Endophytic Organisms Research Articles

Distribution of Plasmopara viticola Causing Downy Mildew in Russian Far East Grapevines

Downy mildew is a severe disease that leads to significant losses in grape yields worldwide. It is caused by the oomycete Plasmopara viticola. The study of the distribution of this agent and the search for endophytic organisms that inhibit the growth of P. viticola are essential objectives to facilitate the transition to sustainable and high-yield agriculture, while respecting the environment. In this study, high-throughput sequencing of the ITS (ITS1f/ITS2 region) and 16S (V4 region) amplicons was employed to analyze 80 samples of leaves and stems from different grapevine species and cultivars grown in the Russian Far East (Vitis amurensis Rupr., Vitis coignetiae Pulliat, and several grapevine cultivars). The analysis revealed the presence of P. viticola in 53.75% of the grape samples. The pathogen P. viticola was not detected in V. amurensis samples collected near Vladivostok and Russky Island. Among the P. viticola-affected samples, only two (out of the eighty analyzed grape samples) from the Makarevich vineyard in Primorsky Krai exhibited disease symptoms, while the majority appeared visually healthy. We also found six distinct P. viticola ASVs in our metagenomic data. Based on phylogenetic analysis, we hypothesize that the P. viticola population in the Russian Far East may have originated from the invasive P. viticola clade aestivalis, which has spread around the world from North America. To identify putative microbial antagonists of P. viticola, a differential analysis of high-throughput sequencing data was conducted using the DESeq2 method to compare healthy and P. viticola-affected samples. The in silico analysis revealed an increased representation of certain taxa in healthy samples compared to P. viticola-affected ones: fungi—Kabatina sp., Aureobasidium sp., and Vishniacozyma sp.; bacteria—Hymenobacter spp., Sphingomonas spp., Massilia spp., Methylobacterium-Methylorubrum spp., and Chryseobacterium spp. This in-silico-obtained information on the potential microbial antagonists of P. viticola serves as a theoretical basis for the development of biocontrol agents for grapevine downy mildew.

Screening of salt tolerant endophytic bacteria with plant growth promoting characters isolated from Acanthus ilicifolius L., a species of mangrove ecosystem located at Corangi wildlife sanctuary, Andhra Pradesh

Mangroves harbour many beneficial microorganisms in their rhizosphere, phyllosphere and endophytically, which forms an ideal ecological habitation for isolating halotolerant endophytic bacteria with unique characteristics. Endophytes can produce numerous bioactive secondary metabolites and phytohormones, which may be directly or in some way beneficial to the host plant. The present study aimed to identify novel endophytes capable of producing plant growth-promoting substances. The mangrove plants Acanthus ilicifolius L. at Corangi Wildlife Sanctuary were selected, and their leaves and roots were collected for endophyte isolation. Eight isolates from the leaves and roots were collected, purified and preserved. All these isolates were subjected to morphological, phenotypical and biochemical studies. Isolates were grown best at 3% NaCl nutrient agar and could tolerate salinity upto 8%NaCl. Most of them could grow upto 42°C. The majority were gram’s positive, motile, aerobic, rod-shaped and some were gram’s negative, rod-shaped organisms. Many of the endophytic organisms had the ability to synthesize Indole-3-acetic acid(IAA) varied from 0.7 µg/ml (AIL1) to 51.0 µg/ml (AIL2) and the highest phosphate solubilizing ability was recorded with AIR3 (3.71 ppm) followed by AIR4 (3.00 ppm) and lowest was recorded by AIL4 (1.80 ppm). Among total isolates, AIL2 (51µg/ml) showed promising potential in producing IAA and had phosphate solubilization ability. Based on 16S ribosomal RNA molecular method the isolate AIL2 was identified as Bacillus altitudinis. This is the first to report that B.altitudinis strain AIL2 isolated from A.ilicifolius L. could produce IAA, which can be used as a bioinoculant in agriculture and allied sector.

