Plant.

In numerous countries, the utilization of plants for both nutritional and therapeutic purposes is a common practice. However, the inadvertent use of these plants can pose risks due to their active molecules or microbiota. The traditional use of Herniaria glabra L. (H. glabra) plant in treating various diseases is well-known; however, its application in yogurt production raises concerns. In this study, Bacillus pumilus isolated from H. glabra was identified through 16s rRNA sequencing and MALDI-TOF MS (Matriks Assisted Lazer Desorption Ionization Time of Flight Massspectrometry). The bacterium's resistance under simulated gastrointestinal tract (GIT) conditions was assessed, followed by investigations into its aggregation ability, antibiotic resistance, hemolytic activity, and antagonistic potential through in vitro tests. The study revealed that B. pumilus exhibited 100% resistance to GIT conditions. Notably, the bacterium demonstrated strong autoaggregation (34.48%) and coaggregation abilities (49.82% for Escherichia coli, 49.13% for Listeria monocytogenes), signifying a potent aggregative potential. Sensitivity to most tested antibiotics was observed, while no antagonistic activity against tested bacteria was evident. Furthermore, the bacterium exhibited β-hemolytic activity, indicative of potential virulence. The findings suggest that this resistant yet virulent bacterium, with its hemolytic activity, could disrupt the GIT balance, posing serious health risks. The study underscores the need for caution and awareness regarding the potential dangers posed by bacteria in plant microbiota in herbal therapies.

Integrated large-scale metagenome assembly and multi-kingdom network analyses identify sex differences in the human nasal microbiome.

Respiratory diseases impose an immense health burden worldwide. Epidemiological studies have revealed extensive disparities in the incidence and severity of respiratory tract infections between men and women. It has been hypothesized that there might also be a nasal microbiome axis contributing to the observed sex disparities. Here, we study the nasal microbiome of healthy young adults in the largest cohort to date with 1593 individuals, using shotgun metagenomic sequencing. We compile the most comprehensive reference catalog for the nasal bacterial community containing 4197 metagenome-assembled genomes and integrate the mycobiome, to provide a valuable resource and a more holistic perspective for the understudied human nasal microbiome. We systematically evaluate sex differences and reveal extensive sex-specific features in both taxonomic and functional levels in the nasal microbiome. Through network analyses, we capture markedly higher ecological stability and antagonistic potentials in the female nasal microbiome compared to the male's. The analysis of the keystone bacteria reveals that the sex-dependent evolutionary characteristics might have contributed to these differences. In summary, we construct the most comprehensive catalog of metagenome-assembled-genomes for the nasal bacterial community to provide a valuable resource for the understudied human nasal microbiome. On top of that, comparative analysis in relative abundance and microbial co-occurrence networks identify extensive sex differences in the respiratory tract community, which may help to further our understanding of the observed sex disparities in the respiratory diseases.

Antagonistic potential of Fusarium oxysporum as an endophyte isolated from Horse-chestnut tree in the management of Rhizoctonia solani under in-vitro conditions

Symbiotic relationships are established by endophytic microorganisms with their host, resulting in the provision of diverse advantages, such as protection against plant pathogens. Soil-borne pathogens have become a devastating source of infection in many plant species. The environmentally friendly approaches are scare in managing these soil-borne pathogens. This study was aimed to manage one soil-borne pathogen (Rhizoctonia solani) by employing another fungal endophyte (Fusarium oxysporum) via mean inhibition zone technique. The fungal endophyte was isolated from horse-chestnut tree leaves. The R. solani was extracted from the vegetable’s plants showing typical symptoms of root rot and damping off. Both endophyte and pathogen were grown on suitable culture media. The antagonistic activity of collected endophyte for soil-borne pathogen was checked via mean inhibition zone technique under in-vitro condition. The diversity indices and isolation frequency analysis revealed that this tree specie has versatile endophytic range. The results from the dual culture experiment assessing the antagonistic activity of endophyte against the soil-borne pathogen (R. solani) revealed a significant (P <0.001) impact of the endophyte, evaluation times, and the interaction between endophyte and evaluation times on the size of the pathogen colony. The endophyte exhibited a substantial decrease in pathogen development compared to the control, except between days 11 and 15 after inoculation. The data indicate that F. oxysporum contains endophytic potential, which might be investigated for potential biocontrol agents against other soil-borne diseases.

