Studies On Grafting And Variation In The Graft Union

Grafting has been widely applied to agriculture, forestry and horticulture. Graft can be used as an important means to science research. Grafting-induced genetic variation in the resultant plants has been reported. The mechanism of these variations was proposed to be due to gene transformation from the rootstock to the scion. But it is not clear whether cell fusion or genetic variations occur in the graft union. Till now, reports related to interaction between cells at the grafting interface have not been seen and such supposition has not been confirmed yet because of being lack of credible genetic evidence.In this study, by the methods of biochemistry, histology, cytology and molecularbiology , a series of experiments were carried out in an attempt to clarify if geneticvariation is involved in the tissues of the graft union.1 A successful grafting technique for tomato and eggplant was developed and factors that affected the graft success and scion growth including combination of grafting parents, age of seedling, rootstock cotyledon and external hormonal solutions were investigated. Higher grafting success rate and larger scion size were observed when 7d-old tomato seedlings were used as rootstock by the horizontal grafting method. Rootstock cotyledon had a positive effect on success rate, while its sprouting axillary shoots had a negative effect on scion growth. Suitable external hormone may also significantly promote grafting survival rate. There was a lower survival rate and a slower scion growth in the combination of tomato/cucumber or eggplant/cucumber than in the combination of eggplant/tomato. In field grafting, the wedge graft method was more beneficial to survival rate and scion growth than the hole grafting. The survival rate was highest (100.00%) and scion length was longest (15.7cm) in S36/ tomato combination. In the combinations of eggplant/tomato and tomato/eggplant, survival rate and scion growth vigor were obviously different.2 Systemic histology and cytology in compatible combination (eggplant/tomato) and imcompatible combination (eggplant/ cucumber) were observed with light microscopy and electron microscopy. The results showed that isolation layer, calluses at the interface, new nucleus and chloroplast were gradually formed in all of the combinations in early period after grafting. In latter period, in compatible combination isolation layer disappeared...