Grafts have been performed for more than two thousand years, and among agricultural technology
it is one of the oldest and indispensable technique to be used to date. With enormous experience
accumulating, it is known that there are restrictions on combinations of grafts, and this limit
has never been resolved. In general, it is possible to graft to closely related plants, but grafts
are less likely to be established as far as the other is located, and it is considered impossible
to graft between the plant of taxonomically different families. However, in our laboratory recently
we discovered that plants belong to Nicotiana genus, relative of tobacco, have a rare grafting
ability and can graft with a wide range of plant species on land. When grafting the plant of Nicotiana
genus between two distantly related plants which can not be grafted originally, grafts of the three
plants can be established at a constant rate. This means the possibility that the graft combination
can be expanded has come out （iPAG，PAT.No.6222720）.
However, in order to develop the iPAG method to practical level, further technical improvement is necessary.
In our previous studies, adhesion may not be sufficient due to the grafted partner distantly related plants.
In addition, the development of the passage organization to carry water and nutrition is not sufficiently good
with grafted by the iPAG method, and the growth of grafted seedlings is not sufficiently strong. Therefore,
in order to truly practical use of the iPAG method, we are promoting research considering the importance of
establishing (1) technology to improve adhesion and (2) technology to promote the development of passage organization.