Population and Pathogenicity of Fusarium Species Associated with Fusarium Head Blight in a Wheat–Maize Cropping System in Sichuan Province, China

Fusarium head blight (FHB) is a serious disease worldwide that leads to substantial economic losses. Wheat‒maize cropping is the dominant system in Sichuan Province, China. However, FHB has become increasingly severe in this system, such that Fusarium rot disease is also becoming a severe threat to maize. To understand the composition and pathogenicity of the Fusarium species associated with FHB, samples of typical symptomatic wheat spikes were collected from wheat‒maize cropping fields in 16 administrative districts of Sichuan Province, and Fusarium perithecia were obtained from both wheat straw and maize stubble. On the basis of morphological and molecular identification, 175 isolates from symptomatic wheat spikes were identified as five Fusarium species: F. asiaticum , F. avenaceum , F. graminearum , F. meridionale and F. proliferatum . Among them, F. asiaticum and F. graminearum were the dominant pathogenic species, with isolation frequencies of 75.43% and 20.57%, respectively. Additionally, 136 single-ascospore isolates from wheat straw or maize stubble were identified as F. asiaticum , F. equiseti , F. graminearum , F. meridionale , F. proliferatum and F. temperatum . Pathogenicity assays revealed that the Fusarium strains from all sources were capable of successfully infecting both wheat and maize. F. graminearum was highly pathogenic to both crops, whereas F. asiaticum appeared to be more strongly pathogenic to wheat than maize. This work will be helpful for understanding the cyclic infection caused by Fusarium species in wheat‒maize cropping systems and provide valuable data for the effective control of Fusarium rot disease in both wheat and maize.