Fusarium crown rot of wheat has become more prevalent in China. To investigate the phylogenetic structure of Fusarium causing wheat crown rot in China, wheat basal stems with symptoms of the disease were collected from 2009 to 2013 in Jiangsu, Anhui, Henan, Hebei, and Shandong provinces. In total, 175 Fusarium isolates were collected and their mycotoxin chemotypes and distribution were identified. Among the 175 isolates, 123 were Fusarium asiaticum; 95 of these were the chemotype 3-acetyl-deoxynivalenol (3-AcDON) and 28 were nivalenol (NIV). Thirty-seven isolates belonged to F. graminearum, which were all 15-AcDON. Smaller numbers of isolates consisted of F. acuminatum, F. pseudograminearum, and F. avenaceum. The virulence of F. asiaticum and F. graminearum isolates on wheat crowns and heads was comparable. The virulence of isolates of the DON and NIV chemotype were statistically similar, but DON tended to be more aggressive. The DON concentrations in grains from wheat heads inoculated with isolates causing either Fusarium head blight or crown rot were similar. In the five provinces, F. asiaticum of the 3-AcDON chemotype was the predominant pathogen causing crown rot, followed by F. graminearum. Recent changes in causal Fusarium species, chemotypes, and distribution in China are discussed.

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 the FGSC in the major winter-wheat-producing areas of China, 530 isolates were collected from diseased wheat during the years 2008, 2009, and 2010, and typed using a polymerase chain reaction-based trichothecene genotype assay. Virulence of isolates with different chemotypes was also compared. Of the 530 isolates typed, 348 were F. asiaticum and 182 were F. graminearum. Subdividing the 530 isolates by the trichothecene predicted to be expressed, 482 were of the deoxynivalenol (DON) chemotype and 48 were nivalenol (NIV). Acetylated derivatives of DON included 3-acetyldeoxynivalenol (3-AcDON; 300 isolates), and 15-acetyldeoxynivalenol (15-AcDON; 182 isolates). Chemotypes of the F. asiaticum isolates were either 3-AcDON or NIV, with 3-AcDON being predominant. F. graminearum isolates were all of the 15-AcDON chemotype. F. asiaticum was the predominant phylogenetic species in the Yangtze River Basin and F. graminearum was dominant in the north of China. Two areas of co-occurrence of trichothecene chemotypes were found. The 3-AcDON and 15-AcDON isolates had similar levels of virulence. The DON isolates were significantly more virulent than those of the NIV. The 3-AcDON and 15-AcDON chemotypes were predominant in the Yangtze River Basin and areas north of the Yangtze River Basin, respectively, and it is suggested that geographic distribution is associated with differences in temperature as well as crop rotation systems.