Search

Wood treatments based on oleoresins from Aucoumea Klaineana, Canarium schweinfurthii and Dacryodes edulis have shown interesting anti-termites properties but poor resistance to fungi and leaching. Oleoresins were combined with tebuconazole to produce both antifungal and anti-termite wood preservatives formulations with an expected better fixation of chemicals mixtures in the wood. Beech and Scots pine wood block samples were impregnated by these different formulations and exposed to white and brown rot, respectively, as well as to European termite (Reticulitermes flavipes). The use of aqueous formulations of each oleoresin of combined to tebuconazole improved the wood resistance against termites and mainly brown rot. In addition, the best formulation was found by using the raw resin from Aucoumea Klaineana. These results are mainly due to the antifungal activity of tebuconazole. In addition, the presence of antioxidant chemicals in the wood resins inhibits the wood decay fungi growth and acts as enzyme and metabolism inhibitors disturbing the treated wood digestion process by termites. For the future, the promising protection obtained should be formulated to be resistant to leaching.

Mycotoxins may be present in nuts, coffee, cereals, and grapes, among other products. Increasing concerns about human health and environmental protection have driven the application of biological control techniques that can inhibit fungal contaminants. In this study, the growth inhibition of the ochratoxigenic fungus Aspergillus carbonarius Ac 162 was evaluated using 5 lactic acid bacteria (LAB). The LAB studied were Lactobacillus plantarum MZ801739 (J), Lactobacillus plantarum MZ809351 (31) and Lactobacillus plantarum MZ809350 (34), isolated in the Ivory Coast, and Lactobacillus plantarum MN982928 (3) and Leuconostoc citreum MZ801735 (23), isolated in Mexico. J, 31, 34, 3 and 23 are the internal strain codes from our laboratory. LAB were cultivated in De Man, Rogosa and Sharpe (MRS) broth, and different polyols (glycerol, mannitol, sorbitol, and xylitol) were added to the culture broth to stimulate the production of antifungal compounds. The fungal inhibition studies were performed using the poisoned food technique. The highest inhibition of A. carbonarius growth was obtained by cultivating L. plantarum MZ809351 in the presence of xylitol and glycerol. Under these conditions, 1 L of the L. plantarum MZ809351 cultures were used to identify antifungal compounds. The compounds were concentrated by solid-phase extraction and then characterized by GC–MS. In addition to 9-octadecenoic acid, 3 diketopiperazines or cyclic dipeptides were identified, including cyclo (Leu-Leu), cyclo (Pro-Gly) and cyclo (Val-Phe), which were compounds related to microbial antifungal activities. Xylitol and glycerol induced the production of these antifungal compounds against A. carbonarius Ac 162. On the other hand, adding xylitol and glycerol to the MRS broth reduced the Ochratoxin A (OTA) content to 56.8 and 54.7%, respectively. This study shows the potential for using L. plantarum MZ809351 as a biocontrol agent to prevent the growth of A. carbonarius and reduce the production of OTA in foods.

International audience; Sugarcane bagasse was pyrolyzed using a laboratory fixed bed reactor to produce char and its by-product (pyrolysis liquid). The pyrolysis experiments were carried out using different temperatures (400 degrees C and 500 degrees C), heating rate (1 degrees C/min and 10 degrees C/min), and holding time (30 min and 60 min). Char was characterized according to its thermal properties, while the pyrolysis liquid was tested for its anti-fungal and anti-termite activities. Pyrolysis temperature and heating rate had a significant influence on the char properties and the yield of char and pyrolysis liquid, where a high-quality char and high yield of pyrolysis liquid can be obtained at a temperature of 500 degrees C and a heating rate of 10 degrees C/min. The yield of char and pyrolysis liquid was 28.97% and 55.46%, respectively. The principal compounds of pyrolysis liquid were water, acetic acid, glycolaldehyde, 1-hydroxy-2-propanone, methanol, formic acid, levoglucosan, furfural, followed by some phenol compounds and guaiacol derivatives. Pyrolysis liquid at a concentration of 0.20% and 0.25% (v/v) caused a 100% inhibition of Coniophora puteana and Trametes versicolor, respectively, when performing inhibition growth tests in Petri dishes. Filter paper treated with 10% of pyrolysis liquid caused 100% of termite mortality, while only 5.65%-7.03% of the treated filter papers consumed by termites at such concentration. Pyrolysis liquid is potentially effective to be used in the formulation of wood protection against fungi and termites.

