Evaluation of Resistance Induction Promoted by Bioactive Compounds of Pseudomonas aeruginosa LV Strain against Asian Soybean Rust

Abstract

Pseudomonas are known as higher producers of secondary metabolites with antimicrobial properties and plant growth promoters, including resistance induction. These mechanisms should be an alternative to pesticide use in crop production. Phakopsora pachyrhizi causes Asian soybean rust, representing a high loss of yield around the world. The objective of this paper was to evaluate the application of secondary metabolites produced by Pseudomonas aeruginosa LV strain from the semi-purified fraction F4A in soybean plants to induce plant resistance against P. pachyrhizi in field conditions. The experimental design was performed in randomized blocks with three replicates using two F4A doses (1 and 10 μg mL−1) combined or not with fungicides (Unizeb Gold® or Sphere Max®). The control treatment, with Uni + Sph, saponins, flavonoids, and sphingolipids, showed higher intensities in the plants. In contrast, plants treated with the F4A fraction mainly exhibited fatty acid derivatives and some non-identified compounds with nitrogen. Plants treated with Sphere Max®, with or without F4A10, showed higher intensities of glycosylated flavonoids, such as kaempferol, luteolin, narigenin, and apigenin. Plants treated with F4A showed higher intensities of genistein and fatty acid derivatives. These increases in flavonoid compound biosynthesis and antioxidant properties probably contribute to the protection against reactive oxygen species (ROS).