Genetic Characteristics and Formation Mechanisms of Distinctive Traits in Two Types of Sinningia speciosa Corolla Tubes Based on Complete Diallel Cross and Multi-Generation Selfing

Methods Based on two corolla tube types(L-T,C-T), 256 F1 individuals from a complete diallel cross involving, 5000 F2 individuals and 100 S6 (selfed for six generations) populations. Phenotypic traits, cytology, qRT-PCR, and CRISPR/Cas9 assays were conducted to examine genetic differential expression between the two corolla types. Results The order of dominance in hybrids was labiate > campanulate; For shared typical traits, the dominance order was angled > pubescent > veined. Dorsal and ventral cells of the L-T differed significantly, exhibiting thin walls, fewer stomata, and more trichomes; Whereas the C-T displayed uniformly arranged cells, thicker walls, and more stomata. Gene analysis revealed that 20 genes from five classes (A, B, C, E, and AGL6 subfamily) of the MIKCC-type MADS-box family, 30–32 genes from the TCP family, 8 genes from the YABBY family, and 12 genes from the WOX family transcription factors were involved in regulating typical corolla tube traits. Continuous selfing for six generations did not cause significant changes in the related regulatory genes, with the L-T exhibiting higher stability than the C-T. Both corolla tube types underwent six distinct developmental stages. The L-T was primarily activated by CYC/DICH genes, while the C-T was activated by RAD genes, leading to global expression of MADS-box identity transcription factors. The regulatory patterns, genes involved, and formation mechanisms differed significantly Conclusion The corolla tube of Sinningia speciosa exhibits high genetic stability, and the formation of its typical traits demonstrates significant representativeness and classification characteristics.