Biological Suppression of Sclerotium rolfsii in Groundnut Cultivation: A Path Towards Sustainable Disease Management

Stem rot of groundnut caused by Sclerotium rolfsii Sacc, is a major soil borne disease which impact on groundnut cultivation both in India and globally. The primary objective of this study was to assess the antagonistic potential of biocontrol agents against the pathogen, both individually and in combination, under In vitro and glasshouse conditions. The results of the present investigation indicated that the application of microbial consortia was more effective against Sclerotium rolfsii than individual bioagents. Specifically, seed treatment with microbial consortia MC1, MC2, MC3, and MC4 resulted in lower disease incidence with 13.80%, 16.01%, 20.0%, and 22.60% respectively, compared to the pathogen check, which had a 74.12% PDI. Additionally, these treatments also enhanced plant growth through improved plant growth-promoting traits under glasshouse conditions.

The microbiome of continuous wheat rotations: minor shifts in bacterial and archaeal communities but a source for functionally active plant-beneficial bacteria

Continuous wheat cropping often leads to yield decline, with suspected causes including increased pathogen susceptibility, decreased root growth, or low nutrient use efficiency, though the exact causes remain unknown. Here, we investigated soil and root-associated bacterial and archaeal communities in wheat under rotation versus continuous cultivation, monitored fungal pathogen presence, and used beneficial bacteria to mitigate Gaeumannomyces tritici (Ggt) symptoms in greenhouse experiments. Sampling was conducted at two field sites with different soil textures over two years and at two plant developmental stages, capturing site-specific and seasonal fluctuations. By cultivation, 767 bacterial isolates were screened for plant-beneficial traits. Amplicon sequencing revealed minor effects on community structure due to wheat rotational position but pronounced effects related to site, year, and microhabitat. Rhizoplane isolates with plant-beneficial traits were mainly Flavobacterium, Microbacterium, Pedobacter, Pseudomonas, Stenotrophomonas, and Variovorax. Continuous wheat rotations showed the highest proportion of bacteria with fungal antagonistic potential, indicating plant roots’ recruitment of beneficial bacteria. Introducing Ggt in the greenhouse experiment altered the bacterial and archaeal community, confirming field study results and demonstrating that applying beneficial bacteria early in the season at the seedling stage can control Ggt and improve plant growth. This study highlights the dynamic nature of wheat's below-ground bacterial and archaeal community, influenced by soil type, season, and microhabitat, with wheat rotation playing a minor role. In addition, it confirms the potential of selected Bacillus and Pseudomonas isolates, whether used individually or in consortia, for microbe-assisted mitigation of yield decline in intensive wheat production.

Identification and Antagonistic Potential of Bacillus atrophaeus against Wheat Crown Rot Caused by Fusarium pseudograminearum

Fusarium pseudograminearum (Fpg) is a significant pathogen responsible for fusarium crown rot (FCR) in wheat (Triticum aestivum L.), a disease with devastating impacts on crop yield. The utilization of biocontrol bacteria to combat fungal diseases in plants is a cost-effective, eco-friendly, and sustainable strategy. In this trial, an endophytic bacterial species, designated as SW, was isolated from the roots of wheat. The strain exhibited potent antagonistic effects against Fpg and reduced the FCR disease severity index by 76.07 ± 0.33% in a greenhouse pot trial. Here, 106 colony-forming units (CFUs)/mL of the SW strain was determined to be the minimum dose required to exhibit the antagonism against Fpg. The strain was identified as Bacillus atrophaeus using genome sequencing and comparison with type strains in the NCBI database. Whole-genome sequencing analysis revealed that SW harbors genes for siderophores, antifungal metabolites, and antibiotics, which are key contributors to its antagonistic activity. Additionally, the strain’s ability to utilize various carbon and nitrogen sources, successfully colonize wheat root tissues as an endophyte, and form biofilms are critical attributes for promoting plant growth. In summary, these findings demonstrate the ability of Bacillus atrophaeus to control FCR disease in wheat in a sustainable agricultural setting.

Co-existence of two antibiotic-producing marine bacteria: Pseudoalteromonas piscicida reduce gene expression and production of the antibacterial compound, tropodithietic acid, in Phaeobacter sp.