Dacryodes edulis (G. Don) H.J. Lam resin was hydro-distilled to recover essential oil (EO), and further purified to produce a heavy fraction constituting less volatile compounds. Chemical composition was investigated by gas chromatography-mass spectrometry (GC-MS), and indicated that different monoterpenes and triterpenes were present depending on the analyzed fraction. Bioassays were performed on the different fractions to evaluate their anti-fungal and anti-termite properties. Results indicated that crude resin, its heavy fraction and its EO all had proved termicidal properties, which decrease on drying for EO and crude resin due to evaporation of monoterpenes. Conversely, no anti-fungal properties were observed for any fraction. Dacryodes edulis resin is therefore a new valuable bioactive ingredient for the formulation of wood protection products with anti-termite properties.

International audience; The endophytic bacteria were isolated from coffee roots and seeds in Vietnam and identified with 16S rDNA sequencing as belonging to the Actinobacteria, Firmicutes and Proteobacteria phyla with the Nocardia, Bacillus and Burkholderia as dominant genera, respectively. Out of the thirty genera recovered from Coffea canephora and Coffea liberica, twelve were reported for the first time in endophytic association with coffee including members of the genera Brachybacterium, Caballeronia, Kitasatospora, Lechevalieria, Leifsonia, Luteibacter, Lysinibacillus, Mycolicibacterium, Nakamurella, Paracoccus, Sinomonas and Sphingobium. A total of eighty bacterial endophytes were characterized in vitro for several plant growth promoting and biocontrol traits including: the phosphate solubilization, the indolic compounds, siderophores, HCN, esterase, lipase, gelatinase and chitinase production. A subset of fifty selected bacteria were tested for their potential as biocontrol agents with in vitro confrontations with the fungal pathogen Fusarium oxysporum as well as the coffee parasitic nematodes Radopholus duriophilus and Pratylenchus coffeae. The three most efficient isolates on F. oxysporum belonging to the Bacillus, Burkholderia, and Streptomyces genera displayed a growth inhibition rate higher than 40%. Finally, five isolates from the Bacillus genus were able to lead to 100% of mortality in 24 h on both R. duriophilus and P. coffeae.

Lactoperoxidase system (LPOS) was incorporated into chitosan solutions (0.5, 1, and 1.5%) to protect mangoes against two strains of fungi. Coating solutions effectiveness in vitro (in Petri dish) and in vivo (on mango) were studied on fungal (Phomopsis sp. RP257 and Pestalotiopsis sp.) growth isolated from mango cv Amelie . In vitro, chitosan concentration at least 1% containing or not LPOS effectively inhibited Pestalotiopsis sp. growth at 100%. Presence of LPOS or Lactoperoxydase system with iodine (LPOSI) in chitosan at 0.5% increased the percentage of inhibition from 26 to 93%. Edible films with LPOS inhibited Phomopsis sp. RP257 particularly when LPOS was incorporated in chitosan concentrations of 1 and 1.5%. Iodine did not influenced antifungal activity of LPOS against Pestalotiopsis sp. but decreased activity antifungal toward Phomopsis sp. RP257. The properties (water vapor permeability and mechanical properties) of chitosan films were not significantly changed by the incorporation of the enzyme system. in vivo condition, chitosan coating at 1 and 1.5% with or without enzyme system was sufficient to inhibit totally (100%) Pestalotiopsis sp. and was 60% efficient against Phomopsis sp. with chitosan only at 1 and 1.5%. However, when coating solution mainly at 1 and 1.5% was enhanced by LPOS with or without iodine, it inhibited totally (100%) Phomopsis sp. RP257. The presence of iodine slightly reduced antifungal activity against Phomopsis sp. RP257.

