Infection of Embryonic Callus with Agrobacterium Enables High-Speed Transformation of Maize

Several approaches have recently been adopted to improve Agrobacterium-mediated transformation of maize; however, about eight months of in vitro culture are still required to isolate transgenic plants. Furthermore, genetic transformation of maize depends on immature embryos, which greatly increases costs. Here, we report a method that ensures the competency of an embryogenic callus secondary culture under laboratory conditions for Agrobacterium-mediated transformation. Moreover, pretreatment of the cell wall with a mixed lytic enzyme solution prior to Agrobacterium infection, significantly improved transformation efficiency and stability. Average stable transformation efficiency was approximately 30.39%, with peaks of 94.46%. Expression and phenotypic analysis of the Rsc reporter gene were tested in the T(0) generation of transgenic plants. Using this system, we successfully regenerated transgenic maize plantlets within three months of the emergence of the embryogenic callus. Additionally, we reduced somaclonal variation accompanying prolonged culture of maize cells in the dedifferentiated state, thus facilitating the molecular breeding of maize.