PHYTOCHEMICAL ANALYSIS AND MOLECULAR CHARACTERIZATION OF MORINGA OLEIFERA AND ITS ENDOPHYTIC FUNGI

Objective: Moringa oleifera Lam (Moringaceae) is a highly valued plant which has an impressive range of medicinal uses with high nutritional value. Different parts of the plant were being used for the treatment of illness due to the presence of various secondary metabolites that gives the plant anti-bacterial, anti-oxidant and other properties. These secondary metabolites are synthesized by endophytic organisms, which are present inside the tissues of plant. Methods: ITS regions were amplified using a polymerase chain reaction for molecular identification. The sequences were analysed using BLAST n and DNA barcoding of plant was done for the identification of species. The organisms were refined on Potato Dextrose stock for identification of metabolites. Results: It was found that fungi obtained are Aspergillus fumigatus and Tricoderma turrialbense with percentage identity of 96% and 98%, respectively, as obtained from NCBI BLAST; the metabolites were extracted with ethanol extract and Flavonoids and terpenoids are the main phytoconstituents present in endophytic fungi. Conclusion: The results obtained support the medicinal properties of plant, which gets enhanced due to the presence of endophytic fungi present in them.

Chemical and Biological Studies of Endophytes Isolated from Marchantia polymorpha.

Natural bioresources, predominantly plants, have always been regarded as the richest source of drugs for diseases threatening humanity. Additionally, microorganism-originating metabolites have been extensively explored as weapons against bacterial, fungal, and viral infections. However, the biological potential of metabolites produced by plant endophytes still remains understudied, despite significant efforts reflected in recently published papers. Thus, our goal was to evaluate the metabolites produced by endophytes isolated from Marchantia polymorpha and to study their biological properties, namely anticancer and antiviral potential. The cytotoxicity and anticancer potential were assessed using the microculture tetrazolium technique (MTT) against non-cancerous VERO cells and cancer cells-namely the HeLa, RKO, and FaDu cell lines. The antiviral potential was tested against the human herpesvirus type-1 replicating in VERO cells by observing the influence of the extract on the virus-infected cells and measuring the viral infectious titer and viral load. The most characteristic metabolites identified in the ethyl acetate extract and fractions obtained by use of centrifugal partition chromatography (CPC) were volatile cyclic dipeptides, cyclo(l-phenylalanyl-l-prolyl), cyclo(l-leucyl-l-prolyl), and their stereoisomers. In addition to the diketopiperazine derivatives, this liverwort endophyte also produced arylethylamides and fatty acids amides. The presence of N-phenethylacetamide and oleic acid amide was confirmed. The endophyte extract and isolated fractions showed a potential selective anticancer influence on all tested cancer cell lines. Moreover, the extract and the first separated fraction noticeably diminished the formation of the HHV-1-induced cytopathic effect and reduced the virus infectious titer by 0.61-1.16 log and the viral load by 0.93-1.03 log. Endophytic organisms produced metabolites with potential anticancer and antiviral activity; thus, future studies should aim to isolate pure compounds and evaluate their biological activities.

Microbial endophytes: application towards sustainable agriculture and food security.

Microbial endophytes are ubiquitous and exist in each recognised plant species reported till date. Within the host plant, the entire community of microbes lives non-invasively within the active internal tissues without causing any harm to the plant. Endophytes interact with their host plant via metabolic communication enables them to generate signal molecules. In addition, the host plant's genetic recombination with endophytes helps them to imitate the host's physicochemical functions and develop identical active molecules. Therefore, when cultured separately, they begin producing the host plant phytochemicals. The fungal species Penicillium chrysogenum has portrayed the glory days of antibiotics with the invention of the antibiotic penicillin. Therefore, fungi have substantially supported social health by developing many bioactive molecules utilised as antioxidant, antibacterial, antiviral, immunomodulatory and anticancerous agents. But plant-related microbes have emanated as fountainheads of biologically functional compounds with higher levels of medicinal perspective in recent years. Researchers have been motivated by the endless need for potent drugs to investigate alternate ways to find new endophytes and bioactive molecules, which tend to be a probable aim for drug discovery. The current research trends with these promising endophytic organisms are reviewed in this review paper. KEY POINTS: • Identified 54 important bioactive compounds as agricultural relevance • Role of genome mining of endophytes and "Multi-Omics" tools in sustainable agriculture • A thorough description and graphical presentation of agricultural significance of plant endophytes.

Does Abiotic Host Stress Favour Dothideomycete-Induced Disease Development?