Mankind is on the verge of a postantibiotic era. New concepts are needed in our battle to attenuate infectious diseases around the world and broad spectrum plant-inspired synergistic pharmaceutical preparations should find their place in the global fight against pathogenic microorganisms. To progress towards the discovery of potent antifungal agents against human pathologies, we embarked upon developing chemometric approach coupled with statistical design to unravel the origin of the anticandidal potential of a set of 66 essential oils (EOs). EOs were analyzed by GC-MS and tested against Candida albicans and C. parapsilosis (Minimal Inhibitory Concentration, MIC). An Orthogonal Partial Least Square (OPLS) analysis allowed us to identify six molecules presumably responsible for the anticandidal activity of the oils: (Z)-ligustilide, eugenol, eugenyl acetate, citral, thymol, and β-citronellol. These compounds were combined following a full factorial experimental design approach in order to optimize the anticandidal activity and selectivity index (SI = IC50(MRC5 cells)/MIC) through reconstituted mixtures. (Z)-Ligustilide and citral were the most active compounds, while (Z)-ligustilide and eugenol were the two main factors that most contributed to the increase of the SI. These two terpenes can, therefore, be used to construct bioinspired synergistic anticandidal mixtures.

Objectives This study set out to highlight the in vitro and in vivo antifungal activity of an Ethanolic Extract of Red Brazilian Propolis (EERBP) and identify bioactive fractions effective against Colletotrichum musae. Methods Active fractions were detected by the thin-layer chromatography-bioautography method and characterised by HPLC-MSn. Results The in vitro results showed that EERBP had strong antifungal properties against C. musae (81 ± 1% inhibition at 1.6 g GAE L−1). Medicarpin, (3S)-vestitol and (3S)-neovestitol were the main compounds identified in the EERBP extract (45% of all detected peaks). Two isolated fractions displayed inhibition percentages of 35 ± 4 and 42 ± 1%, respectively, on C. musae mycelial growth compared to the EERBP extract. The biological activity of the two fractions displayed an additive effect. Conclusion A further in vivo investigation revealed that EERBP is a potential natural alternative for controlling banana crown rot.

Consumer's demand for naturally preserved food products is growing and the use of bioprotective cultures is an alternative to chemical preservatives or a complementary tool to hurdle technologies to avoid or delay fungal spoilage of dairy products. To develop antifungal cultures for the dairy product biopreservation, experiments were conducted both in vitro and in situ. Firstly, the antifungal activity of 32 strains of lactic acid bacteria (LAB) and propionibacteria was screened alone, and then on combinations based on 5 selected lactobacilli strains. This screening was performed in yogurt and cheese models against four major spoilage fungi previously isolated from contaminated dairy products (Penicillium commune, Mucor racemosus, Galactomyces geotrichum, and Yarrowia lipolytica). Selected combinations were then tested as adjunct cultures in sour cream and semi-hard cheeses produced at a pilot scale to evaluate their antifungal activity during challenge tests against selected fungal targets (P. commune, M. racemosus, and Rhodotorula mucilaginosa) and shelf life tests; and their impact on product organoleptic properties. The screening step allowed selecting two binary combinations, A1 and A3 composed of Lactobacillus plantarum L244 and either Lactobacillus harbinensis L172 or Lactobacillus rhamnosus CIRM-BIA1113, respectively. In situ assays showed that the A1 combination delayed the growth of P. commune, M. racemosus and R. mucilaginosa for 2–24 days on sour cream depending of the antifungal culture inoculum, without effect on organoleptic properties at low inoculum (106 colony-forming units (CFU)/mL). Moreover, the A1 and A3 combinations also delayed the growth of P. commune in semi-hard cheese for 1–6 days and 1 day, respectively. Antifungal cultures neither impacted the growth of starter cultures in both sour cream and cheese nor the products' pH, although post acidification was observed in sour cream supplemented with these combinations at the highest concentrations (2.107 CFU/mL). The combination of both in vitro and in situ screening assays allowed developing 2 antifungal combinations exhibiting significant antifungal activity and providing future prospects for use as bioprotective cultures in dairy products.

