Salt-Tolerant PGPR Confer Salt Tolerance to Maize Through Enhanced Soil Biological Health, Enzymatic Activities, Nutrient Uptake and Antioxidant Defense

Abstract

Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can improve soil enzyme activities, which are indicators of the biological health of the soil, and can overcome the nutritional imbalance in plants. A pot trial was executed to evaluate the effect of inoculation of different salt-tolerant PGPR strains in improving soil enzyme activities. Three different salinity levels (original, 5, and 10 dS m–1) were used and maize seeds were coated with the freshly prepared inocula of ten different PGPR strains. Among different strains, inoculation of SUA-14 (Acinetobacter johnsonii) caused a maximum increment in urease (1.58-fold), acid (1.38-fold), and alkaline phosphatase (3.04-fold) and dehydrogenase (72%) activities as compared to their respective uninoculated control. Acid phosphatase activities were found to be positively correlated with P contents in maize straw (r = 0.96) and grains (r = 0.94). Similarly, a positive correlation was found between alkaline phosphatase activities and P contents in straw (r = 0.77) and grains (r = 0.75). In addition, urease activities also exhibited positive correlation with N contents in maize straw (r = 0.92) and grains (r = 0.91). Moreover, inoculation of Acinetobacter johnsonii caused a significant decline in catalase (39%), superoxide dismutase (26%) activities, and malondialdehyde contents (27%). The PGPR inoculation improved the soil’s biological health and increased the uptake of essential nutrients and conferred salinity tolerance in maize. We conclude that the inoculation of salt-tolerant PGPR improves soil enzyme activities and soil biological health, overcomes nutritional imbalance, and thereby improves nutrient acquisition by the plant under salt stress.

Plant salt response: Perception, signaling, and tolerance

“…Notably, multiple groups of root-associated microbes, including plantgrowth-promoting rhizobacteria (PGPR) and endophytic bacteria, are essential to improve plant tolerance to high salinity (Figure 3) (Qin et al, 2016;Vives-Peris et al, 2018). PGPR alleviates the toxicity of salt stress on plants mainly by regulating ionic homeostasis, accumulating osmolytes, activating antioxidant capacity, and enhancing essential nutrient uptake (Santos et al, 2018;Ha-Tran et al, 2021;Shabaan et al, 2022). For instance, a recent study suggested that the bacterial strain E. cloacae PM23 mediated salt tolerance in maize by modulating plant physiology, antioxidant defense, and compatible solute accumulation (Ali et al, 2022).…”

Stress-Tolerant Endophytic Isolate Priestia aryabhattai BPR-9 Modulates Physio-Biochemical Mechanisms in Wheat (Triticum aestivum L.) for Enhanced Salt Tolerance

“…Several studies have discovered that endophytic bacteria are important in alleviating salt stress in a range of agricultural plants [ 16 , 17 ]. For instance, PGP endophytic bacterium Cronobacter sp.…”

Dominance of Bacillus species in the wheat (Triticum aestivum L.) rhizosphere and their plant growth promoting potential under salt stress conditions

“… Akram et al (2016) also reported that some bacterial isolates from maize tolerate higher salinity levels and most of the bacterial growth was inhibited at a higher level of NaCl. Similarly, Shabaan et al (2022) also reported the existence of salt-tolerant PGPR conferring salt tolerance in maize plants.…”