2017 ASHS Annual Conference

Micro-grafting, an increasingly popular method, involves grafting an aseptic scion onto an in vitro-grown rootstock. Success of micro-grafting is largely depended on firm contact between rootstock and scion at the graft junction. Success rates of micro-grafting are generally low. In this study, we used a root-predominant gene promoter (SbUGT) to drive the expression of a tryptophan-2-mono oxygenase gene (iaaM) from Agrobacterium tumefaciens to increase auxin levels in rootstock. Tobacco was used as a model plant for this study. Our results showed that over-expression of the iaaM gene enhanced development of vascular system in stem tissues. We observed that expression of the SbUGT::iaaM gene in rootstock helped to form tighter junctions with scions, and therefore increased success rate of micro-grafting. Also, we have shown that the SbUGT::iaaM rootstock can be easily rooted. Furthermore, the expression of the iaaM gene in rootstock did not disrupt normal growth and developmental patterns of wild-type scions. In conclusion, the SbUGT::iaaM gene may be effective in improving success rates of micro-grafting for many crop plant species.