Abstract
In recent years, Fusarium head blight (FHB) outbreaks have occurred much more frequently in China. The reduction of burning of the preceding crop residues is suggested to contribute to more severe epidemics as it may increase the initial inoculum. In this study, a large number of Fusarium isolates was collected from blighted wheat spikes as well as from rice stubble with perithecia originating from nine sampling sites in five provinces in Southern China. Fusarium asiaticum dominated both wheat and rice populations, although rice populations showed a higher species diversity. Chemotype analysis showed that rice is the preferred niche for NIV mycotoxin producers that were shown to be less virulent on wheat. In contrast, 3ADON producers are more prevalent on wheat and in wheat producing areas. The 3ADON producers were shown to be more virulent on wheat, revealing the selection pressure of wheat on 3ADON producers. For the first time, members of the Incarnatum-clade of Fusarium Incarnatum-Equiseti Species Complex (FIESC) were found to reproduce sexually on rice stubble. The pathogenicity of FIESC isolates on wheat proved very low and this may cause the apparent absence of this species in the main wheat producing provinces. This is the first report of the Fusarium population structure including rice stubble as well as a direct comparison with the population on wheat heads in the same fields. Our results confirm that the perithecia on rice stubble are the primary inoculum of FHB on wheat and that cropping systems affect the local Fusarium population.
Highlights
Fusarium head blight (FHB) is a devastating disease of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and other small grains worldwide [1,2]
F. asiaticum dominated in regions where rice is grown in rotation with wheat, as can be found in China and Korea, whereas F. graminearum was more common in wheat-maize rotation systems [2,12]
A similar situation was observed in the USA [13], while in Brazil, F. graminearum was found to be dominant in wheat [14], F. asiaticum in rice [15], and F. meridionale was determined as the predominant Fusarium graminearum species complex (FGSC) species on maize ears and stalks [16]
Summary
Fusarium head blight (FHB) is a devastating disease of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and other small grains worldwide [1,2]. The presence of crop debris is essential for the overwintering of Fusarium In agreement with this hypothesis, several studies have found a strong association between the distribution of FGSC species and cropping systems (host preference). A similar situation was observed in the USA [13], while in Brazil, F. graminearum was found to be dominant in wheat [14], F. asiaticum in rice [15], and F. meridionale was determined as the predominant FGSC species on maize ears and stalks [16]. Most studies in different agroecosystems focus on the pathogenic stage of Fusarium and there are few reports on the saprophytic stage on crops residues, which is crucial to the lifecycle and epidemiology of the pathogen
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