Date of Graduation

Spring 2020


Master of Science in Biology



Committee Chair

Alexander Wait


The microbiome is an important determinant of plant health, growth and resistance to stress. This study was conducted to determine the efficacy of the phyllosphere-microbiome on managing Pseudomonas syringae pv. Glycinea (Psg), gas exchange and growth of Glycine max L. Merrill. A greenhouse study was conducted in the summer of 2019. A field isolated and cultured soybean phyllosphere-microbiome was applied to purposely infected and uninfected soybean. Gas exchange, Psg density, chlorophyll concentrations, and percent nitrogen and carbon in the leaves were measured during the V3-V6 stages of soybean. Not surprisingly, there was a two-fold reduction in copies of Pseudomonas syringae pv. Glycinea per leaf disc in the microbiome-Psg treated group. The microbiome had a significant positive effect on the dry shoot biomass. Surprisingly, mean dry shoot biomass of the microbiome treated group was 5% higher than the control group and this was significantly different. The microbiome had a significant effect on the fresh weight and the number of nodules. Mean chlorophyll concentration doubled in the microbiome augmented treated group. Percent nitrogen per leaf disc was significantly higher in the microbiome treated plants. Furthermore, transpiration rate was significantly increased in the microbiome treated plants. Interestingly, water use efficiency of the microbiome treated plants was significantly reduced, but not at a cost to overall carbon gain. Photosynthetic rate was reduced by the infection, with higher photosaturated photosynthetic rates (Amax) and ambient photosynthetic rates (Aamb) being significantly higher in the control, microbiome, microbiome +pathogen than the Pseudomonas syringae pv. Glycinea treatment. Overall, dry shoot biomass, root nodules, chlorophyll concentrations, percent nitrogen and photosynthetic activity were significantly increased by the presence of the microbiome on both infected and non-infected plants. Therefore, the phyllosphere-microbiome suggests the potential for increasing crop yield and plant probiotics against pathogens.


microbiome, Glycine max L. Merrill, phyllosphere, Pseudomonas syringae pv. Glycinea, chlorophyll, probiotics

Subject Categories

Agriculture | Biology | Microbiology | Plant Sciences


© Charles Agbavor

Open Access