Endophytic Isolates Research Articles

Identification and Characterization of Endophytic Fungi from Garcinia atroviridis for Potential Antagonistic Against Phytopathogenic, Colletotrichum gloeosporioides

Biological control is referred to as the “use of natural or modified organisms, genes” to minimize the effects of undesirable pests, pathogenic microorganisms, and diseases on plant crops. This measure has become a suitable and safe alternative for chemical fungicides in plant disease management. Endophytic fungi have received much attention as biological control agents against many plant pathogens through antibiosis, parasitism, invading spores, mycelium, and cells of the pathogen, and secreting bioactive metabolites. While the therapeutic properties of Garcinia atroviridis have been studied, the existence of microbial endophytes and their properties is still less documented. In this research, G. atroviridis endophytic fungi were isolated and identified by fungal colony morphology observation combined with the PCR-amplified fungal internal transcribed spacer (ITS) sequence analyses. Fungal endophytes were assessed for their biocontrol potential against Colletotrichum gloeosporioides. In total, 111 endophytic fungal isolates harboring inside the leaf, branch, and fruit of G. atroviridis belonged to 5 different species with 3 different genera and two unidentified genera. All the endophytic fungal species isolated were evaluated using an in vitro dual culture assay against C. gloeosporioides, a common pathogen that causes anthracnose disease. The results of the present study clearly showed that seven species of isolated fungal endophytes were capable of inhibiting the mycelial colony growth of C. gloeosporioides with an inhibition percentage between 54.67% to 87.94%. Among these species, Nigrospora sphaerica recorded the highest PIRG with 87.94%. Our work indicates that endophytic fungi isolated from G. atroviridis have a biocontrol effect on C. gloeosporioides and are expected to be a potential source of bioactive metabolites.

Addition of Five Novel Fungal Flora to the Xylariomycetidae (Sordariomycetes, Ascomycota) in Northern Thailand.

The deviation of conventional fungal niches is an important factor in the implications of hidden fungal diversity and global fungal numbers. The Xylariomycetidae (Sordariomycetes, Ascomycota), which is also referred to as xylarialean taxa, has a wide range of species that demonstrate a high degree of variation in their stromatic characteristics, showing either conspicuous or inconspicuous forms. In this study, samples were collected while focusing on temporal and spatial parameters and substrate characteristics. Based on internal transcribed spacer (ITS), 28S large subunit rDNA (LSU), RNA polymerase II second largest subunit (RPB2), and β-tubulin (TUB2) multigene phylogeny and morphology, five new species are introduced as Muscodor brunneascosporus, M. lamphunensis (Xylariaceae), Nigropunctata hydei, N. saccata (Incertae sedis), and Xenoanthostomella parvispora (Gyrotrichaceae). Plant substrates in the early stages of decay and attached to the host were feasible sample niches, with an emphasis on the collection of inconspicuous, hidden xylarialean species. The appearance of inconspicuous saprobic xylarialean forms during the rainy season may be linked to the change in nutritional mode, from endophytic mode during the dry season to saprobic in the wet. Therefore, it would be fascinating to concentrate future research on how seasonal fluctuations affect nutritional mode shifts, especially in northern Thailand, which would provide the optimal spatial characteristics. In order to establish a comprehensive linkage between endophytic and saprobic modes, it is imperative to have a substantial representation of endophytic isolate sequences resembling inconspicuous xylariaceous fungi within publicly accessible databases.

Agrobacterium tumefaciens-mediated transformation of Nigrospora sp. isolated from switchgrass leaves and antagonistic toward plant pathogens

Nigrospora is a diverse genus of fungi colonizing plants through endophytic, pathogenic, or saprobic interactions. Endophytic isolates can improve growth and development of host plants, as well as their resistance to microbial pathogens, but exactly how they do so remains poorly understood. Developing a reliable transformation method is crucial to investigate these mechanisms, in particular to identify pivotal genes for specific functions that correlate with specific traits. In this study, we identified eight isolates of Nigrospora sp. internally colonizing the leaves of switchgrass plants cultivated in North Carolina. Using an Agrobacterium tumefaciens-mediated transformation approach with control and GFP-expressing vectors, we report the first successful transformation of two Nigrospora isolates. Finally, we demonstrate that wild-type and transgenic isolates both negatively impact the growth of two plant pathogens in co-culture conditions, Bipolaris maydis and Parastagonospora nodorum, responsible for the Southern Leaf Blight and Septoria Nodorum Blotch diseases, respectively. The GFP-transformed strains developed here can therefore serve as accurate reporters of spatial interactions in future studies of Nigrospora and pathogens in the plant. Finally, the transformation method we describe lays the foundation for further genetic research on the Nigrospora genus to expand our mechanistic understanding of plant-endophyte interactions.

