Filtrates from cultures of endophytic fungi isolated from leaves of Copaifera oblongifolia (Fabaceae) affect germination and seedling development differently / Fungos endofíticos isolados de folhas de Copaifera oblongifolia (Fabaceae) afetam diferentemente a germinação e o desenvolvimento das plântulas

Interactions between endophytic fungi (EFs) and their host plants range from positive to neutral to negative. The results of such interactions can vary depending on the organ of the infected host plant. EFs isolated from the leaves of some species of plants have potential for use as agents to inhibit seed germination and control invasive plants. The objectives of this study were to identify EFs present in the leaves of Copaifera oblongifolia and to evaluate the role of these fungi in seed germination and seedling development. A total of 11 species of EFs were isolated, which were identified using the internal transcribed spacers (ITS) sequence of the nuclear ribosomal DNA. The isolated species of EFs are generalists and probably are transmitted horizontally. Laboratory tests revealed that filtrates of these fungal isolates differently affect seed germination and seedling development of C. oblongifolia. The species Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum and Phomopsis sp. negatively affected seed germination, with N. parvum standing out for its negative effects, inhibiting seedling germination and survival in 89 and 222%, respectively. In addition, Cochliobolus intermedius negatively affected seedling development. Thus, the combined use of N. parvum and C. intermedius, or products from the metabolism of these microorganisms, in the control of invasive plants deserves attention from future studies.

As interações entre fungos endofíticos (FEs) e suas plantas hospedeiras variam de positivas, neutras a negativas. Os resultados destas interações podem variar dependendo do órgão da planta hospedeira infectada. FEs isolados de folhas de algumas espécies de plantas têm potencial para serem usados como agentes inibidores da germinação de sementes e no controle de plantas invasoras. Os objetivos deste estudo foram identificar os FEs presentes nas folhas de Copaifera oblongifolia e avaliar o papel destes fungos na germinação das sementes e no desenvolvimento das plântulas. Um total de 11 espécies de FEs foi isolado das folhas de C. oblongifolia e identificado através da sequência dos espaçadores internos transcritos do DNA ribossomal nuclear. As espécies de FEs isoladas são generalistas e provavelmente devem ser transmitidas horizontalmente. Os resultados dos testes de germinação mostraram que filtrados destes isolados fúngicos podem afetar diferentemente a germinação das sementes e o desenvolvimento das plântulas de C. oblongifolia. As espécies Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum e Phomopsis sp. afetaram negativamente a germinação das sementes de C. oblongifolia. Dentre estas espécies devemos destacar que N. parvum reduziu a germinação e a sobrevivência das plântulas em 89 e 222%, respectivamente. Além disso, Cochiliobolus intermedius afetou negativamente o desenvolvimento das plântulas. Assim, o uso combinado de N. parvum e C. intermedius, ou de produtos do metabolismo destas espécies de fungos, têm potencial para serem usados no manejo de plantas invasoras.

Filtrates from cultures of endophytic fungi isolated from leaves of Copaifera oblongifolia (Fabaceae) affect germination and seedling development differently

Abstract Interactions between endophytic fungi (EFs) and their host plants range from positive to neutral to negative. The results of such interactions can vary depending on the organ of the infected host plant. EFs isolated from the leaves of some species of plants have potential for use as agents to inhibit seed germination and control invasive plants. The objectives of this study were to identify EFs present in the leaves of Copaifera oblongifolia and to evaluate the role of these fungi in seed germination and seedling development. A total of 11 species of EFs were isolated, which were identified using the internal transcribed spacers (ITS) sequence of the nuclear ribosomal DNA. The isolated species of EFs are generalists and probably are transmitted horizontally. Laboratory tests revealed that filtrates of these fungal isolates differently affect seed germination and seedling development of C. oblongifolia. The species Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum and Phomopsis sp. negatively affected seed germination, with N. parvum standing out for its negative effects, inhibiting seedling germination and survival in 89 and 222%, respectively. In addition, Cochliobolus intermedius negatively affected seedling development. Thus, the combined use of N. parvum and C. intermedius, or products from the metabolism of these microorganisms, in the control of invasive plants deserves attention from future studies.