Dothideomycetes represent one of the largest and diverse class of fungi. This class exhibits a wide diversity of lifestyles, including endophytic, saprophytic, pathogenic and parasitic organisms. Plant pathogenic fungi are particularly common within the Dothideomycetes and are primarily found within the orders of Pleosporales, Botryosphaeriales and Capnodiales. As many Dothideomycetes can infect crops used as staple foods around the world, such as rice, wheat, maize or banana, this class of fungi is highly relevant to food security. In the context of climate change, food security faces unprecedented pressure. The benefits of a more plant-based diet to both health and climate have long been established, therefore the demand for crop production is expected to increase. Further adding pressure on food security, both the prevalence of diseases caused by fungi and the yield losses associated with abiotic stresses on crops are forecast to increase in all climate change scenarios. Furthermore, abiotic stresses can greatly influence the outcome of the host-pathogen interaction. This review focuses on the impact of abiotic stresses on the host in the development of diseases caused by Dothideomycete fungi.

Endophytic fungi of Brunfelsia uniflora: isolation, cryopreservation, and determination of enzymatic and antioxidant activity.

Brunfelsia uniflora (Pohl.) D. Don (Solanaceae), commonly known as manacá-de-cheiro, is widely distributed in Brazil and used by local indigenous peoples as an antirheumatic, antisyphilitic, depurative, emetic, vermifuge, and purgative agent. Several studies have examined the biological activities and phytochemical profile of Brunfelsia; however, few have focused on the diversity of endophytic microorganisms that colonize members of the genus. This study aimed to isolate and cryopreserve endophytic fungi from B. uniflora and determine their cellulase, laccase, and antioxidant activities. Endophytic fungi were isolated from B. uniflora stems, cultured on wheat grains, immersed in a 150gL-1 aqueous sucrose solution, and cryopreserved at -80°C for 1 and 6months. Cellulase activity was determined by a qualitative test using carboxymethylcellulose medium and laccase activity by a quantitative test based on the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate). Prior to antioxidant activity assays, fungi were grown in malt extract broth for production of mycelial biomass. A methanolic extract was prepared for evaluation of DPPH· scavenging activity, FRAP activity, and total phenolic content. A total of 46 endophytic fungal isolates were obtained from B. uniflora stems and classified into 24 groups according to morphological similarities. B. uniflora was shown to harbor different genera of ascomycete fungi as endophytic organisms. Mycelial viability was observed after 1 and 6months of cryopreservation at - 80°C. Fungi exhibited cellulase and laccase activities. Isolate CE23 had the highest laccase activity after 7days of cultivation. Twelve isolates were found to have low total phenolic contents and DPPH· and FRAP activities.

Endophytic isolates of Bacillus subtilis: prospects of application for improving the quality of food raw materials

Endophytic microorganisms are most closely in contact with agricultural plants, inhabit their internal tissues, provide protection from pathogens, and have a direct impact on plant health and productivity. This is the relevance of studying the properties of endophytic organisms for the regulation of population density of pathogenic micromycetes. In this work, a comparative assessment of the antifungal activity of endophytic isolates B. subtilis EFS3, B. subtilis EFS9, B. subtilis EFS13 was carried out with respect to field isolates of microscopic fungi of the genera Fusarium, Aspergillus, Penicillium, Mucor. The studied endophytic bacilli inhibited the growth of micromycetes both due to the antibiotic substances produced and by direct contact, i.e., antibiotic and alimentary types of antagonism were noted in the mechanism of antifungal action. Thus, the studied endophytic bacteria are able to influence the development of pathogenic fungi and can be used to develop biological products that contribute to improving the quality of food raw materials of plant origin.

