Harnessing the Potential of Symbiotic Endophytic Fungi and Plant Growth-Promoting Rhizobacteria to Enhance Soil Quality in Saline Soils

Zahra Rouydel,Ramesh Raju Vetukuri,Mir Hassan Rasouli-Sadaghiani,Mohsen Barin,Sandeep Kushwaha,Maryam Khezri

doi:10.3390/pr9101810

Abstract

Soil salinity is one of the most important abiotic stresses limiting crop growth and production worldwide. Some microorganisms can improve the plants’ tolerance to salinity. For this purpose, a greenhouse experiment was performed to understand the influence of various microorganisms on soil biological indices and wheat growth under different saline conditions. The factors varied in the experiment were the microbial treatment (rhizobacteria, mycorrhizal fungi, endophytic fungus, and control) and salinity stress (0.5, 8, and 14 dS m−1). Rhizobacteria were isolated from saline soils, but the fungi were prepared from a microbial bank. Overall, ten isolates were purified, and three with promising growth-promoting properties were identified using phenotypic and molecular methods. The selected isolates belonged to the genera Pseudomonas (P. aeruginosa Ur83 and P. fluorescens Ur67) and Stenotrophomonas (S. maltophilia Ur52). Soil quality indices were found to decrease with increasing salinity, but inoculation with microorganisms alleviated this decline. Inoculation with plant growth-promoting rhizobacteria (PGPRs) increased basal respiration, substrate-induced respiration, microbial biomass carbon, acid and alkaline phosphatase activities, and carbon availability by factors of 1.37, 1.27, 1.83, 3.07, 1.29, and 1.11, respectively. These results show that inoculation with symbiotic microorganisms can improve agricultural soil quality under saline conditions and may thus be valuable in agriculture.

Highlights

Soil salinity is a major threat to agricultural sustainability, especially in arid and semiarid regions [1], and is common environmental stress limiting agricultural production inIran [2]
Various methods have been developed for improving soil quality indices using microorganisms, such as plant growth-promoting rhizobacteria (PGPRs), arbuscular mycorrhizal fungi (AMF), and endophytic fungi [9,10]
Three of these isolates were selected for molecular identification on the basis of PGPR-specific tests

Summary

Introduction

Soil salinity is a major threat to agricultural sustainability, especially in arid and semiarid regions [1], and is common environmental stress limiting agricultural production inIran [2]. Soil salinity has several adverse effects on plant growth: it causes osmotic stress by reducing the osmotic potential of the soil solution, salinity stress by increasing the concentrations of specific ions, imbalances in the soil’s content of nutrient elements [4,5], and changes the soil’s physical and chemical properties [4,6,7]. Various methods have been developed for improving soil quality indices using microorganisms, such as plant growth-promoting rhizobacteria (PGPRs), arbuscular mycorrhizal fungi (AMF), and endophytic fungi [9,10]. PGPRs isolated from saline regions are resistant to high salt concentrations and enhance plant resistance to salinity stress by increasing hydraulic and osmotic conductivity, promoting osmotic adjustment, reducing the toxic impacts of Na+, and protecting photosynthesis

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Conclusion