Surface hydrophobicity and electrical properties of Bacillus subtilis strains, potential phytopathogen antagonists in tomato crops

Abstract

Adhesion on the fruit surface is an important property governing the biocontrol of plant diseases by phytopathogen antagonists. Tomato surfaces and the surface properties of seven Bacillus subtilis strains have been studied in order to evaluate the aptitude of the surfaces for sticking to each other and thus preventing phytopathogen adhesion to tomato surface. The properties were evaluated by water contact angle and electrophoretic mobility measurements. Contact angles on tomato cuticles do not vary with the maturity of the tomatoes. The tomato surfaces remain hydrophobic during their lifetime. In contrast, Bacillus subtilis strains show a changing hydrophobicity with ageing. The Bacillus subtilis strain also has great influence on the hydrophobicity value. It is shown that three strains are very hydrophobic and the hydrophobicity of two others clearly depends on their physiological state. The trend emerging from experiments shows that a good correlation exists between hydrophobic properties and electrophoretic mobilities. Other examples referring to this type of relationship exist in the literature. This may be very useful for the selection of phytopathogen antagonists, in spite of the fact that other mechanisms such as nutrient competition, induced resistance and antifungal metabolite production are also involved in surface colonization.