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Rab GTPases are key regulators of membrane and intracellular vesicle transports. However, the biological functions of FgRab1 are still unclear in the devastating wheat pathogen <i>Fusarium graminearum</i>. In this study, we generated constitutively active (CA) and dominant-negative (DN) forms of <i>FgRAB1</i> from the wild-type PH-1 background for functional analyses. Phenotypic analyses of these mutants showed that FgRab1 is important for vegetative growth, cell wall integrity and hyphal branching. Compared to the PH-1 strain, the number of spores produced by the <i>Fgrab1DN</i> strain was significantly reduced, with obviously abnormal conidial morphology. The number of septa in the conidia of the <i>Fgrab1DN</i> mutant was fewer than that observed in the PH-1 conidia. <i>Fgrab1DN</i> was dramatically reduced in its ability to cause Fusarium head blight symptoms on wheat heads. GFP-FgRab1 was observed to partly localize to the Golgi apparatus, endoplasmic reticulum and Spitzenkörper. Furthermore, we found that FgRab1 inactivation blocks not only the transport of the v-SNARE protein FgSnc1 from the Golgi to the plasma membrane but also the fusion of endocytic vesicles with their target membranes and general autophagy. In summary, our results indicate that FgRab1 plays vital roles in vegetative growth, conidiogenesis, pathogenicity, autophagy, vesicle fusion and trafficking in <i>F. graminearum</i>.