What type of study is this?

This is a Observational study (also classified as: Greenhouse Assay, Bacterial Isolation, 16S rRNA Gene Sequencing).

September 10, 2025Open Access

Rhizosphere-Associated Bacteria of Saltgrass Distichlis spicata (L.) Greene Show Enhanced Ability to Tolerate Saline Environments and Stimulate Plant Growth

ÁMÁngel Mena-GarcíaColegio de Postgraduados AAAlejandro AlarcónColegio de Postgraduados FGFernando Carlos Gómez‐MerinoColegio de Postgraduados

Key Points

Inoculation with selected bacteria enhanced tomato growth, and up to 30% increase in biomass was observed compared to controls.
The halotolerant bacterial strains maintain growth under saline stress, demonstrating resilience in harsh conditions.
Isolation and characterization revealed key traits, such as IAA production and salinity tolerance, that benefit plant growth.
Identified strains include Pseudomonas sp. and Zhihengliuella halotolerans, highlighting their importance in improving crop performance.

Abstract

The use of plant growth-promoting bacteria (PGPB) tolerant to abiotic stress factors can enhance plant performance when applied under both optimal and stress conditions in crops. In this study, bacterial strains associated with the rhizosphere of the halophyte Distichlis spicata were isolated and characterized for their ability to produce siderophores, solubilize phosphate, synthesize indole-3-acetic acid (IAA) and exopolysaccharides (EPS), and tolerate salinity. IAA production and antioxidant capacity were further assessed under saline stress. As expected, salinity negatively impacted bacterial growth, IAA biosynthesis, and antioxidant activity—even in strains from a salt-tolerant plant. Nevertheless, all strains except RD2 maintained growth and IAA production in LB broth supplemented with up to 1 M NaCl. Five halotolerant strains (RD2, RD4, RD17, RD26, and RD27) were selected for greenhouse inoculation assays in tomato (Solanum lycopersicum) seedlings. Inoculation with RD26 significantly enhanced seedling performance, promoting tomato growth, increasing leaf area by 22%, stem diameter by 17%, shoot dry biomass by 30%, and root biomass by 27% as compared to the uninoculated control. RD27 and RD4 also improved shoot biomass by 25 and 23%, respectively. Based on 16S rRNA gene sequencing, RD26 was identified as Pseudomonas sp. and RD27 as Zhihengliuella halotolerans. These findings demonstrate that salt stress impairs plant growth-promoting traits in rhizospheric bacteria, yet selected strains such as RD26 and RD27 can significantly promote plant growth. Their use as bioinoculants represents a promising strategy for improving crop performance in saline environments.

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