Monitoring of <i>Fusarium</i> Species and Trichothecene Genotypes Associated with <i>Fusarium</i> Head Blight on Wheat in Hebei Province, China

To clarify the changes in field populations of Fusarium head blight (FHB) pathogens over a decade, <i>Fusarium</i> species and trichothecene genotypes associated with FHB on wheat were monitored in Hebei province during the periods 2005&#8722;2006 and 2013&#8722;2016. <i>Fusarium</i> species determination was carried out by morphological identification, species-specific amplification and partial translation elongation factor (TEF-1&#945;) gene sequencing. Trichothecene genotype prediction was carried out by primers 3CON/3NA/3D15A/3D3 or Tri13F/Tri13R, Tri303F/Tri303R and Tri315F/Tri315R. A total of 778 purified <i>Fusarium</i> isolates were recovered from 42 sampling sites in 17 counties during the period 2005&#8722;2006 and 1002 <i>Fusarium</i> isolates were recovered from 122 sampling sites in 65 counties during the period 2013&#8722;2016. <i>F. graminearum</i> was the predominant pathogen recovered during the periods 2005&#8722;2006 and 2013&#8722;2016. However, the pathogen composition differed slightly between the two periods. In 2005&#8722;2006, 752 out of 778 (96.7%) of the isolates belonged to <i>F. graminearum</i>. Two were identified as <i>F. culmorum</i>. Five other <i>Fusarium</i> species were also recovered, <i>F. equiseti</i>, <i>F. verticillioides</i>, <i>F. proliferatum</i>, <i>F. subglutinans</i> and <i>F. chlamydosporum</i>, with lower recoveries of 0.4%, 0.8%, 0.8%, 0.1% and 1.0%, respectively. Trichothecene genotype prediction showed that all the 752 <i>F. graminearum</i> isolates were of the 15-ADON genotype. Five <i>Fusarium</i> species were recovered from samples collected over the period 2013&#8722;2016. <i>F. graminearum</i> was again the predominant pathogen with an isolation frequency of 97.6%. <i>F. pseudograminearum</i>, <i>F. asiaticum</i>, <i>F. culmorum</i> and <i>F. negundis</i> were also isolated at a recovery of 1.4%, 0.7%, 0.2% and 0.1%, respectively. For the 2013&#8722;2016 isolates, 971 of the 978 <i>F. graminearum</i> strains were 15-ADON whereas seven isolates were of the 3-ADON type. All seven <i>F. asiaticum</i> isolates were of the NIV type and fourteen <i>F. pseudograminearum</i> isolates were classified as 3-ADON. <i>F. pseudograminearum</i> was first isolated from FHB in Hebei in 2013. Although the recovery of <i>F. pseudograminearum</i> is still low, it represents a small shift in the pathogen composition and trichothecene genotypes associated with FHB in Hebei province. As Fusarium crown rot of wheat caused by <i>F. pseudograminearum</i> is an increasing problem in Hebei province, it is appropriate to monitor the role of <i>F. pseudograminearum</i> in FHB in the future.