Graft can induce inheritable variations in the progenies of the scion plants. Seedling of mungbean ( Vigna radiata (L.) Wilczek) was grafted onto the stem of sweet potato ( Ipomoea batatas (L.) Lam.). The growth of the scion was maintained until the scion produced selfed seeds. We sowed the seeds for several generations under normal conditions. Distinct genetic variations appeared in the progenies. Similar variations did not appear in the generations of the scion sowed normally without graft. The variations seemed to be induced by the graft and they inherited steadily. For understanding the possible mechanism of the phenomenon (graft_induced inheritable variation), we analyzed the cytoplasmic and genomic DNA of the variations. The results showed that there was no restriction fragment length polymorphism (RFLP) in the cytoplasmic DNA between the original scion and the variation. However, significant difference between the scion and variation was recognized by random amplified polymorphic DNA (RAPD) analysis. In addition, there was no evidence that indicated the gene transformation from stock to scion. Our results suggest that the non_specific grafting has a pragmatic potential for plant breeding and crop improvement and, the genetic variation seems not to be caused simply by DNA transformation but most likely the stress induced mutation.
