Isolation and identification of native microalgae from the Yellow River Delta: A dual-focus study on the tolerance assessment of microalgae and their growth enhancement on Sesbania cannabina under saline-alkali stress

Abstract

Saline and alkaline land improvement and restoration are imminent, and the application of microalgae has received great attention as an effective strategy. In this study, we focused on microalgae isolated from the Yellow River Delta in Dongying, China, and identified and characterized them by light microscopy and 18S rDNA gene sequence analysis, and five new algal strains were identified as Chlorella spp. in the family Chlorophyceae. The growth response of the algal strains under different stress conditions was evaluated by measuring the growth status, biomass, pH, and salt removal rate. The results showed that the LDC and YHH strains were more tolerant to salinity stress. In addition, the effects of two applications, via seed soaking and root irrigation, on the morphological index of Sesbania cannabina under normal conditions as well as under different NaCl, NaHCO₃, and NaCl and NaHCO₃ (1:1 mixture) stresses (100 mM, 200 mM) were investigated. The combined results showed that living microalgae promoted seed germination and seedling growth of S. cannabina under saline stress, with the LDC strain showing superior growth-promoting effects, and its stress-relieving effect outweighed the growth-stimulating effect. These results provide strong support for the sustainable application of native saline-tolerant microalgae in halophytic crop production in saline agriculture.