Objective  Conserve and special functions of Rab4 protein of Colletotrichum graminicola (Cg) were studied.

  Method  Based upon the principle of homologous recombination, CgRAB4 was knocked out from the DNA of Cg to obtain mutants with the target gene deleted. A hygromycin-resistance screening and PCR verification were performed on the mutants prior to a functional analysis on Cg development and pathogenesis.

  Result   Three CgRAB4-deleted and one ectopic mutants were secured by the designed process. The phenotypic analysis revealed that the deletion promoted the hypha growth but did not affect the mycelial morphology, nor regulate the response to external stress or significant change in the spore production and morphology, appressorium germination or the pathogenicity on the mutants.

  Conclusion  CgRAB4 was successfully removed from Cg to unveil the involvement of the gene in regulating the mycelial growth. Understanding on the roles of Rab proteins played in the development and pathogenesis of Cg provided a guiding direction for further research on the prevention and treatment of corn anthrax.