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Lipid composition of the extracellular matrix of Botrytis cinerea germlings.

Six simple lipid classes (mono-, di- and tri-acylglycerols, free fatty acids, free fatty alcohols and wax esters) were identified by TLC in the extracellular matrix of Botrytis cinerea germlings and the molecular components of each class were characterized using GC-MS. The relative amounts of fatty acids and fatty alcohols within each lipid class were determined by GC-FID. Over all the lipid classes, the most abundant saturated fatty acids were palmitic (ca. 30%) and stearic acid (ca. 22%). Palmitoleic and oleic acids made up ca. 21% and 24% (respectively) of the free fatty acids, while erucic (ca. 4.1%) and linoleic (ca. 3.6%) acids were the most abundant unsaturated fatty acids in the acylglycerides. The acylglycerides also contained almost 35% long chain fatty acids (C20:0 to C28:0). Six fatty acids were identified which had odd-numbered carbon chain lengths (C15:0, C17:0, C19:0, C21:0, C23:0 and C25:0). Of these, pentacosanoic acid made up almost 14% of the fatty acids in the acylglycerides. Three methyl-branched chain fatty acids, namely isopalmitic, isoheptadecanoic and anteisopalmitic, were identified in the ECM, all in small amounts. Of the fatty alcohols identified, only palmityl and stearyl alcohols were found in the free form (ca. 57% and 43%, respectively) but arachidyl alcohol (ca. 47%) and 1-octacosanol (ca. 30%) were the most abundant fatty alcohols found in the wax ester fraction.

Botrytis↗

Inactivation of conidia of Botrytis cinerea and Monilinia fructigena using UV-C and heat treatment.

The effect of UV-C (lambda = 254 nm) and heat treatment was investigated on the inactivation of conidia of Botrytis cinerea and Monilinia fructigena, two major postharvest spoilage fungi of strawberries and cherries, respectively. Both fungi were grown at 21 degrees C in the dark and conidia were isolated after 1 week by washing the mycelium with a mild detergent solution. After filtration and resuspension in phosphate buffer to a titer of 10(5) to 10(6) cfu/ml, the conidia were subjected to different treatments. The applied UV-C doses varied from 0.01 to 1.50 J/cm2, and the conditions for the thermal treatment were 3, 5, 10, 15 and 20 min at temperatures ranging from 35 to 48 degrees C. Both techniques were applied individually and in combination. Spore inactivation increased with increasing intensity of single treatments. No surviving spores of B. cinerea were observed after 15 min at 45 degrees C or an UV-C treatment of 1.00 J/cm2. M. fructigena was more sensitive and a thermal treatment of 3 min at 45 degrees C or an UV-C treatment of 0.50 J/cm2 resulted in complete spore inactivation. Combination of both techniques reduced the required intensity of the treatment for inactivation of both fungi. The order of the applications had a significant effect on the degree of inactivation. The inactivation of B. cinerea conidia was greater when the heat treatment came first, and for M. fructigena, most inactivation was achieved when the heat treatment was preceded with an UV-C irradiation.

Ascomycota↗

Combinations of pulsed white light and UV-C or mild heat treatment to inactivate conidia of Botrytis cinerea and Monilia fructigena.

The use of pulses of intense white light to inactivate conidia of the fungi Botrytis cinerea and Monilia fructigena, responsible for important economical losses during postharvest storage and transport of strawberries and sweet cherries, was investigated in this study. In the first stage, a light treatment applying pulses of 30 micros at a frequency of 15 Hz was investigated, resulting in a treatment duration varying from 1 to 250 s. The conidia of both fungi showed similar behaviour to pulsed light, with a maximal inactivation of 3 and 4 log units for B. cinerea and M. fructigena, respectively. The inactivation of the conidia increased with increasing treatment intensity, but no complete inactivation was achieved. The sigmoidal inactivation pattern obtained by the pulsed light treatment was described using a modification of the model of Geeraerd et al. [Int. J. Food Microbiol. 59 (2000) 185]. Hereto, the shoulder length was incorporated explicitly and relative values for the microbial populations were used. In the second stage, combinations of light pulses and ultraviolet-C or heat were applied. The UV light used in the experiments is the short-wave band or UV-C, running from 180 to 280 nm with a peak at 254 nm (UV-B runs from 280 to 320 nm and UV-A from 320 to 380 nm). The UV-C doses were 0.025, 0.05 and 0.10 J/cm(2), and the temperatures for the thermal treatment ranged from 35 to 45 degrees C during 3-15 min. When combining UV-C and light pulses, there was an increase in inactivation for both B. cinerea and M. fructigena, and synergism was observed. There was no effect of the order of the treatments. For the heat-light pulses combination, there was a difference between both fungi. The order of the treatments was highly significant for B. cinerea, but not for M. fructigena. Combining heat and light treatments improved the inactivation, and synergism between both methods was again observed. Complete inactivation of M. fructigena conidia was obtained after, e.g., a 40-s pulsed light treatment and 15 min at 41 degrees C, or after an 80-s light treatment and 10 min at 41 degrees C.