Key words: antifungal activity, screening, bacteria, molds, dairy products Introduction In dairy products, bioprotective cultures and their metabolites represent an interesting alternative to chemical preservatives. The aim of this study was to develop dairy ingredients with antifungal properties, active against a large diversity of spoilage fungi and to test their efficiency and organoleptic impact in real products. Materials and methods First, the biodiversity of spoilage fungi in a large variety of dairy products was investigated using molecular methods in order to select the most appropriate fungal targets. Then, the antifungal activity of fermentates obtained from 698 lactic acid bacteria, propionibacteria and fungal strains were screened in vitro using a novel high-throughput method in a cheese mimicking model. After optimizing fermentation conditions to improve antifungal activity, the best fermentates were tested at a pilot scale in uncooked pressed cheese (UPC) and sour cream to evaluate their antifungal activity using challenge and durability tests and their impact on organoleptic properties using sensorial analysis. Results The in vitro screening allowed selecting antifungal ingredients that were also active in situ. Durability tests revealed that a Lactobacillus rhamnosus fermentate had a promising activity in sour cream. For UPC, a Propionibacterium jensenii–based ingredient could be used instead of natamycin delaying Mucor racemosus and Penicillium commune for up to 16 days. Conclusion These approaches led to the development of new antifungal dairy-based ingredients that might replace natamycin in UPC.

Poster présenté à Spoilers2017 http://www.spoilers2017.com/; IntroductionFood spoilage is a major issue for the food industry, leading to important food waste and economic losses. Dairy products, despite their microbial stability, are susceptible to acid-tolerant fungal contaminants. In this context, antifungal cultures are of growing interest as an alternative to chemical preservatives or a complement tool to hurdle technologies. Materials and methods In order to select antifungal culture associations, 32 strains (19 Lactobacillus, 4 Leuconostoc, and 9 Propionibacterium) were screened, alone and in combination, and compared to commercial bioprotective cultures against 4 fungal common contaminants of dairy products (Mucor racemosus, Penicillium commune, Yarrowia lipolytica, and Galactomyces geotrichum). Since the matrix can modulate the activity of antifungal adjunct cultures, the screening was performed in cheese and yogurt-mimicking models. For three selected associations, the metabolites potentially associated with antifungal activity were investigated using 4 liquid and gas chromatographic methods.Results Antifungal screening allowed for the selection of 5 Lactobacillus strains, their use in combination showed that 3 binary associations were of interest as potential antifungal bioprotective cultures. From the metabolic point of view, 16 molecules of interest were identified and differential metabolite production was observed according to the considered model. Conclusion The 3 selected associations and their metabolites are natural antifungal alternatives of interest for the dairy industry.

Natural extractives are proposed as potential sustainable bioactive compounds for wood preservative formulations and an enzyme-mediated reaction is employed to fix them onto the wood surface. This environmentally friendly process takes place thanks to the activity of the laccase enzyme and leads to the formation of covalent bonds between these compounds and the wood itself. This then diminishes the problem of its future leaching, giving rise to long-lasting wood protection treatments. Overall, our data show suitable biocidal properties for the raw extracts of Pinus spp. and Criptomeria japonica. Phenolic compounds such as pinosylvin, pinosylvin monomethyl ether, pinocembrin, naringenin and pinobanksin were found in the extracts of pine together with totarol and sugiol in the C. japonica extract and could explain the anti-fungal properties found. Fungal tests have revealed mass losses below 7% for wood treated with the toluene extracts of Pinus spp. and the ethanolic extract of C. japonica, pointing to this enzymatic green methodology as a promising alternative in the wood preservation field. Furthermore, potential inclusion of these enzymatic strategies in the wood industry today is discussed and analyzed in a "green" scenario.

The antifungal activity of spruce bark (Picea abies (L.) Kars. Pinaceae) extract against downy mildew (Plasmopara viticola) was investigated. The analysis of the extract using UHPLC–MS allowed stilbenes to be targeted as the main components. The structure of stilbenes isolated from the hydro-alcoholic extract by preparative HPLC was determined by mass and NMR analysis. In addition to aglycone and glycosylated monomeric forms such as piceatannol, astringin, resveratrol, piceid, isorhapontigenin and isorhapontin, several stilbene glycoside dimers were also identified. Six new compounds (piceasides I-N) are reported for the first time in the literature and the plant kingdom. The extract as well as pure compounds showed significant antifungal activity with an inhibition of the zoospore mobility and mycelium growth of P. viticola. Our results show that spruce bark extract, which is considered as a wood industry co-product, could potentially be used as a natural fungicide against downy mildew.

