Distant-Graft Mutagenesis Technology in Soybean

As we know, sexual hybridization is the primary means of creating genetic variation in the conventional breeding methods, all kinds of new varieties are mainly developed through this means. However, sexual hybridization can only be carried out between species. The distant-graft mutagenesis technology developed rapidly in recent years just made it possible to bypass the natural obstacles of incompatibility or hybrid embryos sterile of sexual hybridization between distantly-related species and integrate the different sources of rootstock and scion organically, and allow the scion to grow, develop and fruit normally. As the sequence of it, a wide range of mutations can be induced under the adverse conditions of distant grafting and all kinds of the unique new plant types can also be created. Qian (1993), the well-known Chinese scientist, had ever pointed out: We should develop a technical science---The graft-transformed science of plants, whose role must be no less than genetic engineering. Compared to other mutagenesis technologies, the distant-graft mutagenesis technology can integrate the advantages of rootstock and scion and further expand the genetic base of target crop. Besides, it characters as: (1) the mutated traits stabilize quickly, which may shorten the breeding period; (2) the operation technique is simple and easy to grasp; (3) the required test conditions and input are comparatively lower than other mutagenesis technologies. Now, the distant-graft mutagenesis technology has been applied in resources innovation and genetic improvement of crops such as wheat, millet, cotton, peanut, mungbean, corn, and soybean etc, and a lot of new plant materials have been created, from which many new varieties with the strong resistance to stress and diseases or the improved yield and quality have been bred out. For example, sweet potato/mungbean, castor/cotton, yam/soybean, sweet potato/soybean and castor/soybean etc are all bred out from the progeny of distant graft. Here we introduce the history, definition, types of distant graft, the procedure and key influencing factors for soybean distant-graft mutagenesis, the types and the possible mechanism of soybean distant-graft mutagenesis and prospect of soybean distant-graft mutagenesis, hoping that this technology can be popularized to widely use in resources