Resumo As interações entre fungos endofíticos (FEs) e suas plantas hospedeiras variam de positivas, neutras a negativas. Os resultados destas interações podem variar dependendo do órgão da planta hospedeira infectada. FEs isolados de folhas de algumas espécies de plantas têm potencial para serem usados como agentes inibidores da germinação de sementes e no controle de plantas invasoras. Os objetivos deste estudo foram identificar os FEs presentes nas folhas de Copaifera oblongifolia e avaliar o papel destes fungos na germinação das sementes e no desenvolvimento das plântulas. Um total de 11 espécies de FEs foi isolado das folhas de C. oblongifolia e identificado através da sequência dos espaçadores internos transcritos do DNA ribossomal nuclear. As espécies de FEs isoladas são generalistas e provavelmente devem ser transmitidas horizontalmente. Os resultados dos testes de germinação mostraram que filtrados destes isolados fúngicos podem afetar diferentemente a germinação das sementes e o desenvolvimento das plântulas de C. oblongifolia. As espécies Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum e Phomopsis sp. afetaram negativamente a germinação das sementes de C. oblongifolia. Dentre estas espécies devemos destacar que N. parvum reduziu a germinação e a sobrevivência das plântulas em 89 e 222%, respectivamente. Além disso, Cochiliobolus intermedius afetou negativamente o desenvolvimento das plântulas. Assim, o uso combinado de N. parvum e C. intermedius, ou de produtos do metabolismo destas espécies de fungos, têm potencial para serem usados no manejo de plantas invasoras.

Filtrates from cultures of endophytic fungi isolated from leaves of Copaifera oblongifolia (Fabaceae) affect germination and seedling development differently / Fungos endofíticos isolados de folhas de Copaifera oblongifolia (Fabaceae) afetam diferentemente a germinação e o desenvolvimento das plântulas

Abstract Interactions between endophytic fungi (EFs) and their host plants range from positive to neutral to negative. The results of such interactions can vary depending on the organ of the infected host plant. EFs isolated from the leaves of some species of plants have potential for use as agents to inhibit seed germination and control invasive plants. The objectives of this study were to identify EFs present in the leaves of Copaifera oblongifolia and to evaluate the role of these fungi in seed germination and seedling development. A total of 11 species of EFs were isolated, which were identified using the internal transcribed spacers (ITS) sequence of the nuclear ribosomal DNA. The isolated species of EFs are generalists and probably are transmitted horizontally. Laboratory tests revealed that filtrates of these fungal isolates differently affect seed germination and seedling development of C. oblongifolia. The species Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum and Phomopsis sp. negatively affected seed germination, with N. parvum standing out for its negative effects, inhibiting seedling germination and survival in 89 and 222%, respectively. In addition, Cochliobolus intermedius negatively affected seedling development. Thus, the combined use of N. parvum and C. intermedius, or products from the metabolism of these microorganisms, in the control of invasive plants deserves attention from future studies.

Resumo As interações entre fungos endofíticos (FEs) e suas plantas hospedeiras variam de positivas, neutras a negativas. Os resultados destas interações podem variar dependendo do órgão da planta hospedeira infectada. FEs isolados de folhas de algumas espécies de plantas têm potencial para serem usados como agentes inibidores da germinação de sementes e no controle de plantas invasoras. Os objetivos deste estudo foram identificar os FEs presentes nas folhas de Copaifera oblongifolia e avaliar o papel destes fungos na germinação das sementes e no desenvolvimento das plântulas. Um total de 11 espécies de FEs foi isolado das folhas de C. oblongifolia e identificado através da sequência dos espaçadores internos transcritos do DNA ribossomal nuclear. As espécies de FEs isoladas são generalistas e provavelmente devem ser transmitidas horizontalmente. Os resultados dos testes de germinação mostraram que filtrados destes isolados fúngicos podem afetar diferentemente a germinação das sementes e o desenvolvimento das plântulas de C. oblongifolia. As espécies Curvularia intermedia, Neofusicoccum parvum, Pseudofusicoccum stromaticum e Phomopsis sp. afetaram negativamente a germinação das sementes de C. oblongifolia. Dentre estas espécies devemos destacar que N. parvum reduziu a germinação e a sobrevivência das plântulas em 89 e 222%, respectivamente. Além disso, Cochiliobolus intermedius afetou negativamente o desenvolvimento das plântulas. Assim, o uso combinado de N. parvum e C. intermedius, ou de produtos do metabolismo destas espécies de fungos, têm potencial para serem usados no manejo de plantas invasoras.