Seasonal diversity & spaciotemporal distribution of fungal endophytes associated with the medicinal plant Coleus forskohlii Briq.

Fungi that colonize the healthy tissues of the plants without showing any disease symptoms in the host plants are termed as fungal endophytes. The presence of fungal endophytes provides a positive effect on the host’s growth & development and also triggers the production of some essential bioactive compounds in the host. This study was undertaken to isolate, identify and understand the spaciotemporal distribution and seasonal diversity of fungal endophytes associated with the leaf, stem & root of Coleus forskohlii, an important and endangered medicinal plant. Sampling was done for a period of 12 months between May 2020–April 2021. A total of 950 fungal endophytes were isolated from a total of 1680 tissues of the leaf, stem & root of C. forskohlii. The fungi were identified based on their morphological features and some of them were identified by molecular identification by 18S rRNA sequencing. The endophytic isolates belonged to 10 different orders belonging to 3 different classes-Sordariomycetes (Hypocreales, Xylariales, Microascales, Trichosphaeriales, Glomerellales & Sordariales), Dothiomycetes (Pleosporales, Capnodiales, Botryosphaeriales) & Eurotiomyctes (Eurotiales). About 81.26% of the isolates belonged to Ascomycota & 2.63% of the isolates belonged to Mucoromycota. Chaetomium globosum, Collariella bostrychodes, C. robusta, Colletotrichum gloeosporioides, Fusarium chlamydosporum, Sterile hyaline mycelia, Aspergillus niger, Xylaria curta, X. grammica, Mucor circinelloides & Trichoderma harizianum were the frequently isolated species of fungi. C. globosum, C. bostrychodes, C. gloeosporioides, sterile hyaline mycelia & X. curta were found distributed in all the tissues of the plant. C. forskohlii has thus revealed a rich diversity of fungal endophytes that could be isolated & cultured to yield some pharmacologically important bioactive compounds.

GC-MS profile of extracts of an endophytic fungus Alternaria and evaluation of its anticancer and antibacterial potentialities

Abstract Using microbial endophytes to produce bioactive compounds is a reliable scientific method. This investigation aimed to use the Acacia plant for isolating an endophytic fungal strain that has a bio-ability to produce a bio-crude extract. This study also encompassed the assessment of the extract’s biological efficacy as an antibacterial and anticancer agent. Samples of the Acacia plant were collected from “Shuaib Huraymila,” in Riyadh, Saudi Arabia. The isolation and identification of fungal endophytes was done, and then, the production of crude extract was performed using the isolated endophytes. The profile gas chromatography-mass spectroscopy of the extract was determined, followed by the assessment of its biological activity against drug-resistant infections and cancer cells through in vitro examination. The findings showed that the fungal endophyte was Alternaria (Alternaria sorghi), according to internal transcribed spacer sequencing and basic local alignment search tool analysis. The minimum inhibitory concentrations of the extract were 9.1 and 4.5 mg/mL for methicillin-resistant Staphylococcus aureus and drug-resistant Candida auris, respectively, and the IC50% values were 46.6 and 23.7 mg/mL for MCF-7 and A549, respectively. The findings showed that this strain had no antagonistic action against Culex pipiens. This study concluded that the fungal endophyte isolated from the Acacia plant has the bio-ability to produce antimicrobial and anticancer agents.

Plant-Disease-Suppressive and Growth-Promoting Activities of Endophytic and Rhizobacterial Isolates Associated with Citrullus colocynthis.

