Scent of a Killer: Microbial Volatilome and Its Role in the Biological Control of Plant Pathogens

Abstract

The use of synthetic fungicides represents the most common strategy to control plant pathogens. Excessive and/or long-term distribution of chemicals is responsible for increased levels of environmental pollution, as well as adverse health consequence to humans and animals. These issues are deeply influencing public perception, as reflected by the increasing demand for safer and eco-friendly agricultural commodities and their by-products. A steadily increasing number of research efforts is now devoted to explore the use of safer and innovative approaches to control plant pathogens. The use of microorganisms as biological control agents (BCAs) represents one of the most durable and promising strategies. Among the panoply of microbial mechanisms exerted by BCAs, the production of volatile organic compounds (VOCs) represents an intriguing issue, mostly exploitable in circumstances where a direct contact between the pathogen and its antagonist is not practicable. VOCs are potentially produced by all living microorganisms, and may be active in the biocontrol of phytopathogenic oomycetes, fungi, and bacteria by means of antimicrobial activity and/or other cross-talk interactions. Their biological effects, the reduced residuals in the environment and on agricultural commodities, and the ease of application in different agricultural systems make the use of VOCs a promising and sustainable approach to replace synthetic fungicides in the control of plant pathogens. In this review, we focus on VOCs produced by bacteria and fungi and on their role in the cross-talk existing between the plant pathogens and their host. Biologic systemic effect of the microbial volatile blends on both pathogen and host plant cells is also briefly reviewed.

Fungal Microbiota of Sea Buckthorn Berries at Two Ripening Stages and Volatile Profiling of Potential Biocontrol Yeasts

“…It was revealed that some Aureobasidium species demonstrated biological control activity against phytopathogens, such as Botrytis, Bacillus, Colletotrichum, Penicillium [43,52,53]. The antagonistic activity of A. pullulans mainly includes nutrient competition and production of volatile organic compounds or glucanases, chitinases, and extracellular proteases [40,46]. Taphrina and Cladosporium were the next numerous fungal microorganisms observed on unripe sea buckthorn berries in our study (Table S1, Figure 2).…”

“…Various microorganisms act as biological control agents of phytopathogens and have a role in postharvest decay and toxin contamination by emitting volatile organic compounds [40,43]. Several biocontrol yeasts (e.g., Candida oleophila, Aureobasidium pullulans, Metschnikowia fructicola, Cryptococcus albidus, Saccharomyces cerevisiae) have already been used for the production of commercial plant protection products, encouraging the deeper exploration of the fascinating traits and application possibilities of other yeasts as well [16,44,45].…”

“…apples, grapes, or strawberries [59,60]. Numerous yeasts belonging to the Hanseniaspora genus display antagonistic properties against the development of fruit spoilage causing molds [40,61]. Metschnikowia spp.…”

“…Cyberlindnera jadinii, Lachancea thermotolerans, Candida intermedia, Candida friedrichii, Saccharomyces cerevisiae, Wickerhamomyces anomalus) affecting numerous pathogens (e.g. Aspergillus carbonarius, Aspergillus flavus, Aspergillus ochraceus, Penicillium digitatum, Phyllosticta citricarpa) (see [40] and references therein). Among tested strains, H. uvarum SB-18-31 and M. pulcherrima SB-18-34 produced the highest amount of 2-phenylethanol, whereas A. pullulans SB-18-2 excelled at ethanol generation, while volatilome of C. wieringae SB-18-25 was dominated by 3-methylbutanol.…”

“…Four yeast strains, belonging to different genera identified by metagenomics analysis of UB and RB microbiota with referred potential biocontrol properties [15,16,40] (Table S1, Figure 5), were selected for VOCs analysis. Morphologically different SB-18-2 and SB-18-25 yeast strains were recovered from UB berries while SB-18-34 and SB-18-31 yeast strains were isolated from RB berries.…”