AUTHOR=Mir Mohammad Imran , Hameeda Bee , Quadriya Humera , Kumar B. Kiran , Ilyas Noshin , Kee Zuan Ali Tan , El Enshasy Hesham Ali , Dailin Daniel Joe , Kassem Hazem S. , Gafur Abdul , Sayyed R. Z. 

TITLE=Multifarious Indigenous Diazotrophic Rhizobacteria of Rice (Oryza sativa L.) Rhizosphere and Their Effect on Plant Growth Promotion

JOURNAL=Frontiers in Nutrition

VOLUME=8

YEAR=2022

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2021.781764

DOI=10.3389/fnut.2021.781764

ISSN=2296-861X

ABSTRACT=<p>A diverse group of rhizobacteria persists in the rhizospheric soil, on the surface of roots, or in association with rice plants. These bacteria colonize plant root systems, enhance plant growth and crop yield. Indigenous rhizobacteria are known to promote soil health, grain production quality and serve as sustainable bioinoculant. The present study was aimed to isolate, identify and characterize indigenous plant growth promoting (PGP) diazotrophic bacteria associated with the rhizosphere of rice fields from different areas of Jammu and Kashmir, India. A total of 15 bacteria were isolated and evaluated for various PGP traits, antagonistic activity against phytopathogens, production of hydrolytic enzymes and biofilm formation under <italic>in-vitro</italic> conditions. The majority of the isolated bacteria were Gram-negative. Out of 15 bacterial isolates, nine isolates produced IAA (12.24 ± 2.86 to 250.3 ± 1.15 μg/ml), 6 isolates exhibited phosphate solubilization activity (36.69 ± 1.63 to 312.4 ± 1.15 μg/ml), 7 isolates exhibited rock phosphate solubilization while 5 isolates solubilized zinc (10–18 mm), 7 isolates showed siderophore production, 8 isolates exhibited HCN production, 6 isolates exhibited aminocyclopropane-1-carboxylate (ACC) deaminase activity, 13 isolates exhibited cellulase activity, nine isolates exhibited amylase and lipase activity and six isolates exhibited chitinase activity. In addition, 5 isolates showed amplification with <italic>the nifH</italic> gene and showed a significant amount of nitrogenase activity in a range of 0.127–4.39 μmol C<sub>2</sub>H<sub>4</sub>/mg protein/h. Five isolates viz., IHK-1, IHK-3, IHK-13, IHK-15 and IHK-25 exhibited most PGP attributes and successfully limited the mycelial growth of <italic>Rhizoctonia solani</italic> and <italic>Fusarium</italic> oxysporum <italic>in-vitro</italic>. All the five bacterial isolates were identified based on morphological, biochemical and 16S rDNA gene sequencing study, as <italic>Stenotrophomonas maltophilia, Enterobacter</italic> sp., <italic>Bacillus</italic> sp., <italic>Ochrobactrum haematophilum</italic> and <italic>Pseudomonas aeruginosa</italic>. Rice plants developed from seeds inoculated with these PGP strains individually had considerably higher germination percentage, seed vigor index and total dry biomass when compared to control. These findings strongly imply that the PGP diazotrophic bacteria identified in this work could be employed as plant growth stimulators in rice.</p>