Abstract
The present research was conducted to characterize the indigenous plant growth promoting (PGP) Azotobacter strains isolated from plant root interface of semi-arid regions of Rajasthan (India) and to study their potential to be used as bio-fertilizers. A total of 172 Azotobacter strains were isolated, purified and based on the morphological test i.e. gram staining, pigmentation, cyst formation, fluorescence etc, broadly classified as Azotobacter. Further the secluded strains were examined for biochemical analysis and plant growth promoting characters. All the isolates showed different biochemical characteristics and significant PGP traits. IAA activity of the Azotobacter strains ranges from 54.5-6000 µg/mL. Ammonia, HCN and siderophore was produced by 92.4%, 78.4% and 80.23% of the total isolates respectively. Solubilization of phosphate was observed in 97.6% of the total isolates. These strains were also characterized for qualitative and quantitative N2 fixation abilities and the result indicated that 114 strains showed positive results on nitrogen free malate agar medium (NFMM) containing bromothymol blue (BTB) and able to produce 18.93-475.6 N-moles C2H4 mg protein−1 h−1 of acetylene reduced by Azotobacter strains. In vitro pot studies revealed that the selected native Azotobacter strains having high ARA results significantly increase the plant growth characters. Shoot length, root length, root number and chlorophyll content and leaf number increases by 45.62%, 17.60%, 97.49%, 49.69% and 27.83% respectively in pot inoculated with AZO23-3 as compared to control. These effective strains can further be utilized for development of effective microbial formulations.
Highlights
Excessive use of inorganic chemical-based fertilizers is cost intensive and creates the problem of soil, agriculture and environmental management strategies
The present research was conducted to characterize the indigenous plant growth promoting (PGP) Azotobacter strains isolated from plant root interface of semi-arid regions of Rajasthan (India) and to study their potential to be used as bio-fertilizers
These strains were characterized for qualitative and quantitative N2 fixation abilities and the result indicated that 114 strains showed positive results on nitrogen free malate agar medium (NFMM) containing bromothymol blue (BTB) and able to produce 18.93-475.6 N-moles C2H4 mg protein−1 h−1 of acetylene reduced by Azotobacter strains
Summary
Excessive use of inorganic chemical-based fertilizers is cost intensive and creates the problem of soil, agriculture and environmental management strategies. Biofertilizers are organic fertilizers, which are composed of beneficial living microbial inoculants These microorganisms promotes growth of plants and the healthy structure of soils by converting nutritionally nitrogen, phosphorus, potassium and many essential elements from unavailable to available form for plants[2]. One of important bio-inoculants is Azotobacter which is gram negative, aerobic and free-living N2-fixing bacteria non-symbiotically fixes the atmospheric nitrogen, degrades cellulose, phosphates and most importantly it degrades lignin in trace amounts[4,5]. It is oval or spherical in shape and capable for forming thick-walled cysts under favorable condition[6]. This study was designed to isolate and characterize Azotobacter for their various plant growth promoting characteristics and N2 fixing attributes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
