Induction of Autopolyploidy and Preliminary Investigation of the Dwarfing Mechanism in Hedychium coccineum

In this study, <i>Hedychium coccineum</i> tetraploid plants and octaploid plants induced by colchicine were used as materials. The ploidy levels were precisely identified by combining root tip squash and flow cytometry analyses, and the differences between plants of different ploidy levels were systematically investigated at cytological, morphological, and molecular levels. The results showed that the highest polyploid induction efficiency was achieved when callus tissues were treated with 0.1 g/L colchicine for 4 days. The fluorescence peak value of the induced plants was twice that of the tetraploids, confirming their octaploid status. Compared with tetraploids, octaploid plants exhibited almost no apparent dormancy period, significantly slower growth, earlier flowering, and notably smaller inflorescences. Morphologically, they showed a dwarf phenotype characterized by narrower and lighter-colored leaves, fewer leaves per shoot, shorter internodes, and wider leaf angles, along with enhanced stress tolerance. Cytological observation revealed that cell area in internode tissues at the bud and seedling stages was generally larger in tetraploids than in octaploids, suggesting a reduction in cell size following genome duplication. Furthermore, transcriptome comparison between tetraploids and octaploids identified <i>HcPCNA1</i> as a candidate gene closely associated with plant height. Functional validation showed that overexpression of <i>HcPCNA1</i> in <i>Arabidopsis thaliana</i> significantly increased plant height, whereas silencing of <i>HcPCNA1</i> in <i>H</i>. <i>coccineum</i> via Virus-induced gene silencing (VIGS) resulted in a distinct dwarf phenotype with smaller leaves. Cytological and molecular evidence together indicate that <i>HcPCNA1</i> may influence plant height in <i>H. coccineum</i> through its role in promoting cell division and elongation. This finding provides new insights into the molecular mechanisms underlying plant architecture development in polyploid species.