Halotolerant PGPR Stenotrophomonas maltophilia BJ01 Induces Salt Tolerance by Modulating Physiology and Biochemical Activities of Arachis hypogaea

Abstract

Arachis hypogaea (Peanut) is one of the most important cash crops grown for food and oil production. Salinity is a major constraint for loss of peanut productivity, and halotolerant plant growth promoting bacteria not only enhance plant-growth but also provide tolerance against salt stress. The potential of halotolerant bacterium Stenotrophomonas maltophilia BJ01 isolated from saline-soil was explored to enhance the growth of peanut plants under salt stress conditions. Interaction of S. maltophilia BJ01 enhances the growth of the peanut plants and protects photosynthetic pigments under salt stress. Lower electrolyte leakage (about 20%), lipid peroxidation (2.1 μmol g –1 Fw), proline (2.9 μg mg –1 Fw) content and H 2 O 2 (55 μmol g –1 Fw) content were observed in plants, co-cultivated with PGPR compared to untreated plants under stress condition. The growth hormone auxin (0.4 mg g –1 Fw) and total amino acid content (0.3 mg g –1 Fw) were enhanced in plants co-cultivated with PGPR under stress conditions. Overall, these results indicate the beneficial effect of S. maltophilia BJ01 on peanut plants under salt (100 mM NaCl) stress conditions. In conclusion, bacterium S . maltophilia BJ01 could be explored further as an efficient PGPR for growing legumes especially peanuts under salt stress conditions. However, a detailed agronomic study would be needed to ascertain its commercial role.

Roles of Plant Growth-Promoting Rhizobacteria (PGPR) in Stimulating Salinity Stress Defense in Plants: A Review

“…Likewise, an increase in SL, RL, SFW, RFW, and Tchl was observed in the L. adecarboxylata -inoculated tomato plants with 22%, 16%, 28%, 51%, and 13% higher than those in the control plants, respectively [ 104 ]. The same trend in increased vegetative parameters was found in the studies of Li and Jiang [ 42 ], Khan et al [ 40 ], Sapre et al [ 44 ], Sarkar et al [ 49 ], Akram et al [ 45 ], and Alexander et al [ 48 ]. The increase in Tchl was widely observed in various studies, however, the extent to which these pigments increased depends on PGPR strains, NaCl treatments, and plant species.…”

“…[ 41 ], maize ( Zea mays L.) [ 42 ], and cucumber ( Cucumis sativus L.) [ 43 ] seedlings, respectively. However, contrary to these studies, the reduced contents of Tchl were tremendously varied from 22% in oat ( Avena sativa ) seedlings [ 44 ], 41–42% in tomato ( Solanum lycopersicum L.) seedlings [ 45 , 46 ], 44% in tomato ( Solanum lycopersicum L.) plants [ 47 ], 50% in peanut ( Arachis hypogaea ) seedlings [ 48 ], 56% in rice ( Oryza sativa L.) seedlings [ 49 ] to 61% in rapeseed ( Brassica napus L.) plants [ 30 ], respectively. In addition, under salt detriment, 16% of Car decreased in the ginseng plantlets, 19% of Car reduced in the mung bean plants, and 49% of Car decreased in the tomato seedings were reported by Sukweenadhi et al (2018) [ 50 ], Shahid et al (2021) [ 36 ], and Akram et al (2019) [ 45 ], respectively.…”

“…As a byproduct of LP, malonaldehyde (MDA) has been largely used as an important indicator to evaluate the extent of damaging effects caused by ROS and oxidative stress combination on membrane lipids to reduce membrane stability [ 56 ]. The MDA content was tremendously increased by 36% in ginseng root plantlets [ 50 ], 39% in maize [ 42 ], 47% in peanut [ 48 ], 70% in chickpea [ 35 ], 131% in oat [ 44 ], 153% in mung bean [ 36 ], and 300% in rice seedlings [ 57 ], indicating an severe damage to cell membrane integrity and/or membrane permeability during salinity exposure [ 58 ].…”

“…The increase in Tchl was widely observed in various studies, however, the extent to which these pigments increased depends on PGPR strains, NaCl treatments, and plant species. For instance, only a 5% Chl increase in maize seedling bacterized with B. aquimaris DY-3 was noticed by Li and Jiang (2017) [ 42 ], whereas a 12% increase in P. putida H-2-3-inoculated soybean seedlings [ 41 ], a 17% increase in S. maltophilia BJ01-peanut seedlings [ 48 ], a 29% increase in K. sacchari -treated mung bean seedlings [ 36 ], a 41% increase in Bacillus megaterium BMA12-bacterized tomato seedlings [ 45 ], 46% in B. pupilus -inoculated rice seedlings [ 40 ], and 60% in A. brasilense -treated white clover plants [ 58 ].…”

“…However, the reduction or increase of these enzymes in PGPB-inoculated plants in response to salt conditions remains controversial. The decreased profiles of OS and/or ROS-scavenging enzymes were remarked by Kang et al (2014 a) [ 43 ], Kang et al (2014 b) [ 41 ], Barnawal et al (2014) [ 95 ], Khan et al (2016) [ 40 ], Bhise et al (2017) [ 99 ], Abd_Allah et al (2018) [ 35 ], Sapre et al (2018) [ 44 ], Ansari et al (2019) [ 51 ], Alexander et al (2020) [ 48 ], Misra and Chauhan (2020) [ 106 ], and Shahid et al (2021) [ 36 ]. Specifically, in the study of Kang et al (2014a) [ 43 ], the activities of CAT, PPO, and POD enzymes and the PPs contents in the inoculated plants (e.g., B. cepacia SE4, Promicromonospora sp.…”