Stilbene-enriched extracts from Vitis vinifera waste (cane, wood, and root) were characterized by UHPLC-MS. Eleven stilbenes were identified and quantified as follows: ampelopsin A, (E)-piceatannol, pallidol, (E)-resveratrol, hopeaphenol, isohopeaphenol, (E)-ε-viniferin, (E)-miyabenol C, (E)-ω-viniferin, r2-viniferin, and r-viniferin. The fungicide concentration inhibiting 50% of growth of Plasmopara viticola sporulation (IC50) was determined for the extracts and also for the main compounds isolated. r-Viniferin followed by hopeaphenol and r2-viniferin showed low IC50 and thus high efficacy against Plasmopara viticola. Regarding stilbene extracts, wood extract followed by root extract showed the highest antifungal activities. These data suggest that stilbene complex mixtures from Vitis vinifera waste could be used as a cheap source of bioactive stilbenes for the development of natural fungicides.

Food spoilage is a major issue for the food industry, leading to food waste, substantial economic losses for manufacturers and consumers, and a negative impact on brand names. Among causes, fungal contamination can be encountered at various stages of the food chain (e.g., post-harvest, during processing or storage). Fungal development leads to food sensory defects varying from visual deterioration to noticeable odor, flavor, or texture changes but can also have negative health impacts via mycotoxin production by some molds. In order to avoid microbial spoilage and thus extend product shelf life, different treatments—including fungicides and chemical preservatives—are used. In parallel, public authorities encourage the food industry to limit the use of these chemical compounds and develop natural methods for food preservation. This is accompanied by a strong societal demand for ‘clean label’ food products, as consumers are looking for more natural, less severely processed and safer products. In this context, microbial agents corresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules, exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation. This review presents the main fungal spoilers encountered in food products, the antifungal microorganisms tested for food bioprotection, and their mechanisms of action. A focus is made in particular on the recent in situ studies and the constraints associated with the use of antifungal microbial agents for food biopreservation.[br/]

correction DOI: 10.1016/j.postharvbio.2017.12.009 (WOS:000418891000018); Preventive antifungal activity of postharvest treatments with SPI (soy protein isolate) −coatings forming solutions against blue mould decay were evaluated on Persian lime (Citrus latifolia Tanaka) artificially inoculated in rind wounds with Penicillium italicum. Stimulatory effects were observed with the use of citral, however with the use of limonene an inhibitory effect was obtained. After 13 d of storage, significant preventive activity against blue mould was observed with a 20% of disease incidence applying SPI-coating forming solutions with limonene added. SEM micrographs showed that limonene could act as an inhibitor of germ tube elongation, delaying the process of infection. Quality parameters like water losses, change in colour and aroma compounds release were assessed on fruit coated. Depending to storage condition, SPI-coating forming solutions were effective to reduce water losses, maintain colour and controlling the liberation of active agent.

International audience; Plant cells secrete a wide range of proteins in extracellular spaces in response to pathogen attack. The poplar rust-induced secreted protein (RISP) is a small cationic protein of unknown function that was identified as the most induced gene in poplar leaves during immune responses to the leaf rust pathogen Melampsora larici-populina, an obligate biotrophic parasite. Here, we combined in planta and in vitro molecular biology approaches to tackle the function of RISP. Using a RISP-mCherry fusion transiently expressed in Nicotiana benthamiana leaves, we demonstrated that RISP is secreted into the apoplast. A recombinant RISP specifically binds to M. larici-populina urediniospores and inhibits their germination. It also arrests the growth of the fungus in vitro and on poplar leaves. Interestingly, RISP also triggers poplar cell culture alkalinisation and is cleaved at the C-terminus by a plant-encoded mechanism. Altogether our results indicate that RISP is an antifungal protein that has the ability to trigger cellular responses.

Enzymatic grafting represents a promising tool for wood protection. This strategy is based in the covalent anchoring of target compounds onto wood by an enzyme-based reaction. It is an environmental-friendly and simple treatment and has the advantage of the covalent fixation of the substrates onto the wood surface. As a consequence, leaching is avoided and long-lasting treatments are obtained. In this work, we propose the extraction of several commercial wood species followed by an enzymatic grafting of wood extractives as a new approach for fungal rot resistance. Considering the specificity of the enzyme employed, laccase, particular attention was paid for quantification and identification of the phenolic extractives.

