Diaporthe endophytica and D. terebinthifolii from medicinal plants for biological control of Phyllosticta citricarpa

Identification of natural CTXM-15 inhibitors from aqueous extract of endophytic bacteria Cronobactersakazaki

Nyctanthes arbor-tristis is one of India's valuable and populous medicinal plants which belongs to the family Oleaceae, and widely recognize as night jasmine. Over the years till date, different parts of the plant are used to treat or cure different ailments via various means of traditional medicine. Endophytes are organisms that live in the cell or body of other organisms with no apparent negative impact on the host which they inhabit and are of great source of novel bioactive compounds possessing important economic value. Secondary metabolites were identified in the aqueous extract of Cronobactersakazakii through quantitative phytochemical and GC-MS analysis. Antibacterial activity of the extract against clinical and ATCC strains of E. coli was assessed. Biological activity spectra of these compounds were predicted and categorized either as probably active (Pa) or probably inactive (Pi). Drug-likeness of bioactive compounds was determined as well as their ability to target protein (CTXM-15) responsible for antibiotic resistance in Gram-negative bacteria. Results revealed the presence of active compounds with pharmacological activities and considerable pharmacokinetics parameters. In addition, ligand-protein interactions of compounds with CTXM-15 proteins were identified. These results suggest that bioactive compounds of endophytic Cronobactersakazakii could contain novel chemical entities for the development of antibiotics against pathogenic microbes and other drugs for the amelioration of several infections.

Diaporthe species associated with the maritime grass Festuca rubra subsp. pruinosa

Festuca rubra subsp. pruinosa is a perennial grass growing in sea cliffs where plants are highly exposed to salinity and marine winds, and often grow in rock fissures where soil is absent. Diaporthe species are one of the most abundant components of the root microbiome of this grass and several Diaporthe isolates have been found to produce beneficial effects in their host and other plant species of agronomic importance. In this study, 22 strains of Diaporthe isolated as endophytes from roots of Festuca rubra subsp. pruinosa were characterized by molecular, morphological, and biochemical analyses. Sequences of the nuclear ribosomal internal transcribed spacers (ITS), translation elongation factor 1-α (TEF1), beta-tubulin (TUB), histone-3 (HIS), and calmodulin (CAL) genes were analyzed to identify the isolates. A multi-locus phylogenetic analysis of the combined five gene regions led to the identification of two new species named Diaporthe atlantica and Diaporthe iberica. Diaporthe atlantica is the most abundant Diaporthe species in its host plant, and Diaporthe iberica was also isolated from Celtica gigantea, another grass species growing in semiarid inland habitats. An in vitro biochemical characterization showed that all cultures of D. atlantica produced indole-3-acetic acid and ammonium, and the strains of D. iberica produced indole 3-acetic acid, ammonium, siderophores, and cellulase. Diaporthe atlantica is closely related to D. sclerotioides, a pathogen of cucurbits, and caused a growth reduction when inoculated in cucumber, melon, and watermelon.

Endophytic bacteria of Fagonia indica Burm. f revealed to harbour rich secondary antibacterial metabolites

Endophytic bacteria are the source of novel bioactive compounds, used as therapeutic agent. Molecular docking is a computational technique use frequently, to find novel drugs targets and drugs-receptors interactions. The current study was designed to isolate and identify endophytic bacteria for the extraction of bioactive compounds. Further, to characterized extracts and to explore compounds interactions with bacterial cell wall and outer membrane synthesizing proteins. Endophytes were identified using 16s rRNA amplification technique. For bioactive compounds, solvent extraction method was followed and characterized further through GC-MS analysis. To find targets and drugs-receptors interactions, molecular docking studies and biological assays were performed. The isolated endophytes belong to five different genera namely Enterobacter, Bacillus, Erwinia, Stenotrophomonas and Pantoea. In case of antibacterial assay Stenotrophomonas maltophilia extract showed significant inhibitory zones (15.11±0.11mm and 11.3±0.16) against Staphylococcus caseolyticus and Acinetobacter baumanni, with MIC 33.3 and 50μg/mL respectively. Among the characterized fifty compounds, from endophytic bacteria "antibacterial compound" N-(5-benzyl-10b-hydroxy-2-methyl-3,6-dioxooctahydro-8H-oxazolo[3,2-α] pyrrolo[2,1c] pyrazin-2-yl)-7-methyl2,3,3a,3a1,6,6a,7,8,9,10,10a,10b-dodecahydro-1H-4λ2-indolo[4,3-fg]quinoline-9-carboxamide of bacteria Stenotrophomonas maltophilia were an excellent binder with MurF ligase active site, with binding energy of -10.2 kcal/mol. Extracts of endophytic bacteria composed of various pharmacologically active ingredients such as antibacterial compounds. Molecular docking studies provide important information regarding drug-receptor interaction, thus can be used in novel drug discovery.

Endophytic Diaporthe as Promising Leads for the Development of Biopesticides and Biofertilizers for a Sustainable Agriculture

Plant pathogens are responsible for causing economic and production losses in several crops worldwide, thus reducing the quality and quantity of agricultural supplies. To reduce the usage of chemically synthesized pesticides, strategies and approaches using microorganisms are being used in plant disease management. Most of the studies concerning plant-growth promotion and biological agents to control plant diseases are mainly focused on bacteria. In addition, a great portion of registered and commercialized biopesticides are bacterial-based products. Despite fungal endophytes having been identified as promising candidates for their use in biological control, it is of the utmost importance to develop and improve the existing knowledge on this research field. The genus Diaporthe, encompasses plant pathogens, saprobes and endophytes that have been screened for secondary metabolite, mainly due to their production of polyketides and a variety of unique bioactive metabolites with agronomic importance. Some of these metabolites exhibit antifungal and antibacterial activity for controlling plant pathogens, and phytotoxic activity for the development of potential mycoherbicides. Moreover, species of Diaporthe are reported as promising agents in the development of biofertilizers. For this reason, in this review we summarize the potential of Diaporthe species to produce natural products with application in agriculture and describe the benefits of these fungi to promote their host plant's growth.

