In order to protect and utilize the germplasm resource better, it is highly necessary to carry out a study on the genetic diversity of Camellia chekiangoleosa Hu. However, systematic research on population genetics analysis of the species is comparatively rare. Herein, 16 highly variable simple sequence repeat (SSR) markers were used for genetic structure assessment in 12 natural C. chekiangoleosa populations. The genetic diversity of C. chekiangoleosa was low (h = 0.596), within which, central populations (such as Damaoshan (DMS), Sanqingshan (SQS), and Gutianshan (GTS)) at the junction of four main mountain ranges presented high diversity and represented the center of the C. chekiangoleosa diversity distribution; the Hengshan (HS) population in the west showed the lowest diversity, and the diversity of the eastern and coastal populations was intermediate. C. chekiangoleosa exhibited a high level of genetic differentiation, and the variation among populations accounted for approximately 24% of the total variation. The major reasons for this situation are the small population scale and bottleneck effects in some populations (HS and Lingshan (LS)), coupled with inbreeding within the population and low gene flow among populations (Nm = 0.796). To scientifically protect the genetic diversity of C. chekiangoleosa, in situ conservation measures should be implemented for high-diversity populations, while low-diversity populations should be restored by reintroduction.

Garden dahlias (Dahlia pinnata) are popular for their wide range of color variations, with polychromatic cultivars enhancing their ornamental value. Previous studies on the anthocyanin biosynthetic pathway (ABP) have indicated that the post-transcriptional suppression of the chalcone synthase gene (CHS) is involved in the formation of the white petals of dahlias. To further explore the complex mechanisms underlying polychromatic petal formation, we selected the bicolor cultivar ‘LiRen’ to identify candidate genetic factors. Through the detection of proanthocyanidin and anthocyanin, it was indicated that the white tips of the petals lacked anthocyanin but accumulated some proanthocyanidin, albeit at significantly lower levels than those at the red bases of the petals. This suggests that the upstream ABP, which involves CHS, is not entirely inactive. Transcription sequencing and quantitative reverse transcription PCR (qRT-PCR) analysis demonstrated that the inactive ABP in the white tips results from the downregulation of ABP structural genes. The low abundance of DpMYB1 appears to be the key factor influencing the lack of strong transcription activation of the structural genes. Additionally, highly upregulated DpSPL9 targeted by the downregulated miR156 in the white tips was identified through qRT-PCR. This suggests that DpSPL9 may act as an anthocyanin depressor to destabilize the MYB-bHLH-WDR complex through interaction with DpMYB1. The findings indicate that the DpMYB1 and miR156-DpSPL9 modules play potential regulatory roles in the formation of bicolor petals. Overall, these results provide new insights into the color patterning of dahlias and will be valuable for further studies regarding the mechanisms underlying polychromatic petal formation.