This study was conducted to investigate the antagonistic potential of endophytic and rhizospheric bacterial isolates obtained from Citrullus colocynthis in suppressing Fusarium solani and Pythium aphanidermatum and promoting the growth of cucumber. Molecular identification of bacterial strains associated with C. colocynthis confirmed that these strains belong to the Achromobacter, Pantoea, Pseudomonas, Rhizobium, Sphingobacterium, Bacillus, Sinorhizobium, Staphylococcus, Cupriavidus, and Exiguobacterium genera. A dual culture assay showed that nine of the bacterial strains exhibited antifungal activity, four of which were effective against both pathogens. Strains B27 (Pantoea dispersa) and B28 (Exiguobacterium indicum) caused the highest percentage of inhibition towards F. solani (48.5% and 48.1%, respectively). P. aphanidermatum growth was impeded by the B21 (Bacillus cereus, 44.7%) and B28 (Exiguobacterium indicum, 51.1%) strains. Scanning electron microscopy showed that the strains caused abnormality in phytopathogens' mycelia. All of the selected bacterial strains showed good IAA production (>500 ppm). A paper towel experiment demonstrated that these strains improved the seed germination, root/shoot growth, and vigor index of cucumber seedlings. Our findings suggest that the bacterial strains from C. colocynthis are suppressive to F. solani and P. aphanidermatum and can promote cucumber growth. This appears to be the first study to report the efficacy of these bacterial strains from C. colocynthis against F. solani and P. aphanidermatum.

Four new endophytic species of Diaporthe (Diaporthaceae, Diaporthales) isolated from Cameroon.

The genus Diaporthe (Diaporthaceae, Diaporthales) is a large group of fungi frequently reported as phytopathogens, with ubiquitous distribution across the globe. Diaporthe have traditionally been characterized by the morphology of their ana- and teleomorphic state, revealing a high degree of heterogeneity as soon as DNA sequencing was utilized across the different members of the group. Their relevance for biotechnology and agriculture attracts the attention of taxonomists and natural product chemists alike in context of plant protection and exploitation for their potential to produce bioactive secondary metabolites. While more than 1000 species are described to date, Africa, as a natural habitat, has so far been under-sampled. Several endophytic fungi belonging to Diaporthe were isolated from different plant hosts in Cameroon over the course of this study. Phylogenetic analyses based on DNA sequence data of the internal transcribed spacer region and intervening 5.8S nrRNA gene, and partial fragments of the calmodulin, beta-tubulin, histone and the translation elongation factor 1-α genes, demonstrated that these isolates represent four new species, i.e. D.brideliae, D.cameroonensis, D.pseudoanacardii and D.rauvolfiae. Moreover, the description of D.isoberliniae is here emended, now incorporating the morphology of beta and gamma conidia produced by two of our endophytic isolates, which had never been documented in previous records. Moreover, the paraphyletic nature of the genus is discussed and suggestions are made for future revision of the genus.

An endophytic Paenibacillus polymyxa hg18 and its biocontrol potential against Fusarium oxysporum f. sp. cucumerinum

Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum is a serious fungal, soil-borne disease that has a dramtic negative impact on the yield and quality of cucumber. In this study, isolates of endophytic bacteria isolated from healthy cucumber plants were evaluated for their ability to inhibit Fusarium wilt. Results indicated that 6 out of 100 of the obtained endophytic bacterial isolates exhibited significant inhibitory activity against mycelial development of F. oxysporum f. sp. cucumerinum, with an inhibition rate > 60 % in dual culture assays. Among the active isolates, strain hg18 exhibited the strongest activity with a 69.57 % rate of inhibition. Strain hg18 was identified as Paenibacillus polymyxa based on morphological, physiological, and biochemical traits, as well as a phylogenetic tree that was constructed using 16S rRNA and rpoB gene sequences. Biological and PCR assays demonstrated that strain hg18 can secrete IAA, a siderophore, hydrolytic enzymes, including protease, cellulase and glucanase, and antimicrobial compounds, such as iturin, fengycin, and non-ribosomal polypeptide synthase, as well as fix nitrogen. Strain hg18 decreased the disease index of cucumber Fusarium wilt and promoted cucumber growth in non-diseased plants in greenhouse experiments, compared to a water treatment. These findings demonstrate the potential of using P. polymyxa hg18 as a biocontrol agent for controlling Fusarium wilt in cucumber.

