Diversity and pathogenicity of Fusarium species associated with Fusarium head blight in wheat and maize cropping systems in Sichuan Province

Fusarium head blight (FHB) is a severe 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, and 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. Based on 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 could successfully infect wheat and maize. F. graminearum exhibited a high degree of pathogenicity towards both crops under investigation, while F. asiaticum demonstrated significantly greater pathogenicity towards wheat than maize. This work will help understand the cyclic infection caused by Fusarium species in wheat‒maize cropping systems and provide valuable data for the effectively controlling Fusarium rot disease in both wheat and maize.