Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Mar;13(3):90.
doi: 10.1007/s13205-023-03503-4. Epub 2023 Feb 20.

Azospirillum-Bacillus associations: synergistic effects on in vitro PGP traits and growth of pearl millet at early seedling stage under limited moisture conditions

Sivakumar Yaadesh  1 , Govind Singh Tomar  1 , Rajeev Kaushik  1 , Radha Prasanna  1 , Minakshi Grover  1
Affiliations

Azospirillum-Bacillus associations: synergistic effects on in vitro PGP traits and growth of pearl millet at early seedling stage under limited moisture conditions

Sivakumar Yaadesh et al. 3 Biotech. 2023 Mar.

Abstract

The association of plant beneficial Azospirillum and Bacillus spp. strains expressing different sets of PGP traits may have complementary or supplementary effects on host plants. In the present investigation, A. formosense and Bacillus spp. strains showing diverse PGP traits (IAA production, nitrogenase activity, phosphate, zinc and potassium solubilization, siderophores, antagonism against phytopathogens, osmotic stress tolerance, etc.) were assessed for compatibility by cross-streaking and co-culturing. Under co-culture (Azospirillum + Bacillus), a significant increase in the expression of PGP traits, nitrogenase activity (up to 89%), phosphate solubilization (upto 236%), siderophore production (upto 20%) was observed as compared to individual Azospirillum culture, indicating synergistic effect of co-culture. IAA production was higher in Azospirillum sp. strains as compared to Bacillus spp. strains, when cultured individually; however, when co-cultured, the IAA levels were in the mid-range indicating the contributory effects of compatible strains. The effect of individual Azospirillum and Bacillus strains and their co-inoculation was also assessed on the growth of pearl millet at early stages under moisture-deficit stress imposed using PEG6000 (0, 10, and 20%). Co-inoculation enhanced seed germination (up to 10, 3, and 6% increase under 0, 10, and 20% PEG, respectively, over individual Azospirillum treatment), root traits (increased root hair density and lateral branches), and seedling vigor indices (up to 22, 32, 43% increase in seed vigor index I and 8, 14, and 10% increase in seed vigor index II under 0, 10, 20% PEG, respectively, over individual Azospirillum treatment) under normal as well as moisture-deficit conditions suggesting the role of Bacillus spp. strains in better adaptation of the plants to stress and higher yield potential. The synergistic effect of co-cultured Azospirillum and Bacillus strains on PGP traits indicated metabolic interplay between the two strains which needs to be further understood. The positive effect of co-inoculation on plant growth under moisture-deficit stress indicated the promise of Azospirillum and Bacillus as a synergistic bioformulation for combating nutrient and drought stress in pearl millet, particularly in nutrient-poor dryland agricultural systems.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-023-03503-4.

Keywords: Antagonism; Nitrogenase; Osmotic stress; Root hair density; Siderophore; Synergism.

PubMed Disclaimer

Conflict of interest statement

Conflict of interestOn behalf of all authors, the corresponding author states that there is no conflict of interest.

Figures

Fig. 1
Fig. 1
Compatibility between Azospirillum and Bacillus spp. strains on LB (a) and Rojo Congo (b) media
Fig. 2
Fig. 2
Microscopic observations of negatively stained AIM57 (a) and AIM57 + IMSB1 co-culture (b)
Fig. 3
Fig. 3
Effect of co-cultivation on PGP traits: IAA production (a), nitrogenase activity (b), P solubilization (c), siderophore production (d)
Fig. 4
Fig. 4
Seed germination as influenced by individual and combined bacterial treatments under different 0, 10, and 20% PEG6000 conditions
See this image and copyright information in PMC

References

    1. Abdul-Baki AA, Anderson JD. Physiological and biochemical deterioration of seeds. In: Koziowski TT, editor. Seed Biology. New York: Academic Press; 1972. pp. 283–315.
    1. Akhtar N, Ilyas N, Mashwani ZR, Hayat R, Yasmin H, Noureldeen A, Ahmad P. Synergistic effects of plant growth promoting rhizobacteria and silicon dioxide nano-particles for amelioration of drought stress in wheat. Plant Physiol Biochem. 2021;166:160–176. doi: 10.1016/j.plaphy.2021.05.039. - DOI - PubMed
    1. Akinrinlola RJ, Yuen GY, Drijber RA, Adesemoye AO. Evaluation of Bacillus strains for plant growth promotion and predictability of efficacy by in vitro physiological traits. Int J Microbiol. 2018 doi: 10.1155/2018/5686874. - DOI - PMC - PubMed
    1. Aleksandrov VG, Blagodyr RN, Ilev IP. Phosphorus acid isolation from apatite produced by silicate bacteria. Mikrobiol Zh. 1967;29:111–114. - PubMed
    1. Bagheri N, Ahmadzadeh M, Mariotte P, et al. Behavior and interactions of the plant growth-promoting bacteria Azospirillum oryzae NBT506 and Bacillus velezensis UTB96 in a co-culture system. World J Microbiol Biotechnol. 2022;38:101. doi: 10.1007/s11274-022-03283-8. - DOI - PMC - PubMed

LinkOut - more resources