Botrytis↗

Characterisation of a new species of Pythium isolated from a wheat field in northern France and its antagonism towards Botrytis cinerea causing the grey mould disease of the grapevine.

A new species, Pythium bifurcatum, isolated from soil samples taken from a wheat field in Lille in northern France is described here. The oomycete occurred thrice out of 50 samples. The type specimen is F-91, which is a slow-growing saprophyte living on vegetable debris and which can be recognised by its antheridial as well as oogonial characteristics, which are different from other known species of Pythium. When grown together with Botrytis cinerea, the causal agent of the grey mould disease of the grapevine, Pythium bifurcatum shows a pronounced antagonism and suppresses its growth. Morphological features of this new species, its antagonism to B. cinerea, the sequences of the ITS region of its nuclear ribosomal DNA, and its comparison with related species are discussed in this article.

Base Sequence↗

A double-stranded RNA mycovirus confers hypovirulence-associated traits to Botrytis cinerea.

Botrytis cinerea CCg425 contains a 33-nm isometric mycovirus whose genome is a 6.8-kb double-stranded RNA (dsRNA) molecule. Virulence bioassays, performed by direct plug mycelial inoculation on bean plant leaves, showed that B. cinerea CCg425 displays less fungal aggressivity than B. cinerea CKg54, a virulent fungal strain that is not infected by dsRNA mycoviruses. B. cinerea CCg425 also showed lower laccase activity and conidiation rate than B. cinerea CKg54. Furthermore, infection of B. cinerea CKg54 with viral particles purified from B. cinerea CCg425 resulted in diminished virulence of the infected fungus. Collectively, our results indicate that mycovirus infection confers hypovirulence to the fungal host.

Botrytis↗

Characterisation of Pythium paroecandrum and its antagonism towards Botrytis cinerea, the causative agent of grey mould disease of grape.

Pythium paroecandrum (B-30), an oomycete, was isolated from soil samples taken from a wheat field in Genlis in the Burgundy region of France and was found to check the growth and development of Botrytis cinerea, a serious grapevine pathogen. The oomycete is a fast-growing organism, living on vegetable debris, and can be recognised by its catenulate hyphal swellings, catenulate oogonia, and monoclinous antheridia. When grown together with B. cinerea, the causal agent of the grey mould disease of the grapevine, P. paroecandrum shows a pronounced antagonism and suppresses its growth and its aptitude to provoke the grey mould symptoms. Morphological features of this oomycete, its antagonism to B. cinerea, the sequences of the internal transcribed spacer region of its nuclear ribosomal DNA, and its comparison with related species are discussed in this article.

Antibiosis↗

The hypersensitive response facilitates plant infection by the necrotrophic pathogen Botrytis cinerea.

BACKGROUND: Plants have evolved efficient mechanisms to combat pathogen attack. One of the earliest responses to attempted pathogen attack is the generation of oxidative burst that can trigger hypersensitive cell death. This is called the hypersensitive response (HR) and is considered to be a major element of plant disease resistance. The HR is thought to deprive the pathogens of a supply of food and confine them to initial infection site. Necrotrophic pathogens, such as the fungi Botrytis cinerea and Sclerotinia sclerotiorum, however, can utilize dead tissue. RESULTS: Inoculation of B. cinerea induced an oxidative burst and hypersensitive cell death in Arabidopsis. The degree of B. cinerea and S. sclerotiorum pathogenicity was directly dependent on the level of generation and accumulation of superoxide or hydrogen peroxide. Plant cells exhibited markers of HR death, such as nuclear condensation and induction of the HR-specific gene HSR203J. Growth of B. cinerea was suppressed in the HR-deficient mutant dnd1, and enhanced by HR caused by simultaneous infection with an avirulent strain of the bacterium Pseudomonas syringae. HR had an opposite (inhibitory) effect on a virulent (biotrophic) strain of P. syringae. Moreover, H(2)O(2) levels during HR correlated positively with B. cinerea growth but negatively with growth of virulent P. syringae. CONCLUSIONS: We show that, although hypersensitive cell death is efficient against biotrophic pathogens, it does not protect plants against infection by the necrotrophic pathogens B. cinerea and S. sclerotiorum. By contrast, B. cinerea triggers HR, which facilitates its colonization of plants. Hence, these fungi can exploit a host defense mechanism for their pathogenicity.