Fungal spoilage is one of the causes of consequential losses in the dairy industry. In this context, the use of bioprotective cultures can be an alternative or a complementary approach to be considered. Lactic acid bacteria (LAB) and propionibacteria, as well as some fungal species, can exhibit antifungal activities with large differences in activity between strains. Therefore, it is necessary to develop high-throughput screening methods to test a large number of strains and find the most efficient ones. In the present study, we developed a miniaturized high-throughput screening technique to rapidly detect antifungal activities in a cheese-like model. This model, distributed in a 24-well plate, consisted of 5-fold concentrated whole milk ultrafiltration retentate (final fat concentration of 45%), rennet (0.03%) and inoculated with a mesophilic lactic commercial starter and a pH indicator. Each well of the plate could be considered as a miniature cheese of ~2 g. Potent antifungal isolates were cultured in two dairy media; (i) a 10%-reconstituted low heat skim milk supplemented with 45% anhydrous milk fat (LH) and (ii) a 6-fold concentrated milk ultrafiltration permeate sterilized by 0.22 μm filtration and complemented with 10 g/l yeast extract and a pH indicator (UF). After cultivation, cultures (100 µl) were deposited on the miniature cheese surfaces followed by inoculation in duplicate with 50 spores or cells of 4 different fungal targets (1 fungi/plate), e.g., Mucor racemosus, Galactomyces geotrichum, Penicillium commune and Yarrowia lipolytica, and incubation at 12°C for up to 15 days. We screened 505 bacterial isolates belonging to Lactobacillus, Lactococcus, Pediococcus, Leuconostoc and Propiobacterium genera and 198 fungal isolates belonging to 28 genera. This high-throughput screening for antifungal activity revealed that 52 and 216 bacteria, and, 53 and 89 fungi, inhibited at least one fungal target after cultivation in UF and LH, respectively. Among the 4 tested fungal targets, P. commune was the most frequently inhibited fungus while only few isolates were able to inhibit M. racemosus or Y. lipolytica. This method opens new possibilities to screen microorganisms for antifungal activities. These results also underline the importance of the culture and screening media used on the expression of antifungal activities by bacteria or fungi.

Latex from Hevea brasiliensis and its subcellular fractions (L-serum and C-serum) were tested for antifungal activity alone or in combination with fluconazole. Candida albicans growth was inhibited with the same efficacy when yeasts were inoculated into culture medium supplemented over the total growth phase with latex as when latex was added during the exponential phase only: the minimum inhibitory concentration (MIC 80%) of H. brasiliensis latex was 123 micrograms protein ml-1. By means of a non-linear regression analysis of the experimental data, two distinct fixation sites for fluconazole (FCZ) could be determined: one of strong affinity (Kaff = 0.0162 microgram-1 protein ml) and another of low affinity (Kaff = 0.0071 microgram-1 protein ml). After addition of a mixture of FCZ and latex during the exponential phase, the affinity constant of yeasts for FCZ was calculated: when latex was in a final concentration of 21 micrograms protein ml-1 (Kaff = 1 microgram-1 protein ml) or 42 micrograms protein ml-1 (Kaff = 0.277 microgram-1 protein ml) and without latex (Kaff = 0.0502 microgram-1 protein ml). In two cases a synergistic effect between latex and FCZ was obtained. The highest efficacy was obtained with a latex concentration of 21 micrograms protein ml-1. The addition of subcellular fractions of latex, L-serum and C-serum, did not cause an antifungal effect. The indispensable role of rubber particles for raising an antifungal effect is demonstrated. Electron microscopy observations indicated a limited cell wall degradation and a high percentage of coagulated yeasts.

Wood preservatives based on protein borates, both obtained by just mixed water solutions of protein and boric acid, as well as in the case of premanufactured protein borates salts are shown to be a good method to greatly retard the leaching of boron from treated timber. Hence just premixed albumin + boric acid, premanufactured albumin borate and soja protein + boric acid all showed good preservative performance and much retarded leaching of boron. Accelerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which are then insolubilised by heat-induced coagulation can yield durability performances comparable to those obtained with CCA wood preservatives. The results of the biological tests show that protein borates, and particularly albumin borate, can be classified as long-term, wide-spectrum, ground-contact, heavy-duty wood preservatives, and are only composed of boric acid, a non-toxic to mammals biocide and of a non-toxic, natural, sometimes waste material, namely a protein. The mechanism is one of partially reversible rather than totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastically diminishing its tendency to leach and greatly retarding its leaching. Boric acid leaching as a function of exposure time appears to tend to an equilibrium value. The timber is treated by just single stage, water-borne vacuum/pressure treating cycles as for traditional wood preservatives.

