Preparation of Emulsions of some Vegetable Oils and Evaluation of Their Effectiveness in Inhibiting Pathogenic Fungus Didymella bryoniae

Abstract

Abstract Five pathogenic fungi were isolated from the infected melon/Cucumis melo, Cucumber/Cucumis sativus, Watermelon/Citrullus lanatus and Squash/Cucurbita pepo with gum stem blight disease. The fungi identified to the species level by the nucleotide sequence analysis method for the ITS region within the 5.8SrRNA gene as Stagonosporopsis cucurbitacearum strain Has. AA-16, S. cucurbitacearum strain Has. AA-17, S. cucurbitacearum strain Has. AA-18, S. cucurbitacearum strain Has. AA-19 and S. cucurbitacearum strain Has. AA-19 and S. cucurbitacearum strain Has. AA-20 then registered in the World Genetic Bank at the NCBI website under the accession numbers OP247683.1, OP247685.1, OP247686.1, OP247709.1 and OP247707.1, respectively. The physical and antagonistic properties of five types of emulsions produced from lavender, thyme, cinnamon and cloves oils with surfactants Inex A and Spam 80 were studied. The results showed a decrease in the surface tension of all emulsions produced from these oils with both surfactants. Increasing the temperature to 40°C led to a more decrease in the surface tension compared to 20°C. The lowest surface tension values for emulsions produced from clove, thyme and cinnamon oils with the Index A (1:6;oil:Inex A) at 40°C, the surface tension reached to 11.98, 13.22 and 14.17 Dyne/cm, respectively. The stability of all emulsions resulting from the studied oils increased with an increase in the ratios of the Inex A and Span 80, the highest stability was reached by decreasing the separation layer when emulsions of thyme and lavender oils with Inex A at a ratio of 1:6 at 20°C, which reached 0.61 and 0.66 cm, respectively. All emulsions consisting of oils and surfactants inhibited the growth of pathogenic fungus D. bryoniae, the highest inhibition zones were 1.9, 1.8, 1.7 and 1.6 cm for emulsions resulting from clove, cinnamon, thyme and lavender oils with Inex A at a ratio of 1:4 at a 20°C, respectively.