Applications of Pythium- and Phytophthora-produced volatiles in plant disease control.

Volatile organic compounds (VOCs) mediate biological interactions and are produced by Pythium and Phytophthora species. These VOCs are biotechnologically relevant because the genera include important plant pathogens, whereby VOCs can aid in disease detection, and biological control agents, whereby VOCs contribute to disease control. Studies on VOC production, identification, and characterization of individual VOCs produced by Pythium and Phytophthora species are reviewed. VOCs detected in plants infected with Phytophthora species are also reviewed as potentially oomycete-derived VOCs. The Pythium- and Phytophthora-produced VOCs are compared with other microorganisms, and the main effects of these VOCs on microbial inhibition and plant-mediated effects are reviewed. These effects are summarized from direct demonstration studies and inferences based on the known functions of the identified Pythium- and Phytophthora-produced VOCs. There are two main applications of VOCs to plant disease control: the use of VOCs to detect pathogenic Pythium and Phytophthora species, e.g., e-nose detecting systems, and the use of VOC-producing biological control agents, e.g., Pythium oligandrum. Future research could understand how the VOCs are produced to engineer VOC levels in strains, analyze more oomycete species and strains, accurately quantify the VOCs produced, and exploit recent developments in analytical chemistry technology. KEY POINTS: • Compiled inventory of volatiles produced by Phytophthora and Pythium species • Volatilomes contain microbe-inhibiting and plant growth-promoting compounds • Volatile potential in disease detection and control supports analyzing more species.