Greenhouse evaluation of in vitro-characterized plant growth-promoting Pseudomonas strains on the growth of Sorghum bicolor seedlings

Befekadu Teshome; Belay Belay; Zerihun  Tsegaye

Authors

Befekadu Teshome Ethiopian Biodiversity Institute, Microbial Biodiversity Research Lead Executive Office, Addis Ababa, Ethiopia
Eleni Belay Ethiopian Biodiversity Institute, Microbial Biodiversity Research Lead Executive Office, Addis Ababa, Ethiopia
Zerihun Tsegaye Ethiopian Biodiversity Institute, Microbial Biodiversity Research Lead Executive Office, Addis Ababa, Ethiopia

Keywords:

Sorghum bicolor, plant growth-promoting rhizobacteria, Pseudomonas, bioinoculant, biomass accumulation

Abstract

Plant growth-promoting rhizobacteria play a vital role in sustainable agriculture by supporting plant development and stress resilience. This study investigated the effects of selected bacterial strains on the growth of Sorghum bicolor seedlings under controlled greenhouse conditions. Four elite in-vitro-characterized plant growth-promoting Pseudomonas strains were assessed for their potential to enhance biomass accumulation, root and shoot length, and leaf chlorophyll content of two local varieties (Zengada and Degalit) of Sorghum bicolor seedlings. The four-plant growth-promoting Pseudomonas strains included were P. extremorientalis, P. brenneri, P. simiae, and P. fluorescens. The greenhouse evaluation was conducted for 17 treatment groups, which were derived from the four Pseudomonas strains and one control. The bacterial treatments had significant effects on a greater number of parameters on Sorghum Zengada variety than the Sorghum Degalit variety. The treatments showed significant effects on the length of shoot and root, and leaf chlorophyll contents of both varieties. But they showed significant effects only on shoot dry weight and leaf width of Zengada variety (P < 0.05). Treatment BCD (A combination of P. extremorientalis, P. simiae, and P. fluorescens) showed a significant effect on Zengada sorghum’s shoot dry weight (3.83 ± 1.68 g) and leaf width (2.67 ± 0.49 cm) compared to the control with 1.12 ± 0.33 g and 1.27 ± 0.2 g, respectively. It also performed well in Degalit sorghum in terms of shoot length (86.3 ± 1.80 cm) compared to the control with 41.87 ± 5.51 cm, making it a strong candidate for bioinoculant development through field trials.

References

Adesemoye, A. O., & Kloepper, J. W. (2009). Plant-microbe interactions in enhanced fertilizer-use effciency. Applied Microbiology and Biotechnology, 85(1), 1–12. https://doi.org/10.1007/s00253-009-2196-0

Akhtar, A., Hisamuddin, M. I., Robab, M. I., Sharf, A., & Sharf, R. (2012). Plant-growth-promoting rhizobacteria: An overview. Journal of Natural Products and Plant Resources, 2(1), 19–31.

Alapati, P. S. N. T., & Saharan, B. S. (2025). Identifcation and functional characterization of plant growth-promoting rhizobacteria enhancing growth and nutritional quality of Sorghum bicolor. Discover Plants, 2(1), 191. https://doi.org/10.1007/s44372-025-00284-3

Ali, S., Hameed, S., Shahid, M., Iqbal, M., Lazarovits, G., & Imran, A. (2020). Functional characterization of potential PGPR exhibiting broad-spectrum antifungal activity. Microbiological Research, 232, 126389. https://doi.org/10.1016/j.micres.2019.126389

Babalola, O. O. (2010). Benefcial bacteria of agricultural importance. Biotechnology Letters, 32(11), 1559–1570. https://doi.org/10.1007/s10529-010-0347-0

Barriuso, J., Solano, B. R., Lucas, J. A., Lobo, A. P., García-Villaraco, A., & Gutiérrez-Mañero, F. J. (2008). Ecology, genetic diversity and screening strategies of plant growth promoting rhizobacteria (PGPR). In I. Ahmad, J. Pichtel, & S. Hayat (Eds.), Plant–Bacteria interactions: Strategies and techniques to promote plant growth (pp. 1–17). Wiley-VCH. https://doi.org/10.1002/9783527621989.ch1

Belay, F. (2024). Yield stability for some selected drought-tolerant sorghum genotypes in dry lowlands of Ethiopia. Asian Journal of Research and Review in Agriculture, 6(1), 525–532.

Beyene, A. A., Hussein, A. S., Pangirayi, T., Fentahun, M., Mark, D. L., & Dawit, G. A. (2016). Sorghum production systems and constraints, and coping strategies under drought-prone agro-ecologies of Ethiopia. South African Journal of Plant and Soil, 33(3), 207–217. https://doi.org/10.1080/02571862.2016.1143043

Cappuccino, J. G., & Sherman, N. (1992). Microbiology: A laboratory manual (3rd ed., pp. 125–179). Benjamin/Cummings Publishing Company.