Hormesis of glyphosate on ferulic acid metabolism and antifungal volatile production in rice root biocontrol endophyte Burkholderia cepacia LS-044

Glyphosate (GP, N-phosphonomethyl glycine) is one of the most popular organophosphate herbicides widely used in agricultural practices worldwide. There have been extensive reports on the biohazard attributes and hormetic impacts of GP on plant and animal systems. However, the effects of GP on plant growth-promoting microbes and its ecological relevance remain unknown. Here, we show that GP does exert a hormetic impact on Burkholderia cepacia LS-044, a rice (Oryza sativa ssp. japonica cv. Tainung 71) root endophytic isolate. We used increasing doses of ferulic acid (FA, 1–25 mM) and GP (0.5–5 mM) to test the growth and antifungal volatile production in LS-044 by electrochemical, liquid chromatographic, gas chromatographic and spectrophotometric means. GP treatment at a low dose (0.5 mM) increased FA utilization and significantly (P < 0.0001) enhanced antifungal volatile activity in LS-044. Although FA (1 mM) was rapidly utilized by LS-044, no chromatographically detectable utilization of GP was observed at tested doses (0.5–5 mM). LS-044 emitted predominant amounts of tropone in addition to moderate-to-minor amounts of diverse ketones and/or their derivatives (acetone, acetophenone, 2-butanone, 1-propanone, 1-(2-furanyl-ethanone, 1-phenyl-1-propanone and 1-(3-pyridinyl)-1-propanone), d-menthol, 2-methoxy-3-(1-methylethyl)-pyrazine, dimethyl disulfide, pyridine and ammonium carbamate when grown under GP supplement. GP hormesis on LS-044 induced phenotypic variations in O. sativa ssp. japonica cv. Tainan 11 as evident through seed germination assay. Genes involved in the transformation of FA, and a key gene encoding 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) with Gly-94 and Tyr-95 residues localized at active site most likely rendering EPSPS sensitivity to GP, were detected in LS-044. This is the first report on the GP hormesis influencing morphological and metabolic aspects including volatile emission in a biocontrol bacterium that could modulate rice plant phenotype.

Inhibition of microbial pathogens and toxicity assessment of noformicin synthesized by Psychrobacter faecalis: An endophyte of Averrhoa carambola

Plants are known to harbor endophytic microbes which primarily reside in tissues beneath the epidermal cells. The current study was focused on exploring the endophytic bacteria of Averrhoa carambola for antimicrobial activity. The metabolites of endophytic isolate VITPMJ7 were found to be effective in cross streak method (antagonistic activity) as it inhibited the growth of Bacillus cereus and Escherichia coli. Furthermore, the effective isolate was fermented and chloroform extract showed antibacterial activity in the well diffusion method against E. coli, B. cereus and Staphylococcus aureus. Chloroform extract was fractionated and the lead molecules were obtained using solid phase extraction column (SPE) and Ultra performance liquid chromatography (UPLC). The purified lead molecule that showed inhibitory effects was identified to be noformicin by GC-MS. The presence of various functional groups such as amine, thiol, alcohol, alkene, sulfoxide identified by FT-IR supported and confirmed the lead molecule to be noformicin. The isolate VITPMJ7 capable of producing the lead compound was identified to be Psychrobacter faecalis by 16 S rRNA gene sequencing. Toxicity assessment of the metabolites in seed germination assay with Vigna radiata, Vigna mungo and Cajanus cajan revealed the non-toxic nature of the compounds.

One stone for two birds: Endophytic fungi promote maize seedlings growth and negatively impact the life history parameters of the fall armyworm, Spodoptera frugiperda.

