Grafting-mediated meristem selection influences rooting success of Quercus rubra

Grafting and rooting trials were established to follow shoot development and rooting ability of individual buds (axillary and apical meristems) of mature Quercus rubra L. Buds from 64 matched pairs of twigs were either individually grafted (budded) onto seedling rootstocks or left to develop in situ. Results showed that shoots from grafts originated from a different population (of proximal twig origins) of buds than shoots developed in situ (of more distal origins). Overall, cuttings from grafts had significantly greater rooting than cuttings developed in situ. However, for cuttings from matched pairs of buds, which produced shoots both when grafted and when left to develop in situ, rooting was independent of grafting. For in situ shoots, rooting success was uniformly low and unrelated to position of origin on the twig. However, for graft shoots, rooting was significantly related to position of origin on the twig. Shoots with the greatest rooting success originated from grafted axillary buds that normally remain dormant in situ. Although increased rooting success mediated by grafting is often attributed to rejuvenation, these results suggest that grafting may serve to select for meristems with potential for higher rooting success by stimulating their development into shoots and indirectly (through reduced shoot development via unsuccessful graft unions) select against meristems that would normally exhibit low rooting success.