Halotolerant bacteria get adapted to a saline environment through modified physiological/structural characteristics and may provide stress tolerance along with enhanced growth to the host plants by different direct and indirect mechanisms. This study reports on multiple halotolerant plant growth-promoting rhizobacteria isolated from the coastal soils in Bangladesh, in fields where the halophytic wild rice Oryza coarctata is endemic. The aim was to find halotolerant bacteria for potential use as biofertilizer under normal/salt-stressed conditions. In this study, eight different strains were selected from a total of 20 rhizobacterial isolates from the saline-prone regions of Debhata and Satkhira based on their higher salt tolerance. 16S rRNA gene sequencing results of the rhizobacterial strains revealed that they belonged to Halobacillus, Bacillus, Acinetobactor, and Enterobactor genera. A total of ten halotolerant rhizobacteria (the other 2 bacteria were previously isolated and already reported as beneficial for rice growth) were used as both single inoculants and in combinations and applied to rice growing in pots. To investigate their capability to improve rice growth, physiological parameters such as shoot and root length and weight, chlorophyll content at the seedling stage as well as survival and yield at the reproductive stage were measured in the absence or presence (in concentration 40 or 80 mmol/L) of NaCl and in the absence or presence of the rhizobacteria. At the reproductive stage, only 50% of the uninoculated plants survived without setting any grains in 80 mmol/L NaCl in contrast to 100% survival of the rice plants inoculated with a combination of the rhizobacteria. The combined halotolerant rhizobacterial inoculations showed significantly higher chlorophyll retention as well as yield under the maximum NaCl concentration applied compared to application of single species. Thus, the use of a combination of halotolerant rhizobacteria as bioinoculants for rice plants under moderate salinity can synergistically alleviate the effects of stress and promote rice growth and yield.

Department of Biochemistry and Biotechnology University of Barishal Barishal Bangladesh

Plant Biotechnology Laboratory Department of Biochemistry and Molecular Biology University of Dhaka Dhaka Bangladesh

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Abdullahi IN, Isah AD, Chuwang PZ (2012) Effect of biofertilizer application on growth of Vitellaria paradoxa seedlings. J Res Environ Sci Toxicol 1:2315–5698

Ambreetha S, Chinnadurai C, Marimuthu P, Balachandar D (2018) Plant-associated Bacillus modulates the expression of auxin-responsive genes of rice and modifies the root architecture. Rhizosphere 5:57–66. https://doi.org/10.1016/j.rhisph.2017.12.001 DOI

Bapiri A, Asgharzadeh A, Mujallali H, Pazira E (2012) Evaluation of zinc solubilization potential by different strains of fluorescent Pseudomonads. J Appl Sci Environ Manag 16:295–298

Berg G (2009) Plant-microbe interactions promoting plant growth and health: perspectives for controlled use of microorganisms in agriculture. Appl Microbiol Biotechnol 84:11–18. https://doi.org/10.1007/s00253-009-2092-7 PubMed DOI

Bharti N, Pandey SS, Barnawal D et al (2016) Plant growth promoting rhizobacteria Dietzia natronolimnaea modulates the expression of stress responsive genes providing protection of wheat from salinity stress. Sci Rep 6:34768. https://doi.org/10.1038/srep34768 PubMed DOI PMC

Biswas S, Razzaque S, Elias SM et al (2015) Effect of the vacuolar Na+/H+ antiporter transgene in a rice landrace and a commercial rice cultivar after its insertion by crossing. Acta Physiol Plant 37:1730. https://doi.org/10.1007/s11738-014-1730-6 DOI

Chavez MD, Maria Berentsen PB, Oenema O, Maria Oude Lansink AGJ (2014) Potential for increasing soil nutrient availability via soil organic matter improvement using pseudo panel data. Agric Sci 05:743–753. https://doi.org/10.4236/as.2014.58078 DOI

Chebotar VK, Asis CA, Akao S (2001) Production of growth-promoting substances and high colonization ability of rhizobacteria enhance the nitrogen fixation of soybean when coinoculated with Bradyrhizobium japonicum. Biol Fertil Soils 34:427–432. https://doi.org/10.1007/s00374-001-0426-4 DOI

Chutia J, Borah SP (2012) Water stress effects on leaf growth and chlorophyll content but not the grain yield in traditional rice (Oryza sativa Linn.) genotypes of Assam, India II. Protein and proline status in seedlings under peg induced water stress. Am J Plant Sci 03:971–980. https://doi.org/10.4236/ajps.2012.37115 DOI

