Semester of Graduation
Spring 2025
Degree
Master of Science (MS)
Department
Plant Pathology and Crop Physiology
Document Type
Thesis
Abstract
Soybean (Glycine max L.) productivity is increasingly threatened by abiotic stresses such as drought, flooding, and salinity, as well as biotic stressors, including Rhizoctonia solani and Cercospora infections. Current agricultural practices rely on chemical pesticides, agronomic interventions, and biotechnological approaches, which are often resource-intensive, complex, and environmentally harmful. A promising alternative is the use of naturally occurring beneficial bacteria in soybean roots and rhizospheric soil, yet most research has focused on individual bacterial strains rather than consortium-based approaches. This study investigates the potential of bacterial consortia for enhancing soybean stress tolerance through seed treatment and elucidating their impact on plant health, microbial community dynamics, and gene expression under stress conditions.
Bacterial consortia, Set2 and Setm4 (composed of Bacillus, Pseudomonas, Enterobacter, Leclercia, Kosakonia, Rhizobium, Streptomyces, Achromobacter, and Ensifer) were formulated using bacteria isolated from soybean roots and rhizospheric soil based on their plant growth-promoting characteristics, including exopolysaccharide production, nitrogen fixation, siderophore production, and phosphate solubilization. Under drought, flooding, and salinity stress conditions, soybean plants treated with these bacterial consortia exhibited significantly improved germination percentage, seedling vigor, biomass accumulation, and water content, demonstrating enhanced abiotic stress tolerance.
In addition to abiotic stress mitigation, bacterial seed treatments contributed to increased resistance against Rhizoctonia solani AG-4 infection, likely through induced systemic resistance. Quantitative PCR analysis revealed significant upregulation of defense-related genes in soybean plants treated with Setm4, supporting its role in enhancing plant immunity. Field trials further demonstrated that Setm4-treated plants exhibited greater tolerance to Cercospora leaf blight infections and soybean pod damage. Microbiome analysis of soybean plants under extreme drought conditions revealed distinct shifts in microbial community composition, with surviving plants exhibiting a higher abundance of Pseudomonas and Pantoea, while non-surviving plants were dominated by Streptomyces. Beneficial bacterial strains, including Acinetobacter pittii and Pseudomonas sp., were isolated from drought-stressed plants and demonstrated growth-promoting effects and drought tolerance enhancement in soybean through seed treatment.
These findings highlight the potential of bacterial consortia having multiple beneficial activities as an environmentally sustainable strategy for improving soybean resilience to various stressors. The results from this study contribute to a deeper understanding of plant-microbe interactions and provide a foundation for developing bioinoculants for large-scale applications in sustainable soybean production.
Date
3-28-2025
Recommended Citation
Gouli, Sandeep, "Enhancing Soybean Resilience to Abiotic and Biotic Stresses Through Bacterial Seed Treatment and Microbiome Analysis" (2025). LSU Master's Theses. 6115.
https://repository.lsu.edu/gradschool_theses/6115
Committee Chair
Ham, Jong H.