Effect of Salt-Tolerant Bacterial Inoculations on Rice Seedlings Differing in Salt-Tolerance under Saline Soil Conditions

Abstract

Salt-tolerant plant growth-promoting rhizobacteria (PGPR) could be an alternative to alleviate salinity problems in rice plants grown in the coastal areas. This study was conducted to isolate and characterize salt-tolerant PGPR and observe their effects on the physiological and biochemical properties of rice plants grown under non-saline and saline glasshouse conditions. Three strains were selected based on their salt-tolerance and plant growth-promoting properties under in vitro saline conditions. These strains were identified as Bacillus tequilensis (UPMRB9), Bacillus aryabhattai (UPMRE6), and Providencia stuartii (UPMRG1) using a 16S rRNA technique. The selected strains were inoculated to three different rice varieties, namely BRRI dhan67 (salt-tolerant), Putra-1 (moderate salt-tolerant), and MR297 (salt-susceptible) under glasshouse conditions. Results showed that the MR297 rice variety inoculated with UPMRB9 produced the highest total chlorophyll content, with an increment of 28%, and lowest electrolyte leakage of 92%. The Putra-1 rice variety also showed a 156% total dry matter increase with the inoculation of this bacterial strain. The highest increase of relative water content and reduction of Na/K ratio were found upon inoculation of UPMRE6 and UPMRB9, respectively. The biggest significant effects of these bacterial inoculations were on relative water content, electrolyte leakage, and the Na/K ratio of the BRRI dhan67 rice variety under saline conditions, suggesting a synergistic effect on the mechanisms of plant salt-tolerance. This study has shown that the application of locally-isolated salt-tolerant PGPR strains could be an effective long-term and sustainable solution for rice cultivation in the coastal areas, which are affected by global climate change.

Rhizospheric Bacillus spp. Rescues Plant Growth Under Salinity Stress via Regulating Gene Expression, Endogenous Hormones, and Antioxidant System of Oryza sativa L

“…Arora et al (2010) reported that, under salinity stress, bacteria can bind Na ions through the secretion of EPS, which reduces Na toxicity in soil. A higher population of EPS-producing bacteria in the root rhizosphere reduces the concentration of Na availability for uptake and alleviates the NaCl effect on plants (Shultana et al, 2020b). In current observations, a decrease in Na content in bacterial-inoculated rice plants might be due to their EPS-producing activity (Supplementary Figure 1B).…”

“…Amacher et al (2000) revealed that PGPB reduces salinity stress in maize and wheat by ∼50%. Similarly, leaf chlorophyll concentration is an indicator of salt tolerance and responds to increasing salinity stress (Habib et al, 2016;Shultana et al, 2020b). Salinity stress increases chlorophyllase activity, decreases chlorophyll synthesis, and destroys pigment proteins, decreasing chlorophyll pigment in alfalfa, lettuce, wheat, okra, and basil (Han and Lee, 2005;Bashan et al, 2006;Heidari and Golpayegani, 2012;Habib et al, 2016;Ansari et al, 2019).…”

Plant Growth-Promoting Bacteria as an Emerging Tool to Manage Bacterial Rice Pathogens

“…Recently, inoculation of salt-tolerant PGPB, namely, Bacillus tequilensis strain UPMRB9 and Bacillus aryabhattai strain UPMRE6 on rice plants were shown to have beneficial effects on photosynthesis, transpiration, and stomatal conductance [ 114 ]. Shultana et al demonstrated that the inoculation of B. tequilensis strain UPMRB9 on the MR297 rice variety improved total chlorophyll content by 28% and reduced electrolyte leakage by 92% [ 115 ]. Increments of relative water content and reduction in the Na/K ratio were also found upon inoculation of B. tequilensis strain UPMRB9 and B. aryabhattai strain UPMRE6 on rice plants.…”

Plant-Growth-Promoting Bacteria Mitigating Soil Salinity Stress in Plants

“…Other studies have reported that the inoculation of PGPB (P. fluorescens biotype F, P. fluorescens CECT 378T, B. tequilensis, B. aryabhattai, Providencia stuartii, Pantoea agglomerans, or Arthrobacter sp.) in plant rhizosphere under salinity stress resulted in an increased K + /Na + ratio [4,76,128,129]. All PGPB presented various PGP traits, the combined action of which leads to the amelioration of salinity stress to plants.…”