Abstract
Fusarium head blight (FHB) caused by Fusarium graminearum (FG) is a destructive disease impacting barley worldwide. The disease reduces the grain yield and contaminates grains with mycotoxins, such as the trichothecene deoxynivalenol (DON). Although the infection mainly affects the grain yield, little is known about its impact on grain structural and biochemical properties. Yet, such information is instrumental to characterize the facets of resistance in the grains. After artificial inoculation of six barley cultivars with FG in a 2 years field test, different levels of symptoms on spikes, of colonisation of grains and of DON content were observed. The infections caused a reduction in grain weight and an average decrease of 10% of the β-glucan content in grains, indicating alterations of grain filling, composition and structure. According to our results, we postulate the presence of two distinct resistance mechanisms in the grain, tolerance to grain filling despite infection as well as the inhibition of mycotoxin accumulation. Differently to wheat, in barley, type IV resistance (tolerance of the grain to infection) is directly linked with type III resistance (resistance against kernel infection). The resistance against toxin accumulation (named type V resistance in wheat) appeared to be independent to all other resistance types. Generally, the resistance was significantly influenced by the environment and by genotype x environment interactions explaining the generally weak stability of resistance in barley. Interestingly, a significant and inverse relationship between DON contamination and β-glucan content in grains suggests that high β-glucan content in grains contributes to type V resistance.
Highlights
Fusarium head blight (FHB) of small grain cereals is caused by different species of the genus Fusarium
In the current study, the resistance of six barley varieties against infection with Fusarium graminearum (FG) was investigated under different field conditions
Besides the symptoms on the spikes, a particular focus was the symptoms of the grains, the accumulation of the mycotoxin deoxynivalol and variations of the β-glucan content
Summary
Fusarium head blight (FHB) of small grain cereals is caused by different species of the genus Fusarium. Infections lead to accumulation of different mycotoxins in the grains and grain deformation, resulting in so called tombstones and reduced process quality (Häller Gärtner et al 2008; Martin et al 2017). The pathogen interferes with grain development, leading to reduction of filling and changes in composition (McMullen et al 1997; Bai and Shaner 2004; Oliveira et al 2013). F. graminearum produces the mycotoxin deoxynivalenol (DON) that accumulates in grains. The contamination of barley grains for human consumption may cause health problems, since mycotoxins remain in the final product (Kushiro 2008; Malachova et al 2012). Maximum limits in unprocessed cereals for human consumption are set to 1250 μg.kg-1 of DON set (European Commission Regulation (EC) No 1881/2006)
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