Phenetic and Molecular Diversity of Nitrogen Fixating Plant Growth Promoting Azotobacter Isolated from Semiarid Regions of India

Devendra Jain,Archna Suman,Vimal Sharma,Ali Asger Bhojiya,Gunnjeet Kaur,Elina Maharjan,Surya Chauhan,Jyoti Sharma,Santosh Ranjan Mohanty,Marta Laranjo

doi:10.1155/2021/6686283

Abstract

In the present study, 24 Azotobacter strains were isolated from soils of different areas of southern Rajasthan and characterized at biochemical, functional, and molecular levels. The isolated Azotobacter strains were gram negative and cyst forming when viewed under the microscope. These strains were also screened for their plant growth promoting activities and the ability of these isolates to survive under abiotic stress conditions viz. salt, pH, temperature, and drought stress. All the isolates showed IAA, siderophore, HCN, and ammonia production, whereas seven Azotobacter strains showed phosphate solubilization. Amplified Ribosomal DNA Restriction Analysis (ARDRA) revealed significant diversity among Azotobacter strains and the dendrogram obtained differentiated twenty-four of the strains into two major clusters at a similarity coefficient of 0.64. Qualitative and quantitative N2 fixation abilities of these strains were also detrained, and the amounts of acetylene reduced by Azotobacter strains were in the range of 1.31 to 846.56 nmol C2H4 mg protein−1 h−1. The strains showing high nitrogen fixation ability with multiple PGP activities were selected for further pot studies, and these Azotobacter strains significantly increased the various plant growth parameters of maize plantlets. Furthermore, the best Azotobacter isolates were subjected to 16S rRNA sequencing and confirmed their identities as Azotobacter sp. The indigenous Azotobacter strains with multiple PGP activities could be further used for commercial production.

Highlights

In agriculture, nitrogen deficiency directly influences the yield and profitability of crop plants worldwide and can be overcome by the application of inorganic chemical fertilizers [1]
Many plant growth promoting microorganisms such as Azotobacter, Rhizobium, and Pseudomonas are used as biofertilizers, which provide plant nutrition and maintain the soil health
Azotobacter is gram-negative, nonsymbiotic diazotrophic bacteria that belongs to the Azotobacteriaceae family that can fix an average of 20 kg N/ha/per year which can be further increased through inoculation of potent strains [5]

Summary

Introduction

Nitrogen deficiency directly influences the yield and profitability of crop plants worldwide and can be overcome by the application of inorganic chemical fertilizers [1]. The increased use of nitrogen based inorganic chemical fertilizers causes serious adverse effects on the physicochemical properties of soil, i.e., degradation of soil organic carbon (SOC) and soil acidification [2]. Thereby decreases the use of these inorganic chemical based fertilizers [3]. Many plant growth promoting microorganisms such as Azotobacter, Rhizobium, and Pseudomonas are used as biofertilizers, which provide plant nutrition and maintain the soil health. Especially from the genus Azotobacter, holds an important role in soil fertility [4], since it can provide fixed N2 to plants and promote plant growth by providing other necessary nutrients to plants. Azotobacter is gram-negative, nonsymbiotic diazotrophic bacteria that belongs to the Azotobacteriaceae family that can fix an average of 20 kg N/ha/per year which can be further increased through inoculation of potent strains [5]

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