Beneficial Soil Bacterium Pseudomonas frederiksbergensis OS261 Augments Salt Tolerance and Promotes Red Pepper Plant Growth

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.

The Pivotal Role of Ethylene in Plant Growth

“…For instance, plants overexpressing NEIP2 or TCTP , genes encoding proteins interacting with the Nicotiana tabacum ethylene receptor, show decreased ethylene sensitivity but improved growth 13 , 14 . Similarly, Pseudomonas frederiksbergensis , a soil bacterium that reduces plant sensitivity to ethylene, promotes the growth of red pepper plants [15] . Finally, some rhizosphere bacteria that promote plant growth do so by expressing ACC-DEAMINASE , decreasing the levels of 1-aminocyclopropane-1-carboxylic acid (ACC) in plants exposed to stress, and this has a positive effect on growth [16] .…”

PGPR‐mediated induction of systemic resistance and physiochemical alterations in plants against the pathogens: Current perspectives

“…The emission of ethylene reduced when the red pepper plant was treated with the Pseudomonas frederiksbergensis compared to the noninoculated plant under saline stress conditions. It also regulated the antioxidant enzymes and decreased hydrogen ion concentration [140].…”

Beneficial Endophytic Bacterial Populations Associated With Medicinal Plant Thymus vulgaris Alleviate Salt Stress and Confer Resistance to Fusarium oxysporum

“…The inoculated seedlings were aseptically transplanted into plastic pots (12 cm high × 10 cm in diameter) filled with autoclaved compost: sand: perlite: peat (1:1:1:1, v/v/v/v) and placed in a growth chamber at 25 ± 2°C and a 14-h photoperiod. After 3 days, 10 ml of the bacterial suspension (10 8 CFU/mL) was added near the root zone and salinity was increased gradually by applying a sodium chloride solution to each pot on alternative days to avoid osmotic shock to reach final salt concentrations of 50, 100, 150, and 200 mM and the desired salt concentrations of 50, 100, 150, and 200 mM were achieved after 2, 4, 6, and 8 days, respectively (Nejad and Johnson, 2000;Chatterjee et al, 2017). Parallel controls were maintained by cultivating tomato plants with autoclaved compost without inoculation of endophytes and irrigating with tap water.…”