Potential for Plant Growth Promotion of Rhizobacteria Associated withSalicorniaGrowing in Tunisian Hypersaline Soils

Francesca Mapelli,Eleonora Rolli,Sara Borin,Marta Barbato,Imen Ouzari,Ramona Marasco,Amel Guesmi,Hanene Cherif,Daniele Daffonchio

doi:10.1155/2013/248078

Francesca Mapelli, Eleonora Rolli + Show 7 more

Open Access

https://doi.org/10.1155/2013/248078

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Abstract

Soil salinity and drought are among the environmental stresses that most severely affect plant growth and production around the world. In this study the rhizospheres of Salicornia plants and bulk soils were collected from Sebkhet and Chott hypersaline ecosystems in Tunisia. Depiction of bacterial microbiome composition by Denaturing Gradient Gel Electrophoresis unveiled the occurrence of a high bacterial diversity associated with Salicornia root system. A large collection of 475 halophilic and halotolerant bacteria was established from Salicornia rhizosphere and the surrounding bulk soil, and the bacteria were characterized for the resistance to temperature, osmotic and saline stresses, and plant growth promotion (PGP) features. Twenty Halomonas strains showed resistance to a wide set of abiotic stresses and were able to perform different PGP activities in vitro at 5% NaCl, including ammonia and indole-3-acetic acid production, phosphate solubilisation, and potential nitrogen fixation. By using a gfp-labelled strain it was possible to demonstrate that Halomonas is capable of successfully colonising Salicornia roots in the laboratory conditions. Our results indicated that the culturable halophilic/halotolerant bacteria inhabiting salty and arid ecosystems have a potential to contribute to promoting plant growth under the harsh salinity and drought conditions. These halophilic/halotolerant strains could be exploited in biofertilizer formulates to sustain crop production in degraded and arid lands.

Highlights

The influence of microbes on plant fitness has been recognized both in conventional and extreme habitats, where the ability of rhizobacteria to facilitate plant adaptation and promote growth and productivity has been reported [1,2,3,4,5,6]
The bulk soils collected from Tunisian Sebkhet and Chott were characterized by extreme dryness and salinity values, Denaturing Gradient Gel Electrophoresis (DGGE) band profiles highlighted that a rich and diverse bacterial microbiome was present in all the samples (Figure 1(a), left panel)
Principal Component Analysis (PCA) performed on the line plots derived from DGGE band profiles (Figure 1(b), left panel) indicated that bulk soils clustered according to the site of provenience

Summary

Introduction

The influence of microbes on plant fitness has been recognized both in conventional and extreme habitats, where the ability of rhizobacteria to facilitate plant adaptation and promote growth and productivity has been reported [1,2,3,4,5,6]. Root-associated bacteria can promote plant growth by direct and indirect mechanisms, the former including nutrient fixation and solubilisation and phytohormones synthesis. The ability to reduce or avoid the harmful effects of phytopathogens. Both the host plant and its associated microbiome gain an evolutionary advantage to survive under harsh conditions by establishing tight interplays. Conditions of high salt concentrations in the soil are very frequent in arid and semiarid regions on Earth, where different halophytic species can be found. Salicornia densely colonises different areas of southern Tunisia, including Sebkhet and Chott ecosystems, dominated by extreme values of aridity

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