**5.2.1 Combination of rootstock and soybean scion**

The grafting combinations between different rootstock and soybean may induce different types of mutant. In our study, it is found that the grafting of different combinations will produce different types of mutations. For example, grafting between soybean and castor often induces seed coat color and oil content mutants in their offspring.

Distant-Graft Mutagenesis Technology in Soybean 279

to the genetic mutation, or the stress conditions caused by distant grafting stimulate the stress-related transposable element transposition, leading to the genome rearrangement or

It is of practically important significance for putting distant-graft technology into innovating excellent soybean materials, broadening genetic base of soybean and promoting breeding of new soybean with good quality, high yield and resistance to stress. However, there is yet no comprehensive system of distant grafting mutagenesis up to now. In particular, the affinity mechanism and the mutation mechanism of distant grafting are not clear, which leads many scholars to disbelief in the distant-graft mutagenesis technology and soybean mutants induced by distant-grafting. Thus, the most important task on distant graft now is to check on genotypes of the known existing soybean lines derived from distant-graft through molecular approach, validating the reliability of applying asexual hybridization (grafting) to soybean breeding. On the basis of it, the affinity mechanism and the mutation mechanism of distant grafting will be exploring, highlighting as soon as possible the true nature of distantgrafting mutagenesis. At the same time, the grafting technology is integrated with the conventional identification and screening approaches of the mutated traits to create soybean germplasm resources with good nitrogen fixation ability, resistance to drought, salt, diseases and aging, and to identify the genetic controlling loci of the related traits. Besides, Grafting technique can be applied in revealing the physiological process mechanisms involved by the signal transduction materials and becomes irreplaceable means to deep understand the interaction of different organs of plant. We believe in the coming future, the distant-grafting mutagenesis technology will be paid more attention by scholars, and play an increasing role on the soybean resources innovation, soybean breeding and gene mining

The authors would like to thank all the researchers in the field of distant-graft mutagenesis for offering us the technological instructions on the methods of research. This work has been funded by the project for scientific and technological achievements transformation of Chinese science and technology department (2010GB24910701), the project for special foundation of technological innovation of Harbin (2008RFQYN127) and the project for forefront innovation of Northeast Institute of Geography and Agroecology, Chinese

Jia Si-Xie. Essential skill to benefit the Qi-people [M]. Annotated by Liao Qi-Yu. Beijing:

Jia zhen and Han Tian-Fu. Application of grafting technology in soybean physiology and

Li Xue-Hua. Preliminary construction of soybean mutant library and identification of mutation types [XL]. Master thesis, Nanjing Agricultural University, 2003. Stegemann S and Bock R. Exchange of genetic material between cells in plant tissue grafts

gene mutation.

**8. Prospects** 

and so forth.

**10. References** 

**9. Acknowledgements** 

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