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  • 【期刊】 Antifungal saponins from bulbs of garlic, Allium sativum L. var. Voghiera

    摘要:http://linkinghub.elsevier.com/retrieve/pii/S0031942212001422
  • 【期刊】 Saponins from Allium minutiflorum with antifungal activity

    摘要:Three saponins, named minutoside A (1), minutoside B (2), minutoside C (3), and two known sapogenins, alliogenin and neoagigenin, were isolated from the bulbs of Allium minutiflorum Regel. Elucidation of their structure was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry. The structures of the new compounds were identified as (25R)-furost-2 alpha,3 beta,6 beta,22 alpha,26-pentaol 3-O-[beta-D-Xyl0pYranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(14)-O-beta-D-galactopyranosyl] 26-O-beta-D-glucopyranoside (1), (25S)-spirostan-2 alpha,3,60-triol 3-O-beta-D-xylopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 4)-O-D-D-galactopyranoside (2), and (25R)-furost-2 alpha,3 beta,5 alpha,6 beta,22 alpha,26-esaol 3-O-[beta-D-xylopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 4)-O-beta-D-galactopyranosyl] 26-O-beta-D-glucopyranoside (3). The isolated compounds were evaluated for their antimicrobial activity. All the novel saponins showed a significant antifungal activity depending on their concentration and with the following rank: minutoside B > minutoside C >> minutoside A. No appreciable antibacterial activity was recorded. The possible role of these saponins in plant-microbe interactions is discussed. (c) 2006 Elsevier Ltd. All rights reserved.
  • 【期刊】 Identifying the characteristics of organic soil amendments that suppress soilborne plant diseases

    刊名:Soil Biology & Biochemistry 作者:Giuliano Bonanomi ; Vincenzo Antignani ; Manuela Capodilupo ; Felice Scala 年份:2010
    摘要:Application of organic amendments has been proposed as a strategy for the management of diseases caused by soilborne pathogens. However, inconsistent results seriously hinder their practical use. In this work we use an extensive data set of 2423 studies derived from 252 papers to explore this strategy. First, we assess the capability of a specific organic amendment to control different diseases; second, we investigate the influence of organic matter (OM) decomposition on disease suppressiveness; and third, we search for physical, chemical and biological parameters able to identify suppressive OM. OM was found to be consistently suppressive to different pathogens in only a few studies where a limited number of pathogens were tested. In the majority of studies a material suppressive to a pathogen was ineffective or even conducive to other pathogens, suggesting that OM suppressiveness is often pathogen-specific. OM decomposition in many studies (73%, n = 426) emerged as a crucial process affecting suppressiveness. During decomposition, disease suppression either increased, decreased, was unchanged or showed more complex responses, such as 'hump-shaped' dynamics. Peat suppressiveness generally decreased during decomposition, while responses of composts and crop residues were more complex. However, due to the many interactions of contributing factors (OM quality, microbial community composition, pathosystem tested and decomposition time), it was difficult to identify specific predictors of disease suppression. Among the 81 parameters analysed, only some of the 643 correlations showed a consistent relationship with disease suppression. The response of pathogen populations to OM amendments was a reliable feature only for some organic matter types (e.g. crop residues and organic wastes with C-to-N ratio lower than similar to 15) and for pathogens with a limited saprophytic ability (e.g., Thielaviopsis basicola and Verticillium dahliae). Instead, population responses of the pathogenic fungi Phytophthora spp., Rhizoctonia solani and Pythium spp. appeared unrelated to disease suppression. Overall, enzymatic and microbiological parameters, rather than chemical ones, were much more informative for predicting suppressiveness. The most useful features were FDA activity, substrate respiration, microbial biomass, total culturable bacteria, fluorescent pseudomonads and Trichoderma populations. We conclude that the integration of different parameters (e.g. FDA hydrolysis and chemical composition by C-13 NMR) may be a promising approach for identification of suppressive amendments. (C) 2009 Elsevier Ltd. All rights reserved.
  • 【期刊】 Synergism between fungal enzymes and bacterial antibiotics may enhance biocontrol

