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.
Carbendazim resistance was detected using 4701 Fusarium graminearum species complex (FGSC) isolates collected from major wheat producing regions in China from 2018 to 2020. A total of 348 carbendazim-resistant isolates were identified. The majority of carbendazim-resistant isolates were detected in Jiangsu and Anhui Provinces. 227 and 88 isolates were obtained from each of Jiangsu and Anhui Provinces with the high resistance frequency of 41.12% and 20.56%. The predominant resistant isolates harboring point mutation F167Y (79.31%), followed by E198Q (16.38%) and F200Y (4.31%). Compared with F. graminearum, F. asiaticum isolates were more likely to produce carbendazim resistance. In this study, we firstly detected carbendazim-resistant isolates in Hebei, Shaanxi, Sichuan and Hunan Province. In Jiangsu, Anhui and Zhejiang, the frequency of carbendazim-resistant isolates maintained a high level resulting in stable carbendazim-resistant populations. We also found the dynamic of carbendazim-resistant frequency in most provinces showed similar trend of the epidemic of FHB. Our results facilitate the understanding of the current situation of carbendazim resistance of FHB pathogens, and will be helpful for fungicides selection in different wheat producing areas in China.
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