Identification of Volatile Organic Compounds Emitted by Two Beneficial Endophytic Pseudomonas Strains from Olive Roots.

Nuria Montes-Osuna,Jesús Mercado-Blanco,Gabriele Berg,Carmen Gómez-Lama Cabanás,Tomislav Cernava

doi:10.3390/plants11030318

Abstract

The production of volatile organic compounds (VOCs) represents a promising strategy of plant-beneficial bacteria to control soil-borne phytopathogens. Pseudomonas sp. PICF6 and Pseudomonas simiae PICF7 are two indigenous inhabitants of olive roots displaying effective biological control against Verticillium dahliae. Additionally, strain PICF7 is able to promote the growth of barley and Arabidopsis thaliana, VOCs being involved in the growth of the latter species. In this study, the antagonistic capacity of these endophytic bacteria against relevant phytopathogens (Verticillium spp., Rhizoctonia solani, Sclerotinia sclerotiorum and Fusarium oxysporum f.sp. lycopersici) was assessed. Under in vitro conditions, PICF6 and PICF7 were only able to antagonize representative isolates of V. dahliae and V. longisporum. Remarkably, both strains produced an impressive portfolio of up to twenty VOCs, that included compounds with reported antifungal (e.g., 1-undecene, (methyldisulfanyl) methane and 1-decene) or plant growth promoting (e.g., tridecane, 1-decene) activities. Moreover, their volatilomes differed strongly in the absence and presence of V. dahliae. For example, when co incubated with the defoliating pathotype of V. dahliae, the antifungal compound 4-methyl-2,6-bis(2-methyl-2-propanyl)phenol was produced. Results suggest that volatiles emitted by these endophytes may differ in their modes of action, and that potential benefits for the host needs further investigation in planta.

Highlights

Soil-borne phytopathogens constitute a major threat affecting crops around the world, compromising global food production and security
Bis(methylsulfanyl)methane and 2-decyloxirane were produced by PICF6, but only in the absence of the pathogen. 2,6,11-trimethyldodecane and methyl thiocyanate were exclusively produced by strain PICF6, independently of the absence or presence of the pathogen. 1-tridecyne, 2-undecanone, 2-undecanol, 2-nonanol and 10-methyl-1-undecene were only identified when strain PICF6 was incubated with V. dahliae V937I (Table 2)
A relevant outcome of this study was to demonstrate that the two selected endophytic Pseudomonas strains from olive roots can produce an impressive portfolio of volatile organic compounds (VOCs) including those with antifungal, nematicidal and plant growth promoting effects

Summary

Introduction

Soil-borne phytopathogens constitute a major threat affecting crops around the world, compromising global food production and security. Some of them can survive in soils for many years in the absence of host plants due to different resistance structures (i.e., microsclerotia, sclerotia, chlamydospores or oospores), hindering their effective control [1]. To name an example of particular interest in our study, Verticillium wilt (Verticillium dahliae Kleb.) is considered one of the most threatening biotic constrains for olive (Olea europaea L.) cultivation and the main limiting factor for olive oil production [9]. These phytopathogenic fungi were traditionally managed by crop rotations and soil treatments. Biological control represents an interesting option within integrated management strategies

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