National audience

L'anthracnose constitue pour plusieurs productions végétales une maladie importante qui engendre des pertes post récoltes considérables. Colletotrichum musae est le responsable de cette maladie chez la banane dessert. L'utilisation d'antimicrobiens naturels comme le système lactoperoxydase (LPS) représente une voie naturelle de lutte intéressante contre l'anthracnose. Dans cette étude, nous avons amélioré le LPS en ajoutant de l'iode dans le système existant ou en substituant le thiocyanate par de l'iode. La substitution du thiocyanate à l'iode a permis d'avoir un effet fongicide du LPS. De plus, d'autres substances comme la lactoferrine, le Bioxeda® et l'huile de Neem ont été étudiées pour leur effet antifongique. Les deux dernières substances ont donné une inhibition supérieure respectivement à 90% et à 40%., tandis qu'il n'y a eu aucun effet de la lactoferrine.

International audience; Analysis of the extracts contained in Burkea africana heartwood is studied with the aim of better understanding the reasons of the exceptional durability of this type of wood. The results obtained show that in spite of the fungicidal and termiticidal properties of certain products contained in the extracts, these properties do not allow to explain entirely the reasons of the durability. The strongly hydrophobic character of wood as its high dimensional stability would be also significant factors of its resistance. Analysis of the products present in the diethylether extracts indicates the presence of fats, waxes and squalene which could be the reason of the preceding results.; À propos de la durabilité du bois de cœur de Burkea africana. L'analyse des matières extractibles contenues dans le Burkea africana est étudiée dans le but de mieux comprendre les raisons de la durabilité exceptionnelle de ce type de bois. Les résultats obtenus montrent que malgré les propriétés fongicides et termiticides de certains produits contenus dans les extraits, ces dernières ne permettent pas d'expliquer entièrement à elles seules les raisons de la durabilité. Le caractère hydrophobe du bois ainsi que sa forte stabilité dimensionnelle seraient également des facteurs importants de sa résistance. L'analyse des produits présents dans les extraits éthérés indique la présence de graisses, de cires et de squalène pouvant être à la base des résultats précédents.

Introduction. Les extraits d'huiles essentielles possedent des proprietes antivirales, antibacteriennes et antifongiques connues de longues dates. Le travail presente a donc cherche a evaluer l'effet d'huiles extraites de differentes varietes d'agrumes sur la croissance mycelienne in vitro de Phaeoramularia angolensis , champignon responsable de la phaeoramulariose des Citrus . Materiel et methodes. Les huiles essentielles extraites par hydrodistillation des pericarpes de fruits de six varietes d'agrumes ont ete analysees pour en determiner la composition chimique et evaluer leur activite antifongique vis-a-vis de P. angolensis . L'activite des extraits a ete evaluee in vitro par la technique d'incorporation decrite par Grover et Moore. Les huiles ont ete analysees par chromatographie en phase gazeuse couplee a la spectrometrie de masse. Resultats. La croissance de P. angolensis a ete inhibee par les huiles essentielles a des degres varies, avec une activite plus prononcee pour les huiles issues de C. latifolia et de C. limon . L'analyse de la composition chimique des huiles testees a montre que les plus actives ont une teneur relativement importante en citrals (neral + geranial ), ce qui s'accorde avec l'existence de proprietes antifongiques connues chez les citrals. Conclusion. Ces resultats preliminaires sont d'autant plus interessants que C. limon et C. latifolia sont des varietes reputees peu sensibles a la phaeoramulariose en conditions naturelles. Le role probable des huiles essentielles dans la resistance varietale vis-a-vis de P. angolensis est discute. La poursuite de ces recherches contribuera a une meilleure comprehension des relations hote-parasite.