Charyulu, D. K., Afari-Sefa, V., & Gumma, M. K. (2024). Trends in global sorghum production: Perspectives and limitations. In E. Habyarimana, M. A. Nadeem, F. S. Baloch, & N. Zencirci (Eds.), Omics and biotechnological approaches for product profle-driven sorghum improvement (pp. 1–19). Springer Singapore. https://doi.org/10.1007/978-981-97-4347-6_1

da Silva Medina, G., Rotondo, R., & Rodríguez, G. R. (2024). Innovations in agricultural bio-inputs: Commercial products developed in Argentina and Brazil. Sustainability, 16(7), Article 2763. https://doi.org/10.3390/su16072763

Dardanelli, M. S., Carletti, S. M., Paulucci, N. S., Medeot, D. B., Rodríguez Cáceres, E. A., Vita, F. A., Bueno, M., Fumero, M. V., & García, M. B. (2010). Benefts of plant growth-promoting rhizobacteria and rhizobia in agriculture. In D. K. Maheshwari (Ed.), Plant growth and health promoting bacteria (Vol. 18, pp. 1–20). Springer. https://doi.org/10.1007/978-3-642-13612-2_1

Egamberdieva, D. (2008). Plant growthpromoting properties of rhizobacteria isolated from wheat and pea grown in loamy sand soil. Turkish Journal of Biology, 32(1), 9–15.

Egamberdieva, D., Kucharova, Z., Davranov, K., Berg, G., Makarova, N., & Azarova, T. (2011). Bacteria able to control foot and root rot and to promote growth of cucumber in salinated soils. Biology and Fertility of Soils, 47(2), 197–205. https://doi.org/10.1007/s00374-010-0523-3

Glick, B. R. (2012). Plant growth-promoting bacteria: Mechanisms and applications. Scientifca, 2012, Article ID 963401.

Hart, M. M., & Trevors, J. T. (2005). Microbe management: Application of mycorrhizal fungi in sustainable agriculture. Frontiers in Ecology and the Environment, 3(10), 533–539. https://doi.org/10.1890/1540-9295(2005)003[0533:MMAOMF]2.0.CO;2

Hoitink, H. A. J., & Boehm, M. J. (1999). Biocontrol within the context of soil microbial communities: A substratedependent phenomenon. Annual Review of Phytopathology, 37, 427–446. https://doi.org/10.1146/annurev.phyto.37.1.427

Idris, A., Labuschagne, N., & Korsten, L. (2009). Effcacy of rhizobacteria for growth promotion in sorghum under greenhouse conditions and selected modes of action studies. Journal of Agricultural Science, 147(1), 17–30. https://doi.org/10.1017/S0021859608008174

Khaskheli, M. A., Nizamani, M. M., Tarafder, E., Das, D., Nosheen, S., Muhae-Ud-Din, G., Khaskheli, R. A., Ren, M. J., Wang, Y., & Yang, S. W. (2025). Sustainable management of major fungal phytopathogens in sorghum (Sorghum bicolor L.) for food security: A comprehensive review. Journal of Fungi, 11(3), 207. https://doi.org/10.3390/jof11030207

Kloepper, J. W., Reddy, M. S., Rodríguez-Kabana, R., Kenney, D. S., Kokalis-Burelle, N., & Martinez-Ochoa, N. (2004). Application for rhizobacteria in transplant production and yield enhancement. Acta Horticulturae, 631, 217–229. https://doi.org/10.17660/ActaHortic.2004.631.28

Kumar, P., Desai, S., Amalraj, L. D., Ahmed, M. H., & Reddy, G. (2012). Plant growth-promoting Pseudomonas spp. from diverse agro-ecosystems of India for Sorghum bicolor L. Journal of Biofertilizers & Biopesticides, 7, S7:001. https://doi.org/10.4172/2155-6202.S7-001

Ling, Q., Huang, W., & Jarvis, P. (2011). Use of a SPAD-502 meter to measure leaf chlorophyll concentration in Arabidopsis thaliana. Photosynthesis Research, 107(2), 209–214. https://doi.org/10.1007/s11120-010-9606-0

Lucy, M., Reed, E., & Glick, B. R. (2004). Applications of free-living plant growth-promoting rhizobacteria. Antonie van Leeuwenhoek, 86(1), 1–25. https://doi.org/10.1023/B:ANTO.0000024903.10757.6e

Naseem, H., Ahsan, M., Shahid, M. A., & Khan, N. (2018). Exopolysaccharides producing rhizobacteria and their role in plant growth and drought tolerance. Journal of Basic Microbiology, 58(12), 1009–1022. https://doi.org/10.1002/jobm.201800309

Patten, C. L., & Glick, B. R. (2002). Role of Pseudomonas putida indoleacetic acid in development of the host plant root system. Applied and Environmental Microbiology, 68(8), 3795–3801. https://doi.org/10.1128/AEM.68.8.3795-3801.2002

Pikovskaya, R. I. (1948). Mobilization of phosphorus in soil in connection with the vital activity of some microbial species. Mikrobiologiya, 17, 362–370.