The fall armyworm (FAW) Spodoptera frugiperda, is a voracious pest of cereals native to the Americas and which invaded Africa in 2016. Chemical control is the main management option, which however remains ineffective and unsustainable. Fungal endophytes are increasingly used as alternative for the management of insect pests of economic importance. This study assessed the potential of eight endophytic fungal isolates to colonize maize plant and their ability to promote seedlings growth through seed and foliar inoculations, as well as their suppressive effects on FAW. Fungal colonization rates of different plant parts by the endophytes varied as per the inoculation methods. Beauveria bassiana ICIPE 279 colonized more than 60% of all the seedling parts while B. bassiana G1LU3 only colonized stem (25%) and leaf (5%) tissues through foliar inoculation. Trichoderma atroviride F2S21, T. asperellum M2RT4, T. harzianum F2R41, Trichoderma sp. F2L41, Hypocrea lixii F3ST1 and Fusarium proliferatum F2S51 successfully colonized all the plant parts and therefore were selected and further evaluated through seed inoculation for their endophytic persistence, effect on plant growth, and pathogenicity to Spodoptera frugiperda immature and adult stages. Weekly assessment showed varied effect of the endophytes on maize plant growth parameters compared to the control. During the first week, percentage colonization of the plant parts ranges between 90%-100%, 65%-100%, and 60%-100%, in the roots, stems, and leaves, respectively for all the five tested isolates. However, the colonization pattern/rates significantly decreased over time for H. lixii F3ST1 in the stems and leaves, and for T. harzianum F2R41 in the leaves and for T. asperellum M2RT4 in the roots. In addition, T. harzianum F2R41 outperformed all the other isolates in boosting the plant height, whereas H. lixii F3ST1 and T. asperellum M2RT4 outperformed all the other isolates in increasing the wet and dry shoots weight. Furthermore, the number of egg masses laid on endophytically-colonized maize plants varied among the treatments. Trichoderma asperellum M2RT4 and H. lixii F3ST1 endophytically-colonized maize plants significantly reduced the number of egg masses and the defoliation/feeding rates of the pest compared to the control. Additionally, T. harzianum F2R41 had the highest negative impact on the pupation and adult emergence of S. frugiperda with a female-biased sex ratio. Our findings indicate that T. asperellum M2RT4, T. harzianum F2R41, and H. lixii F3ST1 hold a potential to be developed as endophytic-fungal-based biopesticides for sustainable management of S. frugiperda and as plant growth promoters.

Endophytic Bacillus aerophilus from the Leaves of Azadirachta indica as a Potential Biocontrol against Staphylococcus aureus

Aims: The study entailed isolation and identification of Bacillus aerophilus in the leaves of young Azadirachta indica plants, establishing the antimicrobial activity of the endophyte against Staphylococcus aureus, and screening for phytochemicals. The study investigated the potential of the endophytic Bacillus aerophilus in pathogen inhibition and phytochemical screening for bioactive compounds produced by the endophyte that can be used in drug development. The research contributes to the wider scientific goal of curbing rising cases of antibiotic resistance.&#x0D; Place and Duration of Study: Sample: collected from Kanyonyoo in Kitui County, between August 2022 and June 2023.&#x0D; Methodology: The bacteria were aseptically isolated and sub-cultured on nutrient agar. For identification, the bacteria underwent biochemical tests and molecular characterization. The 16S rRNA region was amplified and sequenced using universal primers 27F and 1492R. Bacterial isolate K1L003 was identified as Bacillus aerophilus. For antimicrobial testing, the agar disk diffusion method was used against pathogenic Staphylococcus aureus on Mueller Hinton Agar plates (MHA). The controls were doxycycline and vancomycin.&#x0D; Results: The endophytic isolate only inhibited Staphylococcus aureus (P &lt; .001), with an inhibition mean similar to doxycycline (26 mm), against the pathogen. The endophytic isolate produced terpenoids, saponins, alkaloids, and flavonoids.&#x0D; Conclusion: Endophytic Bacillus aerophilus has better antimicrobial inhibition potential than vancomycin, against Staphylococcus aureus and produces diverse bioactive secondary metabolites. The endophyte has the potential to produce compounds that are useful in treating drug-resistant Staphylococcal infections.

Detection of bacterial pathogen on corn plants and test the potential of endophytic microbes to controlling stewart wilt disease in vitro

The use of synthetic pesticides to increase maize production sustainably contributes to increasing the development of pathogens and tends to be less effective in environmental conditions that support pathogens. In addition, the emergence of environmental pollution due to the use of chemicals causes the need for environmentally-friendly control technologies. Endophytic microbes are biological agents that can be used to plant disease control that is environmentally friendly and practical in their application. The study aimed to detect pathogenic bacteria that cause wilt and blight in maize and then examine the potential of several endophytic microbial isolates in controlling Stewart wilt pathogens in maize in vitro. The research was carried out from February to July 2021 at the Cereal Crop Research Institute Laboratory in Maros for morphological identification and microbial potential testing, while serological tests were carried out at the Makassar Plant Quarantine Laboratory, South Sulawesi. The study began with detecting pathogenic bacteria serologically using the Enzyme-Linked Immunosorbent Assay (ELISA) method. The results showed that blight symptoms on corn isolated from the experimental garden of IP2TP Bajeng Gowa Regency PS-4 and PS-5 were detected as bacteria Pantoea stewartii subsp. stewartii. The antagonistic test of endophytic bacterial isolates I.A1, II.D1, III.A2, IV.B2, and endophytic fungi isolates AC-1, AC-3, and DC-5 was able to suppress the growth of pathogenic bacteria isolates PS-4 and PS-5 The growth suppression of pathogenic bacteria was observed by forming inhibitory zones of antibiosis compounds. Pathogenic bacteria Pantoea stewartii subsp. stewartii can be controlled using endophytic microbes.

