Rooting of cuttings of selected Diospyros virginiana clonal rootstocks and bud growth in rooted cuttings

Diospyros virginiana is a common rootstock in several countries growing commercial plantations of persimmon. However, trees grafted on this rootstock, which is exclusively propagated from seeds, are not uniform in both vegetative and reproductive growth. The aim of the present research was to study the effect of various factors on the rooting of D. virginiana cuttings, in order to develop an efficient rooting procedure for selected clonal rootstocks. The clone genotype had a significant effect on the rooting rate, which ranged from zero to close to 100% in the various clones examined. Cuttings collected from different positions on the mother plant shoots did not differ significantly in their rooting rate, suggesting that juvenility does not play an important role in rooting of D. virginiana cuttings. Collecting cuttings at the early stage of the growing season yielded the highest rooting rate, which gradually decreased as the growing season progressed. Using three to 4-node cuttings and treatment with 6000 mg L−1 indole-3-butyric acid (IBA) by quick-dip in solution led to a relatively high rooting rate. Anatomical analysis demonstrated that adventitious root primordia were initiated at the phloem side of the fascicular cambium, with no relationship to the callus tissue that was formed on the cut surface of the cutting base. Out of the examined clones, rooted cuttings of only one clone exhibited a high rate of bud growth, a phenomenon which was also found to be genotype-dependent. Increasing the applied IBA concentration to cuttings of a clone with a high bud growth rate inhibited bud growth, whereas increasing the length of cuttings of clones with a low bud growth rate promoted bud growth. These observations suggest that the IBA applied to promote rooting is transported acropetally and inhibits bud growth. No cutting mortality was observed during rooting and above 90% of the rotted cuttings which exhibited bud growth survived after transplanting into the growing pots.