Phenotypic characterization and transcriptomic analysis of the semi-dwarf mutant <italic>sd3</italic> in Tartary buckwheat

Plant height is a key agronomic trait in Tartary buckwheat, closely associated with lodging resistance, photosynthetic efficiency, and yield formation. Dwarfism is generally advantageous for enhancing lodging resistance and thereby improving yield. To explore dwarf stem gene resources, and to provide a theoretical basis for understanding plant height development and its application in breeding, we conducted phenotypic characterization and transcriptomic analysis of the semi-dwarf mutant sd3, previously generated through EMS mutagenesis. The results showed that compared with the wild type, the plant height of the sd3 at the mature stage reduced 28.43%, and the number of nodes on the main stem decreased by 44.44%. The reduction in node number was the primary cause of the dwarfism in sd3. Cytological observations revealed enhanced lateral cell division at the stem nodes in sd3, which has led to significantly thickened stem walls and an increased basal internode diameter. sd3 is sensitive to gibberellin, and exogenous GA3 can restore its phenotype. Transcriptome analysis identified 3067 differentially expressed genes (DEGs), GO and KEGG pathway enrichment revealed 57 genes potentially involved in regulating plant height. Notably, GID1 in the gibberellin signaling pathway was upregulated in sd3, while GID2, UNE10, and PIF1 were downregulated, suggesting these genes may play a key role in the dwarf phenotype of sd3. Overall, our findings provide preliminary insights into the dwarfing mechanisms of sd3 and offer valuable candidate genes for breeding lodging-resistant varieties and improving plant architecture through genetic approaches.