(1) Reverse transcription quantitative real-time PCR (RT-qPCR) requires reliable reference genes for accurate data normalization; however, optimal reference genes for the economically and ecologically valuable timber species Phoebe zhennan remain uncharacterized; (2) Here, we selected nine candidate reference genes derived from full-length transcriptome sequencing to evaluate their expression stability across abiotic (drought) and biotic (Colletotrichum fructicola infection) stresses. Transcript abundance was analyzed via RT-qPCR using four distinct algorithms (Delta Ct, geNorm, NormFinder, and BestKeeper), with RefFinder used to reconcile analytical discrepancies and generate a definitive consensus ranking; (3) Our analysis showed that expression stability is highly context-dependent: CYP20-1 and HSP70-1 were the most stable reference genes under drought stress, whereas Actin-101 and Actin constituted the optimal pair under disease stress. For cross-condition assessments, Actin-101 and β-Tubulin served as the most reliable baseline combination. Subsequent empirical validation quantifying stress-responsive transcripts demonstrated a significant positive correlation between RT-qPCR relative expression and corresponding RNA-seq data (drought: R = 0.80; disease: R = 0.76); (4) This study identifies and validates the first set of reference genes for P. zhennan, providing a foundation for accurate gene expression analysis in this species, which is crucial for understanding its response to environmental stresses.

Primulina lichuanensis, a new species of Gesneriaceae from Hubei, Central China, is described and illustrated. The new species is morphologically similar to P. subulatisepala in its obliquely ovate leaf blades, but can be distinguished by its thinly papery leaf blades, smaller flowers, and an obliquely campanulate, ventricose corolla. The conservation status and a morphological comparison with similar species are provided.