Priming enhances tolerance of Fusarium graminearum to triazole

Organisms exposed to environmental stimuli can develop "memory" of those experiences, a phenomenon known as priming, which allows them to better adapt to subsequent stimuli. Growing evidence has shown that fungi can "remember" past encounters, but the priming effect remains poorly understood in phytopathogenic fungi. In this study, we examined the priming effect in Fusarium graminearum, the causative agent of Fusarium head blight (FHB), by culturing its conidia in the presence of a median effective concentration (EC₅₀) of triazole fungicide. We observed that primed conidia exhibited significantly higher germination rates and longer hyphal length than unprimed conidia when exposed to double EC₅₀ concentration of triazole. The triazole priming effect in F. graminearum was retained in conidia for an extended period but was not stably heritable. Further investigations revealed that this priming effect was linked to increased over-expression of the fungicide target genes (FgCYP51s) above the level seen in non-primed F. graminearum. This study reveals that F. graminearum develops adaptive resistance following treatment with triazole fungicides, and elucidates the mechanism behind priming, which is regulated by the transcription factor FgSR. This regulation leads to the upregulation of FgCYP51 expression, thereby mediating the observed adaptive resistance. This provides a theoretical basis for understanding the development of resistance in pathogens and offers relevant guidance for the use of triazole fungicides in the control of FHB.