To investigate the function of the small GTPase FgSpgl in fungal pathogen Fusarium gra-minearum,gene deletion and complementation of the wild-type strain PH-1 were performed to obtain the null mutant △FgSpg1 and the complemented strain △FgSpg1-C,respectively.The growth and devel-opment,stress response,virulence,deoxynivalenol(DON)production,and relative expression levels of TRI genes were assayed in the wild-type strain PH-1,the gene disruption mutant △FgSpg1,and the complemented strain △FgSpgl-C.By comparing the differences among these strains,the role of Fg-Spg1 was elucidated.The results showed that the colony diameter of the gene disruption mutant △Fg-Spg1 was significantly reduced,with decreased pigmentation and thinner hyphae compared with the wild-type strain PH-1 and the complemented strain △FgSpg1-C.The proportion of conidia with four-seven septa increased significantly.Sensitivity to NaCl and KC1 decreased,while sensitivity to Congo red,tebuconazole,and pydiflumetofen increased.Virulence on wheat heads and coleoptiles was signifi-cantly reduced,DON production markedly decreased,and the expression levels of TRI genes involved in DON biosynthesis were significantly downregulated.These findings underscore the pivotal role of the small GTPase FgSpgl in vegetative growth,septum formation,response to external stimuli,viru-lence and DON biosynthesis in F.graminearum.