Corwin DL, Lesch SM (2003) Application of soil electrical conductivity to precision agriculture: theory, principles, and guidelines. Agron J 95:455–471

De QF, Zhang B, Wei DL, Su SY (2006) Protein expression analysis of Halobacillus dabanensis D-8T subjected to salt shock. J Microbiol 44:369–374

Desale P, Patel B, Singh S et al (2014) Plant growth promoting properties of Halobacillus sp. and Halomonas sp. in presence of salinity and heavy metals. J Basic Microbiol 54:781–791. https://doi.org/10.1002/jobm.201200778 PubMed DOI

Edwards JA, Santos-Medellín CM, Liechty ZS et al (2018) Compositional shifts in root-associated bacterial and archaeal microbiota track the plant life cycle in field-grown rice. PLoS Biol 16:e2003862. https://doi.org/10.1371/journal.pbio.2003862 PubMed DOI PMC

Elkoca E, Turan M, Donmez MF (2010) Effects of single, dual and triple inoculations with Bacillus subtilis, Bacillus megaterium and Rhizobium leguminosarum bv. phaseoli on nodulation, nutrient uptake, yield and yield parameters of common bean (Phaseolus vulgaris l. cv. ’Elkoca-05’). J Plant Nutr 33:2104–2119. https://doi.org/10.1080/01904167.2010.519084 DOI

Fahad S, Hussain S, Matloob A et al (2015) Phytohormones and plant responses to salinity stress: a review. Plant Growth Regul 75:391–404. https://doi.org/10.1007/s10725-014-0013-y DOI

Ghasemzadeh A, Jaafar HZE, Rahmat A (2010) Synthesis of phenolics and flavonoids in ginger (Zingiber officinale Roscoe) and their effects on photosynthesis rate. Int J Mol Sci 11:4539–4555. https://doi.org/10.3390/ijms11114539 PubMed DOI PMC

Glick BR (2014) Bacteria with ACC deaminase can promote plant growth and help to feed the world. Microbiol Res 169:30–39. https://doi.org/10.1016/j.micres.2013.09.009 PubMed DOI

Gopalakrishnan L, Doriya K, Kumar DS (2016) Moringa oleifera: a review on nutritive importance and its medicinal application. Food Sci Hum Wellness 5:49–56. https://doi.org/10.1016/j.fshw.2016.04.001 DOI

Gouda S, Kerry RG, Das G et al (2018) Revitalization of plant growth promoting rhizobacteria for sustainable development in agriculture. Microbiol Res 206:131–140. https://doi.org/10.1016/j.micres.2017.08.016 PubMed DOI

Gupta G, Pariha SS, Ahirwar NK, Snehi SK, V Singh (2015) Plant growth promoting rhizobacteria (PGPR): current and future prospects for development of sustainable agriculture. J Microb Biochem Technol 7:96–102

Gupta M, Kiran S, Gulati A et al (2012) Isolation and identification of phosphate solubilizing bacteria able to enhance the growth and aloin-A biosynthesis of Aloe barbadensis Miller. Microbiol Res 167:358–363. https://doi.org/10.1016/j.micres.2012.02.004 PubMed DOI

Hasan M, Bano A, Hassan SG et al (2014) Enhancement of rice growth and production of growth-promoting phytohormones by inoculation with Rhizobium and other Rhizobacteria. World Appl Sci J 31:1734–1743

Iqbal T (2018) Rice straw amendment ameliorates harmful effect of salinity and increases nitrogen availability in a saline paddy soil. J Saudi Soc Agric Sci 17:445–453. https://doi.org/10.1016/j.jssas.2016.11.002 DOI

James O, Emmanuel UC (2011) Comparative studies on the protein and mineral composition of some selected Nigerian vegetables. J Food Sci 5:22–25

Jha CK, Aeron A, Patel BV et al (2011a) Enterobacter: role in plant growth promotion. In: Maheshwari DK (ed) Bacteria in Agrobiology: Plant Growth Responses. Springer, Berlin, Heidelberg, pp 159–182. https://doi.org/10.1007/978-3-642-20332-9_8 DOI

Jha Y, Subramanian RB, Patel S (2011b) Combination of endophytic and rhizospheric plant growth promoting rhizobacteria in Oryza sativa shows higher accumulation of osmoprotectant against saline stress. Acta Physiol Plant 33:797–802. https://doi.org/10.1007/s11738-010-0604-9 DOI

