Effects of the vegetative propagation method on juvenility in Robinia pseudoacacia L.

Vegetative propagation is an important method of reproduction and rejuvenation in forestry. The growth and development of asexually propagated trees are influenced by the age and position of the propagule on the plant, effects referred to as cyclophysis and topophysis, respectively. Due to the long lifespans and large body sizes of woody trees, the selection of propagules is critically important. Here, we used three vegetative propagation methods (shoot cutting, root sprouting, and root cutting) to study the effect of different regeneration methods on juvenility of the resulting black locust plants, with seed-derived seedlings used as a control. Most characteristics of plantlets generated by root-sprouting were similar to those of seed-derived seedlings, including leaf traits and leaf anatomical structure. However, there were significant differences between the plantlets derived from shoot-cuttings and seedlings from seeds. Furthermore, the data showed that some of these age-related small RNAs and genes differed in expression among propagation methods and between plantlets/seedlings and mature trees. These age-related small RNAs, genes, and transcription factors may be used as molecular markers of juvenility and phase transitions in black locust. Our results provide useful information for the optimal propagation of woody trees and for further research into the mechanisms of root regeneration.