Abstract
Plants and fungi emit volatile organic compounds (VOCs) that are either constitutively produced or are produced in response to changes in their physico-chemical status. We hypothesized that these chemical signals could be utilized as diagnostic tools for plant diseases. VOCs from several common wheat pathogens in pure culture (Fusarium graminearum, Fusarium culmorum, Fusarium avenaceum, Fusarium poae, and Parastagonospora nodorum) were collected and compared among isolates of the same fungus, between pathogens from different species, and between pathogens causing different disease groups [Fusarium head blight (FHB) and Septoria nodorum blotch (SNB)]. In addition, we inoculated two wheat varieties with either F. graminearum or P. nodorum, while one variety was also inoculated with Blumeria graminis f.sp. tritici (powdery mildew, PM). VOCs were collected 7, 14, and 21 days after inoculation. Each fungal species in pure culture emitted a different VOC blend, and each isolate could be classified into its respective disease group based on VOCs with an accuracy of 71.4 and 84.2% for FHB and SNB, respectively. When all collection times were combined, the classification of the tested diseases was correct in 84 and 86% of all cases evaluated. Germacrene D and sativene, which were associated with FHB infection, and mellein and heptadecanone, which were associated with SNB infection, were consistently emitted by both wheat varieties. Wheat plants infected with PM emitted significant amounts of 1-octen-3-ol and 3,5,5-trimethyl-2-hexene. Our study suggests that VOC blends could be used to classify wheat diseases. This is the first step toward a real-time disease detection in the field based on chemical signatures of wheat diseases.
Highlights
As part of their metabolism, plants and fungi release diverse volatile organic compounds (VOCs) into the air
The application of fungicides guided by pathogen-specific VOCs could significantly reduce the amounts of active compounds needed for disease control in the field (Gebbers and Adamchuk, 2010). The objective of this manuscript was to determine if VOC profiles are specific for different wheat pathogens and the diseases they are causing in wheat. We addressed these specific hypotheses: (i) Fungal isolates causing diseases in wheat have their own characteristic VOC or VOC blend produced in pure culture. (ii) Plant pathogenic fungal isolates can be grouped into their genera/disease group based on their VOC profiles. (iii) Pathogen VOCs produced in pure culture will be produced in plants infected with these pathogens. (iv) Infected plants will emit VOC profiles that are specific to a pathogen, allowing correct classification of the different diseases, even when different wheat varieties are used. (v) The release of pathogen-specific VOCs correlates with disease index over time
Our studies showed that different fungal species produced different VOC profiles and could be grouped into their respective isolate and disease group based on these profiles with a medium to high accuracy (84.2% for both)
Summary
As part of their metabolism, plants and fungi release diverse volatile organic compounds (VOCs) into the air. Plant VOCs are emitted in response to biotic and abiotic stresses and play an important role in defense signaling and communication between plants (Brilli et al, 2019). They can serve as priming agents to enhance resistance to both herbivores (Kim and Felton, 2013) and plant pathogens (Ameye et al, 2015) and can serve as important. The rate of emission of VOCs from plants and fungi varies depending on the physico-chemical and biological factors and the nature of the interaction between the pathogen and the plant (Sankaran et al, 2010; Morath et al, 2012). Fungal VOCs have been used as attractants and deterrents to insects and other invertebrates (Morath et al, 2012) and as resistance inducers (Naznin et al, 2013, 2014), but not as biomarkers for disease detection in the field
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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