Investigations of specialised metabolites of endophyte Diaporthe destruens hosted in Illigera orbiculata C. Y. Wu

A chemical investigation of the endophytic fungus Diaporthe destruens from the Hernandiaceae plant Illigera orbiculata C. Y. Wu collected from southern Yunnan Province, China, led to the isolation of six undescribed compounds, including two azaphilone analogs, which are a pair of epimers (13R-hydroxy-chermesinone A and 13S-hydroxy-chermesinone A); a pyrrole derivative (1-(4-(methoxymethyl)-1H-pyrrol-3-yl)ethan-1-one); an isoindolone derivative (4-hydroxy-6-methoxyisoindolin-1-one); a benzylbenzene derivative (destruensine A) and a conjectural fragment of polyketide ((2R,4R)-2-(methoxymethyl)pentane-1,4-diol) along with nine known compounds. Their structures were elucidated by spectroscopic methods and HRESIMS, and the absolute configurations were further confirmed by electronic circular dichroism (ECD) and chemical derivatization. The antimicrobial activities, anti-acetylcholinesterase activities, antiproliferation, and NO production inhibitory effects of compounds 1-15 were evaluated.

Endophytic Fungi as a Source of Antibacterial Compounds-A Focus on Gram-Negative Bacteria

Bacterial resistance has become one of the main motives in the worldwide race for undescribed antibacterial agents. The difficulties in the treatment of bacterial infections are a public health issue that increasingly highlights the need for antimicrobial agents. Endophytic microorganisms are a promising alternative in the search for drugs, due to the vast number of metabolites produced with unique characteristics and bioactive potential. This review highlights the importance of endophytic microorganisms as a source of secondary metabolites in the search for active molecules against bacteria of medical importance, with a special focus on gram-negative species. This fact is supported by the findings raised in this review, which brings an arsenal of 166 molecules with characterized chemical structures and their antibacterial activities. In addition, the low cost, ease of maintenance, and optimization-controlled fermentation conditions favor reproducibility in commercial scale. Given their importance, it is necessary to intensify the search for new molecules from endophytic microorganisms, and to increasingly invest in this very promising font.

Endophytes of Brazilian Medicinal Plants With Activity Against Phytopathogens

Plant diseases caused by phytopathogens are responsible for significant crop losses worldwide. Resistance induction and biological control have been exploited in agriculture due to their enormous potential. In this study, we investigated the antimicrobial potential of endophytic fungi of leaves and petioles of medicinal plants Vochysia divergens and Stryphnodendron adstringens located in two regions of high diversity in Brazil, Pantanal, and Cerrado, respectively. We recovered 1,304 fungal isolates and based on the characteristics of the culture, were assigned to 159 phenotypes. One isolate was selected as representative of each phenotype and studied for antimicrobial activity against phytopathogens. Isolates with better biological activities were identified based on DNA sequences and phylogenetic analyzes. Among the 159 representative isolates, extracts from 12 endophytes that inhibited the mycelial growth (IG) of Colletotrichum abscissum (≥40%) were selected to expand the antimicrobial analysis. The minimum inhibitory concentrations (MIC) of the extracts were determined against citrus pathogens, C. abscissum, Phyllosticta citricarpa and Xanthomonas citri subsp. citri and the maize pathogen Fusarium graminearum. The highest activity against C. abscissum were from extracts of Pseudofusicoccum stromaticum CMRP4328 (IG: 83% and MIC: 40 μg/mL) and Diaporthe vochysiae CMRP4322 (IG: 75% and MIC: 1 μg/mL), both extracts also inhibited the development of post-bloom fruit drop symptoms in citrus flowers. The extracts were promising in inhibiting the mycelial growth of P. citricarpa and reducing the production of pycnidia in citrus leaves. Among the isolates that showed activity, the genus Diaporthe was the most common, including the new species D. cerradensis described in this study. In addition, high performance liquid chromatography, UV detection, and mass spectrometry and thin layer chromatography analyzes of extracts produced by endophytes that showed high activity, indicated D. vochysiae CMRP4322 and P. stromaticum CMRP4328 as promising strains that produce new bioactive natural products. We report here the capacity of endophytic fungi of medicinal plants to produce secondary metabolites with biological activities against phytopathogenic fungi and bacteria. The description of the new species D. cerradensis, reinforces the ability of medicinal plants found in Brazil to host a diverse group of fungi with biotechnological potential.

Efficient Agrobacterium tumefaciens-mediated transformation system of Diaporthe caulivora

This is the first report describing the genetic transformation of Diaporthe caulivora, the soybean stem canker fungus. A simple and 100% efficient protocol of Agrobacterium tumefaciens-mediated transformation used mycelium as starting material and the hygromycin B resistance and green fluorescent protein (GFP) as a selection and reporter agents, respectively. All transgenic isolates were mitotically stable in two independent experiments and polymerase chain reaction with hygromycin B resistance primers confirmed successful T-DNA integration into the fungal genome. Plant-fungus interaction studies, including pathogenicity, latency, and endophytism, as well as further studies of random and targeted mutagenesis will be possible with GFP-expressing isolates of D. caulivora and other species in the Diaporthe / Phomopsis complex.