    摘要:The interactions between biocontrol fungi and bacteria may play a key role in the natural process of biocontrol, although the molecular mechanisms involved are still largely unknown. Synergism can occur when different agents are applied together, and cell wall degrading enzymes (CWDEs) produced by fungi can increase the efficacy of bacteria. Pseudomonas spp. produce membrane-disrupting lipodepsipeptides (LDPs) syringotoxins (SP) and syringomycins (SR). SR are considered responsible for the antimicrobial activity, and SP for the phytotoxicity. CWDEs of Trichoderma spp. synergistically increased the toxicity of SP25-A or SRE purified from P. syringae against fungal pathogens. For instance, the fungal enzymes made Botrytis cinerea and other phytopathogenic fungi, normally resistant to SP25-A alone, more susceptible to this antibiotic. Pseudomonas produced CWDEs in culture conditions that allow the synthesis of the LDPs. Purified bacterial enzymes and metabolites were also synergistic against fungal pathogens, although this mixture was less powerful than the combination with the Trichoderma CWDEs. The positive interaction between LDPs and CWDEs may be part of the biocontrol mechanism in some Pseudomonas strains, and co-induction of different antifungal compounds in both biocontrol bacteria and fungi may occur.
  • 【期刊】 Compost amendments enhance peat suppressiveness to Pythium ultimum, Rhizoctonia solani and Sclerotinia minor

    摘要:Peat is the most common organic material used for the preparation of potting mix because of its homogeneous and favorable agronomic characteristics. However, this organic material is poorly suppressive against soilborne pathogens and fungicides are routinely used to manage damping-off diseases. In the present study, we investigated the suppressive capability of five compost – peat mixtures towards the plant pathogens Pythium ultimum, Rhizoctonia solani and Sclerotinia minor – Lepidium sativum pathosystems. For all organic media, 18 parameters were measured including enzymatic activities (glucanase, N-acetyl-glucosaminidase, chitobiosidase and hydrolysis of fluorescein diacetate), microbiological (BIOLOG® EcoPlates™, culturable bacteria and fungi), and chemical features (pH, EC, total, extractable and humic carbon, total and organic N, NH4–N, total protein and water content). In addition, 13C-CPMAS-NMR spectroscopy was used to characterize the organic materials. Peat amended with composts reduced disease damping-off caused by P. ultimum, R. solani and S. minor in 60%of the mixtures and compost derived from animal manure showed the largest and most consistent disease suppression. Sterilization decreased or eliminated suppressiveness of 42.8%of the mixtures. The most useful parameters to predict disease suppression were different for each pathogen: extractable carbon, O-aryl C and C/N ratio for P. ultimum, alkyl/O-alkyl ratio, N-acetyl-glucosaminidase and chitobiosidase enzymatic activities for R. solani and EC for S. minor. Our results demonstrate that the addition of composts to peat could be useful for the control of soilborne pathogens.
  • 【期刊】 Purification and properties of two chitinolytic enzymes of Serratia plymuthica HRO-C48

    刊名:Archives of Microbiology 作者:Jens Frankowski ; Matteo Lorito ; Felice Scala ; Roland Schmid ; Gabriele Berg and Hubert Bahl 年份:2001
    摘要:The chitinolytic rhizobacterium Serratia plymuthica HRO-C48 was previously selected as a biocontrol agent of phytopathogenic fungi. One endochitinase (E.C. 3.2.1.14), CHIT60, and one N-acetyl-#-1,4-D-hexosaminidase (E.C. 3.2.1.52), CHIT100, were purified and characterized. The endochitinase CHIT60, with an apparent molecular mass of 60.5 kDa, had a N-terminal amino acid sequence highly similar to that of chitinases A from Serratia liquefaciens and Serratia marcescens. The enzyme activity had its peak at 55 °C and pH 5.4, and increased by more than 20%in the presence of 10 mM Ca2+, Co2+ or Mn2+. Activity was inhibited by 80%in the presence of 10 mM Cu2+. CHIT100 appeared to be a monomeric enzyme with a molecular mass of 95.6 kDa and a pI of 6.8. Optimal activity was obtained at 43 °C and pH 6.6, and decreased by more than 90%in the presence of 10 mM Co2+ or Cu2+. CHIT100 (100 µg ml-1) inhibited spore germination and germ tube elongation of the phytopathogenic fungus Botrytis cinerea by 28%and 31.6%, respectively. With CHIT60 (100 µg ml-1), the effect was more pronounced: 78%inhibition of of germination and 63.9%inhibition of germ tube elongation.
  • 【期刊】 Olive mill residues affect saprophytic growth and disease incidence of foliar and soilborne plant fungal pathogens

