Long-term improvement in the rooting of plum cuttings following apparent rejuvenation

Abstract

SummaryNine years after plants of the dwarfing plum rootstock Prunus insititia cv. Pixy were taken from culture in vitro and grown as stockplant hedges in the field, cuttings taken from these hedges rooted in greater percentages and produced more roots than cuttings taken from hedges of conventional stockplants. Pruning the stockplants severely in winter enhanced rooting of both the conventional and in vitro-derived cuttings compared with lighter pruning. The overall benefit due to severe pruning was similar to that from the in vitro-derived source, and the highest rooting level and most roots were produced by cuttings from severely pruned plants from the in vitro source. The nature of the enhanced rooting due to the micropropagation source and severe pruning was that roots developed earlier than in cuttings from conventional and lightly pruned stockplants, with the likely benefit of reducing cutting exposure to sub-optimal environmental conditions. The increased rooting potential was more consistent from year to year in winter cuttings made from the proximal portion of shoots which had completed their annual growth than in summer cuttings made from the distal portion of actively growing shoots in early summer. Shoot apices taken from field-grown stockplants in the eighth summer after leaving cúlture in vitro initially grew more vigorously than those from the conventional source when taken back into culture in vitro.