Effects of serial grafting, ontogeny, and genotype on rooting ofQuercus rubracuttings

Abstract

Bud grafts, up to three series over 3 years, were made on seedling and tree rootstocks using scions from juvenile and mature northern red oak (Quercus rubra L.). Serial grafts on juvenile rootstock used buds collected from shoots developed from grafted scions of prior years. Rooting trials were performed in years 2 and 3 with shoot cuttings developed in situ on seedlings and trees and developed from successful grafts. Without grafting, cuttings from seedlings rooted more frequently and had more roots than cuttings from trees. Significant variation within maturation groups due to genotype and ontogeny obscured absolute between-group differences. Grafting scions of juvenile origins onto seedling rootstock had little effect on percent rooting and the number of roots for cuttings. Grafting onto seedling rootstock tended to increase rooting and the number of roots for cuttings from mature origins, but the effect was not progressive with increasing grafting series. Grafting onto mature rootstock did not affect rooting of cuttings from juvenile or mature origins collected in the first growing season after grafting, but cuttings from juvenile scions collected in the second growing season exhibited reduced percent rooting compared with cuttings from seedling controls. Results suggest that northern red oak buds are predetermined in their developmental fate relative to rooting parameters and are only minimally influenced by grafting. The true effect of grafting on the subsequent rooting of cuttings may be mediated through processes other than rejuvenation.