Arabidopsis↗

Disruption of Botrytis cinerea class I chitin synthase gene Bcchs1 results in cell wall weakening and reduced virulence.

To get a better insight into the relationship between cell wall integrity and pathogenicity of the fungus Botrytis cinerea, we have constructed chitin synthase mutants. A 620 bp class I chitin synthase gene fragment (Bcchs1) obtained by PCR amplification was used to disrupt the corresponding gene in the genome. Disruption of Bcchs1 occurred at a frequency of 8%. Nine independent mutants were obtained and the Bcchs1 mutant phenotype compared to that of transformants in which the gene was not disrupted. These disruption mutants were dramatically reduced in their in vitro Mg2+, Mn2+, and Co2+-dependent chitin synthase activity. Chitin content was reduced by 30%, indicating that Bcchs1p contributes substantially to cell wall composition. Enzymatic degradation by a cocktail of glucanases revealed cell wall weakening in the mutant. Bcchs1 was transcribed at a constant level during vegetative exponential growth, suggesting that it was necessary throughout hyphal development. Bcchs1 mutant growth was identical to undisrupted control transformant growth, however, the mutant exhibited reduced pathogenicity on vine leaves. It can be assumed that disruption of Bcchs1 leads to cell wall weakening which might slow down in planta fungal progression.

Botrytis↗

Metabolism of cymoxanil and analogs in strains of the fungus Botrytis cinerea using high-performance liquid chromatography and ion-pair high-performance thin-layer chromatography.

The metabolism of cyano-oxime fungicide 1-(2-cyano-2-methoxyiminoacetyl)-3-ethylurea (cymoxanil) and analogs was studied on several strains of the fungus Botrytis cinerea owing to their difference in sensitivity towards cymoxanil. Chromatographic analysis of the unextracted culture medium was simpler and more accurate, particularly for ionizable metabolites because it avoids problems associated with extraction. Reversed-phase high-performance liquid chromatography was applied to compare the decrease of cymoxanil and analogs caused by different strains of B. cinerea, by periodic injections of incubated culture medium aliquots, directly on a C4 wide-pore column. Furthermore, a thin-layer chromatographic monitoring on C18 bonded silica gel with ion-pairing allowed the monitoring of the ionizable metabolites for substrates that were demonstrated to decompose most rapidly. These complementary analyses showed that the sensitivity of the highly sensitive strain towards cymoxanil was related to the disappearance of cyano-oximes studied from culture medium, namely to the ability of the strain B. cinerea to metabolize them.

Acetamides↗

pH modulation of zopfiellin antifungal activity to Colletotrichum and Botrytis.

Zopfiellin, a novel cyclooctanoid natural product isolated from Zopfiella curvata No. 37-3, was evaluated in a 96-well microtiter assay for fungicidal activity against Botrytis cinerea, Colletotrichum acutatum, Colletotrichum fragariae, Colletotrichum gloeosporioides, and Fusarium oxysporum. Zopfiellin exhibited pH-dependent activity, with the most mycelial growth inhibition demonstrated at pH 5.0. Mass spectrometry and nuclear magnetic resonance spectroscopy studies indicated that zopfiellin undergoes structural changes with changes in pH. At pH 5.0, zopfiellin showed the greatest activity against B. cinerea (IC(80) = 10 microM), C. gloeosporioides (IC(80) = 10 microM), and C. fragariae (IC(80) = 10 microM) and intermediate activity against C. acutatum (IC(80) = 30 microM), and was not active against F. oxysporum (IC(80) > 100 microM).

Ascomycota↗

Characterization of the antifungal activity on Botrytis cinerea of the natural diterpenoids kaurenoic acid and 3beta-hydroxy-kaurenoic acid.

The antifungal activity on Botrytis cinerea of the diterpenoids 3beta-hydroxy-kaurenoic acid and kaurenoic acid, obtained from the resinous exudates of Pseudognaphalium vira vira, was determined. 3beta-Hydroxy-kaurenoic acid reduced the mycelial growth of B. cinerea in solid and liquid media. Additionally, the damage produced by the fungus on the surface of tomato leaves in the presence of the diterpenoids was evaluated. A higher protective effect was observed in the presence of the hydroxylated diterpene. On the other hand, the effect of the diterpenoids on the production of enzymes that participate in the plant infection by B. cinerea was analyzed. p-Nitrophenylbutyrate esterase production was induced by both diterpenoids, whereas laccase production was only induced by the hydroxylated diterpene. In the study of the mechanism of action of these compounds, it was determined that 3beta-hydroxy-kaurenoic acid would produce permeabilization of the cell membrane of B. cinerea.