Antifungal Potential of Bacillus velezensis CE 100 for the Control of Different Colletotrichum Species through Isolation of Active Dipeptide, Cyclo-(D-phenylalanyl-D-prolyl).

Colletotrichum species are important fungal pathogens causing anthracnose of tropical and subtropical fruit and vegetable crops. Dual culture assay indicated that Bacillus velezensis CE 100 was a strong antagonist against C. acutatum, C. coccodes, C. dematium, and C. gloeosporioides. The volatile organic compounds produced by B. velezensis CE 100 affected mycelial growth of Colletotrichum species tested in our study and caused twisted hyphal structures of all these fungal species. Chloroform crude compounds of B. velezensis CE 100 inhibited four Colletotrichum species in a concentration-dependent manner and induced severe damage in hyphal morphology of these fungal pathogens, including swelling, bulging, and multiple branching. Moreover, the active cyclic dipeptide, cyclo-(D-phenylalanyl-D-prolyl), was isolated from chloroform crude extract and identified by nuclear magnetic resonance (NMR) and mass spectrometry. The inhibitory effect of cyclo-(D-phenylalanyl-D-prolyl) on conidial germination of C. gloeosporioides occurred in a concentration-dependent manner. The conidial germination rate was completely inhibited by a concentration of 3 mg/mL of cyclo-(D-phenylalanyl-D-prolyl). Scanning electron micrographs revealed that the exposure to cyclic dipeptide resulted in seriously deformed hyphae and conidia with shriveled surfaces in dipeptide-treated C. gloeosporioides. Therefore, active dipeptide-producing B. velezensis CE 100 is a promising biocontrol agent for Colletotrichum species causing anthracnose.

Screening for potential mycoherbicides within the endophyte community of Phelipanche ramosa parasitizing tobacco.

Branched broomrape (Phelipanche ramosa (L.) Pomel) is an achlorophyllous root parasitic plant with a wide host range. Its complex management is leading to the abandonment of tobacco or oilseed rape cultivation in the most affected regions in France. Among broomrape regulation factors, soil microorganisms such as fungi seem to be a relevant biocontrol lever. The aim of this work was to detect potential mycoherbicides among fungal endophytic colonizers of P. ramosa parasitizing tobacco. Our hypothesis was that both the inhibitory of broomrape seed germination and the necrotic activities are characteristic of the fungal isolates whatever their taxonomic position. To test this hypothesis, we analysed the taxonomic and functional diversity of fungal isolates of symptomatic P. ramosa collected from infested tobacco-growing regions in France in order to identify one or more fungal strains for future biocontrol. The fungal isolates were characterized using morphological and molecular identification tools and tested for their ability to inhibit the germination of P. ramosa seeds, their necrotic activity on the stems of the pest and their non-pathogenicity to the host plant. We highlighted the specific richness of fungal colonizers associated with symptomatic P. ramosa. Among the 374 collected isolates, nearly 80% belonged to 19 Fusarium species. Eighty-seven isolates representative of this diversity also showed functional diversity by inhibiting seed germination of the parasite. The 20 best-performing isolates showed differences in germination inhibition of P. ramosa at the intraspecific level. Among these 20 fungal isolates, a set of 15 randomly selected isolates was tested for their necrotic activity on the parasite stems. Fusarium venenatum isolates showed dual competence, i.e. germination inhibition and necrotic activity, and were non-pathogenic to tobacco. This led us to discuss the potential mycoherbicidal effect of this fungal species on P. ramosa.

Ecotoxicological test to assess effects of herbicides on spore germination of Rhizophagus clarus and Gigaspora albida.

