Interfamilier Grafting Using a Plant Genus Nicotiana

Plant grafting has been an important technique in horticulture as well as in agriculture to perpetuate clones, to obtain the benefits of certain rootstocks such as disease resistance and tolerance of unfavorable soil conditions and to control fruit production. However, like as immunological resistance found in animals, plant grafting also has a limitation in combinations to graft. In general, it has been thought that grafting can be done successfully between the same species, genus, and family, but not between different families because of graft incompatibility. Recently, we found that a Solanaceae species, Nicotiana, can be grafted onto a Brassicaceae, Arabidopsis, where a population of mRNA was transported from Arabidopsis stocks to Nicotiana scions (Notaguchi et al., 2015). We further showed that Nicotiana has a capability to reduce or overcome the graft incompatibility. Nicotiana was successfully grafted with a wide range of plants, including magnoliids, monocots and dicots. In our anatomical analyses, vasculature reconstruction at the graft junction, which is normally observed in grafting of compatible combinations, was not observed. But, alternatively, parenchyma tissues were proliferated at their junction where xylem and phloem tissues were newly developed in unorganized manners, resulting in incidental connection for xylem, but seemingly not for phloem. In these grafts, both apoplasmic and symplasmic transports were achieved. Also the transports of proteins and mRNAs were detected. TEM analysis evidenced the de novo secondary plasmodesmata formation at the graft boundaries. Thus, we consider that Nicotiana interfamilier grafting, which belongs to incompatible combinations, is functional and practical.