Geographic Distribution Of Trichothecene Chemotypes And Pathogenicity, Biocontrol Of The Fusarium Graminearum Species Complex In Major Winter Wheat Production Areas Of China

Fusarium head blight, caused by members of the Fusarium graminearum species complex (FGSC), is among the most destructive and economically important diseases of small grain crops, including wheat. To determine the phylogenetic species and mycotoxin (trichothecene) chemotypes of FGSC in the major winter wheat producing areas of China, 302 isolates were gathered from diseased wheat in six different areas during the years 2009 and 2010, and examined for their phylogenetic species. Of the total 302 isolates,148 were F. asiaticum and 154 were F. graminearum. It was indicated that F. asiaticum and F. graminearum were the two main pathogens of FHB in he major winter wheat production areas of China. We also found F. asiaticum was the predominant phylogenetic species in the Yangtze River, while F. graminearum was dominant in the Huai River Basin and north of China. Subdividing the 302 isolates by the trichothecene metabolites they expressed using PCR,281 were of the Deoxynivalenol (DON) chemotype (I) and 21 were Nivalenol (NIV) chemotype (II). Of the 281 DON isolates,127 were 3-AcDON and 154 were 15-AcDON. The F. graminearum isolates were all of the 15-AcDON chemotype. The chemotypes of the F. asiaticum isolates were either 3-AcDON or NIV, with 3-AcDON being predominant with the percent of 86% followed by NIV chemotype, and no 15-AcDON chemotype isolates were found.The virulence of the identified chemotypes was also compared at anthesis. The results suggest that isolates were different in virulence. The DON isolates were significantly more virulent than those of the NIV, while isolates of F. graminearum and F. asiaticum showed similar levels of aggressiveness toward wheat. The 3-AcDON and 15-AcDON isolates had similar levels of virulence.HPLC method was used to determine deoxynivalenol (DON) concentration in mycotoxin samples of scab-infected wheat grains. The statistical analysis showed that there was huge difference between different isolates. The DON chemotype isolates produced higher DON than NIV chemotype isolates. The 3-AcDON chemotype isolates produced more DON than 15-AcDON chemotype isolates. While DON production of F. asiaticum isolates is equal to F. graminearum. Correlation analysis indicated that there was a significant correlation between the virulence and DON accumulation.According to the identification of the 105 root rot fungus collected from wheat in Jiangsu, Anhui and so on, we found that most of the Fusarium species causing wheat root rot belonged to Fusarium graminearum species complex (FGSC), consisted of three chemotypes:3-AcDON,15-AcDON and NIV. F.graminearum and F.asiaticum were still two main populations. The target of this research was screening the biocontrol treatments against the wheat root rot caused by F. graminearum. The experiments demonstrated that 23 of 97 strains had better flat antagonist activity in laboratory and greenhouse biological control and growth-promoting effects in different habitats. This is the first report about the composition of the pathogen of wheat root rot.