Resistance of Telluric Fungi to Chemical Fungicides

Our work focuses on the identification of resistance of telluric fungi to commonly used fungicidesin chemical control. We investigate the resistance of telluric fungi (Fusarium sp., Chalara sp., Sporonema sp., Stiebum sp., Didymabotrium sp., Dothichiza sp. and Sclerotopsis sp.) from cereal fields to four fungicides (Propicone, Vapcotop, Curitine V and Kazir). This study was based on direct contact of the telluric isolates with fungicides on Petri dishes. For the four tested fungicides different rates of resistance and susceptibility were observed according to the isolate and the used concentration. One of the isolates showed a high resistance to Vapcotop with 500 mg%252Fl. Generally the statistical analysis revealed that there are no significant differences in the effect of fungicides concentrations against isolates, while significant differences are observed between isolates

IN VITRO EVALUATION OF BIOLOGICAL ACTIVITIES OF PISTACIA LENTISCUS AQUEOUS EXTRACT

Objective: The aim of this study was to study the antioxidant potential and the antibacterial activity of leaves aqueous extract of Pistacia Lentiscus as well as the protective effect of this extract against the haemolysis in hypotonic condition, in oxidative stress and in the existence of saponin injury.Methods: We studied the antioxidant capacity through the DPPH assay, H2O2 scavenging activity, Ferric-reducing power (FRAP) assay, total antioxidant assay and the antibacterial activity using the disc diffusion method. We also investigated the haemolytic activity with the spectrophotometric method.Results: The result showed that the aqueous extract had a good antioxidant capacity, which was calculated as IC50. IC50 of the aqueous extract was found to be 9.89±0.7µg/ml for DPPH scavenging, 200±18.02µg/ml for H2O2 scavenging assay, 54.06±12.66µg/ml for Ferric-reducing power (FRAP) and 500±22.3 µg/ml for total antioxidant capacity. The aqueous extract also inhibited the growth of the tested bacterial strains with a maximum inhibition zone of 30.33±5.5 mm observed on Pseudomonas aeruginosa for wood-seed and a moderate activity against all other strain. The haemolytic analysis showed that the aqueous extract is not toxic for the human erythrocytes and protects them against the oxidative and osmotic stress and also against saponin injury.Conclusion: The results of our study suggest that the aqueous extract of leaves of Pistacia lentiscus possess potent anti-haemolytic activity, are a good source of natural antioxidant.Â

Chemical composition and antibacterial activity of Algerian propolis against fish pathogenic bacteria

Five different varieties of propolis from four sites from Sétif region (East of Algeria) (Babor, Setif; Ain-Abbassa and El-Hamma), and one site from the center of Algeria (Tizi-Ouzou) were chemically analysed by gas chromatography-mass spectrometry. One hundred and two compounds were identified including aromatic acids, linear hydrocarbons and their acids, terpenes and alcaloïdes. Furthermore, the in vitro bacteriostatic and bactericidal activities of the aqueous extracts were evaluated against one Gram positive (Bacillus subtilis, used as probiotics in aquaculture) and two Gram negative (Vibrio anguillarum and Vibrio harveyi, pathogenic for fish) bacteria. The obtained results showed that all aqueous extracts of propolis inhibit the growth of B. Subtilis while the growth inhibition of fish pathogens was achieved when using higher propolis concentrations. These antibacterial properties would warrant further studies on the clinical applications of propolis in aquaculture field. Keywords: Bactericidal activity; Chemical characterization; Propolis; Vibrio

Isolation, Identification and antimicrobial activity of pseudomonads isolated from the rhiszosphere of popatoes growing in Algeria

International audienceFourteen bacterial isolates from the rhizosphere of potato plants growing near Sétif, (Algeria) were characterised as fluorescent Pseudomonads by phenotypical methods and one was identified as Pseudomonas chlororaphis by sequencing ribosomal DNA. In dual culture, this isolate inhibited the growth of the phytopathogenic fungi Fusarium oxysporum f. sp. lycopersici, F. oxysporum f. sp. albedinis, F. solani and Rhizoctonia solani and the oomycete Pythium ultimum. Extracts of supernatants from liquid cultures of the Ps. chlororaphis isolate completely inhibited these organisms when incorporated into potato dextrose agar at a rate equivalent to 0.31 ml culture filtrate/ml, or greater. In a disc assay, extracts equivalent to 0.31 ml supernatant gave inhibition zones of 15 mm and 25 mm for the Gram-positive bacteria Bacillus subtilis and Paracoccus paratrophus, respectively. Fractionation of extracts of supernatants by TLC and HPLC with diode array detection allowed the identification of phenazine carboxylic acid as one of the antimicrobial compounds and the tentative identification of two others as 2-hydroxy phenazine carboxylic acid and 2-hydroxy phenazine

Antimicrobial secondary metabolites from agriculturally important fungi as next biocontrol agents

Synthetic chemical pesticides have been used for many years to increase the yield of agricultural crops. However, in the future, this approach is likely to be limited due to negative impacts on human health and the environment. Therefore, studies of the secondary metabolites produced by agriculturally important microorganisms have an important role in improving the quality of the crops entering the human food chain. In this review, we have compiled information about the most important secondary metabolites of fungal species currently used in agriculture pest and disease management