Given the essential role of arbuscular mycorrhizal fungi (AMF) in soil systems and agriculture, their use as biological indicators has risen in all fields of microbiology research. However, AMF sensitivity to chemical pesticides is poorly understood in field conditions, and not explored in ecotoxicology protocols. Hence, the goal of this study was to evaluate the effects of different concentrations of glyphosate (Roundup®) and diuron+paraquat (Gramocil®) on the germination of spores of Gigaspora albida and Rhizophagus clarus in a tropical artificial soil. This study was conducted in 2019 at the Soil Ecology and Ecotoxicology Laboratory of the Universidade do Estado de Santa Catarina. The nominal concentrations of glyphosate were 0, 10, 50, 100, 250, 500, 750 and 1000 mg a.i. kg-1. For diuron+paraquat, the concentrations tested were 0, 10 + 20, 50 + 100, 100 + 200, 250 + 500, 500 + 1000, 750 + 1500 and 1000 + 2000 mg a.i. kg-1. Glyphosate did not alter germination of G. albida, but germination inhibition of R. clarus spores was of 30.8% at 1000 mg kg-1. Diuron+paraquat inhibited by 8.0% germination of G. albida, but only at the highest concentration tested. On the other hand, effects on R. clarus were detected at 50 + 100 mg kg-1 concentration and above, and inhibition was as high as 57.7% at the highest concentration evaluated. These results suggest distinct response mechanisms of Rhizophagus and Gigaspora when exposed to herbicides, with the former being more sensitive than the later.

Untargeted metabolomics as a hypothesis-generation tool in plant protection product discovery: Highlighting the potential of trehalose and glycerol metabolism of fungal conidiospores as novel targets.

INTRODUCTION: The production of high quality and safe food represents a main priority for the agri-food sector in the effort to sustain the exponentially growing human population. Nonetheless, there are major challenges that require the discovery of new, alternative, and improved plant protection products (PPPs). Focusing on fungal plant pathogens, the dissection of mechanisms that are essential for their survival provides insights that could be exploited towards the achievement of the aforementioned aim. In this context, the germination of fungal spores, which are essential structures for their dispersal, survival, and pathogenesis, represents a target of high potential for PPPs. To the best of our knowledge, no PPPs that target the germination of fungal spores currently exist. OBJECTIVES: Within this context, we have mined for changes in the metabolite profiles of the model fungus Aspergillus nidulans FGSC A4 conidiospores during germination, in an effort to discover key metabolites and reactions that could potentially become targets of PPPs. METHODS: Untargeted GC/EI-TOF/MS metabolomics and multivariate analyses were employed to monitor time-resolved changes in the metabolomes of germinating A. nidulans conidiospores. RESULTS: Analyses revealed that trehalose hydrolysis plays a pivotal role in conidiospore germination and highlighted the osmoregulating role of the sugar alcohols, glycerol, and mannitol. CONCLUSION: The ineffectiveness to introduce active ingredients that exhibit new mode(s)-of-action as fungicides, dictates the urge for the discovery of PPPs, which could be exploited to combat major plant protection issues. Based on the crucial role of trehalose hydrolysis in conidiospore dormancy breakage, and the subsequent involvement of glycerol in their germination, it is plausible to suggest their biosynthesis pathways as potential novel targets for the next-generation antifungal PPPs. Our study confirmed the applicability of untargeted metabolomics as a hypothesis-generation tool in PPPs' research and discovery.

Targeted induction of a silent fungal gene cluster encoding the bacteria-specific germination inhibitor fumigermin.

Microorganisms produce numerous secondary metabolites (SMs) with various biological activities. Many of their encoding gene clusters are silent under standard laboratory conditions because for their activation they need the ecological context, such as the presence of other microorganisms. The true ecological function of most SMs remains obscure, but understanding of both the activation of silent gene clusters and the ecological function of the produced compounds is of importance to reveal functional interactions in microbiomes. Here, we report the identification of an as-yet uncharacterized silent gene cluster of the fungus Aspergillus fumigatus, which is activated by the bacterium Streptomyces rapamycinicus during the bacterial-fungal interaction. The resulting natural product is the novel fungal metabolite fumigermin, the biosynthesis of which requires the polyketide synthase FgnA. Fumigermin inhibits germination of spores of the inducing S. rapamycinicus, and thus helps the fungus to defend resources in the shared habitat against a bacterial competitor.

Combining spore germination and heat inactivation to decontaminate materials contaminated with Bacillus anthracis spores.

