Study of sodium 3-hydroxycoumarin as inhibitors in vitro, in vivo and in silico of Moniliophthora perniciosa fungus

The inhibition of the fungus Moniliophthora perniciosa, which is the causal agent of witches’ broom disease in Theobroma cacao L., is the main focus of the present study. The use of phytoalexins has provided disease control that is as efficient as control with the use of fungicides, with the advantage of not harming humans and the environment. In this sense, the objective was to evaluate the action of 3-hydroxycoumarin compared with the standard defence activator acibenzolar-S-methyl (Bion® 500 WG) and systemic fungicide tebuconazole (Folicur® 200 CE), and study the possible mechanisms of action. Initially, basidiospore germination inhibition assays (in vitro) were performed using four different concentrations of 3-hydroxycoumarin. The result was 100% inhibition at the concentration of 1000 ppm. Thereafter, this substance was used in four different treatments (in vivo) of cacao seedlings of the SIC-23 genotype, with regard to the order of application. The data analysis showed greater inhibition when 3-hydroxycoumarin was applied after inoculation (TAI test), and suggested a curative effect on Theobroma cacao seedlings. In silico, it was used the enzyme chitin synthase because this action as key enzyme in chitin biosynthetic pathway. The in silico tests show that 3-hydroxycoumarin inhibited the production of chitin synthase by the fungus. Therefore, the present study identifies a potential inhibitor of M. perniciosa and suggests the best application methodology.