Abstract
Use of Plant growth promoting rhizobacteria (PGPR) is a promising strategy to improve the crop production under optimal or sub-optimal conditions. In the present study, five diazotrophic salt tolerant bacteria were isolated from the roots of a halophyte, Arthrocnemum indicum. The isolates were partially characterized in vitro for plant growth promoting traits and evaluated for their potential to promote growth and enhanced salt tolerance in peanut. The 16S rRNA gene sequence homology indicated that these bacterial isolates belong to the genera, Klebsiella, Pseudomonas, Agrobacterium, and Ochrobactrum. All isolates were nifH positive and able to produce indole -3-acetic acid (ranging from 11.5 to 19.1 μg ml−1). The isolates showed phosphate solubilisation activity (ranging from 1.4 to 55.6 μg phosphate /mg dry weight), 1-aminocyclopropane-1-carboxylate deaminase activity (0.1 to 0.31 μmol α-kB/μg protein/h) and were capable of reducing acetylene in acetylene reduction assay (ranging from 0.95 to 1.8 μmol C2H4 mg protein/h). These isolates successfully colonized the peanut roots and were capable of promoting the growth under non-stress condition. A significant increase in total nitrogen (N) content (up to 76%) was observed over the non-inoculated control. All isolates showed tolerance to NaCl ranging from 4 to 8% in nutrient broth medium. Under salt stress, inoculated peanut seedlings maintained ion homeostasis, accumulated less reactive oxygen species (ROS) and showed enhanced growth compared to non-inoculated seedlings. Overall, the present study has characterized several potential bacterial strains that showed an enhanced growth promotion effect on peanut under control as well as saline conditions. The results show the possibility to reduce chemical fertilizer inputs and may promote the use of bio-inoculants.
Highlights
Peanut (Arachis hypogaea L) is an important cash crop of the leguminous family, grown in most of the arid, and semi-arid regions
Five different bacterial isolates (MBE01, MBE02, MBE03, MBE04, and MBE05) obtained from roots of A. indicum were capable to grow on nitrogen free semi-solid NFb medium containing up to 4% NaCl and malate as sole carbon source
The growth of bacteria under these conditions indicated the ability of bacterial isolates to fix atmospheric N, which was further confirmed by amplification of nifH gene and the acetylene reduction assay
Summary
Peanut (Arachis hypogaea L) is an important cash crop of the leguminous family, grown in most of the arid, and semi-arid regions. Salinity stress has detrimental effects on almost every aspect of peanut growth and development including seed germination, early seedling establishment, photosynthesis, pod formation, total biomass, and on yield production (Salwa et al, 2010; Qin et al, 2011; El-Akhal et al, 2013). It is, necessary to improve the salinity tolerance of peanut to minimize the yield loss
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