AIMS: To add a spore germination step in order to reduce decontamination temperature and time requirements compared to the current hot, humid air decontamination parameters, which are 75-80°C, ≥72 h, 70-90% RH, down to ≤60°C and ≤24 h total decontamination time. METHODS AND RESULTS: Bacillus anthracis spore germination with l-alanine+inosine+calcium dipicolinate (CaDPA) was quantified at 0-40°C, several time points and spore concentrations of 5-9 log10 per ml. Germination efficiency at 0-40°C was >99% at <8 log10 spores per ml. The temperature optimum was 20°C. Germination efficiency was significantly higher but slower at 0°C compared to ≥30°C at ≥8 log10 spores per ml. A single germinant application followed by 60°C, 1-h treatment consistently inactivated >2 log10 (>99%) of spores. However, a repeat application of germinant was needed to achieve the objective of ≥6 log10 spore inactivation out of a 7 log10 challenge (≥99·9999%) for ≤24 h total decontamination time for nylon and aircraft performance coating. CONCLUSIONS: l-alanine+inosine+CaDPA stimulated germination across wide temperature and spore concentration ranges. SIGNIFICANCE AND IMPACT OF THE STUDY: Germination expands the scope of spore decontamination to include materials from any industry sector that can be sprayed with an aqueous germinant solution.

Coumarins from the peel of citrus grown in Colombia: composition, elicitation and antifungal activity.

The present work analyses the chromatographic profile of the peels from fruits of different citrus cultivated in Colombia: sweet orange (Citrus sinensis [L.] Osbeck var. Valencia), mandarins (Citrus reticulata L. var. Arrayana and Oneco), Key lime (Citrus aurantifolia [Christ.] Swingle var. Pajarito), Mandarine lime (Citrus x limonia, a hybrid between Citrus reticulata and Citrus x limon) and Tahitian lime (C. latifolia Tanaka, syn. Persian lime). Coumarins, furanocoumarins and polymethoxylated flavones are the major compounds. Then, six coumarins were isolated and identified from fruits of Tahitian and Key lime corresponding to 5-geranyloxy-7-methoxycoumarin; 5,7-dimethoxycoumarin (syn. limettin); 5,8-dimethoxypsoralen (syn. isopimpinellin); 5-methoxypsoralen (syn. bergaptene); 5-geranoxypsoralen (syn. bergamottin) and 5-(2,3-dihydroxy-3-methylbutoxy) psoralen (syn. oxypeucedanin hydrate). Coumarins and furanocoumarins were quantified by liquid chromatography (HPLC-DAD). Results show that the prenylated compounds were present in high concentrations in Tahitian and Key lime but in very low amounts in mandarins and sweet orange. Subsequently, the antifungal activity (inhibition of mycelial growth and germination of spores) of the coumarins against the fungus causing the anthracnose, Colletotrichum sp. (isolated from aerial parts of Tahitian lime) was determined. The compounds limettin and bergaptene, as well as mixtures of them, showed significant inhibitory effect (radial growth and spore germination) when compared to the control. Finally, the effect of some recognized elicitors to induce the coumarin production in fruits of C. latifolia was evaluated. The results showed that the chemical profiles are dependent on the applied elicitor and the post-induction time. As a result of the induction, a high concentration of some coumarins and furanocoumarins was maintained in the course of time for the Tahitian lime. In conclusion, isolated coumarins could be involved in the defense mechanisms of C. latifolia, C. aurantifolia and C. limonia and their accumulation may be modulated by the application of elicitors.

Biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination.

Cresols are ubiquitous due to industrial production and natural presence. o-cresol (2-methyl phenol) is highly toxic to both fauna and flora. It has been included in the EPA list as one of the priority pollutants. The deleterious effects of pesticides, herbicides, and many other chemical compounds on seed germination are known. However, the effect of o-cresol on seed germination is not known. Therefore, it is of interest to study the effect of o-cresol on germination of 13 different vegetable crop seeds using standard Filter Paper Method. There is no effect on germination for brinjal, red chili, and (green gram, chickpea, cucumber, tomato, fenugreek, cowpea, Green pea, coriander, and spinach, seeds even at 1500 mg/l of o-cresol However, okra and mustard were found to be sensitive to ocresol. Germination of mustard under controlled concentration of o-cresol showed similar results by soil method. It was found that germination percentage and seedling vigour (Vigour Index) was reduced by o-cresol. The percent germination was reduced to 64 and 12 at 25 and 50 mg o-cresol/kg soil as against 100% in the case of untreated control. The vigour index was reduced to 160 and 10, respectively as against of 646 that for the control. The viability of seeds by 2,3,5 - tetrazolium trichloride (TTC) test showed that a considerable reduction was observed at 200mg/l o-cresol. Reduced protease and amylase activity in o-cresol shows inhibited mustard generation. However, mustard generation inhibition was restored by the bioremediation of o-cresol using Pseudomonas monteilii SHY. Thus, the biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination are shown.