Rizvi, A., Ahmed, B., Khan, M. S., Umar, S., & Lee, J. (2021). Sorghum-phosphate solubilizers interactions: Crop nutrition, biotic stress alleviation, and yield optimization. Frontiers in Plant Science, 12, Article 746780. https://doi.org/10.3389/fpls.2021.746780

Rodríguez, H., Fraga, R., González, T., & Bashan, Y. (2006). Genetics of phosphate solubilization and its potential applications for improving plant growth-promoting bacteria. Plant and Soil, 287(1–2), 15–21. https://doi.org/10.1007/s11104-006-9056-9

Sadarahalli, U. P., Manjunatha, G. N., & Kuttappa, T. C. (2024). Application of Pseudomonas strains for biocontrol of commercial crops susceptible to plant pathogens: A review. Agricultural Reviews, 45(4), 600–608. https://doi.org/10.18805/ag.R-2451

Sah, S., Krishnani, S., & Singh, R. (2021). Pseudomonas mediated nutritional and growth promotional activities for sustainable food security. Current Research in Microbial Sciences, 2, Article 100084. https://doi.org/10.1016/j.crmicr.2021.100084

Saharan, B. S., & Nehra, V. (2011). Plant growth promoting rhizobacteria: A critical review. Life Sciences and Medicine Research, 21, 1–30.

Sheng, X. F. (2005). Growth promotion and increased potassium uptake of cotton and rape by a potassium releasing strain of Bacillus edaphicus. Soil Biology and Biochemistry, 37(10), 1918–1922. https://doi.org/10.1016/j.soilbio.2005.02.026

Srivastava, A. K., Riaz, A., Jiang, J., Li, X., Uzair, M., Mishra, P., Zeb, A., Zhang, J., Singh, R. P., Luo, L., Chen, S., Yang, S., Zhao, Y., & Xie, X. (2025). Advancing climate-resilient sorghum: The synergistic role of plant biotechnology and microbial interactions. Rice, 18, Article 41. https://doi.org/10.1186/s12284-025-00796-2

Teshome, B., Belay, E., Mengesha, B., Tsegaye, Z., Akley, E. K., & Frederick, A. (2025). Selection and identifcation of Pseudomonas and Bacillus rhizobacteria with bioinoculant potential for sorghum cultivation. International Journal of Science, Technology, Engineering and Mathematics, 5(2), 38–59. https://doi.org/10.53378/ijstem.353191

Thanh, D. T. N., & Diep, C. N. (2014). Isolation and identifcation of rhizospheric bacteria in Acrisols of maize (Zea mays L.) in the eastern of South Vietnam. American Journal of Life Sciences, 2(2), 82–89. https://doi.org/10.11648/j.ajls.20140202.18

Tsegaye, Z., Alemu, T., Desta, A. F., & Assefa, F. (2022). Plant growth-promoting rhizobacterial inoculation to improve growth, yield, and grain nutrient uptake of teff varieties. Frontiers in Microbiology, 13, Article 896770. https://doi.org/10.3389/fmicb.2022.896770

Vessey, J. K. (2003). Plant growth promoting rhizobacteria as biofertilizers. Plant and Soil, 255(2), 571–586. https://doi.org/10.1023/A:1026037216893

Widawati, S., & Suliasih. (2018). The effect of plant growth-promoting rhizobacteria (PGPR) on germination and seedling growth of Sorghum bicolor L. Moench. IOP Conference Series: Earth and Environmental Science, 166, 012022. https://doi.org/10.1088/1755-1315/166/1/012022

Worede, F., Mamo, M., Assefa, S., Gebremariam, T., & Beze, Y. (2020). Yield stability and adaptability of lowland sorghum (Sorghum bicolor (L.) Moench) in moisture-defcit areas of Northeast Ethiopia. Cogent Food and Agriculture, 6(1), Article 1736865. https://doi.org/10.1080/23311932.2020.1736865

Zahir, Z. A., Munir, A., Asghar, H. N., Shaharoona, B., & Arshad, M. (2008). Effectiveness of rhizobacteria containing ACC deaminase for growth promotion of peas (Pisum sativum) under drought conditions. Journal of Microbiology and Biotechnology, 18(5), 958–963.