Abstract
Along with barley and rice, maize provides staple food for more than half of the world population. Maize ears are regularly infected with fungal pathogens of the Fusarium genus, which, besides reducing yield, also taint grains with toxic metabolites. In an earlier work, we have shown that maize ears infection with single Fusarium strains was detectable through volatile sensing. In nature, infection most commonly occurs with more than a single fungal strain; hence we tested how the interactions of two strains would modulate volatile emission from infected ears. For this purpose, ears of a hybrid and a dwarf maize variety were simultaneously infected with different strains of Fusarium graminearum and F. verticillioides and, the resulting volatile profiles were compared to the ones of ears infected with single strains. Disease severity, fungal biomass, and the concentration of the oxylipin 9-hydroxy octadecadienoic acid, a signaling molecule involved in plant defense, were monitored and correlated to volatile profiles. Our results demonstrate that in simultaneous infections of hybrid and dwarf maize, the most competitive fungal strains had the largest influence on the volatile profile of infected ears. In both concurrent and single inoculations, volatile profiles reflected disease severity. Additionally, the data further indicate that dwarf maize and hybrid maize might emit common (i.e., sesquiterpenoids) and specific markers upon fungal infection. Overall this suggests that volatile profiles might be a good proxy for disease severity regardless of the fungal competition taking place in maize ears. With the appropriate sensitivity and reliability, volatile sensing thus appears as a promising tool for detecting fungal infection of maize ears under field conditions.
Highlights
Maize fields cover about 180 million hectares worldwide and provide, along with wheat and rice, staple food for more than half of the world population (FAO, 1995)
Hybrid and dwarf maize were (i) infected with single strains of F. graminearum and F. verticillioides, (ii) simultaneously infected with different strains belonging to the two aforementioned species, and (iii) uninfected (“mock-inoculated” with water)
Hybrid maize was infected with either F. graminearum (FG) strain FG1, F. verticillioides (FV) strain FV1 and mixed strains FG1+FV1 or with FG2, FV2, and mixed strains FG2+FV2
Summary
Maize fields cover about 180 million hectares worldwide and provide, along with wheat and rice, staple food for more than half of the world population (FAO, 1995). Maize cultivation suffers from numerous pathogens, which infect plant roots, stems, leaves, and ears in the field. Some of the most devastating pathogens of maize belong to the Fusarium genus which is responsible for 10–30% yield. Volatiles in Maize/Fusarium Interactions loss in major crops throughout the globe (Agrios, 2005). Apart from causing yield losses, Fusarium species infecting maize produce mycotoxins potentially endangering the health of consumers and farm animals. Controlling and detecting early infection of maize by Fusarium spp. is challenging. Comparison of volatile profiles of infected and non-infected plants might allow the identification of volatile biomarkers that can be used to monitor fungal infection in real time using non-invasive techniques
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