Linking hydrogen-enhanced rice aluminum tolerance with the reestablishment of GA/ABA balance and miRNA-modulated gene expression: A case study on germination.

Although previous results showed that exogenous hydrogen (H2) alleviated aluminum (Al) toxicity, the detailed mechanism remains unclear. Here, we reported that the exposure of germinating rice seeds to Al triggered H2 production, followed by a decrease of GA/ABA ratio and seed germination inhibition. Compared to inert gas (argon), H2 pretreatment not only strengthened H2 production and alleviated Al-induced germination inhibition, but also partially reestablished the balance between GA and ABA. By contrast, a GA biosynthesis inhibitor paclobutrazol (PAC) could block the H2-alleviated germination inhibition. The expression of GA biosynthesis genes (GA20ox1 and GA20ox2) and ABA catabolism genes (ABA8ox1 and ABA8ox2), was also induced by H2. Above results indicated that GA/ABA might be partially involved in H2 responses. Subsequent results revealed that compared with Al alone, transcripts of miR398a and miR159a were decreased by H2, and expression levels of their target genes OsSOD2 and OsGAMYB were up-regulated. Whereas, miR528 and miR160a transcripts were increased differentially, and contrasting tendencies were observed in the changes of their target genes (OsAO and OsARF10). The transcripts of Al-tolerant gene OsSTAR1/OsSTAR2 and OsFRDL4 were up-regulated. Above results were consistent with the anti-oxidant defense, decreased Al accumulation, and enhanced citrate efflux. Together, our results provided insight into the mechanism underlying H2-triggered Al tolerance in plants.

Phytotoxic phenylpropanoids isolated from Ophryosporus charua (Griseb.) Hieron.

Bioguided isolation of the EtOH extract from the medicinal native plant, Ophryosporus charua, against Raphanus sativus, yielded three phenylpropanoids, charuol A [(Z)-4-((1S,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate], charuepoxide [(Z)-4-((2S,3R)-3-(acetoxymethyl oxiran-2-yl)phenyl) 2-methylbut-2-enoate] and charuol B [(Z)-4-((1R,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate]. Their structures and absolute configuration were established by extensive spectroscopic analyses. The effective concentrations for 50% inhibition of germination (ECg50) and root (ECr50) and shoot (ECs50) elongations were determined for these compounds against P. miliaceum (monocot) and Raphanus sativus (dicot). Charuol A was the most active in the inhibition of germination of P. miliaceum (ECg50 = 0.97 mM), followed by charuol B and charuepoxide, although charuol B was the most effective in regulating the root growth of P. miliaceum seedlings, with an ECr50 of 1.0 mM. Charuol A inhibited the germination of R. sativus, while its seedling development was also affected by all three compounds with different effectiveness. Charuol A was also highly effective in the 0.09-0.30 mM range against other test species such as Lactuca sativa, Eruca sativa, Allium ampeloprasum and Secale cereale.

Antifungal activity of ß-carbolines on Penicillium digitatum and Botrytis cinerea.

ß-carbolines (ßCs) are alkaloids widely distributed in nature that have demonstrated antimicrobial properties. Here, we tested in vitro six ßCs against Penicillium digitatum and Botrytis cinerea, causal agents of postharvest diseases on fruit and vegetables. Full aromatic ßCs (harmine, harmol, norharmane and harmane) exhibited a marked inhibitory effect on conidia germination at concentrations between 0.5 and 1 mM, while dihydro-ßCs (harmalina and harmalol) only caused germination delay. Harmol showed the highest inhibitory effect on both fungal pathogens. After 24 h of exposure to 1 mM harmol, conidia revealed a severe cellular damage, exhibiting disorganized cytoplasm and thickened cell wall. Harmol antimicrobial effect was fungicidal on B. cinerea, while it was fungistatic on P. digitatum. Conidia membrane permeabilization was detected in treatments with harmol at sub-inhibitory and inhibitory concentrations, for both pathogens. In addition, residual infectivity of P. digitatum on lemons and B. cinerea on blueberries was significantly reduced after exposure to this alkaloid. It also inhibited mycelial growth, preventing sporulation at the highest concentration tested. These results indicate that harmol might be a promising candidate as a new antifungal molecule to control causal agents of fruit diseases.

