Abstract: This paper described the infection process of vesicular arbuscular mycorrhizal fungus Gigaspora margarita in transformed Ri T-DNA carrot roots under axenic condition Agrobacterium rhizogenes was used to introduce Ri T-DNA into the root cells of carrot and then the adventitious roots of carrot were used as host Four routine methods of surface sterilization were compared and one was selected for obtaining maximum amount of pure mycorrhizal fungal spores After two months of dual culture, the infection of transformed Ri T-DNA carrot roots by VA mycorrhizal fungus was observed and mature spores were obtained Under suitable conditions, the harvested spores were capable of germinating and subsequently infecting the host roots immediately