Mitigation of NaCl Stress in Wheat by Rhizosphere Engineering Using Salt Habitat Adapted PGPR Halotolerant Bacteria

Souhila Kerbab,Lassaad Belbahri,Allaoua Silini,Hafsa Cherif-Silini,Ali Chenari Bouket,Nour El Houda Rabhi,Manal Eshelli

doi:10.3390/app11031034

Abstract

There is a great interest in mitigating soil salinity that limits plant growth and productivity. In this study, eighty-nine strains were isolated from the rhizosphere and endosphere of two halophyte species (Suaeda mollis and Salsola tetrandra) collected from three chotts in Algeria. They were screened for diverse plant growth-promoting traits, antifungal activity and tolerance to different physico-chemical conditions (pH, PEG, and NaCl) to evaluate their efficiency in mitigating salt stress and enhancing the growth of Arabidopsis thaliana and durum wheat under NaCl–stress conditions. Three bacterial strains BR5, OR15, and RB13 were finally selected and identified as Bacillus atropheus. The Bacterial strains (separately and combined) were then used for inoculating Arabidopsis thaliana and durum wheat during the seed germination stage under NaCl stress conditions. Results indicated that inoculation of both plant spp. with the bacterial strains separately or combined considerably improved the growth parameters. Three soils with different salinity levels (S1 = 0.48, S2 = 3.81, and S3 = 2.80 mS/cm) were used to investigate the effects of selected strains (BR5, OR15, and RB13; separately and combined) on several growth parameters of wheat plants. The inoculation (notably the multi-strain consortium) proved a better approach to increase the chlorophyll and carotenoid contents as compared to control plants. However, proline content, lipid peroxidation, and activities of antioxidant enzymes decreased after inoculation with the plant growth-promoting rhizobacteria (PGPR) that can attenuate the adverse effects of salt stress by reducing the reactive oxygen species (ROS) production. These results indicated that under saline soil conditions, halotolerant PGPR strains are promising candidates as biofertilizers under salt stress conditions.

Highlights

Salinity is a serious problem that limits plant growth and productivity [1,2,3], hampers agricultural economy, and leads to serious land degradation in many countries [1,3,4]
A total of 98 strains differing in colony morphology were isolated from root halophytes where they are thriving as endophytes, rhizosphere soil as well as salty soil surrounding the halophytes in three salt-affected sites in the East of Algeria (Figure 1A–C, Table 1)
Results showed that 27.55% of the isolates were from salty soil, 44.89% from rhizosphere soil and 27.55% were root endophytes. 21, 34 and 43 of them were recovered from Chott Bazer Sakhra (21.42%), Chott Tinsilt (34.69%), and Chott El Hodna (43.87%), respectively (Figure 1D)

Summary

Introduction

Salinity is a serious problem that limits plant growth and productivity [1,2,3], hampers agricultural economy, and leads to serious land degradation in many countries [1,3,4]. Salinity deleterious effects on plant growth and development include water deficit within the plant, ion toxicity mainly Na+ and Cl-, reduction of nutrient uptake and/or transport to the shoot that leads to nutritional imbalance [3], production and accumulation of reactive oxygen species (ROS) [1], ethylene generation and plasmolysis. These physiological imbalances limit seed germination, seedling growth, flowering and fruit set in consequence [6]. Multifaceted and versatile biocontrol agents are being described and developed in formulations that allow their efficient use as biofertilizers [3]

Methods

Results

Discussion

Conclusion