In vitro antagonism test of endophytic isolates from the ciplukan plant (Physalis angulata L.) against Ralstonia solanacearums

Ralstonia solanacearum was a pathogenic bacteria that causes wilt disease which can cause up to one hundred percent damage to horticultural plants. Therefore, a control effort was needed to overcome this problem. The use of pesticides was an alternative that can be used to suppress the growth of the pathogen R. solanacearum. However, its continuous use poses a high risk to the environment so friendly and safe control efforts are needed. One way was by utilizing endophytic bacteria. This study aims to test the ability of endophytic bacterial isolates from ciplukan plant (Physalis angulata L.) to suppress the growth of the pathogenic bacteria R. solanacearum in vitro. The method in this research includes rejuvenating endophytic bacterial isolates BA2(3), BA3(1), DA1(4) and BU3(5) from ciplukan plants (Physalis angulata L.) obtained from research conducted by Setianah (2020), observations macroscopic and microscopic endophyte isolates, hypersensitivity test of endophytic bacteria on tobacco plants (Nicotiana tabacum L.), then continued with an in vitro antagonist test using the Kirby Baurer technique. Research data shows that of the four candidates, two isolates of endophytic bacteria, namely BA2(3) and BU3(5), showed a negative hypersensitivity reaction which was characterized by the absence of necrosis symptoms in the hypersensitivity test, so these isolates could be tested for antagonists. The results of the antagonist test showed that isolates BA2(3) and BU3(5) had the potential to inhibit the growth of R. solanacearum which had an inhibitory diameter of 3.03 mm and 1.60 mm in the first 24 hours of incubation. It is hoped that the ability of endophyte isolates BA2(3) and BU3(5) to inhibit the growth of the pathogen R. solanacearum can be used as a biological agent to reduce the use of pesticides in treating plant diseases.

Exploring the potential of halotolerant bacteria from coastal regions to mitigate salinity stress in wheat: physiological, molecular, and biochemical insights.

Salinity stress, a significant global abiotic stress, is caused by various factors such as irrigation with saline water, fertilizer overuse, and drought conditions, resulting in reduced agricultural production and sustainability. In this study, we investigated the use of halotolerant bacteria from coastal regions characterized by high salinity as a solution to address the major environmental challenge of salinity stress. To identify effective microbial strains, we isolated and characterized 81 halophilic bacteria from various sources, such as plants, rhizosphere, algae, lichen, sea sediments, and sea water. We screened these bacterial strains for their plant growth-promoting activities, such as indole acetic acid (IAA), phosphate solubilization, and siderophore production. Similarly, the evaluation of bacterial isolates through bioassay revealed that approximately 22% of the endophytic isolates and 14% of rhizospheric isolates exhibited a favorable influence on seed germination and seedling growth. Among the tested isolates, GREB3, GRRB3, and SPSB2 displayed a significant improvement in all growth parameters compared to the control. As a result, these three isolates were utilized to evaluate their efficacy in alleviating the negative impacts of salt stress (150 mM, 300 mM, and seawater (SW)) on the growth of wheat plants. The result showed that shoot length significantly increased in plants inoculated with bacterial isolates up to 15% (GREB3), 16% (GRRB3), and 24% (SPSB2), respectively, compared to the control. The SPSB2 strain was particularly effective in promoting plant growth and alleviating salt stress. All the isolates exhibited a more promotory effect on root length than shoot length. Under salt stress conditions, the GRRB3 strain significantly impacted root length, leading to a boost of up to 6%, 5%, and 3.8% at 150 mM, 300 mM, and seawater stress levels, respectively. The bacterial isolates also positively impacted the plant's secondary metabolites and antioxidant enzymes. The study also identified the WDREB2 gene as highly upregulated under salt stress, whereas DREB6 was downregulated. These findings demonstrate the potential of beneficial microbes as a sustainable approach to mitigate salinity stress in agriculture.

