Effects of Inoculation with Phosphate Solubilizing Bacteria on the Physiology, Biochemistry, and Expression of Genes Related to the Protective Enzyme System of Fritillaria taipaiensis P. Y. Li

Fritillaria taipaiensis P. Y. Li is a widely used medicinal herb in treating pulmonary diseases. In recent years, its wild resources have become scarce, and the demand for efficient artificial cultivation has significantly increased. This article is the first to apply phosphate solubilizing bacteria isolated from the rhizosphere soil of F. taipaiensis P. Y. Li to the cultivation process of F. taipaiensis P. Y. Li. The aim is to identify suitable reference strains for the artificial cultivation and industrial development of F. taipaiensis P. Y. Li by examining the effects of various phosphate solubilizing bacteria and their combinations on photosynthesis, physiological and biochemical properties, and gene expression related to the protective enzyme system in F. taipaiensis P. Y. Li. The experiment, conducted in pots at room temperature, included a control group (CK) and groups inoculated with inorganic phosphorus-solubilizing bacteria: W1 (Bacillus cereus), W2 (Serratia plymuthica), W12 (Bacillus cereus and Serratia plymuthica), and groups inoculated with organophosphorus-solubilizing bacteria: Y1 (Bacillus cereus), Y2 (Bacillus cereus), Y12 (Bacillus cereus and Bacillus cereus), totaling seven groups. Compared to CK, most growth indices in the bacterial addition groups showed significant differences, with W12 achieving the highest values in all indices except the leaf area index. The content of photosynthetic pigments, photosynthetic parameters, and osmoregulatory substances increased variably in each bacterial treatment group. W12 exhibited the highest content of chlorophyll a and soluble protein, while W1 had the highest free proline content. The activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in all inoculated groups were higher than in CK, with significant changes in SOD and CAT activities. The malondialdehyde (MDA) content in all inoculated groups was lower than in CK, with Y12 being the lowest, at approximately 30% of CK. Gene expression corresponding to these three enzymes also increased variably, with POD expression in Y2 being the highest at 2.73 times that of CK. SOD and CAT expression in Y12 were the highest, at 1.84 and 4.39 times that of CK, respectively. These results indicate that inoculating phosphate solubilizing bacteria can enhance the growth of F. taipaiensis P. Y. Li, with the mixed inoculation groups W12 and Y12 demonstrating superior effects. This lays a theoretical foundation for selecting bacterial fertilizers in the cultivation process of F. taipaiensis P. Y. Li.