Soil and microbe interactions in two populations of Appalachian black cohosh (Actaea racemosa L.)1

Soil and whole plant samples were collected from two natural populations of Appalachian black cohosh (Actaea racemose L.) to assess soil-plant-microbe interactions and determine seasonal mineral acquisition by the species. A. racemosa is one among medicinal forest plants subject to excessive harvesting, and there is increasing concern over the sustainability of natural populations. Following standard procedures, mineral content and chemistry of soils sampled from the two sites were determined, and monthly (May to August) A. racemosa root, stem, and leaf mineral content were analyzed. Fresh tissue samples were processed for isolation and genotyping of associated endophytic organisms, and classical root staining was used to assess presence and extent of the arbuscular mycorrhizal (AM) symbiosis. Results showed that forest soils in the natural habitat of A. racemosa are slightly acidic (pH 4.5–6.0; 40–70% base saturation) with high organic matter (6–25%) and microelement content. Significant (P ≤ 0.05) variation was observed in seasonal concentration of key elements in leaf, stem, and root samples, with high levels of iron (Fe), aluminum (Al), manganese (Mn), and zinc (Zn) sequestered in root tissues. Root colonization by AM fungi was found to be high (85–100%) at both locations throughout the sampling period. A total of 22 fungal and 24 bacterial endophytes were isolated from A. racemosa root, shoot, and flower organs. Molecular characterization revealed bacterial isolates to be primarily Bacillus, Pseudomonas, and Serratia spp., whereas fungal isolates included Alternaria, Cadophora, Diaporthe, Penicillium, and Volutella spp. We conclude that potential exists for managed cultivation of black cohosh in arable land. Further, our findings confirm endophytic (mycorrhizal and nonmycorrhizal) associations in A. racemosa. We believe associated organisms could play a role in the adaptation of A. racemosa to the Appalachian ecosystem and recommend further examination of these relationships.

Drought-tolerant and plant growth-promoting endophytic Staphylococcus sp. having synergistic effect with silicate supplementation.

Endophytic bacteria have been reported to have symbiotic, mutualistic, commensalistic or trophobiotic relationships with various plant parts. As part of its adaptation, many endophytic organisms are known to exhibit properties with multiple beneficial effects to the plant system. Even though many bacterial genera have been identified to have endophytic association, isolation of those which were previously demonstrated well for human association is quite interesting. In the study, endophytic bacteria Ceb1 isolated from the rhizome of Curcuma longa was identified by 16S rDNA sequencing as Staphylococcus sp. Further, Ceb1 was observed to have the ability to tolerate drought stress. While screening for the plant growth-promoting traits, Ceb1 was found to be positive for IAA production both under drought-stressed and normal conditions as confirmed by HPLC. The Ceb1 priming with Vigna unguiculata was observed to enhance the growth parameters of the plant. Analysis of Ceb1-treated plants by ICP-MS further showed modulation of both macro- and micronutrients. Upon drought stress induction in Vigna unguiculata, Ceb1 was found to provide synergistic plant growth-promoting effect to the plant along with the supplemented silicate sources. Under the changing agroclimatic conditions, exploring the plant stress-alleviating effects of endophytes is highly significant.

Acute Oral Toxicity Studies of the Crude Extract of Endophytic Fungi Isolated from Annona senegalensis Pers

Establishment of safety and toxicity profiles of metabolites of endophytic organisms from known medicinal plants are crucial in their pharmacological and biological applications. The aim of this study was to evaluate the oral acute toxicity (LD50) of crude extract of endophytic fungi isolated from Annona senegalensis Pers. The endophytic fungal metabolite was extracted with ethyl acetate. The LD50 was estimated following the method described by Lorke. Three dose levels (10, 100, and 1000 mg/kg) of the crude extract were administered to three mice each for the first phase using oral gavage needle in a single dose disposable syringe. The animals were observed for possible deaths or other side effects of the test substance in each group within 24 hours of the treatment. In the second phase, which was deduced from the first phase, eight mice were sub-divided into four groups of two mice each and they were treated with doses of 1200, 1600, 2900 and 5000 mg/kg orally. They were also observed within 24 hours and final LD50 value was determined. Results showed that the endophytic fungal extract exhibited no mortality or any histological defect in the liver tissues of the mice. More so, the immunological parameter tested showed significant increase in neutrophils and lymphocytes relative to the control in all the fungal isolates. Additionally, the LD50 for the crude metabolites was > 5000 mg/kg. This study has revealed that crude extract of endophytic fungi isolated from Annona senegalensis Pers did not show oral acute toxicity in mice. Further studies will evaluate long term-toxicity of the crude extract.
 Keywords: Endophytes, LD50, Annona senegalensis, Metabolites, Fungi

Endophytes producing podophyllotoxin from Podophyllum sp. and other plants: A review on isolation, extraction and bottlenecks

