<p><i>Morus nigra</i> L. (hereafter MN) is a 22-ploid (2n = 22x = 308) deciduous fruit tree enriched with antioxidant and anti-inflammatory properties. Besides the restricted genetic diversity, MN also exhibited loss of growth superiority and premature senescence. The present study emphasized the characterization of premature senescence in MN by phenotypic and transcriptional approaches. The first signs of senescence in basal leaves and cessation of apical growth were recorded during the second and third weeks of post-emergence. To substantiate the premature senescence phenotype with molecular evidence, de novo transcriptome assembly was reconstructed using heterogeneous RNA-Seq datasets. The core gene family (GFs) completeness score of the transcriptome assembly is about 0.98, and the identified major GFs are reverse transcriptase and DNA integration. Transcriptome-wide, a total of 52 transcription factor (TF) family genes were predicted. The significantly enriched functions of overrepresented TFs yielded multiple pathways associated with senescence and ethylene signalling. TF regulatory network analyses revealed the mechanism of leaf senescence linked with the development of reproductive and vegetative processes. Furthermore, qPCR analysis was performed to detect and quantify the expression pattern of senescence-associated genes (<i>SGR1</i> and <i>GBSS1</i>) and ethylene-responsive putative TFs (<i>RAP2.4</i>). Phenotypic observation, significantly enriched GO terms, TF regulatory networks and gene expression studies provide evidence for the mechanistic coherence of the premature senescence wave in extreme polyploid MN.</p> Graphical Abstract <p></p>