Regulatory mechanisms of two epiphytic cultivation modes of Cunninghamia lanceolata on growth, disease resistance and root-stem characteristics of Dendrobium devonianum

Dendrobium devonianum (purple-skinned Dendrobium ) is a pillar crop in Longling, Yunnan, the “Hometown of Purple-skinned Dendrobium”. Understory wild-simulated epiphytic cultivation is critical for high-quality organic production and regional industrial sustainability. This study compared two Cunninghamia lanceolata- based modes (dead tree frame cultivation vs. living standing tree cultivation) to optimize D. devonianum cultivation. Results showed that: (1) dead tree frame increased stem diameter (+ 28.0%), stem length (+ 21.6%), and fresh weight (+ 8.4%, P < 0.05) but caused significantly higher rust incidence (68.40% ± 0.05% vs. 41.80% ± 0.08%) and black spot disease index (14.60 ± 2.94 vs. 7.88 ± 1.12, P < 0.05). (2) High-throughput sequencing revealed the living standing tree group had significantly higher abundances of Actinobacteria (+ 35.2%), Acidobacteriota (+ 42.1%), and Bacteroidota (+ 28.6%, P < 0.05), which were negatively correlated with disease incidence. In contrast, the dead tree frame group was dominated by opportunistic pathogen-related phyla. (3) LC-MS/MS analysis showed that dead tree frame cultivation upregulated stress-responsive metabolites (fatty acyls, prenol lipids), while living standing tree cultivation significantly enriched flavonoids (+ 36.7%) and polysaccharides (+ 169.8%, P < 0.05). The living standing tree mode achieves synergistic improvements in disease resistance and medicinal quality, supporting a regulatory cascade linking cultivation mode, root endophytic microbes, metabolic reprogramming, and plant performance. This makes it more suitable for high-quality, eco-friendly D. devonianum cultivation in Longling, providing technical support for industrial upgrading.