Investigation on the secondary metabolites of endophytic organisms colonized within plant body is now giving emphasis on the medicinal properties of those products aiming to the finding of new drug molecules. Podophyllotoxin is a non-alkaloid lignan of plant origin found in some species of Podophyllum and several other genera such as Sinopodophyllum, Juniperus, Dysosma, Diphylleia, Linum, Lithospermum and so on. A few endophytic fungi which produce podophyllotoxin as secondary-metabolite are explored and reported in some available literatures. Isolation of specific endophytic fungal strains and their metabolite extraction can be done by using standard methods. Further research for the discovery of many other podophyllotoxin producing fungal endophytes and use of industrial fermentation technology may help in mass production. Survey of podophyllotoxin producing bacterial endophytic strains is also a prerequisite regarding commercial enrichment. It will certainly limit the overuse of the respective medicinal plant resources. Therefore, proper care must be taken and necessary policy may be formed by the appropriate authority to conserve these commercially valuable botanicals associated with endophytes. Informative knowledge about the wider distribution of endophytic microbes depending on the internal and external condition of the plant tissue may help to comprehend the role of those organisms in the production of bioactive metabolites.

Fusarium Head Blight Modifies Fungal Endophytic Communities During Infection of Wheat Spikes

Fusarium head blight (FHB) is a devastating disease of wheat heads. It is caused by several species from the genus Fusarium. Several endophytic fungi also colonize wheat spikes asymptomatically. Pathogenic and commensal fungi share and compete for the same niche and thereby influence plant performance. Understanding the natural dynamics of the fungal community and how the pre-established species react to pathogen attack can provide useful information on the disease biology and the potential use of some of these endophytic organisms in disease control strategies. Fungal community composition was assessed during anthesis as well as during FHB attack in wheat spikes during 2016 and 2017 in two locations. Community metabarcoding revealed that endophyte communities are dominated by basidiomycete yeasts before anthesis and shift towards a more opportunistic ascomycete-rich community during kernel development. These dynamics are interrupted when Fusarium spp. colonize wheat spikes. The Fusarium pathogens appear to exclude other fungi from floral tissues as they are associated with a reduction in community diversity, especially in the kernel which they colonize rapidly. Similarly, the presence of several endophytes was negatively correlated with Fusarium spp. and linked with spikes that stayed healthy despite exposure to the pathogen. These endophytes belonged to the genera Cladosporium, Itersonillia and Holtermanniella. These findings support the hypothesis that some naturally occurring endophytes could outcompete or prevent FHB and represent a source of potential biological control agents in wheat.

Bioactive Compounds Isolated from Marine-Derived Microbes in China: 2009-2018.

This review outlines the research that was carried out regarding the isolation of bioactive compounds from marine-derived bacteria and fungi by China-based research groups from 2009–2018, with 897 publications being surveyed. Endophytic organisms featured heavily, with endophytes from mangroves, marine invertebrates, and marine algae making up more than 60% of the microbial strains investigated. There was also a strong focus on fungi as a source of active compounds, with 80% of publications focusing on this area. The rapid increase in the number of publications in the field is perhaps most notable, which have increased more than sevenfold over the past decade, and suggests that China-based researchers will play a major role in marine microbial natural products drug discovery in years to come.

Endophyte-mediated synthesis of silver nanoparticles and their biological applications.

Biosynthesis has emerged as a frontier technology for fabrication of functionally diverse nanoparticles that possess tremendous therapeutic implications. Various biological resources have already demonstrated their potential to produce nanoparticles with interesting features. Endophytic microbes live in a symbiotic relationship with plants possessing a unique and versatile reservoir of potentially therapeutic secondary metabolites having the tendency to reduce metallic ions into nanoparticles. Successful biosynthesis of AgNPs using endophytic organisms has already been reported; however, the overall picture about its synthesis and applications is still not clear. In the current article, a comprehensive review of literature was performed for comparing different physical and biological properties of endophytic microbe-derived AgNPs. In addition, the present paper mechanistically explains the synthesis of AgNPs and their diverse pharmacognostic properties. Further studies are encouraged to understand the mechanism of biopharmaceutical effects of these endophyte-mediated NPs.