Trente six clones d'hévéa ont été inoculés en chambre climatisée avec des conidies de #Microcyclus ulei#, responsable de la maladie sud-américaine des feuilles. Les composantes de la résistance à la maladie comme la durée de la période d'incubation, le temps nécessaire avant sporulation, la taille et le nombre des lésions, le pourcentage de surface foliaire endommagée, la production de spores et le temps nécessaire à l'apparition des structures stromatiques, ont été étudiés lors d'un seul cycle d'infection. Les clones sont aisément séparés en évaluant ces composants de la résistance lors d'essais en chambre climatique. Certains de ces composants sont corrélés significativement l'un à l'autre. Ainsi, la taille, le nombre de lésions, et la production de spores sont étroitement corrélés avec le pourcentage de surface foliaire endommagée. D'autres composants sont faiblement corrélés, tels le temps nécessaire à l'apparition des stromas avec tous les autres composants, la période d'incubation et la période de latence infectieuse avec la densité des lésions. Dans le cadre de la sélection de variétés-clones, la surface foliaire attaquée et la production de spores pourraient être les composants les plus pertinents à utiliser. Ces clones ont également été testés quant à leur capacité à produire la scopolétine, phytoalexine de l'hévéa, et à synthétiser de la lignine dans les zones infectées. Une étroite corrélation a été mise en évidence entre l'accumulation de la scopolétine et la résistance clonale. De plus, des accumulations importantes de lignine sont souvent associées aux durées de génération des stromas les plus longues. Ces deux réactions physiologiques pourraient intervenir dans la limitation du développement fongique chez plusieurs clones. Cependant, l'accumulation de scopolétine ou de lignine ne peuvent pas à elles seules expliquer le comportement de tous les clones

Wood preservatives based on protein borates and in particular albumin borate greatly retarded the leaching of boron from treated timber. Accelerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which are then insolubilised by heat-induced coagulation can yield durability comparable to that obtained with CCA wood preservatives. The results of the biological tests show that protein borates, and particularly albumin borate, can be classified as long-term, wide-spectrum, ground-contact, heavy-duty wood preservatives, and are only composed of boric acid. a non-toxic to mammals biocide and of a non-toxic, natural, sometimes waste material, namely a protein. Investigation of the chemical mechanisms of boric acid fixation by the protein indicated that both acid-base salt formation occurs, as well as the further formation at increasing boric acid proportions of additional boric acid/protein complexes. The mechanism is hence only one of partially reversible rather than totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastically diminishing its tendency to leach and greatly retarding its leaching. Boric acid leaching as a function of exposure time appears to tend to an equilibrium value which is different for each type of protein used and differs in the case of treated timber from that obtained by just leaching of the protein borate coagulum.

La maladie Sud-Américaine des feuilles causées par Microcyclus ulei, est le principal facteur limitant de l'hévéaculture en Amérique latine. Les clones inoculés par des conidies de M. ulei présentent, soit une résistance totale, soit une résistance partielle. Deux réactions physiologiques des feuilles d'Hevea infectées ont été identifiées et caractérisées. Une première réaction de défense précoce implique une phytoalexine, la scopolétine. Cette coumarine est visualisée dès 12 h chez les clones à résistance totale et partielle de bon niveau et le niveau de résistance est en relation avec sa rapidité et son intensité d'accumulation. Son effet fongitoxique est testé sur deux autres pathogènes foliaires de l'Hevea, Colletotrichum gloeosporioides et Corynespora cassiicola. Quatre jours après inoculation, des lignines sont révélées autour des lésions chez les clones à résistance partielle. Leur accumulation intense bloquerait le pathogène au centre de la lésion. Ces deux réactions de défense ont été vérifiées sur une large gamme de clones testés vis-à-vis de deux isolats de M. ulei, d'origine géographique différente. Toutefois, elles n'expliquent pas tous les cas de résistance

After inoculation with Microcyclus ulei, Hevea leaflets produced a coumarin, scopoletin, in the infected zones. The degree of resistance of four clones was related to the rapidity and intensity of scopoletin accumulation. Thus, 24 h after inoculation, the clones with total resistance and those with a high level of partial resistance displayed an early accumulation of scopoletin that intensified and lasted longer than 48 h in the fully resistant clones. The level of partial resistance was positively correlated with scopoletin concentration 48 h after inoculation. The fungitoxic effect of scopoletin was verified in vitro on M. ulei where 2 mM concentrations were sufficient to strongly inhibit germ tube elongation and conidium germination. In situ , 24 h after inoculation, conidium germination and number of infection sites were lower in the most resistant clones. The fungitoxic effect of scopoletin was tested on two other leaf pathogens of the rubber-tree, Colletotrichum gloeosporioides and Corynespora cassiicola . Concentrations double or more than those tested on M. ulei were required for total inhibition of germination and germ tube elongation.