Dual Microbial Inoculation, a Game Changer? – Bacterial Biostimulants With Multifunctional Growth Promoting Traits to Mitigate Salinity Stress in Spring Mungbean

Abstract

Soil microbes play a vital role in improving plant growth, soil health, ameliorate biotic/abiotic stress and enhance crop productivity. The present study was aimed to investigate a coordinated effect of compatible consortium [salt tolerating Rhizobium and rhizobacterium with 1-aminocyclopropane-1-carboxylate (ACC) deaminase] in enhancing plant growth promoting (PGP) traits, symbiotic efficiency, nutrient acquisition, anti-oxidative enzymes, grain yield and associated profitability in spring mungbean. We identified a non-pathogenic compatible Rhizobium sp. LSMR-32 (MH644039.1) and Enterococcus mundtii LSMRS-3 (MH644178.1) from salt affected areas of Punjab, India and the same were assessed to develop consortium biofertilizer based on salt tolerance, multifarious PGP traits, antagonistic defense activities and presence of nifH, acds, pqq, and ipdc genes. Indole Acetic acid (IAA), P-solubilization, biofilm formation, exo-polysaccharides, siderophore, salt tolerance, ACC deaminase activities were all found highly significant in dual inoculant (LSMR-32 + LSMRS-3) treatment compared to LSMR-32 alone. Under saline soil conditions, dual inoculant showed a higher seed germination, plant height, biomass, chlorophyll content and macro and micro-nutrient uptake, than un-inoculated control. However, symbiotic (nodulation, nodule biomass and leghaemoglobin content) and soil quality parameters (phosphatase and soil dehydrogenase enzymes) increased numerically with LSMR-32 + LSMRS-3 over Rhizobium sp. LSMR-32 alone. Dual bacterial inoculation (LSMR-32 + LSMRS-3) increased the proline content (2.05 fold), anti-oxidative enzymes viz., superoxide dismutase (1.50 fold), catalase (1.43 fold) and peroxidase (3.88 folds) in contrast to control treatment. Decreased Na+ accumulation and increased K+ uptake resulted in favorable K+/Na+ ratio through ion homeostasis. Co-inoculation of Rhizobium sp. LSMR-32 and Enterococcus mundtii LSMRS-3 significantly improved the grain yield by 8.92% and led to superior B: C ratio over Rhizobium sp. alone under salt stress. To best of our knowledge this is perhaps the first field report from Indian soils that largely describes dual inoculation of Rhizobium sp. LSMR-32 and Enterococcus mundtii LSMRS-3 and the same can be considered as a game-changer approach to simultaneously induce salt tolerance and improve productivity in spring mungbean under saline stress conditions.

Differential Root Exudation and Architecture for Improved Growth of Wheat Mediated by Phosphate Solubilizing Bacteria

“…Besides making soluble P available for plant uptake, P-solubilizing bacteria are involved in plant growth promotion by the production of beneficial metabolites, such as phytohormones like indole acetic acid (IAA), antibiotics or siderophores, aminocyclopropane-1-carboxylate deaminase (ACC), nitrogen fixation, zinc solubilization, and antimicrobial activity against soil-borne plant pathogens (Olanrewaju et al, 2017;Chouyia et al, 2020;Kumawat et al, 2020;Hakim et al, 2021). Furthermore, plant growth-promoting rhizobacteria (PGPR) may indirectly stimulate plant growth and help the plants to alleviate oxidative stress by enhanced production of antioxidant enzymes [e.g., catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD)] in plant tissues (Batool et al, 2020;Bhat et al, 2020;Ha-Tran et al, 2021).…”

Use of Microbial Biostimulants to Increase the Salinity Tolerance of Vegetable Transplants

“…Every microorganism inoculated through the microbial biostimulants could have determined the growth-promoting effect on lettuce and tomato seedlings. The interaction between AMF, PGPR, and other microbes (microbial consortium) may determine a synergistic effect that was confirmed by improved plant growth, nutrition, and yield as well as mitigated salinity stress in lettuce, tomato, and other crops [13,56,82,85,[117][118][119]. As showed by the values of the morpho-physiological parameters and PCA, the consortium of microorganisms with the highest biodiversity was more effective in alleviating salt stress.…”

“…Many strategies can be used to increase salt tolerance of vegetable crops, such as conventional breeding, gene cloning, and genetic engineering but the complex salinity tolerance mechanism and limited genetic variability that can be found in germplasm lead to limited or no success in alleviating salt stress [13,14]. The difficulties found in the development of salt-tolerant cultivars can be ascribed to the lack of knowledge about the genetics of vegetable crops, the composite polygenic nature of the salt tolerance characters, and the wide variation of gene response in different environmental conditions [15].…”

Amelioration of Saline Stress on Chia (Salvia hispanica L.) Seedlings Inoculated With Halotolerant Plant Growth-Promoting Bacteria Isolated From Hypersaline Environments

“…They hold the biotechnological potential to produce secondary metabolites antibiotics, antitumor agents, and enzymes, and to favor beneficial plant-microbe interactions through plant growth-promoting features (Jorquera et al, 2016). Many authors have described the use of bacteria isolated from hypersaline environments, particularly from the rhizosphere of halotolerant plants located in saline deserts, hypersaline soils, and salt-affected areas, as growth promoters in traditional crops (Sáenz-Mata et al, 2016;Mukhtar et al, 2019;Wu et al, 2019;Kumawat et al, 2021). Thus, rhizosphere microbiomes play an essential role in the survival of plants in nature, and growthpromoting rhizobacteria isolated from salt-tolerant plants could be crucial for alleviating soil salinity stress during plant growth (Banerjee et al, 2019).…”