Xylem Sap Proteomics Reveals Distinct Differences Between R Gene- and Endophyte-Mediated Resistance Against Fusarium Wilt Disease in Tomato.

Resistance (R) genes and endophytic organisms can both protect plants against pathogens. Although the outcome of both processes is the same, little is known about the commonalities and differences between both immune responses. Here we set out to phenotypically characterize both responses in the tomato-Fusarium pathosystem, and to identify markers to distinguish these responses at the molecular level. As endophyte Fusarium oxysporum (Fo) strain Fo47 was employed, which confers protection against various pathogens, including the vascular wilt fungus F. oxysporum f.sp. lycopersici (Fol). As R-gene conferring Fol resistance, the I-2 gene of tomato (Solanum lycopersicum) was used. Fol colonizes the xylem vessels of susceptible and I-2 resistant tomato plants, but only causes disease in the former. Fol was found to colonize the vasculature of endophyte-colonized plants, and could be isolated from stems of non-diseased plants co-inoculated with Fo47 and Fol. Because the xylem vessels form the main interface between plant and pathogen, the xylem sap proteomes during R gene- and Endophyte-Mediated Resistance (RMR and EMR) were compared using label-free quantitative nLC-MS/MS. Surprisingly, both proteomes were remarkably similar to the mock, revealing only one or two differentially accumulated proteins in the respective resistant interactions. Whereas in I-2 plants the accumulation of the pathogenesis-related protein PR-5x was strongly induced by Fol, the endophyte triggered induction of both NP24, another PR-5 isoform, and of a β-glucanase in the presence of Fol. Notably, over 54% of the identified xylem sap proteins have a predicted intracellular localization, which implies that these might be present in exosomes. In conclusion, whereas both resistance mechanisms permit the pathogen to colonize the vasculature, this does not result in disease and this resistance coincides with specific induction of two distinct PR-5 isoforms and a β-glucanase.

Melatonin and its relationship to plant hormones.

Plant melatonin appears to be a multi-regulatory molecule, similar to those observed in animals, with many specific functions in plant physiology. In recent years, the number of studies on melatonin in plants has increased significantly. One of the most studied actions of melatonin in plants is its effect on biotic and abiotic stress, such as that produced by drought, extreme temperatures, salinity, chemical pollution and UV radiation, among others. This review looks at studies in which some aspects of the relationship between melatonin and the plant hormones auxin, cytokinin, gibberellins, abscisic acid, ethylene, jasmonic acid and salicylic acid are presented. The effects that some melatonin treatments have on endogenous plant hormone levels, their related genes (biosynthesis, catabolism, receptors and transcription factors) and the physiological actions induced by melatonin, mainly in stress conditions, are discussed. Melatonin is an important modulator of gene expression related to plant hormones, e.g. in auxin carrier proteins, as well as in metabolism of indole-3-acetic acid (IAA), gibberellins, cytokinins, abscisic acid and ethylene. Most of the studies performed have dealt with the auxin-like activity of melatonin which, in a similar way to IAA, is able to induce growth in shoots and roots and stimulate root generation, giving rise to new lateral and adventitious roots. Melatonin is also able to delay senescence, protecting photosynthetic systems and related sub-cellular structures and processes. Also, its role in fruit ripening and post-harvest processes as a gene regulator of ethylene-related factors is relevant. Another decisive aspect is its role in the pathogen-plant interaction. Melatonin appears to act as a key molecule in the plant immune response, together with other well-known molecules such as nitric oxide and hormones, such as jasmonic acid and salicylic acid. In this sense, the discovery of elevated levels of melatonin in endophytic organisms associated with plants has thrown light on a possible novel form of communication between beneficial endophytes and host plants via melatonin.

