Screening of Salt-alkali Tolerant Endophytic Bacteria from JUNCAO and their Promoting Effect on Maize

Objective This study aims to isolate salt-alkali tolerant endophytic bacteria from JUNCAO in the saline-alkali soils of Pingtan, Fujian, clarify their taxonomic status, salt-alkali tolerance, physiological and biochemical characteristics, and their growth-promoting effects on maize, providing theoretical support for the improvement of saline-alkali land and the application of JUNCAO.

Method The salt-tolerant bacterial strains PXY-25 and PXY-28 were obtained through screening with 1.0 mol/L NaCl. Their salt-alkali tolerance was determined using salt concentration gradients and pH gradients, combined with molecular identification through 16S rRNA sequence analysis. Plate assays were used to study their physiological and biochemical characteristics as well as their antagonistic abilities against four pathogenic fungi. Additionally, pot experiments were conducted to analyze their effects on corn underground growth indicators, antioxidant enzyme activity, and chlorophyll content.

Result Two salt-alkali tolerant endophytic bacteria were identified as Enterobacter ludwigii. PXY-25 can grow in LB medium with 1.5 mol/L NaCl, 0.05 mol/L Na₂CO₃, and a pH of 10.0, while PXY-28 can grow in LB medium with 1.5 mol/L NaCl, 0.05 mol/L Na₂CO₃, and a pH of 9.0. Both strains can dissolve inorganic phosphorus, produce contact enzymes and weak iron carriers, and have a certain effect on the anthracnose bacteria (PHZ-8). In the corn pot experiment, PXY-25 significantly increased root length, with an increase of 56.95% compared to the control. The root length of corn treated with PXY-28 increased by 19.79% compared to the control. Both strains reduced the malondialdehyde (MDA) content in corn, decreasing it by 49.09% and 60.92% respectively compared to the control. Among them, PXY-25 significantly increased the total chlorophyll content, with an increase of 94.78% compared to the control.

Conclusion PXY-25 has strong salt-alkali tolerance and significant growth-promoting characteristics for maize, making it a potential strain for the improvement of saline-alkali land and the promotion of crop growth.