Abstract
Soil salinity, being a part of natural ecosystems, is an increasing problem in agricultural soils throughout the world. Pseudomonas frederiksbergensis OS261 has already been proved to be an effective bio-inoculant for enhancing cold stress tolerance in plants, however, its effect on salt stress tolerance is unknown. The main aim of the present study was to elucidate P. frederiksbergensis OS261 mediated salt stress tolerance in red pepper. The plants were exposed to a salt stress using NaCl at the concentrations of 50, 100, and 150 mM after 12 days of transplantation, while plant growth and enzyme activity were estimated 50 days after sowing. The height in P. frederiksbergensis OS261 inoculated plants was significantly increased by 19.05, 34.35, 57.25, and 61.07% compared to un-inoculated controls at 0, 50, 100, and 150 mM of NaCl concentrations, respectively, under greenhouse conditions. The dry biomass of the plants increased by 31.97, 37.47, 62.67, and 67.84% under 0, 50, 100, and 150 mM of NaCl concentrations, respectively. A high emission of ethylene was observed in un-inoculated red pepper plants under salinity stress. P. frederiksbergensis OS261 inoculation significantly reduced ethylene emission by 20.03, 18.01, and 20.07% at 50, 100, and 150 mM of NaCl concentrations, respectively. Furthermore, the activity of antioxidant enzymes (ascorbate peroxidase, superoxide dismutase, and catalase) also varied in the inoculated red pepper plants. Salt stress resistance in the bacterized plants was evident from the improved antioxidant activity in leaf tissues and the decreased hydrogen ion concentration. Thus, we conclude that P. frederiksbergensis OS261 possesses stress mitigating property which can enhance plant growth under high soil salinity by reducing the emission of ethylene and regulating antioxidant enzymes.
Highlights
Abiotic stresses exert a serious impact on crop productivity throughout the world
A single colony of P. frederiksbergensis OS261 grown on a nutrient agar (NA) plate was transferred to 5 mL nutrient broth (NB) and incubated at 30◦C on a shaker (150 rpm) for 24 h
The plants inoculated with the bacterium developed longer roots (Figure 1A) compared to the un-inoculated controls after a period of 14 days under salinity stress
Summary
Abiotic stresses exert a serious impact on crop productivity throughout the world. Soil salinity is an alarming stress, which limits plant growth and affects crop production to a large extent (Allakhverdiev et al, 2000; Bano and Fatima, 2009; Bacilio et al, 2016). High amounts of potassium or calcium ions are needed for the proper functioning of plant metabolism, whereas increased uptake of sodium ion due to high salinity reduces the ionic uptake of potassium and calcium ions (Cheng et al, 2007), thereby negatively affecting the growth of plants. It disturbs plant cell division and elongation and reduces the rate of photosynthesis (Munns and Tester, 2008; Forieri et al, 2016). The microbes provide plants resistance to stress by enhancing the activity of the antioxidant enzymes and other non-enzymatic antioxidants (Gururani et al, 2013)
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