Agrobacterium tumefaciens-Mediated Transformation of Fonsecaea monophora and Fonsecaea erecta for Host-Environment Interaction Studies

The fungal genus Fonsecaea contains etiological agents of human chromoblastomycosis, a (sub)tropical, (sub)cutaneous implantation disease caused by plant contact. The invasive potential differs significantly between species. Infections by Fonsecaea monophora are believed to originate from the environment and the species has been reported as one of the main causative agents of the disease, but also of cases of primary brain infection. The epidemiology of the disease has not been fully elucidated and questions related to its infection route and virulence are still to be clarified. The environmental species Fonsecaea erecta was isolated from organic material and living plants in endemic areas for chromoblastomycosis in Brazil. The present paper describes Agrobacteriumtumefaciens-mediated transformation (AMT) of the environmental species F. erecta and the pathogenic species F. monophora. We propose the use of Agrobacterium transformation for future gene function studies related to Fonsecaea virulence and pathogenicity. We evaluated the co-cultivation ratios 1:1, 10:1 and 100:1 (Agrobacterium:conidia) at 28 °C during 72 h. pAD1625 and pCAMDsRed plasmids were inserted into both species. Confirmation of transformation was realized by hph gene amplification and Southern blot determined the amount of foreign DNA integrated into the genome. In order to evaluate a potential link between environmental and clinical strains, we obtained red fluorescent transformants after pCAMDsRed insertion. We observed by confocal fluorescence microscopy that both F. monophora and F. erecta were able to colonize the palm Bactris gasipaes, penetrating the epidermis. These results contribute to understanding the ability of Fonsecaea species to adapt to different environmental and host conditions.

Fungal Composition and Diversity of the Tobacco Leaf Phyllosphere During Curing of Leaves

Rhizopus oryzae causes tobacco pole rot in China during tobacco flue-curing. Flue-curing is a post-harvest process done to prepare tobacco leaves and involves three different stages: the yellowing stage has the lowest temperatures and highest humidity, then the color-fixing stage has higher temperatures and medium humidity, and finally the stem-drying stage has the highest temperatures and lowest humidity. In this study, fungal culturing and IonS5XL high-throughput sequencing techniques were used to reveal the fungal community of the petioles and lamina of tobacco leaves infected with pole rot during flue-curing. A total of 108 fungal isolates belonging to 6 genera were isolated on media. The most common fungal species isolated was the pathogen, R. oryzae, that was most often found equally on petioles and laminas in the color-fixing stage, followed by saprotrophs, mostly Aspergillus spp. High-throughput sequencing revealed saprotrophs with Alternaria being the most abundant genus, followed by Phoma, Cercospora, and Aspergillus, whereas Rhizopus was the tenth most abundant genus, which was mostly found on petioles at the yellowing stage. Both culturable fungal diversity and fungal sequence diversity was higher at stem-drying stage than the yellowing and color-fixing stages, and diversity was higher with leaf lamina than petioles revealing that the changes in fungal composition and diversity during the curing process were similar with both methods. This study demonstrates that the curing process affects the leaf microbiome of tobacco during the curing process, and future work could examine if any of these saprotrophic fungi detected during the curing of tobacco leaves may be potential biocontrol agents for with pole rot in curing chambers.

Diversity and Antimicrobial Potential of Cultivable Endophytic Actinobacteria Associated With the Medicinal Plant Thymus roseus

We report for the first time the isolation of endophytic actinobacteria associated with wild populations of the Chinese medicinal herb Thymus roseus Schipcz obtained from the arid land in Ili and Tacheng of the Xinjiang Province, China. Strains were isolated by special pretreatment of plant tissues and identified based on their 16S rRNA gene sequences, and their antimicrobial activities in vitro were evaluated. A total of 126 endophytic actinobacteria belonging to two classes, eight orders, 14 families, and 24 genera were isolated from different organs at the Ili and Tacheng sites. In addition, the diversity of culturable endophytic actinobacteria genera was higher at Tacheng site (n = 71, 56.35%) than the Ili site (n = 55, 43.65%). A neighbor-joining tree of 126 isolated actinobacteria showing the phylogenetic relationships based on 16S rRNA gene sequences and the genus Streptomyces was the most dominant isolate. The number of endophytic actinobacteria genera obtained from root tissues (n = 54, 42.86%) was higher compared to stem (n = 35, 27.78%) and leaf tissue (n = 37, 29.36%). Among 126 endophytic actinobacteria, 54 strains were antagonistic against at least one or more indicator organisms in vitro. Notably, most strains of Streptomyces proved antagonistic activities. For example, strain T4SB028, namely Streptomyces polyantibioticus, showed the highest inhibition ratio reached 67.06, 64.20, and 70.55% against Alternaria solani, Valsa malicola, and Valsa mali, respectively. The results demonstrate that about 30.95%, 23.01% of the tested endophytic actinobacteria were capable of producing siderophores and chitinase, respectively. Additionally, the results of the amplification of biosynthetic genes polyketide synthetase (PKS-I) and non-ribosomal peptide synthetase (NRPS) indicated that at least one antibiotic biosynthetic gene was detected in 27 (50%) of the tested strains. Our result emphasizes that the endophytic actinobacteria communities are different based on the plant tissues and the geographical environment of the sampled area. Thus, we conclude that T. roseus Schipcz. provided a rich source of endophytic actinobacteria that exhibited a broad-spectrum antimicrobial agent.

Phyllosticta citricarpa and sister species of global importance to Citrus

Several Phyllosticta species are known as pathogens of Citrus spp., and are responsible for various disease symptoms including leaf and fruit spots. One of the most important species is P. citricarpa, which causes a foliar and fruit disease called citrus black spot. The Phyllosticta species occurring on citrus can most effectively be distinguished from P. citricarpa by means of multilocus DNA sequence data. Recent studies also demonstrated P. citricarpa to be heterothallic, and reported successful mating in the laboratory. Since the domestication of citrus, different clones of P. citricarpa have escaped Asia to other continents via trade routes, with obvious disease management consequences. This pathogen profile represents a comprehensive literature review of this pathogen and allied taxa associated with citrus, focusing on identification, distribution, genomics, epidemiology and disease management. This review also considers the knowledge emerging from seven genomes of Phyllosticta spp., demonstrating unknown aspects of these species, including their mating behaviour.