Botrytis↗

Benzothiadiazole enhances resveratrol and anthocyanin biosynthesis in grapevine, meanwhile improving resistance to Botrytis cinerea.

Pre-harvest multiple treatments of grapevine (cv. Merlot) with the plant activator benzothiadiazole (BTH, 0.3 mM) enhanced trans-resveratrol content in berries by about 40%. An even more striking effect was observed on anthocyanin synthesis, particularly on malvidine 3-glucoside, malvidine 3-(6-O-acetyl)glucoside and malvidine 3-(6-O-p-coumaroyl)glucoside, whose amounts were more than doubled. These data were obtained with a novel and time-saving HPLC method, set up for the simultaneous detection of stilbenes and anthocyanins, using an RF-10Axl fluorimetric detector instrument, with excitation at 330 nm and emission at 374 nm, and a SPD-Avp UV detector with absorption at 520 nm. Furthermore, BTH treatments induced systemic acquired resistance in grapevine, as assessed by inoculating clusters from treated and untreated plants with Botrytis cinerea. Disease severity, estimated according to the percentage of infected berries per cluster, was significantly reduced in grapes from BTH-treated plants. These results indicate that BTH treatments, besides improving the content of two important classes of nutraceuticals, with their well-known antioxidant, antitumoral, and phytoestrogenic activities, could be exploited in vineyard to protect grape against gray mould infection, thereby limiting an excessive use of fungicides

Anthocyanins↗

Antifungal activity and biotransformation of diisophorone by Botrytis cinerea.

Diisophorone (1) was tested against two strains of the necrotrophic plant pathogen Botrytis cinerea. Fungal sensitivity varied according to the strain. B. cinera 2100 was more sensitive than B. cinereaUCA992: its mycelial growth was significantly inhibited at concentrations of 50 ppm and above. Although diisophorone (1) showed an effective control of B. cinerea, a detoxification mechanism was present. The detoxification of racemic diisophorone (1) by B. cinerea was investigated. Incubation with two strains of B. cinerea gave one and four biotransformation products (2-5), respectively. Their structures were established as the known 8beta-hydroxydiisophorone (2), 6alpha-hydroxydiisophorone (3), 6beta-hydroxydiisophorone (4) and 8beta,14beta-dihydroxydiisophorone (5) on the basis of their spectroscopic data, including two-dimensional NMR analysis [heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), and nuclear Overhauser enhancement spectroscopy (NOESY)] and an X-ray crystallographic study.

Biotransformation↗

Screening study of lead compounds for natural product-based fungicides: antifungal activity and biotransformation of 6alpha,7alpha-dihydroxy-beta-himachalene by Botrytis cinerea.

Eleven beta-himachalene derivatives were tested, using the poisoning food technique, for their potential antifungal activity against the phytopathogen Botrytis cinerea. Compounds 1-11 displayed moderate activity, whereas the 6,7-diol derivative (12) produced an inhibition of 91% after 6 days. The microbial transformation of 12 was investigated and yielded four new compounds hydroxylated at positions C-5 (13), C-2 (14), C-4 (15), and C-12 (16). The structures were established on the basis of their spectroscopic data including two-dimensional NMR analysis (HMQC, HMBC, nOesy) and nOes. The results obtained from biotransformation experiments shed further light on the detoxification mechanism of the phytopathogenic fungus against this compound and give an indication of the structural modifications that may be necessary if substrates of this type are to be further developed as selective fungal control agents for B. cinerea.

Benzoates↗

In vitro sensitivity of Botrytis cinerea to anthraquinone and anthrahydroquinone derivatives.

The effect on mycelial growth of the fungus Botrytis cinerea of a set of structurally related tricyclic hydroquinones [9,10-dihydroxy-4,4-dimethyl-2,3,5,8-tetrahydroantracen-1(4H)-one and 9,10-dihydroxy-4,4-dimethyl-5,8-dihydroanthracen-1(4H)-one derivatives] and tricyclic quinones [4,4-dimethylanthracen-1,9,10(4H)-trione derivatives] was studied. In general, the anthraquinones presented higher activity than the anthrahydroquinones. Anthraquinone and anthrahydroquinone derivatives with methyl groups on the A ring showed higher antifungal activity than the unsubstituted ones, 4,4,6,7-tetramethyl-(4H)-anthracene-1,9,10-trione being the most active compound of this set. The presence of a polar group such as hydroxymethyl reduced the activity. The effect of two anthrahydroquinones and two anthraquinones on the conidia germination of the fungus was also determined. Anthrahydroquinones did not affect the germination. The most active compound was 4,4-dimethylanthracene-1,9,10(4H)-trione, with 100% inhibition of germination at 7 h of incubation. These results again suggest that the structure of the anthraquinones is important in exerting an antifungal effect on B. cinerea. Furthermore, possible mechanisms of action of compound 4,4-dimethylanthracene-1,9,10(4H)-trione were studied. This compound did not produce lipoperoxidation of membrane and did not induce the formation of oxygen reactive species, but it was able to permeabilize the plasmatic membrane of B. cinerea, increasing the phosphorus concentration in the intracellular medium.