    摘要:Olive oil mill residues constitute a major environmental problem. Although these wastes have a high fertilizer value when applied to the soil, there is concern about their use because of their antimicrobial and phytotoxic properties. Furthermore, their effect on saprophytic growth and pathogenicity of soilborne and foliar fungi is poorly known.In this study we investigated the effects of olive mill dry residue (DOR) on: (a) growth of the four crop species Lepidium sativum, Lycopersicon esculentum, Lactuca sativa and Triticum aestivum; (b) saprophytic growth of the four phytopathogenic fungi Fusarilon oxysporum f.sp. lycopersici (FOL), Fusarium culniortim (FC), Sclerotinia minor (SM) and Botrytis cinerea (BQ; (c) influence of soil amendment with DOR on the three plant-soilborne pathogen systems, L esculentum-FOL, T aestivum-FC, L. sativa-SM, and the two plant-foliar pathogen systems, L. esculentum-BC and L. sativa-BC.Residues resulted phytotoxic, both in laboratory and greenhouse bioassays, for all plant species in relation to their concentrations. L. sativum and L. sativa were the most sensitive species to the residues, followed by L. esculentum and T aestivum. In contrast with the results observed with plant species, the performances (radial growth and hyphae density) of the tested phytopathogenic fungi were positively affected by DOR. In greenhouse bioassays, L. saliva mortality imputable to SM increased on soil amended with DOR. BC foliar disease dramatically increased on L. sativa and L. esculentum plants grown on soil amended with DOR at all used concentrations. Differently, soil amendment with DOR did not significantly affect the disease incidence of FC on T aestivum and FOL on L. esculentum.Our study demonstrates that, in controlled conditions, undecomposed DOR affects the growth of crop species (phytotoxic effect) and phytopathogenic fungi (substrate effect), and that the interaction between these factors, in some cases, drives to an increase of fungal disease incidence. (c) 2006 Elsevier B.V. All rights reserved.
  • 【期刊】 Study of the three-way interaction betweenTrichoderma atroviride, plant and fungal pathogens by using a proteomic approach

    摘要:The main molecular factors involved in the complex interactions occurring between plants (bean), two different fungal pathogens (Botrytis cinerea, Rhizoctonia solani) and an antagonistic strain of the genus Trichoderma were investigated. Two-dimensional (2-D) electrophoresis was used to analyze separately collected proteomes from each single, two- or three-partner interaction (i.e., plant, pathogenic and antagonistic fungus alone and in all possible combinations). Differential proteins were subjected to mass spectrometry and in silico analysis to search for homologies with known proteins. In the plant proteome, specific pathogenesis-related proteins and other disease-related factors (i.e., potential resistance genes) seem to be associated with the interaction with either one of the two pathogens and/or T. atroviride. This finding is in agreement with the demonstrated ability of Trichoderma spp. to induce systemic resistance against various microbial pathogens. On the other side, many differential proteins obtained from the T. atroviride interaction proteome showed interesting homologies with a fungal hydrophobin, ABC transporters, etc. Virulence factors, like cyclophilins, were up-regulated in the pathogen proteome during the interaction with the plant alone or with the antagonist too. We isolated and confidently identified a large number of protein factors associated to the multi-player interactions examined.
  • 【期刊】 Phytotoxicity, not nitrogen immobilization, explains plant litter inhibitory effects: evidence from solid-state 13C NMR spectroscopy

    摘要:Litter decomposition provides nutrients that sustain ecosystem productivity, but litter may also hamper root proliferation. The objectives of this work were to assess the inhibitory effect of litter decomposition on seedling growth and root proliferation; to study the role of nutrient immobilization and phytotoxicity; and to characterize decomposing litter by (13)C NMR spectroscopy. A litter-bag experiment was carried out for 180 d with 16 litter types. Litter inhibitory effects were assessed by two bioassays: seed germination and root proliferation bioassays. Activated carbon (C) and nutrient solutions were used to evaluate the effects of phytotoxic factors and nutrient immobilization. An inhibitory effect was found for all species in the early phase of decomposition, followed by a decrease over time. The addition of activated C to litter removed this inhibition. No evidence of nutrient immobilization was found in the analysis of nitrogen dynamics. NMR revealed consistent chemical changes during decomposition, with a decrease in O-alkyl and an increase in alkyl and methoxyl C. Significant correlations were found among inhibitory effects, the litter decay rate and indices derived from NMR. The results show that it is possible to predict litter inhibitory effects across a range of litter types on the basis of their chemical composition. 2011 The Authors. New Phytologist 2011 New Phytologist Trust.
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