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

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.

Halotolerant Plant Growth-Promoting Rhizobacteria Isolated From Saline Soil Improve Nitrogen Fixation and Alleviate Salt Stress in Rice Plants

“…Rhizobacteria can act as stimulants and produce hormones such as auxins and gibberellins to help promote plant growth ( Jain et al, 2021 ). Salinity stress can inhibit enzyme activity and cause metabolic changes in plant cells due to the accumulation of too high salts in the cytoplasm.…”

Biofertilizers: An ecofriendly technology for nutrient recycling and environmental sustainability

“…Different species of Azotobacter fix 20–40 Kg/ha/year of nitrogen and inoculation of selected strains enhanced germination and vigour of young plants along with grain yield in wheat ( Kader et al, 2002 ). Jain et al (2021) found that all the isolated 24 Azotobacter strains showed IAA, siderophore, HCN, and ammonia production, whereas seven Azotobacter strains showed phosphate solubilization. Significant diversity was revealed among all the isolates by Amplified Ribosomal DNA Restriction Analysis (ARDRA) and the dendrogram differentiated twenty-four of the strains into two major clusters at a similarity coefficient of 0.64.…”

“… Types of biofertilizer Bacterial strain used Plant growth promoting activity Effect on plant productivity parameters References Nitrogen- fixing bacteria Azotobacter sp. strain Avi2 (MCC 3432) Nitrogen fixation, production of IAA, siderophore improved vegetative and reproductive growth in rice Banik and Dangar, 2019 Azotobacter chroococcum, A. vinelandii Nitrogen fixation, P solubilization, production of NH 3 , HCN, IAA Increased shoot and root length, leaf and root number, chlorophyll content of maize Jain et al, 2021 Herbaspirillum seropedicae (strain ZAE94) Nitrogen fixation, production of siderophore, IAA Enhanced mineral uptake, increased diameter, weight, length of ear, number of grains/rows, cob weight and grain yield Ávila et al, 2020 Enterobacter cloacae (PGLO9) Nitrogen fixation, phosphorous solubilization, siderophore production, ACC deaminase Enhanced potato growth and yield, significant increase in vegetative growth parameters including root and shoot length, root as well as shoot biomass Verma and Agrawal, 2018 Bradyrhizobium sp. Nitrogen fixation, siderophore and IAA production, P solubilisation Increased vegetative parameters and seed yield in mung bean Alkurtany et al, 2018 Rhizobium meliloti Nitrogen fixation, production of siderophore and chitinase Increased growth and yield, pods quality and better use of nitrogen in peanut Mondal et al, 2020 Phosphate-solubilizing bacteria (PSB) Pseudomonas stutzeri (CSP03), Bacillus subtilis (TTP02), Pseudomonas putida (PHP03) Solubilization of P and zinc, IAA, N 2 fixation, siderophore, NH 3 production Enhanced plant growth in arid soils El-Sayed et al, 2014 Alcaligenes faecalis sub sp.…”

“…Azotobacter is one of the prime members among free-living diazotrophic bacteria ( Aasfar et al, 2021 ). Different Azotobacter strains have been isolated from neutral to alkaline soil and usually found in the rhizosphere of various non-legume crops including cotton, wheat, rice and vegetables ( Sindhu and Lakshminaryana, 1982 ; Jain et al, 2021 ). Arable cultivated soil is chiefly inhabited by Azotobacter chroococcum along with Azotobacter insignis, A. beijerinckii, A. macrocytogens and A. vinelandii , which potentially fixes up to 2–18 mg N/g of carbon used in culture medium ( Moraditochaee et al, 2014 ; Smercina et al, 2019 ).…”

Overview of biofertilizers in crop production and stress management for sustainable agriculture

“…Inoculation of Bradyrhizobium japonicum in soybean plants improved plant biomass, nodulation, and N fixation (Htwe et al, 2019 ). Azotobacter chroococcum improved the plant height and chlorophyll content in maize plants (Jain et al, 2021 ). Bradyrhizobium sp.…”