Many bacteria co-exist and produce antibiotics, yet we know little about how they cope and occupy the same niche. The purpose of the present study was to determine if and how two potent antibiotic-producing marine bacteria influence the secondary metabolome of each other. We established an agar- and broth-based system allowing co-existence of a Phaeobacter species and Pseudoalteromonas piscicida that, respectively, produce tropodithietic acid (TDA) and bromoalterochromides (BACs). Co-culturing of Phaeobacter sp. strain A36a-5a on Marine Agar with P. piscicida strain B39bio caused a reduction of TDA production in the Phaeobacter colony. We constructed a transcriptional gene reporter fusion in the tdaC gene in the TDA biosynthetic pathway in Phaeobacter and demonstrated that the reduction of TDA by P. piscicida was due to the suppression of the TDA biosynthesis. A stable liquid co-cultivation system was developed, and the expression of tdaC in Phaeobacter was reduced eightfold lower (per cell) in the co-culture compared to the monoculture. Mass spectrometry imaging of co-cultured colonies revealed a reduction of TDA and indicated that BACs diffused into the Phaeobacter colony. BACs were purified from Pseudoalteromonas; however, when added as pure compounds or a mixture they did not influence TDA production. In co-culture, the metabolome was dominated by Pseudoalteromonas features indicating that production of other Phaeobacter compounds besides TDA was reduced. In conclusion, co-existence of two antibiotic-producing bacteria may be allowed by one causing reduction in the antagonistic potential of the other. The reduction (here of TDA) was not caused by degradation but by a yet uncharacterized mechanism allowing Pseudoalteromonas to reduce expression of the TDA biosynthetic pathway.IMPORTANCEThe drug potential of antimicrobial secondary metabolites has been the main driver of research into these compounds. However, in recent years, their natural role in microbial systems and microbiomes has become important to determine the assembly and development of microbiomes. Herein, we demonstrate that two potent antibiotic-producing bacteria can co-exist, and one mechanism allowing the co-existence is the specific reduction of antibiotic production in one bacterium by the other. Understanding the molecular mechanisms in complex interactions provides insights for applied uses, such as when developing TDA-producing bacteria for use as biocontrol in aquaculture.

Harnessing the antagonistic potential and unraveling the bioactive compounds of Streptomyces sp. isolate WAB2 to protect watermelon crop from Colletotrichum orbiculare

ABSTRACT Watermelon (Citrullus lanatus Thumb) is a significant vegetable crop globally and is prone to anthracnose disease caused by Colletotrichum spp. The use of chemical fungicides for managing crop diseases has adverse impacts on the environment and human health. Therefore, it is important to use biocontrol agents for disease management. In this study, streptomycetes were assessed as a potential biocontrol agent against anthracnose pathogen, Colletotrichum orbiculare WEC2. The potent Streptomyces sp. isolate WAB2 was isolated from healthy watermelon plants and showed remarkable antifungal efficacy against C. orbiculare WEC2. Rigorous assays confirmed its performance against C. orbiculare WEC2. Bioactive compounds produced by Streptomyces sp. isolate WAB2 were identified using Gas Chromatography–Mass Spectrometry (GC–MS). An SEM study indicated the parasitic action of Streptomyces sp. isolate WAB2 against the pathogen. The formulated talc-based product of Streptomyces sp. isolate WAB2 was effective when applied as a seed treatment + foliar spray against C. orbiculare WEC2 under pot culture conditions. These treatments reduced the disease incidence (31.81%) and exhibited a higher disease reduction (52.56%), compared to the untreated control. Therefore, treatment with talc-based Streptomyces sp. isolate WAB2 is a sustainable solution for anthracnose disease management, and it facilitates eco-friendly crop protection practices against the disease in watermelon. RESEARCH HIGHLIGHTS Isolated streptomycete strains from healthy watermelon plants and screened for its efficacy against the pathogen, Colletotrichum orbiculare WEC2. Streptomyces sp. isolate WAB2 showed significant antifungal activity against the pathogen. Bio-active compounds produced by Streptomyces sp. isolate WAB2 was identified by Gas Chromatography–Mass Spectrometry (GC–MS). Using scanning electron microscopy (SEM), the parasitic activity of Streptomyces sp. isolate WAB2 against the pathogen was detected. Developed a talc-based formulation of Streptomyces sp. isolate WAB2 and tested it as a seed treatment plus foliar spray, effectively reducing the disease incidence.

