Abstract
Volatile organic compounds (VOC) were extracted and identified from plant growth-promoting fungi (PGPF), Phoma sp., Cladosporium sp. and Ampelomyces sp., using gas chromatography–mass spectrometry (GC-MS). Among the three VOC extracted, two VOC blends (emitted from Ampelomyces sp. and Cladosporium sp.) significantly reduced disease severity in Arabidopsis plants against Pseudomonas syringae pv. tomato DC3000 (Pst). Subsequently, m-cresol and methyl benzoate (MeBA) were identified as major active volatile compounds from Ampelomyces sp. and Cladosporium sp., respectively, and found to elicit induced systemic resistance (ISR) against the pathogen. Molecular signaling for disease suppression by the VOC were investigated by treating different mutants and transgenic Arabidopsis plants impaired in salicylic acid (SA) or Jasmonic acid (JA)/ethylene (ET) signaling pathways with m-cresol and MeBA followed by challenge inoculation with Pst. Results show that the level of protection was significantly lower when JA/ET-impaired mutants were treated with MeBA, and in SA-, and JA/ET-disrupted mutants after m-cresol treatment, indicating the involvement of these signal transduction pathways in the ISR primed by the volatiles. Analysis of defense-related genes by real-time qRT-PCR showed that both the SA-and JA-signaling pathways combine in the m-cresol signaling of ISR, whereas MeBA is mainly involved in the JA-signaling pathway with partial recruitment of SA-signals. The ET-signaling pathway was not employed in ISR by the volatiles. Therefore, this study identified two novel volatile components capable of eliciting ISR that may be promising candidates in biological control strategy to protect plants from diseases.
Highlights
Non-pathogenic, filamentous, saprophytic rhizosphere fungi that significantly enhance the growth of plants are known as plant growth-promoting fungi (PGPF) [1,2]
When the volatile metabolites were extracted from 2-wk-old cultures of three PGPF isolates using headspace solid phase micro extraction (SPME) and identified using gas chromatography–mass spectrometry (GC-MS), most of the volatile organic compounds (VOC) from Phoma sp. and Ampelomyces sp. were C4–C8 hydrocarbons (Table 1)
VOC Emitted from PGPFs Suppress Disease Severity Arabidopsis plants were treated with one of the volatile organic compounds isolated from the 3 PGPFs (Phoma sp., Ampelomyces sp. and Cladosporium sp.) in hydroponic culture (Table 1)
Summary
Non-pathogenic, filamentous, saprophytic rhizosphere fungi that significantly enhance the growth of plants are known as plant growth-promoting fungi (PGPF) [1,2]. In the past few years, PGPF from the genera of Fusarium, Penicillium, Phoma, and Trichoderma have been frequently studied and evaluated for their high suppressive abilities against a variety of plant diseases as a result of direct antagonism against soil-borne pathogens or by inducing systemic resistance in the plant [3,4,5,6,7]. Recent studies have revealed that volatile organic compounds (VOC) released from some PGPF strains can effectively promote plant growth and enhance disease resistance [11,12]. Yamagiwa et al [11] reported that the volatile compound b-caryophyllene emitted from the PGPF Talaromyces wortmannii FS2 significantly enhanced the growth of komatsuna Reports on VOC from PGPF are relatively recent and few in number, the role of volatiles emitted from plants and other microorganisms on plant development have been studied extensively [13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