Anthraquinones↗

Evidence for protein degradation by Botrytis cinerea and relationships with alteration of synthetic wine foaming properties.

Botrytis cinerea is an important fungal pathogen particularly dreaded in the cool climate vineyard. It is responsible for important damage, especially the decrease in foamability of sparkling wines, such as Champagne. Different studies have shown that proteins are largely involved in the stabilization of Champagne foam despite their low concentration. Other works demonstrated changes in the electrophoretic characteristics of must proteins originating from botrytized grapes, although the cause of such alterations was never explained. In the first part of this study, results showed the release by B. cinerea of 3.5 mg/L total proteins in a synthetic liquid medium. Among these proteins, the presence of a protease activity on bovine serum albumin (BSA) and must proteins was demonstrated by using a colorimetric method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the model wine, the Bradford method showed a BSA loss of 66% after 24 h and a loss of 96% after 120 h. In the same model wine, the soluble must protein concentration decreased by 35% after 1 week and by 53% after 2 weeks while the control showed no protein loss. B. cinerea proteases were then able to degrade BSA and must proteins and were above all active at must and wine pH and in the presence of ethanol and SO(2). The second part of this work was dedicated to the relationship between the presence of B. cinerea proteases and its effects on the synthetic wine foaming properties. The addition of a B. cinerea culture medium (1/33 v/v) to the synthetic wine containing 21 mg/L soluble grape proteins induced a decrease in foamability by 60% after 1 week. For BSA in the model wine, the foamability decreased by 32% after 24 h and by 95% after 120 h, as shown by the colorimetric method. These experiments demonstrate for the first time the relationship between B. cinerea protease activity and the decrease in wine foaming properties.

Botrytis↗

The antifungal activity of widdrol and its biotransformation by Colletotrichum gloeosporioides (penz.) Penz. & Sacc. and Botrytis cinerea Pers.: Fr.

Widdrol (1) was tested against the necrotrophic plant pathogens Botrytis cinerea and Colletotrichum gloeosporioides. While 1 was found to be inactive against C. gloeosporioides, it showed a selective and effective control of B. cinerea, significantly inhibiting the mycelial growth of the fungus at concentrations of 100 ppm and above. In addition, the biotransformation of 1 by both fungi was studied. Incubation with C. gloeosporioides and B. cinerea afforded four and one biotransformation products (2-6), respectively. Biotransformation with C. gloeosporioides was highly regioselective, yielding for the most part oxidation products at C-10: 10-oxowiddrol (2), 10beta-hydroxywiddrol (3), 10alpha-hydroxywiddrol (4), and 14alpha-hydroxywiddrol (5). The structures of all products were determined on the basis of their spectroscopic data, including coupling constants, two-dimensional NMR analysis (heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser enhancement spectroscopy), and nuclear Overhauser effect. The biotransformation products were then tested against B. cinerea and found to be inactive. These results shed further light on the structural modifications, which may be necessary to develop selective fungal control agents against B. cinerea.

Benzocycloheptenes↗

Biosynthetic studies on the botcinolide skeleton: new hydroxylated lactones from Botrytis cinerea.

[reaction: see text] The biosynthetic origin of the botcinolide skeleton was investigated by means of feeding 13C- and 2H-labeled precursors to Botrytis cinerea. Three new compounds, two homobotcinolide derivatives, 3-O-acetylhomobotcinolide (5) and 8-methylhomobotcinolide (6), and a new 11-membered lactone (7), were isolated. Their structures were elucidated on the basis of spectroscopic data, including one-bond and long-range 1H-13C correlations. The relative stereochemistries were determined by combined analyses of NOE data and 1H-1H coupling constants. According to the results of feeding experiments with 13C- and 2H-labeled acetate and l-S-methylmethionine, 5 is an acetate-derived polyketide whose methyl groups originate from l-S-methylmethionine. This is a rare example of the incorporation of a methyl from methionine into a supposed C3 starter unit of the polyketide synthesis.

Acetates↗