Abstract: To obtain an effective biocontrol consortium for the management of root rot and promotion of growth in Lycium barbarum. The rhizosphere soil samples from healthy plants were collected, and antifungal bacteria were screened using the dual-culture method, targeting the pathogens Fusarium oxysporum and Fusarium solani. Besides, the bacteria with different plant growth promoting potentials, including nitrogen-fixing, phosphatesolubilizing, and potassium-mobilizing were firstly screened by using different selective media, then quantitative assays of the properties were individually performed by Kjeldahl method, molybdenum-antimony colorimetric method, and flame atomic absorption spectrometry. Composite bacterial consortia were then formulated from strains with desirable traits and no antagonistic interactions. The antagonistic and growth-promoting characteristics of these consortia were evaluated, and the optimal consortium was selected using the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method. Molecular identification of the strains in the optimal consortium was performed, and field trials were conducted to assess their efficacy in disease prevention and plant growth promotion. Results showed that a total of 186 beneficial bacteria were isolated, including 91 antagonistic strains, 138 nitrogen-fixing strains, 77 organic phosphate-solubilizing strains, 76 inorganic phosphate-solubilizing strains, and 21 potassium-mobilizing strains. Among the isolates, strain B14 exhibited the best antagonistic activity against Fusarium oxysporum (75.33% inhibition), while strain B22 had the highest inhibition rate against Fusarium solani (79.59%). The highest nitrogen-fixing capacity (0.111 g/L) was observed in strain O30, and the highest organic phosphate solubilization (188.1 μg/mL) was achieved by strain B13. Strain O28 showed the strongest inorganic phosphate solubilization (828.87 μg/mL), while strain K5 had the highest potassium mobilization (100.2 mg/L). Consortium Q2 showed the best overall performance among the primally 4 determined superior composite bacterial consortia, with an inhibition rate of 82.65%, organic phosphate solubilization of 213.71 μg/mL, inorganic phosphate solubilization of 1034.22 μg/mL, nitrogen fixation of 0.257 g/L, and potassium mobilization of 103.66 mg/L, all of which were higher than those of individual optimal strains. Molecular identification revealed that consortium Q2 included Bacillus mojavensis O30, Bacillus velezensis B22, Bacillus subtilis B10 and O44, and Bacillus halotolerans K5. Field trials demonstrated that consortium Q2 achieved a 90% control efficacy against root rot in Lycium barbarum, increased plant height by 20%, and stem diameter by 9%. Additionally, it improved soil health by reducing salinity and enhancing the availability of nitrogen, phosphorus, potassium, and organic matter. The consortium also shifted the rhizosphere microbial community structure, increasing the abundance of beneficial bacteria and actinomycetes while reducing fungal populations. The findings highlight the potential of the Q2 bacterial consortia as a sustainable strategy for managing root rot, promoting plant growth, reducing the salt-alkali content in the rhizosphere soil, improving soil nutrients, and regulating the soil microbial community structure of Lycium barbarum.

Key words: Lycium bararum, root rot, biocontrol bacteria, PGPR, bacterial consortia