Interactions between Head Blight Pathogens: Consequences for Disease Development and Toxin Production in Wheat Spikes

Abstract

Head blight (HB) is one of the most damaging diseases on wheat, inducing significant yield losses and toxin accumulation in grains. Fungal pathogens responsible for HB include the genus Microdochium, with two species, and the toxin producer genus Fusarium, with several species. Field studies and surveys show that two or more species can coexist within a same field and coinfect the same plant or the same spike. In the current study, we investigated how the concomitant presence of F. graminearum and another of the HB complex species influences the spike colonization and the toxin production by the fungi. To study these interactions, 17 well-characterized isolates representing five species were inoculated alone or in pairs on wheat spikes in greenhouse and field experiments. The fungal DNA in the grains was estimated by quantitative PCR and toxin contents (deoxynivalenol and nivalenol) by ultraperformance liquid chromatography-UV detection-tandem mass spectrometry. The responses of the different isolates to the presence of a competitor were variable and isolate specific more than species specific. The development of the most aggressive isolates was either unchanged or a slightly increased, while the development of the less aggressive isolates was reduced. The main outcome of the study was that no trend of increased toxin production was observed in coinoculations compared to single inoculations. On the contrary, the amount of toxin produced was often lower than expected in coinoculations. We thus conclude against the hypothesis that the co-occurrence of several HB-causing species in the same field might aggravate the risk linked to fusarium toxins in wheat production.

Fusarium Toxins in Cereals: Occurrence, Legislation, Factors Promoting the Appearance and Their Management

“…Some experimental studies performed in wheat do not confirm these results where intraspecies interaction appears to reduce trichothecene yield [179]. Recent findings suggest that the behaviour of different isolates in presence of a competitor is variable mostly depending by Fusarium strain rather than species, with a predominance of aggressive isolates [180]. However, this study also demonstrates a lack of correlation between co-occurrence of several FHB species and an increase of Fusarium toxins risk in wheat production.…”

Mutual Exclusion between Fungal Species of the Fusarium Head Blight Complex in a Wheat Spike

“…A general trend in these studies is that the most competitive species does not colonize the host in coinoculations significantly more extensively than when inoculated alone (i.e., no advantage is provided by the presence of the other species), but the species with the selective disadvantage develops less extensively in the presence of a competitor than when infecting alone (2). This was once again observed by Siou et al (10,11). Such competitive interactions seem to occur at the intraspecific level as well.…”

“…The use of fungal amplicons as a proxy for the biomass of the FHB species was supported by results of previous experiments (11). For each sample (i.e., each spike), the amount of fungal DNA was expressed relative to the amount of plant DNA in the same sample (10).…”

A Metabarcoding Analysis of the Mycobiome of Wheat Ears Across a Topographically Heterogeneous Field

“…Previous studies have shown good potential in suppressing pathogens through the inoculation of antagonistic strains of fungi or bacteria (Schisler et al, 2002; Xue et al, 2014; Baffoni et al, 2015; Palazzini et al, 2016; El-Gremi et al, 2017). Fungal interactions seem to play a role also in causing differences in diseases symptoms and effects; e.g., mycotoxin accumulation has been shown to be influenced by the co-cultivation of different fungi in the laboratory (Korn et al, 2014; Siou et al, 2015). To further develop such concepts, it is important to understand which factors naturally influence the phyllosphere community.…”