Identification of Plant Growth-promoting Strains among Endophytic Bacteria Isolated from Cunninghamia lanceolata

Objective Plant growth-promoting strains in the diverse culturable endophytic bacteria in tissues of Cunninghamia lanceolata were identified for development of biofertilizer.

Methods Roots, stems, and leaves of mature C. lanceolata plants were collected to isolate the endophytic bacteria by a homogenization method. The isolates were tested for plant growth-promoting abilities followed by species identification with 16S rDNA sequencing.

Results A total of 79 endophytic bacteria were isolated from the tissues of C. lanceolata. Thirty-three of them came from the roots that accounted for 41.77% of total; 32 from the stems, accounting for 40.51%; and 14 from the leaves, accounting for 17.72%. On the ability of promoting plant growth, 52 of the isolated strains were found capable of producing IAA, 46 of fixing nitrogen, 17 of solubilizing phosphorus, and 73 of chelating iron. The 16S rDNA sequencing identified the functional Y6, Y25, J3, and G21 as Acinetobacter pittii, Brachybacterium rhamnosum, Bacillus cereus, and Bacillus proteolyticus, respectively.

Conclusion A total of 79 endophytic bacteria were isolated from the root, stem, and leaf tissues of C. lanceolata tissues. Among them, 65.82% exhibited the ability to produce IAA, 58.23% demonstrated nitrogen fixation, 21.52% showed phosphate solubilization, and 92.41% were capable of siderophore production. From these isolates, functional strains Y6, Y25, J3, and G21 with relatively strong comprehensive growth-promoting abilities were selected.