Exploring the mechanisms of endophytic bacteria for suppressing early blight disease in tomato (Solanum lycopersicum L.).

Controlling early blight of tomatoes using endophytic bacteria is an eco-friendly and sustainable approach to manage this common fungal disease caused by Alternaria solani, Alternaria alternata, and Curvularia lunata. Endophytic bacteria are microorganisms that live inside plant tissues without causing harm and can help protect the host plant from pathogens. In this work, twenty endophytic bacterial isolates from tomato healthy plants were tested against pathogenic fungal isolates that caused early blight disease in vitro. Out of the 20 tested isolates, three (B4, B7, and B17) were considered effective isolates against the growth of fungal pathogens. The three isolates were recognized as Enterobacter cloacae HS-6 (B4), Pseudomonas gessardii HS-5 (B 7), and Pseudomonas mediterranea HS-4 (B17) using 16s-rDNA sequencing. Different concentrations of bacterial cultural diltrates at 20, 40, and 60% were tested for their antagonistic effects on the development of pathogenic fungi in vitro. The lowest dry weights of pathogenic isolates in all bacterial culture filtrates were discovered at 60%. In all culture filtrates, phenolic compounds showed the largest peak area. Under greenhouse conditions, the least disease severity of tomato early blight was found for E. cloacae and its culture filtrate compared to other treatments. Real-time PCR was used to examine the expression pattern of the defense response gene β-1.3 glucanase gene in infected tomato plants with pathogenic fungi (control) as well as its relations with efficient biocontrol agent (E. cloacae). The expression of the gene increased substantially and significantly after three days from the inoculation-infected plants with C. lunata and E. cloacae while it reached the maximum after five days from the inoculation with A. alternata, A. solani and E. cloacae. Our study concluded that the endophytic bacterial isolate E. cloacae can be considered a promising biocontrol agent for preventing tomato early blight.

Isolation and Characterization of Fungal Endophytes from Petiveria alliacea and Their Antimicrobial Activities in South Florida

Microorganisms associated with medicinal plants are of great interest as they are the producers of important bioactive compounds effective against common and drug-resistant pathogens. The characterization and biodiversity of fungal endophytes of the Petiveria alliacea plant and their antimicrobial production potential are of great interest as they are known for their antimicrobial and anticancer properties. In this study, we investigated the endophytic fungal microbiome associated with P. alliacea, and the endophytic fungal isolates were classified into 30 morphotypes based on their cultural and morphological characteristics. Ethyl acetate extract of fungal endophytes was obtained by liquid–liquid partitioning of culture broth followed by evaporation. The crude extract dissolved in dimethyl sulfoxide was screened for antimicrobial activity against three bacterial strains (Escherichia coli ATTC 25902, Staphylococcus aureus ATTC 14775, Bacillus subtilis NRRL 5109) and two fungal strains (Candida albicans ATTC 10231 and Aspergillus fumigatus NRRL 5109). Among the crude extracts from endophytes isolated from leaves, 65% of them showed antimicrobial activity against the bacteria tested. Similarly, 71 and 88% of the fungal crude extracts from endophytes isolated from root and stem, respectively, showed inhibitory activities against at least one of the bacterial strains tested. Crude extracts (at a concentration of 10 mg/mL) from ten of the fungal isolates have shown a zone of inhibition of more than 12 mm against both Gram-positive and negative bacteria tested. Sequenced data from isolates showing strong inhibitory activity revealed that Fusarium solani, F. proliferatum, and Fusarium oxysporium are the major endophytes responsible for bioactive potential. These results indicate that Petiveria alliacea harbors fungal endophytes capable of producing antimicrobial metabolites. Future studies need to focus on testing against drug-resistant bacteria (ESKAPE group) and other pathogenic bacteria and fungi.

