Abstract
The present study was conducted to characterize the native plant growth promoting (PGP) bacteria from wheat rhizosphere and root-endosphere in the Himalayan region of Rawalakot, Azad Jammu and Kashmir (AJK), Pakistan. Nine bacterial isolates were purified, screened in vitro for PGP characteristics and evaluated for their beneficial effects on the early growth of wheat (Triticum aestivum L.). Among nine bacterial isolates, seven were able to produce indole-3- acetic acid in tryptophan-supplemented medium; seven were nitrogen fixer, and four were able to solubilize inorganic phosphate in vitro. Four different morphotypes were genotypically identified based on IGS-RFLP fingerprinting and representative of each morphotype was identified by 16S rRNA gene sequencing analysis except Gram-positive putative Bacillus sp. Based on 16S rRNA gene sequence analysis, bacterial isolates AJK-3 and AJK-9 showing multiple PGP-traits were identified as Stenotrophomonas spp. while AJK-7 showed equal homologies to Acetobacter pasteurianus and Stenotrophomonas specie. Plant inoculation studies indicated that these Plant growth-promoting rhizobacteria (PGPR) strains provided a significant increase in shoot and root length, and shoot and root biomass. A significant increase in shoot N contents (up to 76%) and root N contents (up to 32%) was observed over the un-inoculated control. The study indicates the potential of these PGPR for inoculums production or biofertilizers for enhancing growth and nutrient content of wheat and other crops under field conditions. The study is the first report of wheat associated bacterial diversity in the Himalayan region of Rawalakot, AJK.
Highlights
Chemical fertilizers are generally used to supply essential nutrients to the soil–plant system throughout the world
Six bacteria were obtained from wheat rhizosphere soil while three from root interior (Table 1)
The plant growthpromoting rhizobateria (PGPR) isolate AJK-3 was identified as Stenotrophomonas rhizophila strain having 99% similarity with the reported gene sequence
Summary
Chemical fertilizers are generally used to supply essential nutrients to the soil–plant system throughout the world. Several mechanisms have been postulated to explain how PGPR benefit the host plant These include: (a) the ability to produce plant growth regulators or phytohormones such as indole acetic acid (IAA), cytokinins, and gibberellins (Glick, 1995; Marques et al, 2010); (b) enhancing asymbiotic N2 fixation (Sahin et al, 2004; Khan, 2005); (c) solubilizing inorganic phosphate and mineralization of organic phosphate and/ or other nutrients (Glick, 1995; Jeon et al, 2003); (d) antagonistic effect against phytopathogenic microorganisms by production of siderophores, the synthesis of antibiotics, enzymes, and/or fungicidal compounds, and competition with detrimental microorganisms (Dey et al, 2004; Lucy et al, 2004)
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