TAXONOMY

Phyllosticta citricarpa (McAlpine) Aa, 1973. Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Botryosphaeriales, Family Phyllostictaceae, Genus Phyllosticta, Species citricarpa.

HOST RANGE

Confirmed on more than 12 Citrus species, Phyllosticta citricarpa has only been found on plant species in the Rutaceae.

DISEASE SYMPTOMS

P. citricarpa causes diverse symptoms such as hard spot, virulent spot, false melanose and freckle spot on fruit, and necrotic lesions on leaves and twigs.

USEFUL WEBSITES

DOE Joint Genome Institute MycoCosm portals for the Phyllosticta capitalensis (https://genome.jgi.doe.gov/Phycap1), P. citriasiana (https://genome.jgi.doe.gov/Phycit1), P. citribraziliensis (https://genome.jgi.doe.gov/Phcit1), P. citrichinaensis (https://genome.jgi.doe.gov/Phcitr1), P. citricarpa (https://genome.jgi.doe.gov/Phycitr1, https://genome.jgi.doe.gov/Phycpc1), P. paracitricarpa (https://genome.jgi.doe.gov/Phy27169) genomes. All available Phyllosticta genomes on MycoCosm can be viewed at https://genome.jgi.doe.gov/Phyllosticta.

Vochysiamides A and B: Two new bioactive carboxamides produced by the new species Diaporthe vochysiae

Endophytic fungi have been considered a rich source for bioactive secondary metabolites with novel chemical structures. A high diverse group of endophytes, isolated from different medicinal plants, belongs to the genus Diaporthe. In a previously study performed by our group the crude extract of strain LGMF1583 showed considerable antibacterial activity mainly against Gram-negative bacteria. Based on ITS phylogeny analysis, strain LGMF1583 was identified as belonging to Diaporthe genus and may represent a new species. In the present study, we described the new species Diporthe vochysiae based on multilocus phylogeny analysis and morphological characteristics. The species name refers to the host, from which strain LGMF1583 was isolated, the medicinal plant Vochysia divergens. In view of the biotechnological potential of strain LGMF1583, we have also characterized the secondary metabolites produced by D. vochysiae. Chemical assessment of the D. vochysiae LGMF1583 revealed two new carboxamides, vochysiamides A (1) and B (2), in addition to the known metabolite, 2,5-dihydroxybenzyl alcohol (3). In the biological activity analysis, vochysiamide B (2) displayed considerable antibacterial activity against the Gram-negative bacterium Klebsiella pneumoniae (KPC), a producer of carbapenemases, MIC of 80 μg/mL. Carbapenemases are considered a major antimicrobial resistance threat, and infections caused by KPC have been considered a public health problem worldwide, and new compounds with activity against this bacterium are nowadays even more required.

Dihydroisocoumarins produced by Diaporthe cf. heveae LGMF1631 inhibiting citrus pathogens

Citrus black spot (CBS) and post-bloom fruit drop (PFD), caused by Phyllosticta citricarpa and Colletotrichum abscissum, respectively, are two important citrus diseases worldwide. CBS depreciates the market value and prevents exportation of citrus fruits to Europe. PFD under favorable climatic conditions can cause the abscission of flowers, thereby reducing citrus production by 80%. An ecofriendly alternative to control plant diseases is the use of endophytic microorganisms, or secondary metabolites produced by them. Strain LGMF1631, close related to Diaporthe cf. heveae 1, was isolated from the medicinal plant Stryphnodendron adstringens and showed significant antimicrobial activity, in a previous study. In view of the potential presented by strain LGMF1631, and the absence of chemical data for secondary metabolites produced by D. cf. heveae, we decided to characterize the compounds produced by strain LGMF1631. Based on ITS, TEF1, and TUB phylogenetic analysis, strain LGMF1631 was confirmed to belong to D. cf. heveae 1. Chemical assessment of the fungal strain LGMF1631 revealed one new seco-dihydroisocoumarin [cladosporin B (1)] along with six other related, already known dihydroisocoumarin derivatives and one monoterpene [(-)-(1S,2R,3S,4R)-p-menthane-1,2,3-triol (8)]. Among the isolated metabolites, compound 5 drastically reduced the growth of both phytopathogens in vitro and completely inhibited the development of CBS and PFD in citrus fruits and flowers. In addition, compound 5 did not show toxicity against human cancer cell lines or citrus leaves, at concentrations higher than used for the inhibition of the phytopathogens, suggesting the potential use of (-)-(3R,4R)-cis-4-hydroxy-5-methylmellein (5) to control citrus diseases.

Diversity of culture-independent bacteria and antimicrobial activity of culturable endophytic bacteria isolated from different Dendrobium stems

Dendrobium is known for its pharmacological actions including anti-cancer effect, anti-fatigue effect, gastric ulcer protective effect, and so on. At present, only studies on endophytic fungi of Dendrobium affecting the metabolites of host plants have been reported, very little research has been done on endophytic bacteria. In this study, we have demonstrated the great diversity of endophytic bacteria in 6 Dendrobium samples from different origins and cultivars. According to the results of the culture-independent method, the endophytic bacterial community in Dendrobium stems showed obvious different in the 6 samples and was influenced by origin and cultivar. Some bacteria including Ralstonia, Comamonas and Lelliottia were first detected in Dendrobium in this study. Based on the culture-dependent method, a total of 165 cultivable endophytic bacteria isolates were isolated from the sterilized Dendrobium stems, and were classified into 43 species according to the 16S rRNA gene sequence analysis. Moreover, 14 of the 43 strains showed antimicrobial activity against phytopathogen using the Kirby-Bauer method. Strain NA-HTong-7 (Bacillus megaterium, 99.12%) showed the highest antimicrobial activity. This study was the first comprehensive study on endophytic bacteria of Dendrobium from different origins and cultivars, which provides new insights into the endophytic bacteria from Dendrobium.