Loop-mediated isothermal amplification (LAMP) assay proved the mechanism of biological control against root rot pathogens

BackgroundThe soil-borne fungi, Rhizoctonia solani and Sclerotium rolfsii, are major pathogens of Brassicae crops. This study was performed to clarify the relationship between the accumulation pattern of the genus Trichoderma and disease suppression in frequently inoculated soils with binucleate Rhizoctonia (BNR), Rhizoctonia solani and Sclerotium rolfsii.ResultsAs compared to the control group, five Trichoderma virens strains isolated from soil inoculated with R. solani or BNR significantly reduced the severity of S. rolfsii (85.6–100% covering percentage) and R. solani (95.7–100% covering percentage). Similarly, five T. hamatum strains obtained from soil inoculated with R. solani were shown to be highly suppressive against S. rolfsii (83.9–97.1% covering percentages) and R. solani (60.2–96.2% covering percentages). Four out of five T. hamatum strains obtained from soil infected with S. rolfsii exhibited considerable suppression against S. rolfsii (63.7–91.2% covering percentages), while the SM5 strain did not. The phylogenetic analysis of the TEF and ITS regions of Trichoderma hamatum revealed that most isolates were classified into the same cluster with homology of 99–100%. Five strains of each T. virens and T. hamatum were isolated from the suppressive soil with high antagonistic potentials against R. solani and S. rolfsii. Suppression and antagonistic activity of T. hamatum isolated from soil frequently inoculated with sterile barley grains were negligible, whereas T. hamatum isolated from frequently inoculated soil with BNR and R. solani demonstrated considerable suppression of the pathogens and antagonistic activity. Accumulation and quantification of T. virens and T. hamatum were confirmed using loop-mediated isothermal amplification (LAMP).ConclusionIn conclusion, disease suppression in frequently inoculated soil with BNR, R. solani and S. rolfsii was due to Trichoderma spp. accumulated selectively in each replicate of soil inoculation.

Differential Interactions of Flavonoids with the Aryl Hydrocarbon Receptor In Silico and Their Impact on Receptor Activity In Vitro.

The molecular mechanisms underlying the observed anticancer effects of flavonoids remain unclear. Increasing evidence shows that the aryl hydrocarbon receptor (AHR) plays a crucial role in neoplastic disease progression, establishing it as a potential drug target. This study evaluated the potential of hydroxy flavonoids, known for their anticancer properties, to interact with AHR, both in silico and in vitro, aiming to understand the mechanisms of action and identify selective AHR modulators. A PAS-B domain homology model was constructed to evaluate in silico interactions of chrysin, naringenin, quercetin apigenin and agathisflavone. The EROD activity assay measured the effects of flavonoids on AHR's activity in human breast cancer cells (MCF7). Simulations showed that chrysin, apigenin, naringenin, and quercetin have the highest AHR binding affinity scores (-13.14 to -15.31), while agathisflavone showed low scores (-0.57 and -5.14). All tested flavonoids had the potential to inhibit AHR activity in a dose-dependent manner in the presence of an agonist (TCDD) in vitro. This study elucidates the distinct modulatory effects of flavonoids on AHR, emphasizing naringenin's newly described antagonistic potential. It underscores the importance of understanding flavonoid's molecular mechanisms, which is crucial for developing novel cancer therapies based on these molecules.

Root Rot Management in Common Bean (Phaseolus vulgaris L.) Through Integrated Biocontrol Strategies using Metabolites from Trichoderma harzianum, Serratia marcescens, and Vermicompost Tea

Common bean (Phaseolus vulgaris L.) is an essential food staple and source of income for small-holder farmers across Africa. However, yields are greatly threatened by fungal diseases like root rot induced by Rhizoctonia solani. This study aimed to evaluate an integrated approach utilizing vermicompost tea (VCT) and antagonistic microbes for effective and sustainable management of R. solani root rot in common beans. Fourteen fungal strains were first isolated from infected common bean plants collected across three Egyptian governorates, with R. solani being the most virulent isolate with 50% dominance. Subsequently, the antagonistic potential of vermicompost tea (VCT), Serratia sp., and Trichoderma sp. was assessed against this destructive pathogen. Combinations of 10% VCT and the biocontrol agent isolates displayed potent inhibition of R. solani growth in vitro, prompting in planta testing. Under greenhouse conditions, integrated applications of 5 or 10% VCT with Serratia marcescens, Trichoderma harzianum, or effective microorganisms (EM1) afforded up to 95% protection against pre- and post-emergence damping-off induced by R. solani in common bean cv. Giza 6. Similarly, under field conditions, combining VCT with EM1 (VCT + EM1) or Trichoderma harzianum (VCT + Trichoderma harzianum) substantially suppressed disease severity by 65.6% and 64.34%, respectively, relative to untreated plants. These treatments also elicited defense enzyme activity and distinctly improved growth parameters including 136.68% and 132.49% increases in pod weight per plant over control plants. GC–MS profiling of Trichoderma harzianum, Serratia marcescens, and vermicompost tea (VCT) extracts revealed unique compounds dominated by cyclic pregnane, fatty acid methyl esters, linoleic acid derivatives, and free fatty acids like oleic, palmitic, and stearic acids with confirmed biocontrol and plant growth-promoting activities. The results verify VCT-mediated delivery of synergistic microbial consortia as a sustainable platform for integrated management of debilitating soil-borne diseases, enhancing productivity and incomes for smallholder bean farmers through regeneration of soil health. Further large-scale validation can pave the adoption of this climate-resilient approach for securing food and nutrition security.

