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Nordstedt Nathan PhD Dissertation.pdf (10.43 MB)

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Isolation and characterization of novel bacterial strains to alleviate abiotic stress in greenhouse ornamental crops

Nordstedt, Nathan P
http://orcid.org/0000-0003-0843-2820
http://rave.ohiolink.edu/etdc/view?acc_num=osu1617740819791342

Abstract Details

2021, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
The production of greenhouse ornamental crops relies on extensive inputs of water and chemical fertilizers to produce high-quality plants for consumers. These inputs are both economically and resource expensive, leading to increased concerns of sustainability. In addition, ornamental crops can encounter water and nutrient stress throughout their life span, impacting their health, quality, and resiliency for consumers. Water stress decreases the health and quality of horticulture crops by inhibiting photosynthesis, transpiration, and nutrient uptake, contributing to a reduction in plant size and flower number. The lack of bioavailable nutrients for plant uptake negatively impacts plant metabolism, influencing different aspects of plant growth and development. The effect of both abiotic stresses decreases the salability of crops at retail and can impact consumer success in the landscape. Therefore, it is important that the horticulture industry has sustainable tools to decrease resource-intensive inputs while also increasing plant abiotic stress tolerance, without sacrificing crop quality. Plant growth promoting bacteria (PGPB) can increase plant growth under water and nutrient-limiting conditions by enhancing stress tolerance and increasing nutrient availability, uptake, and assimilation by plants. PGPB colonize their plant host and can stimulate plant growth and stress tolerance through a myriad of different mechanisms. The identification of PGPB for greenhouse ornamental crops will contribute to the formulation of commercial productions that can be implemented into greenhouse production systems for the sustainable production of high-quality and resilient crops. This work outlines the identification, evaluation, and characterization of PGPB for greenhouse ornamental crops subjected to water stress and low-nutrient conditions. A core collection of 45 bacterial isolates was utilized to develop a high-throughput approach for the selection and evaluation of PGPB under water and low-nutrient stress. Isolates were first evaluated in vitro for their osmotic stress tolerance and then in planta in a high-throughput preliminary greenhouse trial for their ability to stimulate plant growth under resource-limiting conditions. Pseudomonas poae 29G9 and Pseudomonas fluorescens 90F12-2 were selected and their influence on plant growth was validated in a production-scale greenhouse trial. Both strains positively influenced different aspects of plant growth of three economically-important species subjected to water and low-nutrient stress, and increased tissue nutrient content of plants grown under low-nutrient conditions. Additionally, these methods were used to evaluate Serratia plymuthica MBSA-MJ1’s influence on plant growth under similar conditions. Application of MBSA-MJ1 showed similar positive responses in plants under both water and low-nutrient conditions. While the application of microbe-containing biostimulant products can increase stress tolerance and crop quality, most research in this area has focused on agronomic crops with little emphasis on greenhouse ornamentals. Therefore, a majority of PGPB strains have been isolated from field crops or environmental samples. The formulation of these strains into commercially available biostimulant products has led to inconsistent results when applied in greenhouse production systems. To identify PGPB for greenhouse ornamentals, bacteria were isolated from the rhizosphere of plants collected from greenhouse production facilities. Over 1,000 bacterial isolates were collected and screened in vitro for osmoadaptability and ACC deaminase activity. The selected isolates were then evaluated in planta for their ability to stimulant plant growth and photosynthetic health after recovery from severe water stress. PGPB application increased parameters of plant growth and photosynthetic health, while decreasing the extent of electrolyte leakage after recovery from stress. This work provides one example of how this novel collection of rhizosphere bacteria can be used to identify PGPB for greenhouse ornamentals subjected to abiotic stress. In addition to evaluating PGPB strains in greenhouse trials, this work utilized in vitro experiments and genomic analyses to further characterize two model PGPB strains, Serratia plymuthica MBSA-MJ1 and Leifsonia sp. C5G2. C5G2 belongs to the greenhouse rhizosphere collection and increases growth of plants recovering from water stress. The in vitro experiments evaluated the motile nature, antibiotic resistance, and carbon source utilization of both strains. Further, genomic analyses identified genes putatively involved in bacterial osmotic and oxidative stress responses, synthesis of osmoprotectants and vitamins that could potentially be involved in increasing plant water stress tolerance and increasing the availability and nutrient uptake by plants. Additionally, we performed comparative genomics with the PGPB strain C5G2 with pathogenic Leifsonia xyli subsp. xyli and other Gram-positive bacteria to better understand plant association and growth promotion under abiotic stress. These comparative analyses showed that beneficial and commensal Leifsonia spp. clustered separately from pathogenic Leifsonia xyli subsp. xyli, and the beneficial/commensal strains share biosynthetic gene and orthologous protein clusters that are not shared with known phytopathogens in our analysis. This work provides insight into the diversity and utility of the genus Leifsonia with a better understanding of potential mechanisms utilized by beneficial and pathogenic strains. Collectively, these results show that the combination of in vitro and greenhouse experiments can efficiently identify PGPB that increase the quality of ornamental crops subjected to water and low-nutrient stress. In addition, this work provides insight into the interconnectedness of mechanisms employed by PGPB to increase the growth and stress tolerance of greenhouse ornamental crops. This research serves as a foundation for future exploration of novel PGPB and understanding of mechanisms involved in these valuable plant-microbe interactions.
Michelle Jones (Advisor)
Christopher Taylor (Committee Member)
Ye Xia (Committee Member)
Jyan-Chyun Jang (Committee Member)
377 p.
Horticulture; Plant Biology; Plant Pathology
drought; floriculture; greenhouse production; horticulture; low nutrient; ornamental plants; PGPR; plant-microbe interaction; whole-genome sequence; biofertilizer; biostimulant; genome analysis; nutrient stress; nutrient solubilization; photosynthesis;

Recommended Citations

Citations

  • Nordstedt, N. P. (2021). Isolation and characterization of novel bacterial strains to alleviate abiotic stress in greenhouse ornamental crops [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1617740819791342

    APA Style (7th edition)

  • Nordstedt, Nathan. Isolation and characterization of novel bacterial strains to alleviate abiotic stress in greenhouse ornamental crops. 2021. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1617740819791342.

    MLA Style (8th edition)

  • Nordstedt, Nathan. "Isolation and characterization of novel bacterial strains to alleviate abiotic stress in greenhouse ornamental crops." Doctoral dissertation, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1617740819791342

    Chicago Manual of Style (17th edition)

osu1617740819791342
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