Pseudozyma aphidis Extracts Possess Bioactive Properties That Suppress Plant Pathogens and Enhance Resistance in Tomato Plants

The constant growth in the world population demands a constant increase in agricultural yields. One of the main ways to increase agricultural yields is by improving the control of pests and pathogens. Human health and environmental concerns regarding traditional synthetic pesticides challenge the scientific community to discover novel and less harmful ways of pest control, including the development of biocontrol agents and natural pesticide alternatives. Previous studies have established that the application of live Pseudozyma aphidis can be used for biocontrol of diverse fungal and bacterial phytopathogens. Here, we demonstrate the activity of two semipurified fractions from P. aphidis: one contained antimicrobial metabolites (AMF) and the other contained resistance-inducing metabolites (IRF). Our results from the in vitro experiments with the antimicrobial extract show that P. aphidis metabolites strongly inhibit important fungal and bacterial phytopathogens. In planta experiments demonstrated a significant, dose-dependent reduction in disease infection when a spore suspension of Botrytis cinerea was treated or exposed to the extracted metabolites. In addition, our results showed that the application of a semipurified aqueous fraction from P. aphidis on tomato plants rapidly up-regulated the expression of defence-related genes, which are associated with both the induced systemic resistance and the systemic acquired resistance pathways. This study enhances our understanding of the biochemical mechanisms behind P. aphidis main modes of action: antibiosis and induced resistance. This also demonstrates the significant potential of this unique biocontrol agent as a source for the development of novel natural pesticide formulations and/or compounds that enhance resistance.