Salinity-induced variations in wheat biomass are regulated by the Na+:K+ ratio, root exudates, and keystone species

Salt stress can limit crop productivity, and there are differences in salt tolerance among plant varieties; however, we lack a comprehensive understanding of how keystone species obtained from different plant varieties under salt stress change plant biomass by driving root exudate secretion and regulating the Na+:K+ ratio. We conducted a pot experiment for three wheat varieties (JiMai32 (JM32), XiaoYan60 (XY60), and ShanRong3 (SR3)) under saline/nonsaline soil conditions. Salt stress tended to significantly reduce wheat biomass, and the biomass reduction rates of the different varieties decreased in the order JM32 < XY60 < SR3. The compositions of the bacterial and fungal communities in the root endosphere, rhizosphere and bulk soil were measured, and salt-induced microbial taxa were isolated to identify keystone species from the co-occurrence networks and to study their effects on physiological responses to salinity in wheat varieties. We observed that root exudates participated in the regulation of the Na+:K+ ratio, thereby affecting wheat biomass, and this process was regulated by keystone species. JM32 was enriched in microorganisms that promote plant growth and resistance to salt stress, such as Burkholderiales, Sordariomycetes, Alteromonadaceae, Acremonium, and Dokdonella, and inhibited microorganisms that are sensitive to the environment (salt, nutrients) and plant pathogens, such as Nocardioidaceae, Nitrospira, Cytophagaceae, Syntrophobacteriaceae, and Striaticonidium. XY60 inhibited microorganisms with biological control and disease inhibition potential, such as Agromyces and Kaistobacter. SR3-enriched pathogens, such as Aurantimonadaceae and Pseudogymnoascus, as well as microorganisms with antagonistic pathogen potential and the ability to treat bacterial infections, such as RB41 and Saccharothrix, were inhibited. Our results confirmed the crucial function of salt-induced keystone species in enhancing plant adaptation to salt stress by driving root exudate secretion and regulating the Na+:K+ ratio, with implications for exploring reasonable measures to improve plant salt tolerance.

Screening (ant)agonistic activities of xenobiotics on the retinoic acid receptor alpha (RARα) using in vitro and in silico analysis

Retinoic acid receptors (RARs) are known as crucial endocrine receptors that could mediate a broad diversity of biological processes. However, the data on endocrine disrupting effects of emerging chemicals by targeting RAR (ant)agonism are far from sufficient. Herein, we investigated the RARα agonistic or antagonistic activities for 75 emerging chemicals of concern, and explored their interactions with this receptor. A recombinant two-hybrid yeast assay was used to examine the RARα activities of the test chemicals, wherein 7 showed effects of RARα agonism and 54 exerted potentials of RARα antagonism. The representative chemicals with RARα agonistic activities, i.e. 4-hydroxylphenol (4-HP) and bisphenol AF (BPAF), significantly increased the mRNA levels of CRABP2 and CYP26A1, while 4 select chemicals with RARα antagonistic potentials, including bisphenol A (BPA), tetrabromobisphenol A (TBBPA), 4-tert-octylphenol (4-t-OP), and 4-n-nonylphenol (4-n-NP), conversely decreased the transcriptional levels of the test genes. The in silico molecular docking analysis using 3 different approaches further confirmed the substantial binding between the chemicals with RARα activities and this nuclear receptor protein. This work highlights the promising strategy for screening endocrine-disrupting effects of emerging chemicals of concern by targeting RARα (ant)agonism.