Antibacterial Activities of Fungal Endophytes from Philippine Endemic Plant Dillenia philippinensis

Fungal endophytes represent a group of microorganisms that establish symbiotic associations with plants and hold significant ecological importance. Their ability to produce a diverse array of biologically active secondary metabolites has garnered considerable interest in the search for novel drug leads. In this study a total of 33 fungal endophytes were isolated from leaf specimens of the Philippine endemic tree Dillenia philippinensis (Rolfe). The morphological characterization of the fungal isolates revealed their taxonomic affiliation with the following eight genera: Alternaria sp., Aspergillus sp., Geotrichum sp., Guignardia sp., Nigrospora sp., Paecilomyces sp., Pestalotiopsis sp., and Phialophora sp. A representative set of 22 fungal endophyte isolates was selected from the pool of isolates and subjected to large-scale cultivation, followed by extraction of their bioactive metabolites through liquid-submerged fermentation. The resulting crude extracts were evaluated for their inhibitory potential against two Gram-positive bacteria, namely Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA); and two Gram-negative bacteria, namely Escherichia coli and Multi-drug resistant Pseudomonas aeruginosa (MRPA), using the disc diffusion assay. The results indicate that the crude extracts obtained from endophytic fungi colonizing D. philippinensis represent a promising source of bioactive metabolites that exhibit noteworthy inhibitory activity against S. aureus, E. coli, and MRSA, with an effective concentration of 10 mg/mL. This study demonstrates that the fungal endophytes associated with Dillenia philippinensis foliage represent a rich source of bioactive metabolites with significant inhibitory activity against Gram-positive and Gram-negative bacteria. These lead to exploring the potential of these fungal endophytes as a viable source of novel therapeutics.

Seed Microbiolization Associate With Nitrogen Doses Increase the Nutrition of Tomato Fruits

Endophytic bacteria can promote growth and improve the quality of plant production. The objective of this work was to evaluate the efficiency of inoculation of a mix of non-host endophytic bacteria isolates in the nutrition of tomato fruits cultivated, fertilized with rock powder and different doses of nitrogen. The experimental design was in randomized blocks, in a factorial arrangement (2 &amp;times; 6 + 3), with four replications. The treatments consisted of two methods of inoculation of the mix of endophytic bacteria: seed microbiolization and post-emergence inoculation; six doses of nitrogen fertilization: 0, 129, 258, 387, 516 and 645 kg ha-1; and 3 controls (without inoculation of the bacterial mix). The average export of macro and micronutrients in tomato fruits was, in descending order: K &amp;gt; N &amp;gt; P &amp;gt; Ca &amp;gt; Mg &amp;gt; S (averages of 1.33; 0.46; 0.07; 0.06; 0.05 and 0.05 g plant-1, respectively) and Mn &amp;gt; Cu &amp;gt; Fe &amp;gt; Zn (means of 2.67; 1.98; 1.71 and 0.79 mg plant-1, respectively). The inoculation method by seed microbiolization associated with nitrogen doses promoted significant increment in the dry mass of the fruits and in the content of the nutrients P, Ca, Zn, Fe and Mn.

Role of Bacillus spp. Plant Growth Promoting Properties in Mitigating Biotic and Abiotic Stresses in Lowland Rice (Oryza sativa L.).

The ability of microorganisms to promote plant growth and mitigate abiotic and biotic stresses makes them an interesting tool for sustainable agriculture. Numerous studies aim to identify new, promising bacteria isolates. Traditional culture-based methods, which focus on selecting microorganisms with plant-growth-promoting traits, such as hormone production, nutrient solubilization, and antifungal properties, are widely used. This study aims to investigate the role of plant-growth-promoting properties in bacteria-mediated stress mitigation and the suitability of traditional culture-based methods as a screening tool for the identification of beneficial bacteria. To this end, we tested three endophytic Bacillus isolates, which have previously been shown to affect tolerance against iron toxicity in lowland rice, (a) for their effect on the resistance against brown spot disease, and (b) for plant-growth-promoting traits using common culture-based methods. Both B. pumilus isolates inhibited fungal growth in vitro and reduced brown spot disease in two of three rice cultivars in planta, although they tested negative for all plant-growth-promoting traits. While B. megaterium was negative for ACC deaminase activity and nutrient solubilization, it exhibited auxin production. Nevertheless, B. megaterium did not suppress brown spot disease in any of the three rice cultivars. This study shows that bacteria do not necessarily have to possess classical plant-growth-promoting properties in order to be beneficial to plants, and it emphasizes the limitation of common culture-based methods in effectively identifying beneficial bacteria. Moreover, our results highlight the significance of the interaction between bacteria and plant cultivars in determining the beneficial effects of Bacillus spp. on plants under biotic or abiotic stresses.