PLANT CELL, TISSUE AND ORGAN CULTURE, cilt.163, sa.88, ss.1-10, 2025 (SCI-Expanded, Scopus)
Black mulberry (Morus nigra L.) is a long-lived, highly polyploid (2n = 22x = 308) fruit tree characterized by limited genetic diversity and lack of autonomous reproduction. While tissue culture is widely used in woody perennials, its effects on juvenility in M. nigra remain poorly understood. Here, we combined long-term field trials with molecular analysis to investigate phase transition in micropropagated plants. Remarkably, tissue culture–derived M. nigra remained juvenile for more than six years, whereas grafted and cutting-propagated plants reached reproductive competence within two to five years. Expression profiling revealed sustained upregulation of specific miR156 isoforms (notably miR156e and miR156g) and incomplete induction of miR172, particularly suppression of miR172d, in micropropagated plants. These findings identify M. nigra as a unique case in which micropropagation reinforces developmental immaturity, highlighting species-specific sensitivity of the miR156/miR172 regulatory network and underscoring the need for tailored propagation strategies.