Secondary metabolites produced by Microbacterium sp. LGMB471 with antifungal activity against the phytopathogen Phyllosticta citricarpa

The citrus black spot (CBS), caused by Phyllosticta citricarpa, is one of the most important citrus diseases in subtropical regions of Africa, Asia, Oceania, and the Americas, and fruits with CBS lesions are still subject to quarantine regulations in the European Union. Despite the high application of fungicides, the disease remains present in the citrus crops of Central and South America. In order to find alternatives to help control CBS and reduce the use of fungicides, we explored the antifungal potential of endophytic actinomycetes isolated from the Brazilian medicinal plant Vochysia divergens found in the Pantanal biome. Two different culture media and temperatures were selected to identify the most efficient conditions for the production of active secondary metabolites. The metabolites produced by strain Microbacterium sp. LGMB471 cultured in SG medium at 36 °C considerably inhibited the development of P. citricarpa. Three isoflavones and five diketopiperazines were identified, and the compounds 7-O-β-D-glucosyl-genistein and 7-O-β-D-glucosyl-daidzein showed high activity against P. citricarpa, with the MIC of 33 μg/mL and inhibited the production of asexual spores of P. citricarpa on leaves and citrus fruits. Compounds that inhibit conidia formation may be a promising alternative to reduce the use of fungicides in the control of CBS lesions, especially in regions where sexual reproduction does not occur, as in the USA. Our data suggest the use of Microbacterium sp. LGMB471 or its metabolites as an ecological alternative to be used in association with the fungicides for the control of CBS disease.

Agrobacterium-Mediated Transformation of Diaporthe schini Endophytes Associated with Vitis labrusca L. and Its Antagonistic Activity Against Grapevine Phytopathogens

Fungus-caused diseases are among the greatest losses in grapevine culture. Biological control of pathogens by endophytes may be used to decrease fungicide application rates and environmental impacts. Previously, Diaporthe sp. B46-64 and C27-07 were highlighted as antagonists of grapevine phytopathogens. Herein, molecular multigene (ITS-TUB-TEF1) identification and phylogenetic analysis allowed the identification of these endophytes as belonging to Diaporthe schini species. Agrobacterium tumefaciens-mediated transformation was employed for obtaining 14 stable and traceable gfp- or DsRed-expressing transformants, with high transformation efficiency: 96% for the pFAT-GFP plasmid and 98% for pCAM-DsRed plasmid. Transformants were resistant to hygromycin B with gene hph confirmed by polymerase chain reaction and proved to be mitotically stable, expressing the fluorescent phenotype, with morphological differences in the colonies when compared with wild strains. In vitro antagonism tests revealed an increased antagonistic activity of some transformant strains. The current genetic transformation of D. schini mediated by A. tumefaciens proved to be an efficient technique within the randomized insertion of reporter genes for the monitoring of the strain in the environment.

Muscodor brasiliensis sp. nov. produces volatile organic compounds with activity against Penicillium digitatum

Endophytic fungi belonging to Muscodor genus are considered as promising alternatives to be used in biological control due to the production of volatile organic compounds (VOCs). The strains LGMF1255 and LGMF1256 were isolated from the medicinal plant Schinus terebinthifolius and, by morphological data and phylogenetic analysis, identified as belonging to Muscodor genus. Phylogenetic analysis suggests that strain LGMF1256 is a new species, which is herein introduced as Muscodor brasiliensis sp. nov. The analysis of VOCs production revealed that compounds phenylethyl alcohol, α-curcumene, and E (β) farnesene until now has been reported only from M. brasiliensis, data that supports the classification of strain LGMF1256 as a new species. M. brasiliensis completely inhibited the phytopathogen P. digitatum in vitro. We also evaluated the ability of VOCs from LGMF1256 to inhibit the development of green mold symptoms by inoculation of P. digitatum in detached oranges. M. brasiliensis reduced the severity of diseases in 77%, and showed potential to be used for fruits storage and transportation to prevent the green mold symptoms development, eventually reducing the use of fungicides.

The impact of microbes in the orchestration of plants' resistance to biotic stress: a disease management approach

The struggle for survival is a natural and a continuous process. Microbes are struggling to survive by depending on plants for their nutrition while plants on the other hand are resisting the attack of microbes in order to survive. This interaction is a tug of war and the knowledge of microbe-plant relationship will enable farmers/agriculturists improve crop health, yield, sustain regular food supply, and minimize the use of agrochemicals such as fungicides and pesticides in the fight against plant pathogens. Although, these chemicals are capable of inhibiting pathogens, they also constitute an environmental hazard. However, certain microbes known as plant growth-promoting microbes (PGPM) aid in the sensitization and priming of the plant immune defense arsenal for it to conquer invading pathogens. PGPM perform this function by the production of elicitors such as volatile organic compounds, antimicrobials, and/or through competition. These elicitors are capable of inducing the expression of pathogenesis-related genes in plants through induced systemic resistance or acquired systemic resistance channels. This review discusses the current findings on the influence and participation of microbes in plants' resistance to biotic stress and to suggest integrative approach as a better practice in disease management and control for the achievement of sustainable environment, agriculture, and increasing food production.

