The Effects of Different Companion Fungi on the Growth and Development of Cremastra appendiculata and the Accumulation of Bioactive Components in Its Pseudobulbs

Cremastra appendiculata (D. Don) Makino is a rare orchid species possessing both ornamental and medicinal value. The process by which its protocorms develop into pseudobulbs represents not only a critical stage for seedling establishment but also a key period for the formation and accumulation of pharmacologically active constituents. Mycorrhizal fungi and plant growth-promoting microorganisms are known to promote the growth and development of orchids; however, their integrated regulatory effects on pseudobulb growth and quality formation in C. appendiculata remain unclear. In this study, pseudobulbs of C. appendiculata were used as experimental materials and treated with three companion fungal inoculants, namely Coprinellus micaceus, Coprinellus radians, and Ephemerocybe pseudodisseminata. Since C. appendiculata seeds cannot germinate under sterile conditions, no sterile control group was included in this study; therefore, the results primarily reflect differences among the three fungal treatments rather than absolute growth-promoting effects. Subsequently, plant growth parameters, biomass indices, physiological and biochemical traits, and contents of medicinal quality components were measured, and the comprehensive effects of different companion fungi were evaluated using principal component analysis (PCA) and correlation analysis. The results showed that plants treated with C. micaceus had significantly higher plant height, stem base diameter, leaf area, main root length, and pseudobulb length and width, as well as higher fresh and dry weights of pseudobulbs, compared with the other two treatments. In terms of physiological and biochemical indices, the contents of soluble protein, starch, and crude ash in pseudobulbs were highest under C. micaceus treatment. Quality component analysis revealed that the contents of total flavonoids, total phenolics, polysaccharides, and alkaloids were significantly higher under C. micaceus treatment than under the other treatments, with the alkaloid content reaching 1.66 mg BE·g−1. Principal component analysis indicated that the cumulative contribution rate of PC1 and PC2 reached 95.4%, effectively explaining the variation among different treatments. The comprehensive evaluation results demonstrated that the effects of the different companion fungal treatments ranked as follows: C. micaceus > C. radians > E. pseudodisseminata. In conclusion, among the three companion fungal treatments, C. micaceus showed the best comprehensive performance in promoting pseudobulb growth and medicinal quality formation in C. appendiculata. This fungus can serve as an excellent microbial inoculant for seedling propagation and efficient cultivation of medicinal resources of C. appendiculata, thereby providing a theoretical basis for the artificial cultivation and resource exploitation of this species.