Kakar KU, Ren XL, Nawaz Z et al (2016) A consortium of rhizobacterial strains and biochemical growth elicitors improve cold and drought stress tolerance in rice (Oryza sativa L.). Plant Biol 18:471–483. https://doi.org/10.1111/plb.12427 PubMed DOI

Kalam S, Das SN, Basu A, Podile AR (2017) Population densities of indigenous Acidobacteria change in the presence of plant growth promoting rhizobacteria (PGPR) in rhizosphere. J Basic Microbiol 57:376–385. https://doi.org/10.1002/jobm.201600588 PubMed DOI

Kim K, Jang YJ, Lee SM et al (2014) Alleviation of salt stress by Enterobacter sp. EJ01 in tomato and Arabidopsis is accompanied by up-regulation of conserved salinity responsive factors in plants. Mol Cells 37:109–117. https://doi.org/10.14348/molcells.2014.2239 PubMed DOI PMC

Kreuzer K, Adamczyk J, Iijima M et al (2006) Grazing of a common species of soil protozoa (Acanthamoeba castellanii) affects rhizosphere bacterial community composition and root architecture of rice (Oryza sativa L.). Soil Biol Biochem 38:1665–1672. https://doi.org/10.1016/j.soilbio.2005.11.027 DOI

Kumar P, Dubey RC, Maheshwari DK (2012) Bacillus strains isolated from rhizosphere showed plant growth promoting and antagonistic activity against phytopathogens. Microbiol Res 167:493–499. https://doi.org/10.1016/j.micres.2012.05.002 PubMed DOI

Kumar A, Maurya BR, Raghuwanshi R et al (2017) Co-inoculation with Enterobacter and Rhizobacteria on yield and nutrient uptake by wheat (Triticum aestivum L.) in the alluvial soil under Indo-Gangetic Plain of India. J Plant Growth Regul 36:608–617. https://doi.org/10.1007/s00344-016-9663-5 DOI

Mayak S, Tirosh T, Glick BR (2004) Plant growth-promoting bacteria confer resistance in tomato plants to salt stress. Plant Physiol Biochem 42:565–572. https://doi.org/10.1016/j.plaphy.2004.05.009 PubMed DOI

Miller G, Suzuki N, Ciftci-Yilmaz S, Mittler R (2010) Reactive oxygen species homeostasis and signalling during drought and salinity stresses. Plant Cell Environ 33:453–467. https://doi.org/10.1111/j.1365-3040.2009.02041.x PubMed DOI

Molina-Romero D, Baez A, Quintero-Hernández V et al (2017) Compatible bacterial mixture, tolerant to desiccation, improves maize plant growth. PLoS ONE 12:e0187913. https://doi.org/10.1371/journal.pone.0187913 PubMed DOI PMC

Nascimento FX, Rossi MJ, Glick BR (2018) Ethylene and 1-aminocyclopropane-1-carboxylate (ACC) in plant–bacterial interactions. Front Plant Sci 9:114. https://doi.org/10.3389/fpls.2018.00114 PubMed DOI PMC

Nei M, Kumar S (2000) Molecular Evolution and Phylogenetics. Oxford University Press

Nei M, Naruya S (1987) The neighbor-joining method: a new method for reconstructing phylogenetic trees. Mol Biol Evol 4:406–425 PubMed

Oliveira ALM, Stoffels M, Schmid M et al (2009) Colonization of sugarcane plantlets by mixed inoculations with diazotrophic bacteria. Eur J Soil Biol 45:106–113. https://doi.org/10.1016/j.ejsobi.2008.09.004 DOI

Park M, Kim C, Yang J et al (2005) Isolation and characterization of diazotrophic growth promoting bacteria from rhizosphere of agricultural crops of Korea. Microbiol Res 160:127–133. https://doi.org/10.1016/j.micres.2004.10.003 PubMed DOI

Rima FS, Biswas S, Sarker PK et al (2018) Bacteria endemic to saline coastal belt and their ability to mitigate the effects of salt stress on rice growth and yields. Ann Microbiol 68:525–535. https://doi.org/10.1007/s13213-018-1358-7 DOI

Sambrook J, Green MR (2001) Molecular cloning. A Laboratory Manual

Sand M, De Berardinis V, Mingote A et al (2011) Salt adaptation in Acinetobacter baylyi: identifcation and characterization of a secondary glycine betaine transporter. Arch Microbiol 193:723–730. https://doi.org/10.1007/s00203-011-0713-x PubMed DOI