Bioprospecting and Structure of Fungal Endophyte Communities Found in the Brazilian Biomes, Pantanal, and Cerrado

Medicinal plants have been recognized as hosts of high diverse endophytic microorganisms, including fungi that produce secondary metabolites with biological activity. Two biomes in Brazil, Pantanal (wetland), and Cerrado (savannah), are known as biodiversity hotspots, and despite their importance as a reservoir for several species, knowledge about the fungal biodiversity in these biomes is very limited. Fungal endophytic communities associated with leaves and petioles of the medicinal plants Vochysia divergens (from Pantanal) and Stryphnodendron adstringens (from Cerrado) were analyzed and studied for their antimicrobial activity against human and plant pathogens. A total of 1,146 isolates of endophytic fungi were obtained from plants collected in January and June of 2016 and grouped into 124 morphotypes. One isolate of each morphotype was identified by sequencing of internal transcribed spacer (ITS) region of the rDNA gene, which revealed the presence of 24 genera, including 3 possible new genera, and 48 taxa. Differences in the endophytic community according to the biomes were observed concerning the analyzed morphotypes. However, when we analyzed the diversity of genera and richness, they were similar for both plants, with Diaporthe, Phyllosticta, and Neofusicoccum as dominant genera. In addition, the community composition of V. divergens differs according to the analyzed plant tissues (petiole and leaf). These data suggested that both, the plant species and plant tissues play a role in the composition of endophytic community. As regards the biotechnological potential, 5 isolates showed activity against the phytopathogens Phyllosticta citricarpa, Colletotrichum abscissum, and Fusarium verticilioides, and 8 isolates showed high activity against clinical pathogens and were selected for the production of crude extract in different culture media. Extract from cultivation of Diaporthe sp. LGMF1548 and LGMF1583 and Neofusicoccum brasiliense LGMF1535 showed activity against methicillin-resistant Staphylococcus aureus, Klebssiella pneumonia, and Candida albicans. In addition, extracts of Diaporthe cf. heveae LGMF1631 inhibited 90% of the mycelial growth of the P. citricarpa and 70% of C. abscissum and may represent an alternative to be used in the biological control of these phytopathogens. Future research will focus on the chemical characterization and structural elucidation of these bioactive compounds.

Antifungal Activities of Volatile Secondary Metabolites of Four Diaporthe Strains Isolated from Catharanthus roseus

Four endophytic fungi were isolated from the medicinal plant, Catharanthus roseus, and were identified as Diaporthe spp. with partial translation elongation factor 1-alpha (TEF1), beta-tubulin (TUB), histone H3 (HIS), calmodulin (CAL) genes, and rDNA internal transcribed spacer (ITS) region (TEF1-TUB-HIS--CAL-ITS) multigene phylogeny suggested for species delimitation in the Diaporthe genus. Each fungus produces a unique mixture of volatile organic compounds (VOCs) with an abundant mixture of terpenoids analyzed by headspace solid-phase microextraction (SPME) fiber-GC/MS. These tentatively-detected terpenes included α-muurolene, β-phellandrene, γ-terpinene, and α-thujene, as well as other minor terpenoids, including caryophyllene, patchoulene, cedrene, 2-carene, and thujone. The volatile metabolites of each isolate showed antifungal properties against a wide range of plant pathogenic test fungi and oomycetes, including Alternaria alternata, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium graminearum, and Phytophthora cinnamomi. The growth inhibition of the pathogens varied between 10% and 60% within 72 h of exposure. To our knowledge, the endophytic Diaporthe-like strains are first reported from Catharanthus roseus. VOCs produced by each strain of the endophytic Diaporthe fungi were unique components with dominant monoterpenes comparing to known Diaporthe fungal VOCs. A discussion is presented on the inhibitive bioactivities of secondary metabolites among endophytic Diaporthe fungi and this medicinal plant.

Evaluation of the Antimicrobial Activity of Endophytic Bacterial Populations From Chinese Traditional Medicinal Plant Licorice and Characterization of the Bioactive Secondary Metabolites Produced by Bacillus atrophaeus Against Verticillium dahliae

Endophytic bacteria associated with medicinal plants possess unique strategies that enhance growth and suvival of host plants, many of which are mediated by distinctive secondary metabolites. These bacteria and their secondary metabolites are important subjects for both basic and applied research aimed at sustainable agriculture. In the present study, 114 endophytic strains isolated from the wild ethnomedicinal plant Glycyrrhiza uralensis (licorice) were screened for their in vitro antimicrobial activities against common fungal pathogens of tomato (Fusarium oxysporum f. sp., Fulvia fulva, Alternaria solani), cotton (Fusarium oxysporum f. sp. Vesinfectum, Verticillium dahliae), pomegranite (Ceratocystis fimbriata), Cymbidinium (Colletotrichum gloeosporioides), and Tsao-ko (Pestalotiopsis microspora and Fusarium graminearum) and the common bacteria Staphylococcus aureus, Bacillus cereus, Salmonella enteritidis, and Escherichia coli. Several Bacillus strains, particularly Bacillus atrophaeus and Bacillus mojavensis, had a broad spectrum of antifungal and antibacterial activity. A total of 16 strains, selected based on broad antimicrobial activity, were shown to contain at least one putative secondary metabolite-encoding gene (i.e., polyketide synthase or non-ribosomal peptide synthetase) and/or one lytic enzyme (i.e., protease, cellulase, lipase, chitinase), which may be important mediators of antagonistic activity against pathogens. Five strains, representing Bacillus atrophaeus and Bacillus mojavensis, were selected for plant growth chamber experiments based on strong in vitro antifungal activities. All five strains significantly reduced disease severity in Arabidopsis thaliana plants challenged with V. dahlia infection. Gas-chromatography/mass-spectrometry analysis of cell-free extracts of Bacillus atrophaeus strain XEGI50 showed that at least 13 compounds were produced only during co-cultivation with V. dahlia, including putative compounds known to have antimicrobial activity, such as 1,2-benzenedicarboxylic acid, bis (2-methylpropyl) ester; 9,12-octadecadienoic acid (Z,Z)-, methyl ester; 9-octadecenoic acid, methyl ester, (E)-; and decanedioic acid, bis(2-ethylhexyl) ester. To our knowledge, this study is the first to report that bacteria isolated from G. uralensis have biocontrol abilities. Our findings provide new insights into the antimicrobial activities of natural endophytes, particularly B. atrophaeus, and suggest this species may a promising candidate as a biocontrol agent to confer resistance to Verticillium wilt disease and other phytopathogens in cotton and other crops.

