Characterization of salt-tolerant plant growth-promoting rhizobacteria and the effect on growth and yield of saline-affected rice

Abstract

In this study, we characterized, identified, and determined the effect of salt-tolerant PGPR isolated from coastal saline areas on rice growth and yield. A total of 44 bacterial strains were isolated, and 5 were found to be tolerant at high salt concentration. These isolates were further characterized for salinity tolerance and beneficial traits through a series of quantitative tests. Biochemical characterization showed that bacterial survivability decreases gradually with the increase of salt concentration. One of the strains, UPMRB9, produced the highest amount of exopolysaccharides when exposed to 1.5M of NaCl. Moreover, UPMRB9 absorbed the highest amount of sodium from the 1.5M of NaCl-amended media. The highest floc yield and biofilm were produced by UPMRE6 and UPMRB9 respectively, at 1M of NaCl concentration. The SEM observation confirmed the EPS production of UPMRB9 and UPMRE6 at 1.5M of NaCl concentration. These two isolates were identified as Bacillus tequilensis and Bacillus aryabhattai based on the 16S rRNA gene sequence. The functional group characterization of EPS showed the presence of hydroxyl, carboxyl, and amino groups. This corresponded to the presence of carbohydrates and proteins in the EPS and glucose was identified as the major type of carbohydrate. The functional groups of EPS can help to bind and chelate Na + in the soil and thereby reduces the plant's exposure to the ion under saline conditions. The plant inoculation study revealed significant beneficial effects of bacterial inoculation on photosynthesis, transpiration, and stomatal conductance of the plant which leads to a higher yield. The Bacillus tequilensis and Bacillus aryabhattai strains showed good potential as PGPR for salinity mitigation practice for coastal rice cultivation.

Beneficial effects of endophytic Pantoea ananatis with ability to promote rice growth under saline stress

“…2018; Shultana et al . 2020). For instance, the application of salt‐tolerant Bacillus tequilensis UPMRB9 increased the grain yield of rice by 57·55% in saline conditions (Shultana et al .…”

“…For instance, the application of salt‐tolerant Bacillus tequilensis UPMRB9 increased the grain yield of rice by 57·55% in saline conditions (Shultana et al . 2020). The increase of rice productivity by PGPB inoculation was mainly achieved through the enhancement of nutrient uptake and alleviation of antioxidant stress (Rima et al .…”

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

“…The results suggested that PGPB play multifaceted roles in crosstalk among stresses and phytohormones in rice especially in osmolyte biosynthesis and subsequently osmotic adjustment. 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 ].…”

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

“…Of the 230 million ha of irrigated land worldwide, 45 million ha (20%) has been affected by high salt concentrations (Munns, 2005;Hoang et al, 2016). It is predicted that 50% of arable land will be threatened by 2050 due to soil salinization (Khan et al, 2019b,e;Shultana et al, 2020a). The salinization of agricultural lands occurs because of the accumulation of salts in the soil, particularly sodium and chloride ions, which leads to hypertonic stress (Kumar et al, 2020).…”

“…Currently, the use of plant growthpromoting bacteria (PGPB) to ameliorate abiotic stress is gaining importance in agricultural biotechnology and momentum for consideration (Nautiyal et al, 2013;Santos et al, 2018) by various direct and indirect mechanisms, such as the production of indole-3-acetic acid (IAA), exopolysaccharide (EPS) and organic acid siderophore, and phosphate solubilization (Nautiyal et al, 2013). These beneficial plant-microbe interactions are very frequent in nature and act as elicitors for tolerance to abiotic stress, including salinity stress (Nautiyal et al, 2013;Shultana et al, 2020a). Previously published reports showed that PGPB has been used for the mitigation of salinity stress in cucumber (Kang et al, 2014;Kartik et al, 2020), tomato (Kang et al, 2019), soybean (Khan et al, 2019b,c), rice (Nautiyal et al, 2013;Mukherjee et al, 2019) lettuce, and maize (Rojas-Tapias et al, 2012;Rafiq et al, 2020) plants.…”