Naphthalene Acetic Acid Potassium Salt (NAA-K+) Affects Conidial Germination, Sporulation, Mycelial Growth, Cell Surface Morphology, and Viability of Fusarium oxysporum f. sp. radici-lycopersici and F. oxysporum f. sp. cubense in Vitro.

The response to exogenous addition of naphthalene acetic acid potassium salt (NAA-K+) to Fusarium oxysporum f. sp radici-lycopersici ATCC 60095 and F. oxysporum f. sp. cubense isolated from Michoacan Mexico soil is reported. The in vitro study showed that NAA-K+ might be effective in the control of Fusarium oxysporum. Exogenous application of NAA-K+ affected both spores and mycelium stages of the fungi. Viability testing using acridine orange and propidium iodide showed that NAA-K+ possesses fungal killing properties, doing it effectively in the destruction of conidia of this phytopathogenic fungi. Analysis of treated spores by scanning electron microscopy showed changes in the shape factor and fractal dimension. Moreover, NAA-K+ repressed the expression of brlA and fluG genes. The results disclosed here give evidence of the use of this synthetic growth factor as a substance of biocontrol that presents advantages, and the methods of application in situ should be explored.

Systematic investigation of germination responses of Bacillus subtilis spores in different high-salinity environments.

High-salinity environments play an increasingly important role in ecology regarding soil salinization due to human-induced processes, but also need to be considered in terms of natural soil desiccation and extreme habitats. It has been shown previously that spore germination of the ubiquitous soil bacterium Bacillus subtilis is detrimentally affected by the presence of high NaCl concentrations, but the underlying mechanisms and effects of other salts remained obscure. To address these two points, we performed a systematic analysis with 32 different salts using spectrophotometric and microscopic methods. It could be shown that inhibitory strength varies considerably among different salts. Although osmotic effects seem to play an important role, ionic composition and concentration (especially of the anion) as well as chemical properties seem to be decisive for the extent of germination inhibition. At the current state of knowledge, fluxes of ions, Ca(2+)-DPA and water are likely affected by all salts, whereas the exact inhibition mechanism of each salt might further depend on the respective properties of the involved ions. Hence, the observed inhibition likely is a result of several phenomena interacting with each other. Altogether this study highlights the complex impact of ionic environments on the life cycle of spore formers.

Ryecyanatines A and B and ryecarbonitrilines A and B, substituted cyanatophenol, cyanatobenzo[1,3]dioxole, and benzo[1,3]dioxolecarbonitriles from rye (Secale cereale L.) root exudates: Novel metabolites with allelopathic activity on Orobanche seed germination and radicle growth.

Orobanche and Phelipanche species (the broomrapes) are root parasitic plants, some of which represent serious weed problems causing heavy yield losses on important crops. Current control relies on the use of certain agronomic practices, resistant crop varieties, and herbicides, albeit success has been marginal. Agronomic practices such as the use of allelopathic species in intercropping or cover crops, or the use of direct seedling over residues of allelopathic species incorporate the principle of allelopathy exerted by molecules exuded from roots or released by crop residues to control broomrapes. In addition, the isolation of natural substances from root exudates of plants with potential to inhibit broomrape development opens the door to the design of new herbicides based on natural and benign sources. Ryecyanatines A and B and ryecarbonitrilines A and B, the first new substituted cyanatophenol, substituted cyanatobenzo[1,3]dioxole, and the latter two new substituted benzo[1,3]dioxolecarbonitriles were isolated from rye (Secale cereale L.) root exudates. They were characterized as 4-cyanato-2-methoxyphenol, 2-cyanato-benzo[1,3]dioxole, 2-methoxybenzo[1,3]dioxole-5-carbonitrile and benzo[1,3]dioxole-2-carbonitrile by spectroscopic (essentially NMR and HRESI MS spectra) methods. These compounds were investigated for allelopathic activity on Orobanche germination and development. Ryecarbonitriline A induced germination of Orobanche cumana seeds, and this germination can be considered as suicidal because O. cumana does not parasite rye roots and cannot survive without host resources beyond germination stage. In addition, ryecyanatine A promotes a rapid cessation of O. cumana, Orobanche crenata and Orobanche minor radicle growth with the promotion of a layer of papillae at the radicle tip in O. cumana and O. crenata hampering the contact of the parasite to the host. Ryecarbonitriline B also displayed the same activity although being less active than ryecyanatine A and mainly restricted to O. cumana.

