First Report of Fusarium pseudograminearum Causing Fusarium Head Blight of Wheat in Hebei Province, China

In Hebei Province in the North China Region of China, winter wheat-summer maize rotation is the main cropping system. Wheat production in Hebei is important and it ranks third in China, with a growing area of 2.4 million ha and annual yield of about 12 to 13 million tons. Fusarium head blight (FHB) has been a problem since the 1990s. In the 2013-2014 season, we conducted a survey to clarify the etiology of FHB in 49 fields in 29 counties of Hebei. Premature bleaching heads with browning rachis were collected and shriveled kernels were disinfested with 70% ethanol and plated onto Peptone PCNB Agar. Fusarium-like colonies were subcultured to carnation leaf agar (CLA) and incubated under BLB light. Pure cultures were established and identified by morphological and molecular characteristics. Results showed that F. graminearum was the predominant pathogen in Hebei. However, five isolates from Luancheng (37°53′58.43″ N; 114°37′14.65″ E), Zhao (37°51′12.84″ N; 114°48′52.87″ E), and Fengrun (39°46′56.65″ N;118°02′47.71″ E) counties were identified as F. pseudograminearum. On PDA, colonies had radial growth rates of 6.5 to 7.8 mm/day at 25°C. Typical macroconidia of F. pseudograminearum were formed in sporodochia on CLA, but no perithecia were found. Macroconidia were relatively slender, falcate to almost straight, 5- to 7-septate, and 27.0 to 36.9 × 2.0 to 3.5 μm. The identification of F. pseudograminearum was confirmed by species-specific primers (Fp1-1: CGGGGTAGTTTCACATTTCYG and Fp1-2: GAGAATGTGATGASGACAATA) (Demeke et al. 2005). Expected PCR fragments of 523 bp were produced in the five isolates. For further confirmation, PCR products of the translation elongation factor-1α gene were sequenced (GenBank Accession Nos. KM434217 to KM434221). BLASTn analysis with the Fusarium-ID database revealed 99.52% to 100% sequence identity to F. pseudograminearum. A pathogenicity test was conducted by injecting 1-ml conidial suspensions (105 macroconidia/ml) of each isolate into single-florets of 20 spikelets of Shimai 18. Control treatments were inoculated with sterile water. Pink hyphal growth and salmon sporodochia developed on the inoculated spikelets which contained shriveled, chalky, white kernels. No symptoms were observed on controls. Koch’s postulates were fulfilled by reisolation of the same fungus from the infected kernels. This is the first finding of F. pseudograminearum causing FHB in Hebei. It is not surprising, as the authors have found this fungus to be a common cause of crown rot in Hebei. The accumulating inoculum in the soil probably provides the initial infection source to be splashed onto the head. F. pseudograminearum was first reported to cause FHB in New South Wales, Australia (Burgess et al. 1987). F. pseudograminearum has been reported previously from wheat crown rot and heads in Henan Province, China (Li et al. 2012; Xu et al. 2014). However, there are significant differences in climate between Hebei and Henan as they lie in different latitudes. Henan is wetter in spring than Hebei, a factor that favors a greater incidence of FHB. Furthermore, the dominant varieties grown in Hebei differ from those in Henan. Therefore, this report is significant to China’s wheat program, and the occurrence of F. pseudograminearm as a cause of FHB needs to be monitored. © The American Phytopathological Society.