Bioprospecting of Diaporthe terebinthifolii LGMF907 for antimicrobial compounds

Antibiotic-resistant bacteria have been observed with increasing frequency over the past decades, driving the search for new drugs and stimulating the interest in natural products sources. Endophytic fungi from medicinal plants represent a great source of novel bioactive compounds useful to pharmaceutical and agronomical purposes. Diaporthe terebinthifolii is an endophytic species isolated from Schinus terebinthifolius, a plant used in popular medicine for several health problems. The strain D. terebinthifolii LGMF907 was previously reported by our group to produce secondary metabolites with biological activity against phytopathogens. Based on these data, strain LGMF907 was chosen for bioprospecting against microorganisms of clinical importance and for characterization of major secondary metabolites. In this study, different culture conditions were evaluated and the biological activity of this strain was expanded. The crude extracts demonstrated high antibacterial activity against Escherichia coli, Micrococcus luteus, Saccharomyces cerevisiae, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant S. aureus. The compounds diaporthin and orthosporin were characterized and also showed activity against the clinical microorganisms evaluated. This study discloses the first isolation of diaporthin and orthosporin from D. terebinthifolii, and revealed the potential of this endophytic fungus to produce secondary metabolites with antimicrobial activity.

Diaporthe diversity and pathogenicity revealed from a broad survey of grapevine diseases in Europe

Species of Diaporthe are considered important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Several species are well-known on grapevines, either as agents of pre- or post-harvest infections, including Phomopsis cane and leaf spot, cane bleaching, swelling arm and trunk cankers. In this study we explore the occurrence, diversity and pathogenicity of Diaporthe spp. associated with Vitis vinifera in major grape production areas of Europe and Israel, focusing on nurseries and vineyards. Surveys were conducted in Croatia, Czech Republic, France, Hungary, Israel, Italy, Spain and the UK. A total of 175 Diaporthe strains were isolated from asymptomatic and symptomatic shoots, branches and trunks. A multi-locus phylogeny was established based on five genomic loci (ITS, tef1, cal, his3 and tub2), and the morphological characters of the isolates were determined. Preliminary pathogenicity tests were performed on green grapevine shoots with representative isolates. The most commonly isolated species were D. eres and D. ampelina. Four new Diaporthe species described here as D. bohemiae, D. celeris, D. hispaniae and D. hungariae were found associated with affected vines. Pathogenicity tests revealed D. baccae, D. celeris, D. hispaniae and D. hungariae as pathogens of grapevines. No symptoms were caused by D. bohemiae. This study represents the first report of D. ambigua and D. baccae on grapevines in Europe. The present study improves our understanding of the species associated with several disease symptoms on V. vinifera plants, and provides useful information for effective disease management.

Phaeophleospora vochysiae Savi & Glienke sp. nov. Isolated from Vochysia divergens Found in the Pantanal, Brazil, Produces Bioactive Secondary Metabolites

Microorganisms associated with plants are highly diverse and can produce a large number of secondary metabolites, with antimicrobial, anti-parasitic and cytotoxic activities. We are particularly interested in exploring endophytes from medicinal plants found in the Pantanal, a unique and widely unexplored wetland in Brazil. In a bio-prospecting study, strains LGMF1213 and LGMF1215 were isolated as endophytes from Vochysia divergens, and by morphological and molecular phylogenetic analyses were characterized as Phaeophleospora vochysiae sp. nov. The chemical assessment of this species reveals three major compounds with high biological activity, cercoscosporin (1), isocercosporin (2) and the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone (3). Besides the isolation of P. vochysiae as endophyte, the production of cercosporin compounds suggest that under specific conditions this species causes leaf spots, and may turn into a pathogen, since leaf spots are commonly caused by species of Cercospora that produce related compounds. In addition, the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone showed considerable antimicrobial activity and low cytotoxicity, which needs further exploration.

Emerging citrus diseases in Europe caused by species of Diaporthe

Species of Diaporthe are considered important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Several species are well-known on citrus, either as agents of pre- or post-harvest infections, such as dieback, melanose and stem-end rot on fruit. In this study we explored the occurrence, diversity and pathogenicity of Diaporthe species associated with Citrus and allied genera in European orchards, nurseries, and gardens. Surveys were carried out during 2015 and 2016 in Greece, Italy, Malta, Portugal, and Spain. A total of 79 Diaporthe strains were isolated from symptomatic twigs, branches and trunks. A multi-locus phylogeny was established based on five genomic loci (ITS, tef1, cal, his3 and tub2), and the morphological characters of the isolates determined. Preliminary pathogenicity tests were performed on lemon, lime, and orange plants with representative isolates. The most commonly isolated species were D. foeniculina and D. baccae, while only four isolates of D. novem were collected. Two new Diaporthe species, described here as D. limonicola and D. melitensis spp. nov. were found associated with a new devastating dieback disease of lemon plants. Furthermore, one cluster of sterile Diaporthe isolates was renamed as D. infertilis. Pathogenicity tests revealed most of the Citrus species as susceptible to D. baccae, D. foeniculina, and D. novem. Moreover, D. limonicola and D. melitensis caused serious cankers affecting all the Citrus species tested. This study is the first report of D. baccae and D. novem on citrus in Europe, and the first detection of a new Diaporthe canker disease of citrus in Europe. However, no isolates of D. citri were found. The study improves our understanding of the species associated with several disease symptoms on citrus plants, and provides useful information for effective disease management.