Testing of Bacterial Endophytes from Non-Host Sources as Potential Antagonistic Agents against Tomato Wilt Pathogen <i>Ralstonia solanacearum</i>

The study was taken up with the objective of testing whether the endophytic organisms isolated from crops that are normally non-hosts to the bacterial wilt pathogen Ralstonia solanacearum possessed pathogen-antagonistic activity and to evaluate the selected isolates for the alleviation of wilt disease in the target tomato crop through horizontal movement of promising organisms. Sixteen endophytic bacteria (EB) isolated from the micropropagated cultures of grape, watermelon and papaya were tested for potential antagonistic effects against R. solanacearum tomato isolate “NH-01” through agar-well diffusion assay. Enterobacter cloacae from papaya (EB-11) displayed the maximum antagonistic effect followed by Bacillus subtilis (EB-06) and B. flexus (EB-07) from watermelon and B. pumilus (EB-02) from grape. Testing the above organisms for crop protection through seed fortification of susceptible tomato cv. Arka Vikas at sowing in R. solanacearum inoculated (Ral+) organic cocopeat showed EB-02 and EB-11 promising (33% and 32% survival, respectively, four weeks after sowing against 15% in Ral+ control). A second trial showed 37%, 28%, 21% and 55% seedling survival 6 weeks after sowing for EB-02, EB-06, EB-07 and EB-11 respectively, compared to 2.5% in non-treated control. Assessing the four endophytes for crop protection in Ral+ sick-soil through seedling fortification at transplanting indicated less disease incidence in treated sets (40%, 40%, 20% and 20% survival, respectively, six weeks after transplanting) over non-fortified control (5%). Endophytic fortification of seedlings through hypocotyl inoculation showed some systemic resistance induction upon seedling transplanting to sick soil but not with petiole fortification. Seedling growth was enhanced by the isolates EB-06 and EB-07. The study thus identifies four endophytic organisms from crops unrelated to tomato possessing potential antagonistic activity against the wilt pathogen and prospects for exploitation as biocontrol agents coupled with seedling growth promotion effects.

Exploring Entagonistic Effect of Endophytic Microorganisms AgainstXanthomonas axonopodispv.dieffenbachiae(McCulloch & Pirone) Vauterin Causing Bacterial Blight ofAnthurium

One of the major constraint in anthurium cut flower production is bacterial blight incited by Xanthomonas axonopodis pv. Dieffenbachiae (Xad). It causes considerable economic loss. Considering the serious nature of the disease the present investigation was undertaken to harness the potential of antagonistic endophytes against bacterial blight pathogen. Endophytic microorganisms were isolated from healthy anthurium plants collected from different locations. A quantitative estimation of endophytic micro organisms revealed the abundance of bacteria than fungi. Moreover, more number of endophytes were isolated from roots than from petiole and leaves. Based on cultural characters of endophytic microorganisms, 14 fungal and 37 bacterial endophytes were selected. Antagonistic action of these endophytes against pathogen was studied in comparison with that of reference culture of Pseudomonas fluorescens (KAU), P. fluorescens (TNAU), Trichoderma viride (KAU) and T. harzianum (IISR). The study revealed that, only eight bacterial and two fungal cultures showed antagonistic action against the pathogen. Since fungal endophytes showed less inhibition, they were not selected for further studies. The selected endophytes were subjected to various tests for understanding parameters that may act to produce antagonism as well as enhanced growth of the plants. All the antagonists inhibited growth of the pathogen, promoted plant growth, produced IAA and ammonia. Only two isolates viz., EB-14 and EB-31 are found cyanogenic. Only four isolates viz., EB-15, EB-31, EB-26 and EB-12 were found capable of solubilizing phosphate. All isolates except EB-12 were found capable of producing siderophores.

Phenazine carboxylic acid production and rhizome protective effect of endophytic Pseudomonas aeruginosa isolated from Zingiber officinale.

Ginger (Zingiber officinale) is cultivated commercially in most parts of the world especially in India for its culinary and medicinal applications. One of the major challenges that limit the yield of ginger is rhizome rot disease caused by organisms including Pythium myriotylum. A feasible ecofriendly method is yet to be devised to prevent the plant from this threatening disease. Recent studies on plant microbiome show the possibility of having endophytic organisms with plant protective characteristics associated with the plants. Because of the uniquely evolved underground nature of the ginger rhizome and its peculiar survival in soil for a long time, many interesting endophytic microbes with plant protective characters can be well expected from it. In the current study, previously isolated endophytic Pseudomonas aeruginosa from ginger was investigated in detail for its effect on Pythium myriotylum. The rhizome protective effect of the organism was also studied by co-inoculation studies, which confirmed that Pseudomonas aeruginosa has very potent inhibitory effect on Pythium myriotylum. On further studies, the active antifungal compound was identified as phenazine 1-carboxylic acid.