Germination inhibitory activity of selected plants from Central South of Chile / Actividad inhibitoria de la germinación de plantas seleccionadas del Centro-Sur de Chile

Methanol extract obtained from aerial parts of 24 selected plants from Central Valley and Pre-andean foothill from Ñuble Province of Chile were tested for its inhibitory germination activity against Trifolium repens and Raphanus sativus. Many extracts (13/24 = 54 percent) showed inhibition of T. repens germination with IG percent > 50 percent, but none on R. sativus.

Extractos metanólicos obtenidos de partes aéreas de 24 plantas seleccionadas del valle central y preandino de la Provincia de Ñuble-Chile, fueron ensayados para determinar su capacidad inhibitoria sobre la germinación de semillas de Trifolium repens y Raphanus sativus. Los extractos (13/24 = 54 por ciento) muestran actividad inhibitoria de la germinación de semillas de T. repens con un IG por ciento>50 por ciento, pero no tienen actividad significativa sobre R. sativus.

Synthesis, crystal structure and potential antimicrobial activities of di (4-sulfamoyl-phenyl-ammonium) sulphate.

A new organic-inorganic hybrid SO4[C6H9N2O2S]2, has been synthesized and characterized by X-ray diffraction. This compound crystallizes in the orthorhombic system, spaces group Pbcn. In the title compound, the packing is stabilized by intermolecular N-H⋯O hydrogen bonds and π-π stacking interactions between the phenyl rings, linking the molecules into three-dimensional network. The in vitro antimicrobial activity of di (4-sulfamoyl-phenyl-ammonium) sulphate was determined by the broth dilution method against several strains selected to define their spectrum and potency. Here we show that the synthetic sulfanilamide exhibits promising antibacterial potency. High inhibition was also detected against Candida albicans. In this paper we firstly showed the antifungal activity of the sulfanilamide against two serious phytopathogenic fungi. Interestingly, the new compound was able to suppress mycelial growth as well as the spores germination of tested fungi, values of spore germination vary from 97.6% to 37.5%, respectively for Botrytis cinerea and Fusarium species. The minimal inhibitory concentrations (MIC) ranging from 8 to 100 µg ml(-1) and IC50 values varying from 5.81 to less than 100 µg ml(-1)), showed that the sulfanilamide sulphate had high activity against bacteria, yeast and fungi, compared to others published antifungal compounds.

In vitro antifungal activity of synthetic dsRNA molecules against two pathogens of banana, Fusarium oxysporum f. sp. cubense and Mycosphaerella fijiensis.

BACKGROUND: A key challenge for designing RNAi-based crop protection strategies is the identification of effective target genes in the pathogenic organism. In this study, in vitro antifungal activities of a set of synthetic double-stranded RNA molecules on spore germination of two major pathogenic fungi of banana, Fusarium oxysporum Schlecht f. sp. cubense WC Snyder & HN Hans (Foc) and Mycosphaerella fijiensis Morelet (Mf) were evaluated. RESULTS: All the tested synthetic dsRNAs successfully triggered the silencing of target genes and displayed varying degrees of potential to inhibit spore germination of both tested banana pathogens. When Foc dsRNAs were applied to Foc spores, inhibition ranged from 79.8 to 93.0%, and from 19.9 to 57.8% when Foc dsRNAs were applied to Mf spores. However, when Mf dsRNAs were applied on Mf spores, inhibition ranged from 34.4 to 72.3%, and from 89.7 to 95.9% when Mf dsRNAs were applied to Foc spores. CONCLUSION: The dsRNAs for adenylate cyclase, DNA polymerase alpha subunit and DNA polymerase delta subunit showed high levels of spore germination inhibition during both self- and cross-species tests, making them the most promising targets for RNA-mediated resistance in banana against these fungal pathogens. © 2013 Society of Chemical Industry.