Biological activity of Diaporthe terebinthifolii extracts against Phyllosticta citricarpa

Citrus black spot disease, caused by the phytopathogen Phyllosticta citricarpa, depreciates the market value of citrus fruits and prevents their exportation to disease-free regions. It may also reduce the productivity of citrus fruit orchards. To identify an alternative to conventional disease control measures, isolates of Diaporthe terebinthifolii, active against P. citricarpa, were selected from an endophytic fungal population of Schinus terebinthifolia leaves. Different culture media were screened to identify the culture medium that afforded the most efficient production of biologically active extracts. A particular fraction (fraction VI) of the extract completely protected orange leaves by inhibiting the germination of P. citricarpa conidia with a minimum inhibitory concentration of 0.003 μg.mL-1. The active constituents in D. terebinthifolii extract fractions were identified by gas chromatography coupled to mass spectrometry as verbanol, phenylethyl alcohol, verbenyl acetate and methyl hexadecanoate. The results obtained strongly suggest the existence of a synergistic effect among the metabolites produced. Thus, these fungal metabolites could be used to control the CBS disease. As the asexual spores of P. citricarpa play an important role in fruit lesion development and disease dispersion, fungal extracts that inhibit the spore germination can be used as an effective alternative for directional disease control.

Antibacterial and Antioxidant Metabolites of Diaporthe spp. Isolated from Flowers of Melodorum fruticosum

Fifty-two strains of endophytic fungi were isolated from flowers of the medicinal plant Melodorum fruticosum. Seven genera were identified including Alternaria, Aspergillus, Colletotrichum, Diaporthe, Fusarium, Greeneria and Nigrospora. All strains were cultured for 30 days and further macerated in ethyl acetate solvent for 3 days. The obtained fungal extracts were examined for antibacterial activity using agar disc diffusion against nine pathogenic bacteria: Staphylococcus aureus, Bacillus subtilis, B. cereus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Shigella flexneri, Vibrio cholerae and V. parahaemolyticus. Forty-three fungal extracts exhibited antibacterial activity against at least one tested pathogen. The antioxidant properties of all extracts were also investigated by DPPH scavenging assay. Sixteen extracts displayed high antioxidant capacity (IC₅₀ ranging from 10 to 50 µg/mL) when compared to the gallic acid and trolox standards (IC₅₀ of 12.46 and 2.55 µg/mL, respectively). The crude extracts of Diaporthe sp. MFLUCC16-0682 and Diaporthe sp. MFLUCC16-0693 exhibited notable antibacterial and antioxidant activities. Analysis of chemical composition using gas chromatography-mass spectrometry suggested that the observed antibacterial activity of the two Diaporthe spp. was possibly due to the presence of abienol, 4-methoxy stilbene, phenethyl cinnamate and 2Z,6Z-farnesal, while their potential antioxidant activity could be attributed to phenolic compounds, such as benzene acetaldehyde, benzyl benzoate, salicylaldehyde, benzoin and benzyl cinnamate. The results suggest that the genus Diaporthe is a potential source of metabolites that can be used in a variety of applications.

Antibacterial Activity of Endophytic Actinomycetes Isolated from the Medicinal Plant Vochysia divergens (Pantanal, Brazil)

Endophytic actinomycetes from medicinal plants produce a wide diversity of secondary metabolites (SM). However, to date, the knowledge about endophytes from Brazil remains scarce. Thus, we analyzed the antimicrobial potential of 10 actinomycetes isolated from the medicinal plant Vochysia divergens located in the Pantanal sul-mato-grossense, an unexplored wetland in Brazil. Strains were classified as belonging to the Aeromicrobium, Actinomadura, Microbacterium, Microbispora, Micrococcus, Sphaerisporangium, Streptomyces, and Williamsia genera, through morphological and 16S rRNA phylogenetic analyzes. A susceptibility analysis demonstrated that the strains were largely resistant to the antibiotics oxacillin and nalidixic acid. Additionally, different culture media (SG and R5A), and temperatures (28 and 36°C) were evaluated to select the best culture conditions to produce the active SM. All conditions were analyzed for active metabolites, and the best antibacterial activity was observed from metabolites produced with SG medium at 36°C. The LGMB491 (close related to Aeromicrobium ponti) extract showed the highest activity against methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 0.04 mg/mL, and it was selected for SM identification. Strain LGMB491 produced 1-acetyl-β-carboline (1), indole-3-carbaldehyde (2), 3-(hydroxyacetyl)-indole (4), brevianamide F (5), and cyclo-(L-Pro-L-Phe) (6) as major compounds with antibacterial activity. In this study, we add to the knowledge about the endophytic community from the medicinal plant V. divergens and report the isolation of rare actinomycetes that produce highly active metabolites.

Solid-state fermentation for production of a bioherbicide from Diaporthe sp. and its formulation to enhance the efficacy

In this study, a bioherbicide was produced by solid-state fermentation (SSF) using Diaporthe sp. Adjuvants were employed in a formulation to enhance the herbicidal activity towards the target (Cucumis sativus). The study was divided into two steps: (1) the fermentation condition for bioherbicide production was assessed; (2) evaluation of different formulations containing palm oil, Tween® 80 and Span® 80, in order to increase phytotoxicity. In step 1, the maximum herbicidal activity (1.23% of the leaves had lesions) was obtained at 25 °C, moisture content of 50 wt%, supplemented with 10 wt% of corn steep liquor and soybean bran and inoculum density of 15 wt%. In step 2, the formulation containing 8.2 wt% of palm oil, 8.2 wt% of Tween® 80 and Span® 80, resulting in an HLB of 12.8 showed the highest phytotoxicity on the leaves. At this condition, dry matter and height of target were reduced about 36% in comparison with control. Diaporthe sp. has the potential to produce molecules with herbicidal activity and the use of adjuvants enhanced three times its efficiency.