Saravanan VS, Subramoniam SR, Raj SA (2004) Assessing in vitro solubilization potential of different zinc solubilizing bacterial (ZSB) isolates. Braz J Microbiol 35:121–125. https://doi.org/10.1590/S1517-83822004000100020 DOI

Sarkar A, Ghosh PK, Pramanik K et al (2018) A halotolerant Enterobacter sp. displaying ACC deaminase activity promotes rice seedling growth under salt stress. Res Microbiol 169:20–32. https://doi.org/10.1016/j.resmic.2017.08.005 PubMed DOI

Satyaprakash M, Nikitha T, Reddi EU, Sadhana B, Vani SS (2017) Phosphorous and phosphate solubilising bacteria and their role in plant nutrition. Int J Curr Microbiol Appl Sci 6:2133–2144. https://doi.org/10.20546/ijcmas.2017.604.251 DOI

Schwyn B, Neilands JB (1987) Universal chemical assay for the detection and determination of siderophores. Anal Biochem 160:47–56. https://doi.org/10.1016/0003-2697(87)90612-9 PubMed DOI

Shultana R, Kee Zuan AT, Yusop MR, Saud HM (2020a) Characterization of salt-tolerant plant growth-promoting rhizobacteria and the effect on growth and yield of saline-affected rice. PLoS ONE 15:e0238537. https://doi.org/10.1371/journal.pone.0238537 PubMed DOI PMC

Shultana R, Othman R, Zuan ATK, Yusop MR (2019) Evaluation of growth and nutrient uptake of rice genotypes under different levels of salinity. Res Crop 20:1–9. https://doi.org/10.31830/2348-7542.2019.001 DOI

Shultana R, Zuan ATK, Yusop MR et al (2021) Bacillus tequilensis strain ‘UPMRB9’ improves biochemical attributes and nutrient accumulation in different rice varieties under salinity stress. PLoS ONE 16:e0260869. https://doi.org/10.1371/journal.pone.0260869 PubMed DOI PMC

Shultana R, Zuan ATK, Yusop MR et al (2020b) Effect of salt-tolerant bacterial inoculations on rice seedlings differing in salt-tolerance under saline soil conditions. Agronomy 10:1030. https://doi.org/10.3390/agronomy10071030 DOI

Singh JS, Koushal S, Kumar A et al (2016) Book review: microbial inoculants in sustainable agricultural productivity- Vol. II: Functional Application. Front Microbiol 7:2105. https://doi.org/10.3389/fmicb.2016.02105 DOI PMC

Smith JL, Doran JW (2015) Measurement and use of pH and electrical conductivity for soil quality analysis. Methods Assess Soil Qual 49:169–185. https://doi.org/10.2136/sssaspecpub49.c10 DOI

Tamura K, Stecher G, Kumar S (2021) MEGA11: Molecular Evolutionary Genetics Analysis Version 11. Mol Biol Evol 38:3022–3027. https://doi.org/10.1093/molbev/msab120 PubMed DOI PMC

Tan KZ, Radziah O, Halimi MS et al (2014) Isolation and characterization of rhizobia and plant growth-promoting rhizobacteria and their effects on growth of rice seedlings. Am J Agric Biol Sci 9:342–360. https://doi.org/10.3844/ajabssp.2014.342.360 DOI

Vessey JK (2003) Plant growth promoting rhizobacteria as biofertilizers. Plant Soil 255:571–586. https://doi.org/10.1023/A:1026037216893 DOI

Vimal SR, Patel VK, Singh JS (2019) Plant growth promoting Curtobacterium albidum strain SRV4: an agriculturally important microbe to alleviate salinity stress in paddy plants. Ecol Indic 105:553–562. https://doi.org/10.1016/j.ecolind.2018.05.014 DOI

Wu TY, Wu XQ, Xu XQ et al (2020) Salt tolerance mechanism and species identification of the plant rhizosphere bacterium JYZ-SD2. Curr Microbiol 77:388–395. https://doi.org/10.1007/s00284-019-01835-0 PubMed DOI

Xiong D, Chen J, Yu T et al (2015) SPAD-based leaf nitrogen estimation is impacted by environmental factors and crop leaf characteristics. Sci Rep 5:13389. https://doi.org/10.1038/srep13389 PubMed DOI PMC

Yu X, Li Y, Zhang C et al (2014) Culturable heavy metal-resistant and plant growth promoting bacteria in V-Ti magnetite mine tailing soil from Panzhihua. China Plos One 9:e106618. https://doi.org/10.1371/journal.pone.0106618 PubMed DOI