Graduate Thesis Or Dissertation
 

Multidisciplinary Approach to Evaluate the Effect of Plant Growth Promoting Rhizobacteria (PGPR) on Soil Microbiota and Quality of Strawberries

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gx41mr732

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  • Oregon strawberries are known for their high quality, intense flavor, sweetness, and rich red color. With optimal weather conditions, including rainy and mild seasons, Oregon has one of the best strawberry farming environments. Amongst the factors for a suitable strawberry farming environment, soil significantly influences strawberry growth and quality. The natural soil environment is considered one of the most diverse habitats comprising numerous bacteria, fungi, and larger organisms such as nematodes, insects, or moles. Rhizosphere bacteria play vital roles in plant nutrition and the growth promotion of their host plant. Plant growth-promoting rhizobacteria (PGPR) are a type of beneficial free-living soil bacteria and populate in the rhizosphere that promotes vegetal growth. In the present study, function of three PGPR species: Bacillus subtilis; Bacillus amyloliquefaciens; Pseudomonas monteilii were analyzed. Then, metagenomic and fruit quality evaluation methods applied to the current study were reviewed. For the experimental study, the PGPR were applied to the soil on the strawberry plants in two different concentrations of PGPR, T1 (0.24% PGPR) and T2 (0.48% PGPR), and C (no PGPR) at the strawberry farm in Dayton, Oregon. The PGPR were treated bi-weekly, and the soil samples were collected monthly from August, 2020 to May, 2021. A total of 450 soil samples were collected, and microbiome sequencing based on the V4 region of the 16S rRNA gene was performed. The quality of the strawberries was evaluated by a sensory evaluation and analytical measure of total soluble solids (TSS), total acidity (TA), color, and volatile compound. Application of the PGPR significantly increased the population of the Bacillus and Pseudomonas genus and promoted the growth of nitrogen fixing bacteria. Also, the strawberries from the T2 group contained significantly higher TSS. The color of the strawberries from the T1 and T2 groups appeared significantly darker. The volatile compounds analysis showed that the PGPR contributed to butanoic acid methyl ester (fruity/sweet) and butanoic acid 3-methyl-ethyl ester (sweet) production. Additionally, the sensory evaluation result of the likeness testing and the just about right (JAR) scales testing indicated a non-significant difference between the sensory perception of the strawberries cultivated from the three different treatment groups. The significant discovery of the current research suggests that the consortium of the three PGPR have a potential role as a biofertilizer by enhancing the growth of other microorganisms as part of a synergetic effect to enhance plant growth via nitrogen fixation enhancing tolerance against a pathogen and degrading complex compounds.
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  • This project was funded by Oregon Department of Agriculture (ODA).
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